# Vesta: full reference text > Reference content from vestapeptides.com in one file. Vesta supplies research materials for in vitro laboratory use only. Nothing here describes use, dose or effect in people or animals. Source: https://vestapeptides.com/ · Methodology: https://vestapeptides.com/methodology/ # Compound reference ## 5-Amino-1MQ URL: https://vestapeptides.com/compounds/5-amino-1mq/ Type: Small molecule Also written as: 5-amino-1-methylquinolinium Formula: C10H11N2+ Average molecular weight: 159.21 g/mol Monoisotopic mass: 159.0922 Da CAS: 685079-15-6 5-Amino-1MQ (5-amino-1-methylquinolinium) is a small-molecule compound used as a tool inhibitor of nicotinamide N-methyltransferase (NNMT). NNMT methylates nicotinamide and is studied in metabolism and cancer biology. Published work on small-molecule NNMT inhibitors covers their membrane permeability, selectivity and mechanism, and a recent review in Trends in Pharmacological Sciences discusses the prospects for NNMT inhibitors. In the laboratory it is used as a tool compound when NNMT activity needs to be blocked in cell or enzyme assays. PubChem lists the compound as the cation C10H11N2+ (159.21). Because it is a quinolinium cation it is supplied as a salt with a counter-ion, so the molecular weight printed on a COA will be higher than the cation mass. Analytical notes: - Mass spectrometry detects the cation itself at m/z 159.09; the counter-ion is not seen in positive mode. - Ask which counter-ion is present and for an HPLC-UV chromatogram, as the compound absorbs strongly in the UV. ## Adamax URL: https://vestapeptides.com/compounds/adamax/ Type: Peptide analogue Also written as: Ac-MEHFPGP-adamantyl Formula: C50H69N11O11S (reported, unconfirmed) Average molecular weight: 1032.21 g/mol Monoisotopic mass: 1031.4899 Da Adamax is a research peptide described in public sources as a synthetic analogue of Semax. The structure is not published by the supplier, so the figures on this page come from a public reference and must be confirmed against batch LC-MS data. Semax is a seven-residue peptide, Met-Glu-His-Phe-Pro-Gly-Pro, that combines the ACTH(4-7) sequence with a C-terminal Pro-Gly-Pro tail. Adamax is described as a Semax analogue with chemical changes at both ends: an acetyl group on the N-terminus and an adamantane-containing group on the C-terminus. Adamantane is a rigid, compact hydrocarbon cage. Adding it makes a peptide more hydrophobic, so Adamax is expected to be retained longer than Semax on a reversed-phase column. It also removes the free N-terminal amine, which has consequences for some sequencing and labelling methods. The reported formula is C50H69N11O11S, an average molecular weight of 1032.21 g/mol and a monoisotopic mass of 1031.4899 Da. It matches the Semax sequence, an N-terminal acetyl cap and a C-terminal 3-aminoadamantane-1-carboxamide group, which we checked by adding the parts together. It is not a registry-confirmed value. A PubChem search under this name found no record, and a PubMed search found no paper describing the peptide when this page was prepared. Public descriptions also disagree about the exact C-terminal group, which is another reason to rely on the intact mass and fragmentation data of the batch you hold. Reported structure: Ac-Met-Glu-His-Phe-Pro-Gly-Pro joined through an amide bond to 3-aminoadamantane-1-carboxamide. The N-terminus is acetylated and the C-terminus carries the adamantane group. Analytical notes: - Treat the formula and mass on this page as a hypothesis to test, not as a specification. If the intact mass differs from 1031.49 Da, the vial may contain a different structure. - Ask the supplier for the structure drawing, the intact-mass LC-MS result and, ideally, an MS/MS fragment spectrum that supports the C-terminal assignment. - The N-terminal acetyl group blocks the amine, so Edman degradation does not work on this peptide. - Ask for the HPLC method gradient. Because the molecule is more hydrophobic than Semax, a purity method developed for short polar peptides may under-resolve late-eluting impurities. Q: Is Adamax the same as Semax? A: No. Public sources describe Adamax as a Semax analogue with an N-terminal acetyl group and a C-terminal adamantane-containing group, so it is a different molecule with a different mass. Q: Does Adamax have a CAS number or a PubChem record? A: No record was found under this name in PubChem when this page was prepared, and the peptide has no CAS number in the sources we checked. Identity therefore rests on the batch documents. ## AHK-Cu URL: https://vestapeptides.com/compounds/ahk-cu/ Type: Peptide-copper(II) complex Also written as: Alanyl-histidyl-lysine copper Formula: C15H26N6O4 (AHK peptide component) Average molecular weight: 354.40 g/mol Monoisotopic mass: 354.2016 Da CAS: 682809-81-0 AHK-Cu is the copper(II) complex of the tripeptide alanyl-L-histidyl-L-lysine (AHK), an analogue of GHK in which alanine replaces glycine. AHK-Cu is much less studied than GHK-Cu. A published in-vitro study examined a tripeptide-copper complex in a human hair follicle culture model, and the coordination chemistry is expected to resemble that of GHK. The identity numbers on this page describe the AHK peptide component (PubChem lists it as L-Alanyl-L-histidyl-L-lysine). AHK is Ala-His-Lys. Copper(II) binds through the histidine imidazole and the neighbouring nitrogens, as in GHK-Cu. Analytical notes: - Because the evidence base is small, rely on the batch documents for identity: mass of the peptide, copper content and HPLC purity. - The molecular weight depends on the copper content and the salt form. ## AOD9604 URL: https://vestapeptides.com/compounds/aod9604/ Type: Peptide Also written as: Tyr-hGH 177-191, AOD-9604 Formula: C78H123N23O23S2 Average molecular weight: 1815.08 g/mol Monoisotopic mass: 1813.8604 Da CAS: 221231-10-3 AOD9604 is a synthetic 16-residue peptide made of the C-terminal fragment 177-191 of human growth hormone with an extra N-terminal tyrosine, closed by a disulfide bond. The fragment was studied because it contains the region of growth hormone associated with lipid metabolism in early research, without the full hormone. Reviews and analytical papers describe its profile. Analytical groups have published methods for its detection and its in-vitro metabolism, which are a good reference when verifying identity. The sequence is YLRIVQCRSVEGSCGF with a Cys7-Cys14 disulfide bond. The calculated formula from the sequence matches PubChem exactly. Analytical notes: - The reduced (open) form is 2.016 Da heavier than the oxidised disulfide form in the table. - Cysteine-containing peptides can form dimers on storage; look for a peak at about twice the mass. ## ARA290 URL: https://vestapeptides.com/compounds/ara-290/ Type: Peptide Also written as: Cibinetide, pHBSP Formula: C51H84N16O21 Average molecular weight: 1257.31 g/mol Monoisotopic mass: 1256.5997 Da CAS: 1208243-50-8 ARA290 (cibinetide, pHBSP) is an 11-residue peptide derived from the helix B surface of erythropoietin and described in the literature as lacking erythropoietic activity. The sequence is pGlu-Glu-Gln-Leu-Glu-Arg-Ala-Leu-Asn-Ser-Ser. It was designed to interact with the innate repair receptor, a heteromer of the erythropoietin receptor and the β-common receptor, and papers describe its effects on innate immune cells. Note that one paper on the related pHBSP peptide has been retracted; always read the primary data. The N-terminus is a pyroglutamate. The calculated formula matches PubChem exactly. Analytical notes: - The pyroglutamate N-terminus has no free amine, which affects both ion formation and Edman sequencing. - Acidic residues (Glu) make the peptide polar; use an HPLC gradient that starts at low organic solvent. ## BPC-157 URL: https://vestapeptides.com/compounds/bpc-157/ Type: Peptide Also written as: Body protection compound 157, Pentadecapeptide BPC 157 Formula: C62H98N16O22 Average molecular weight: 1419.54 g/mol Monoisotopic mass: 1418.7042 Da CAS: 137525-51-0 BPC-157 is a synthetic pentadecapeptide (Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val) that corresponds to a partial sequence of a protein found in human gastric juice. The name stands for body protection compound. Most of the published research on BPC-157 comes from a small number of laboratories using rodent models, including studies of tendon, gut and wound tissues; both reviews and critical narrative reviews exist. Because the literature is concentrated, independent analytical confirmation of any batch is the main source of confidence for researchers. The sequence is GEPPPGKPADDAGLV with a free N-terminus and a free C-terminal acid. Three proline residues in a row make the N-terminal half rigid. The calculated formula matches PubChem exactly. Analytical notes: - BPC-157 is supplied in several salt forms, including acetate and arginine salts; the salt form changes the molecular weight on the COA. - Vesta also lists research blends of BPC-157 with TB-500 at several strengths. ## Cagrilintide URL: https://vestapeptides.com/compounds/cagrilintide/ Type: Peptide Also written as: NN9838 Formula: C194H312N54O59S2 Average molecular weight: 4409.01 g/mol Monoisotopic mass: 4406.2515 Da CAS: 1415456-99-3 Cagrilintide is a long-acting synthetic analogue of the pancreatic hormone amylin that acts on amylin and calcitonin receptors. Native amylin is a 37-residue hormone co-secreted with insulin. Cagrilintide was engineered with sequence changes and a fatty diacid side chain, and its development is described in the Journal of Medicinal Chemistry. Structural studies of cagrilintide bound to amylin and calcitonin receptors are published, which makes it useful as a reference ligand for these receptor systems. It is supplied here as a research material. PubChem lists the molecule with two sulfur atoms, consistent with the disulfide bridge found in amylin-type peptides, plus the acylated side chain. Analytical notes: - Disulfide-containing peptides can show a reduced form that is 2.016 Da heavier than the intact molecule; the COA should show that this form is absent or minor. - Vesta also lists research blends that contain cagrilintide together with semaglutide or tirzepatide. ## Cartalax URL: https://vestapeptides.com/compounds/cartalax/ Type: Peptide Also written as: AED, Ala-Glu-Asp Formula: C12H19N3O8 Average molecular weight: 333.29 g/mol Monoisotopic mass: 333.1172 Da CAS: 85806-95-7 Cartalax is the name used for the tripeptide Ala-Glu-Asp (AED), one of the short peptide bioregulators described by the Khavinson group. The tripeptide AED has a molecular weight of 333.29 and no modifications. It is closely related to the tetrapeptide epithalon (AEDG), which adds a glycine at the C-terminus. The published literature on this peptide is limited, and the best-known review is a general overview of peptide bioregulators and ageing. Ala-Glu-Asp is made entirely of standard L-amino acids. The sequence-based formula matches the PubChem record. Analytical notes: - At 333 Da it is detected as a singly charged ion. Adducts such as [M+Na]+ at m/z 356.11 are common and should not be confused with impurities. - Very small, polar peptides are difficult to retain on reversed-phase columns; ask which HPLC conditions were used. ## CJC-1295 URL: https://vestapeptides.com/compounds/cjc-1295/ Type: Peptide Also written as: Modified GRF(1-29), CJC-1295 DAC, DAC:GRF Formula: C165H269N47O46 Average molecular weight: 3647.19 g/mol Monoisotopic mass: 3645.0155 Da CAS: 446262-90-4 CJC-1295 is a synthetic analogue of GHRH(1-29) with four amino acid substitutions; the version with a drug affinity complex (DAC) carries a reactive group that allows covalent binding to serum albumin. The name is used for two different molecules. CJC-1295 without DAC is the tetrasubstituted GRF(1-29) peptide, often written Modified GRF(1-29). CJC-1295 with DAC is the same peptide with a lysine-linked maleimidopropionamide group added. Published work includes the original characterisation of the DAC version and analytical papers on its identification in unknown preparations and in biological samples. The peptide part is YADAIFTQSYRKVLAQLSARKLLQDILSR-NH2 with D-alanine at position 2 and substitutions at positions 8, 15 and 27. The DAC version adds a lysine-based linker with a reactive maleimide group. Analytical notes: - Check that the COA states which form was tested: the masses differ by about 280 Da, so identity is easy to confirm from the intact mass. - The mass for the DAC form in the table is the PubChem value; the mass for the form without DAC is calculated from the sequence and is shown separately. Q: What is the difference between CJC-1295 with DAC and without DAC? A: They are two different molecules. The version without DAC is the modified GRF(1-29) peptide. The version with DAC adds a lysine-linked reactive group so that the peptide can bind serum albumin covalently. Their molecular weights differ, so the intact mass on a COA shows which one was supplied. ## Dihexa URL: https://vestapeptides.com/compounds/dihexa/ Type: Peptide Also written as: PNB-0408, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide Formula: C27H44N4O5 Average molecular weight: 504.66 g/mol Monoisotopic mass: 504.3312 Da CAS: 1401708-83-5 Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide) is a synthetic peptide-like analogue of angiotensin IV that has been described as acting through the hepatocyte growth factor (HGF)/c-Met system. Dihexa was derived from the angiotensin IV peptide family. A pharmacology paper on angiotensin IV-derived peptides shows that their effects depend on activation of the HGF/c-Met pathway, and later studies use it in mouse models of cognition. It is a small peptide-like molecule of about 505 Da, with chemistry that is closer to a modified dipeptide than a classical peptide. The molecule is a hexanoyl-capped tyrosine-isoleucine unit linked to an aminohexanoic amide. PubChem gives the formula C27H44N4O5. Analytical notes: - At about 505 Da it ionises as [M+H]+ at m/z 505.34; ask for the mass spectrum and an HPLC chromatogram. - Because it is not a standard peptide, no sequence-based calculation is shown here. ## Epithalon URL: https://vestapeptides.com/compounds/epithalon/ Type: Peptide Also written as: Epitalon, Ala-Glu-Asp-Gly Formula: C14H22N4O9 Average molecular weight: 390.35 g/mol Monoisotopic mass: 390.1387 Da CAS: 307297-39-8, 64082-79-7 Epithalon (Epitalon) is the synthetic tetrapeptide Ala-Glu-Asp-Gly, designed on the basis of epithalamin, a polypeptide extract from the pineal gland. The peptide was developed by the Khavinson group in St. Petersburg. Early papers examine its effects in Drosophila, rodents and cultured cells, and a recent review summarises this literature. Because the published work comes from a small number of laboratories, independent verification of the identity and purity of any supplied batch is especially important. AEDG has four residues and no unusual modifications. The calculated formula and mass agree with the PubChem record. Analytical notes: - Short, acidic peptides are very polar and may elute close to the solvent front on reversed-phase columns; check that the HPLC method retains the main peak. - Counter-ion content is a large share of the powder mass for a peptide of 390 Da. ## GHK-Cu URL: https://vestapeptides.com/compounds/ghk-cu/ Type: Peptide-copper(II) complex Also written as: Copper tripeptide-1, Glycyl-L-histidyl-L-lysine copper Formula: C14H24N6O4 (GHK peptide component) Average molecular weight: 340.38 g/mol Monoisotopic mass: 340.1859 Da GHK-Cu is the copper(II) complex of the tripeptide glycyl-L-histidyl-L-lysine (GHK), a short peptide first isolated from human plasma that binds copper with high affinity. GHK on its own is a naturally occurring tripeptide, and its copper complex is the form most often studied. The literature covers its coordination chemistry, including crystallographic and computational studies of how GHK binds copper(II), as well as its use in skin biology research. Vesta lists GHK-Cu as a research material. The identity numbers on this page describe the GHK peptide component, because PubChem lists the copper complex only as a charged ion. GHK is Gly-His-Lys. In the complex, copper(II) is bound by the imidazole of histidine, the N-terminal amine and backbone nitrogens, normally in a 1:1 ratio. Solutions of copper-peptide complexes are typically blue. Analytical notes: - The copper content and the form (free acid, acetate or hydrochloride) change the molecular weight on a COA, so ask for the copper assay in addition to the HPLC purity. - Copper has two stable isotopes, 63Cu and 65Cu, so mass spectra of the complex show a doublet pattern. ## GHRP-2 URL: https://vestapeptides.com/compounds/ghrp-2/ Type: Peptide Also written as: Pralmorelin, KP-102 Formula: C45H55N9O6 Average molecular weight: 817.97 g/mol Monoisotopic mass: 817.4275 Da CAS: 158861-67-7 GHRP-2 (pralmorelin) is a synthetic hexapeptide, D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2, that acts as a ghrelin-receptor agonist. GHRP-2 belongs to the family of synthetic growth hormone-releasing peptides. Its pharmacology and metabolism are described in published studies, including LC-MS methods for its detection. Vesta lists it as the acetate salt, which matters for the molecular weight on the batch documents. It contains three unnatural residues (D-Ala, D-2-naphthylalanine, D-Phe) and a C-terminal amide. The calculated formula agrees with PubChem. Analytical notes: - The values in the table are for the free peptide. An acetate salt adds about 60.05 Da per acetate counter-ion, so the molecular weight printed on a COA for the salt is higher. - Net peptide content is lower than 100 % because counter-ions and water are part of the powder. ## GHRP-6 URL: https://vestapeptides.com/compounds/ghrp-6/ Type: Peptide Also written as: Growth hormone releasing peptide-6 Formula: C46H56N12O6 Average molecular weight: 873.01 g/mol Monoisotopic mass: 872.4446 Da GHRP-6 is a synthetic hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, and one of the first synthetic ghrelin-receptor agonists. GHRP-6 was among the earliest growth hormone-releasing peptides discovered. It is used as a reference compound in ghrelin-receptor studies, and detection methods for it in biological samples are published. Vesta lists it as the acetate salt. It differs from GHRP-2 by its N-terminal histidine and D-tryptophan. The sequence-derived formula matches PubChem. Analytical notes: - Tryptophan residues can oxidise, giving +15.995 Da and +31.990 Da species. - The acetate salt is heavier than the free peptide shown in the table; compare like with like when you read a COA. ## GLOW URL: https://vestapeptides.com/compounds/glow/ Type: Research blend Also written as: GLOW 70 mg blend Components: GHK-Cu 50 mg (C14H24N6O4, average 340.38 g/mol); BPC-157 10 mg (C62H98N16O22, average 1419.54 g/mol); TB-500 (thymosin beta-4) 10 mg (C212H350N56O78S, average 4963.44 g/mol) Declared content per vial: 70 mg GLOW is a pre-mixed three-peptide research blend with 70 mg of material per vial: 50 mg GHK-Cu, 10 mg BPC-157 and 10 mg TB-500, according to the manufacturer's specification. A blend places several research peptides in one vial so that they can be reconstituted together. GLOW combines a copper-binding tripeptide (GHK-Cu), a 15-residue peptide derived from a gastric protein sequence (BPC-157) and TB-500, a peptide sold under a name that refers to thymosin beta-4. Each component has its own reference page on this site with its formula, mass and literature. The three components are analytically very different. The GHK peptide is only 340 Da and carries copper, BPC-157 is about 1.4 kDa, and thymosin beta-4 is a 43-residue peptide of about 4.96 kDa. A single vial therefore needs three identity checks, and the chromatogram of a correct sample shows several peaks rather than one. Vesta lists GLOW as a kit of 10 vials with 70 mg per vial. The figure 70 mg is the sum of the three declared component masses, not the amount of any one peptide. Analytical notes: - A single purity percentage does not describe a blend. Ask for a chromatogram on which each component peak is labelled, and for the amount of each component per vial, not only the total mass of powder. - In a generic gradient, peaks from different components can overlap, so extracted-ion chromatograms for each expected mass are more reliable than the UV trace alone. - The 50 mg GHK-Cu figure may refer to the copper complex or to the GHK peptide. Confirm which on the batch documents, because the copper adds roughly 60 Da to each molecule. - Copper has two stable isotopes (63Cu and 65Cu), so the GHK-Cu species appears as a doublet in a mass spectrum, while BPC-157 and thymosin beta-4 show their own multiply charged ions. - Solutions of copper-peptide complexes are normally blue to blue-violet. Colour alone does not prove identity, but a colourless solution would suggest that the copper is missing. - TB-500 is used for the full thymosin beta-4 sequence and, by some sellers, for a short fragment. The mass found in the blend shows which one the vial contains. Q: What does GLOW contain? A: According to the manufacturer's specification each vial contains 50 mg GHK-Cu, 10 mg BPC-157 and 10 mg TB-500, 70 mg in total. The batch certificate of analysis should confirm the identity of each component. Q: How is GLOW different from Klow? A: Klow has the same three components in the same amounts and adds 10 mg of the tripeptide KPV, which brings the total to 80 mg per vial. Q: How can I check all three components in a GLOW vial? A: Run LC-MS and look for each component separately: the GHK peptide at m/z 341.19 ([M+H]+) with a copper-containing species, BPC-157 at its [M+2H]2+ and [M+3H]3+ ions, and thymosin beta-4 at its higher charge states. The expected values are listed in the mass spectrometry section of this page. ## Glutathione URL: https://vestapeptides.com/compounds/glutathione/ Type: Small molecule Also written as: GSH, L-γ-Glutamyl-L-cysteinylglycine Formula: C10H17N3O6S Average molecular weight: 307.32 g/mol Monoisotopic mass: 307.0838 Da CAS: 70-18-8, 106272-20-2 Glutathione (GSH) is the tripeptide γ-L-glutamyl-L-cysteinylglycine, the most abundant low-molecular-weight thiol in animal cells. Glutathione has an unusual γ-peptide bond between glutamate and cysteine and exists in a reduced form (GSH) and an oxidised dimer (GSSG). Its biochemistry is the subject of classic reviews, for example in the Annual Review of Biochemistry. It is used in the laboratory as a reducing agent, as an enzyme cofactor and as a reference thiol. The formula of reduced glutathione is C10H17N3O6S. The oxidised form GSSG is a disulfide dimer of about 612.6 Da. Analytical notes: - Check that the COA states whether the material is the reduced or oxidised form and what percentage of GSSG is present. - Thiols oxidise in air; the amount of GSSG can increase with storage time. ## Gonadorelin URL: https://vestapeptides.com/compounds/gonadorelin/ Type: Peptide Also written as: GnRH, LHRH Formula: C55H75N17O13 Average molecular weight: 1182.29 g/mol Monoisotopic mass: 1181.5730 Da CAS: 33515-09-2 Gonadorelin is the synthetic form of gonadotropin-releasing hormone (GnRH, LHRH), a decapeptide with the sequence pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2. GnRH is released from the hypothalamus and acts on the GnRH receptor of pituitary cells. The structure and function of the receptor, and the analytical techniques used to measure small peptide hormones such as gonadorelin, are covered by recent reviews. In research it is used as the native-sequence reference agonist. The N-terminus is a cyclic pyroglutamate and the C-terminus is an amide, so neither end has a free charge. The calculated formula matches PubChem exactly. Analytical notes: - Pyroglutamate formation from glutamine is a common artefact in synthetic peptides; ensure the COA mass matches the pyroglutamate form. - Gonadorelin is often supplied as an acetate or hydrochloride, which changes the molecular weight on the COA. ## Hexarelin URL: https://vestapeptides.com/compounds/hexarelin/ Type: Peptide Also written as: Examorelin Formula: C47H58N12O6 Average molecular weight: 887.04 g/mol Monoisotopic mass: 886.4602 Da CAS: 140703-51-1, 208251-52-9 Hexarelin is a synthetic hexapeptide, His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, derived from GHRP-6 and acting at the ghrelin receptor. Hexarelin is the 2-methyl-tryptophan analogue of GHRP-6. Besides its growth hormone-releasing activity it has been studied for effects mediated by cardiac receptors, and reviews of its cardiovascular pharmacology are available. It is supplied here as a research material. The only change from GHRP-6 is a methyl group on the indole ring of the D-tryptophan, giving a mass 14.016 Da higher. Analytical notes: - The mass difference to GHRP-6 (14.016 Da) is small but easy to resolve by mass spectrometry; confirm that the COA does not show the GHRP-6 mass. - The values in the table are for the free peptide. ## IGF-1 LR3 URL: https://vestapeptides.com/compounds/igf-1-lr3/ Type: Protein (83 residues) Also written as: Long R3 IGF-I, LR3-IGF-1 Formula: C400H619N111O115S9 Average molecular weight: 9111.45 g/mol Monoisotopic mass: 9105.3487 Da IGF-1 LR3 (Long R3 IGF-I) is an 83-residue analogue of human insulin-like growth factor 1 with an Arg3 substitution and a 13-residue N-terminal extension, giving much lower binding to IGF-binding proteins. The modifications reduce binding to IGF-binding proteins, so the analogue stays active in culture media where native IGF-1 would be sequestered. It is widely used as a growth-factor supplement in cell culture and has been expressed recombinantly in yeast. Animal and cell studies use it as a more potent IGF-1 receptor agonist because it escapes sequestration by binding proteins. The sequence has 83 residues and three disulfide bonds. The formula and masses in this page are calculated from the sequence registered in the FDA Global Substance Registration System, with three disulfides, because PubChem does not list a compound record. Analytical notes: - Correct disulfide pairing matters: misfolded isoforms have the same mass but different retention time, so a single HPLC peak and an intact-mass match should be reported together. - At about 9.1 kDa the molecule is measured as a multiply charged envelope and reported as a deconvoluted average mass. ## Ipamorelin URL: https://vestapeptides.com/compounds/ipamorelin/ Type: Peptide Also written as: NNC 26-0161 Formula: C38H49N9O5 Average molecular weight: 711.85 g/mol Monoisotopic mass: 711.3857 Da CAS: 170851-70-4 Ipamorelin is a synthetic pentapeptide (Aib-His-D-2Nal-D-Phe-Lys-NH2) that acts as an agonist of the ghrelin receptor, also called the growth hormone secretagogue receptor. It was described in 1998 as the first selective growth hormone secretagogue, and later papers cover its pharmacokinetics and the design of related hybrid compounds. Researchers use it as a selective ghrelin-receptor agonist in receptor-binding and signalling studies. It contains two D-amino acids, a non-natural amino acid (D-2-naphthylalanine), an α-aminoisobutyric acid residue and a C-terminal amide. The sequence-based formula matches the PubChem record exactly. Analytical notes: - With a mass near 712 Da it is usually seen as a singly charged ion, [M+H]+ at m/z 712.39. - D-amino acids have the same mass as L-amino acids, so epimerised impurities need chiral or high-resolution chromatographic methods. ## Kisspeptin-10 URL: https://vestapeptides.com/compounds/kisspeptin-10/ Type: Peptide Also written as: Metastin 45-54 Formula: C63H83N17O14 Average molecular weight: 1302.44 g/mol Monoisotopic mass: 1301.6305 Da CAS: 374675-21-5 Kisspeptin-10 is a ten-residue peptide amide (Tyr-Asn-Trp-Asn-Ser-Phe-Gly-Leu-Arg-Phe-NH2) that is the C-terminal fragment 45-54 of the kisspeptin precursor and binds the kisspeptin receptor (KISS1R, GPR54). Kisspeptin signalling is central to the control of the reproductive axis. Reviews cover its role in the hypothalamic-pituitary-gonadal axis, its metabolic regulation and its interaction with neurokinin B. Kisspeptin-10 is the shortest fragment that keeps full receptor binding, which is why it is used as the reference peptide in receptor studies. The C-terminal Arg-Phe-NH2 is essential for binding. The calculated formula matches PubChem exactly. Analytical notes: - The tryptophan residue can oxidise (+15.995 Da). - Expect [M+H]+ at m/z 1302.64 and a strong [M+2H]2+ at m/z 651.82. ## Klow URL: https://vestapeptides.com/compounds/klow/ Type: Research blend Also written as: Klow 80 mg blend Components: GHK-Cu 50 mg (C14H24N6O4, average 340.38 g/mol); BPC-157 10 mg (C62H98N16O22, average 1419.54 g/mol); TB-500 (thymosin beta-4) 10 mg (C212H350N56O78S, average 4963.44 g/mol); KPV 10 mg (C16H30N4O4, average 342.43 g/mol) Declared content per vial: 80 mg Klow is a pre-mixed four-peptide research blend with 80 mg of material per vial: 50 mg GHK-Cu, 10 mg BPC-157, 10 mg TB-500 and 10 mg KPV, according to the manufacturer's specification. Klow extends the GLOW blend with a fourth component, the tripeptide KPV, which corresponds to the C-terminal sequence of alpha-melanocyte-stimulating hormone. Like the other components it has its own reference page with formula, mass and literature. KPV and the GHK peptide are close in mass: KPV has a monoisotopic mass of 342.2267 Da and GHK has 340.1859 Da, so their [M+H]+ ions at m/z 343.23 and 341.19 sit two mass units apart and their isotope envelopes partly overlap on a low-resolution instrument. The two are separated by retention time, which is why a blend needs liquid chromatography in front of the mass spectrometer. Vesta lists Klow as a kit of 10 vials with 80 mg per vial. The figure is the sum of the four declared component masses. Analytical notes: - A single purity percentage does not describe a blend. Ask for a chromatogram on which each component peak is labelled, and for the amount of each component per vial, not only the total mass of powder. - In a generic gradient, peaks from different components can overlap, so extracted-ion chromatograms for each expected mass are more reliable than the UV trace alone. - Check four identities in one sample: the GHK peptide (copper species), BPC-157, thymosin beta-4 and KPV. The expected ions of each are listed on this page. - Because the GHK and KPV ions are only two mass units apart, use retention time together with accurate mass, and check the isotope pattern of each peak. - The 50 mg GHK-Cu figure may refer to the copper complex or to the GHK peptide. Confirm which on the batch documents. - Peptide blends should be compared with the single-component batches by HPLC retention time, so that each peak in the blend can be assigned. - TB-500 is used for the full thymosin beta-4 sequence and, by some sellers, for a short fragment. The table above uses the full sequence; the mass found in the blend shows which one the vial contains. Q: What does Klow contain? A: According to the manufacturer's specification each vial contains 50 mg GHK-Cu, 10 mg BPC-157, 10 mg TB-500 and 10 mg KPV, 80 mg in total. The batch certificate of analysis should confirm the identity of each component. Q: What is the difference between Klow and GLOW? A: Klow is GLOW plus 10 mg of KPV. The other three components and their amounts are the same, so the total rises from 70 mg to 80 mg per vial. Q: Why is KPV hard to tell apart from the GHK peptide by mass alone? A: The two tripeptides differ by only about 2.04 Da (342.2267 Da for KPV, 340.1859 Da for GHK). Their isotope envelopes overlap at low resolution, so retention time and accurate mass should be used together. ## KPV URL: https://vestapeptides.com/compounds/kpv/ Type: Peptide Also written as: α-MSH(11-13), Lys-Pro-Val Formula: C16H30N4O4 Average molecular weight: 342.43 g/mol Monoisotopic mass: 342.2267 Da CAS: 67727-97-3 KPV is the tripeptide Lys-Pro-Val, which corresponds to the C-terminal residues 11-13 of α-melanocyte-stimulating hormone. Studies of α-MSH fragments showed that the C-terminal tripeptide retained anti-inflammatory activity in cell models. A stability-indicating HPLC assay for KPV has been published, which makes KPV a good example of a small peptide that can be assayed precisely. Delivery research on KPV covers topical and nano-carrier formulations. The molecule has three residues and no modification; the calculated formula matches PubChem exactly. Analytical notes: - At 342.4 Da, [M+H]+ is m/z 343.23, and [M+Na]+ at m/z 365.22 is common. - A stability-indicating method resolves KPV from its degradation products; ask which HPLC method was used. ## L-carnitine URL: https://vestapeptides.com/compounds/l-carnitine/ Type: Small molecule Also written as: Levocarnitine Formula: C7H15NO3 Average molecular weight: 161.20 g/mol Monoisotopic mass: 161.1052 Da CAS: 541-15-1, 44985-71-9 L-carnitine is a quaternary ammonium compound (formula C7H15NO3) that transports long-chain fatty acids into mitochondria as part of the carnitine shuttle. It is a small, water-soluble molecule that is found in all animal tissues and is not a peptide. Its metabolic functions are described in reviews of fatty acid oxidation. In the laboratory it is used as a metabolic reagent and as a standard in carnitine and acylcarnitine assays. The biologically active form is the L enantiomer (levocarnitine). The D enantiomer is inactive and can inhibit carnitine-dependent processes, so a COA should state the enantiomeric purity. Analytical notes: - Carnitine is analysed by HPLC with derivatisation or by LC-MS, not by direct UV at 214 nm. - The powder is hygroscopic; water content should be reported. ## Lemon Bottle URL: https://vestapeptides.com/compounds/lemon-bottle/ Type: Multi-component formulation Also written as: Lemon Bottle lipolytic complex Components: Riboflavin (vitamin B2) (C17H20N4O6, average 376.36 g/mol); Bromelain (a mixture of cysteine proteases from pineapple, measured by enzyme activity rather than by mass); Lecithin (a mixture of phospholipids in which phosphatidylcholine usually predominates) Lemon Bottle is described by the manufacturer as a three-component research formulation of riboflavin, bromelain and lecithin, listed at 10 mL per vial. The three ingredients are very different kinds of material. Riboflavin (vitamin B2) is a single small molecule with a defined formula. Bromelain is a mixture of cysteine proteases extracted from pineapple, so it is quantified by enzyme activity rather than by molecular weight. Lecithin is a mixture of phospholipids in which phosphatidylcholine usually predominates. Two of the three ingredients are therefore mixtures with natural variation between lots. Two different batches can be correctly labelled and still differ in enzyme activity or in the fatty-acid composition of the phospholipids, which is why the batch documents should state the grade and the assay method for each. Vesta lists the product as a kit of 10 vials at 10 mL per vial. The physical form of the vial and the concentration of each ingredient are not given in the listing. Analytical notes: - Riboflavin is yellow-green, fluorescent and sensitive to light. It absorbs near 267, 373 and 445 nm, so its presence and amount can be checked by UV-visible spectroscopy or fluorescence. - Bromelain is measured in activity units (for example gelatin-digesting units) rather than milligrams of protein. Ask for the activity per millilitre and the assay used. - Lecithin is usually specified by its phosphatidylcholine content, measured by HPLC with a light-scattering detector or by 31P NMR. A UV chromatogram at 220 nm is not a suitable test. - Bromelain is a protease. It digests peptides and proteins, so keep it separate from peptide stock solutions when planning in vitro experiments. - Ask for the formulation sheet with the concentration of each ingredient and for the physical form, appearance and pH of the vial. Q: What does Lemon Bottle contain? A: The manufacturer describes it as a combination of riboflavin, bromelain and lecithin. Amounts per vial are not published, so request the batch formulation sheet. Q: Can bromelain be mixed with peptide research materials? A: It should not be added to a peptide solution, because bromelain is a protease and cleaves peptides. Keep the two separate in in vitro experiments unless digestion is the purpose. ## Lipo-C URL: https://vestapeptides.com/compounds/lipo-c/ Type: Multi-component formulation Also written as: Lipo C, Lipo-C FatBlaster, LC533, Lipolytic complex, Lipo-C blends Components: not itemised by the manufacturer Lipo-C is a name used for lipotropic research blends. Vesta lists three products under it (Lipo-C, Lipo-C FatBlaster and LC533); their ingredients are not itemised in the listings, so this page explains what to ask for. There is no single standard Lipo-C formula. Public product sheets for products with this name list different ingredients, from methionine, inositol and choline with vitamin B12, to mixtures that also contain L-carnitine, other B vitamins or amino acids. The same name can therefore describe different materials from different sellers. Vesta lists Lipo-C, Lipo-C (FatBlaster) and LC533 as kits of 10 vials at 10 mL per vial, at three different price levels. The manufacturer describes them as multi-compound lipotropic blends and describes LC533 as the concentrated one. The ingredient list and the concentration of each ingredient are not published in the listings. Because the contents are not itemised, this page gives no formula or molecular weight. A blend of small, non-peptide ingredients also has no single molecular weight. The practical step is to request the formulation sheet for the specific batch before any laboratory work. Analytical notes: - Request a formulation sheet that names every ingredient, gives its concentration in mg/mL, states its grade and form (for example free base or salt), and names any preservative or buffer. - Ask what the listed 10 mL contains and what physical form the vial is supplied in. The listing gives the volume only. - A peptide-style HPLC method with UV detection at 220 nm is not suited to these ingredients. Inositol and choline have essentially no UV absorbance and methionine absorbs weakly, so ask which detector produced any purity figure (for example ELSD, CAD, refractive index or mass spectrometry) and what the percentage refers to. - Each ingredient needs its own assay. A single combined purity number cannot show that every declared ingredient is present at the declared level. - Vitamin B12, if present, is easy to quantify by UV-visible absorbance (cyanocobalamin absorbs near 361 nm and 550 nm) and gives solutions a red colour. Q: What is in Lipo-C? A: The ingredients are not itemised in Vesta's listings. Products sold as Lipo-C differ between sellers, so request the formulation sheet for the batch you are buying, with the concentration of every ingredient. Q: What is the difference between Lipo-C, Lipo-C FatBlaster and LC533? A: Vesta lists them as three separate products at 10 mL per vial. The manufacturer describes all three as multi-compound lipotropic blends and describes LC533 as the concentrated one. The listings do not itemise how the formulations differ, so the formulation sheets are the way to compare them. Q: Where can I read about the ingredients that Lipo-C often contains? A: The Lipo-C with B12 (MIC) page lists methionine, inositol, choline and cyanocobalamin with their formulas and masses, and the L-carnitine page covers another ingredient that appears in some formulations. ## Lipo-C with B12 (MIC) URL: https://vestapeptides.com/compounds/mic-b12/ Type: Multi-component formulation Also written as: Lipo C with B12, MIC B12, Methionine inositol choline B12 Components: L-Methionine (C5H11NO2S, average 149.21 g/mol); myo-Inositol (C6H12O6, average 180.16 g/mol); Choline chloride (C5H14ClNO, average 139.62 g/mol); Cyanocobalamin (vitamin B12) (C63H88CoN14O14P, average 1355.37 g/mol) Lipo-C with B12 (MIC) is described by the manufacturer as a methionine, inositol and choline blend with vitamin B12; these four ingredients are small molecules with well-defined formulas. MIC is an abbreviation of methionine, inositol and choline, three small molecules involved in lipid and one-carbon metabolism. The product Vesta lists as Lipo-C with B12 adds vitamin B12 to this combination. Unlike the other Lipo-C listings, its ingredients are named, although their amounts are not published. All four ingredients are well characterised: L-methionine is an amino acid, myo-inositol is a sugar alcohol, choline is a quaternary ammonium cation supplied as a salt, and cyanocobalamin is the cyanide-containing form of vitamin B12. The table on this page gives each formula and mass from PubChem. Vesta lists the product as a kit of 10 vials at 10 mL per vial. The physical form of the vial and the concentration of each ingredient should be taken from the batch documents. Analytical notes: - Three of the four ingredients have little or no UV absorbance at the wavelengths used for peptide HPLC. Ask which detector and method were used for any purity or assay value, and for the amount of each ingredient in mg/mL. - Choline is reported as a cation of mass 104.1070. The salt form (chloride, bitartrate or another) changes the mass of the supplied material, so ask which salt is present. - Cyanocobalamin is intensely coloured (red) and absorbs near 361 nm and 550 nm, which allows a simple UV-visible check of its presence and amount. It is also sensitive to light. - Methionine can oxidise to methionine sulfoxide (+15.995 Da). A mass spectrum showing that shift on the methionine ion points to oxidation in the material. - Myo-inositol is one of several inositol stereoisomers. Confirm that the isomer on the formulation sheet is myo-inositol. Q: What does MIC stand for? A: MIC stands for methionine, inositol and choline. The product listed as Lipo-C with B12 adds vitamin B12 to these three ingredients. Q: What are the molecular weights of the MIC ingredients? A: L-methionine is C5H11NO2S, 149.21 g/mol; myo-inositol is C6H12O6, 180.16 g/mol; choline chloride is C5H14ClNO, 139.62 g/mol; cyanocobalamin is C63H88CoN14O14P, 1355.37 g/mol. Values are from PubChem, and the choline salt form on a batch may differ. Q: How is Lipo-C with B12 different from the other Lipo-C products? A: Its ingredients are named by the manufacturer (methionine, inositol, choline and vitamin B12). The ingredients of Lipo-C, Lipo-C FatBlaster and LC533 are not itemised. ## Liraglutide URL: https://vestapeptides.com/compounds/liraglutide/ Type: Peptide Also written as: NN2211 Formula: C172H265N43O51 Average molecular weight: 3751.20 g/mol Monoisotopic mass: 3748.9465 Da CAS: 204656-20-2 Liraglutide is a synthetic 31-residue GLP-1 analogue in which lysine 26 carries a palmitoyl group through a γ-glutamic acid spacer and lysine 34 is replaced by arginine. Liraglutide and semaglutide were developed in the same medicinal chemistry programme, and the review literature describes both together. The fatty acid side chain gives albumin binding and a longer duration of action than native GLP-1. In research it is a standard GLP-1 receptor agonist for receptor, signalling and animal studies. Vesta supplies it as a research material only. Its backbone is GLP-1(7-37) with one amino acid substitution (Lys34 to Arg), and the C16 palmitoyl chain is attached to Lys26 through γ-glutamic acid. Unlike semaglutide it has no Aib residue. Analytical notes: - The palmitoyl chain makes the peptide more hydrophobic than native GLP-1, so it elutes later in reversed-phase HPLC. - A COA should show an intact mass consistent with the acylated molecule. ## LL-37 URL: https://vestapeptides.com/compounds/ll-37/ Type: Peptide Also written as: Cathelicidin LL-37, hCAP18(134-170) Formula: C205H340N60O53 Average molecular weight: 4493.26 g/mol Monoisotopic mass: 4490.5754 Da CAS: 154947-66-7 LL-37 is the 37-residue C-terminal fragment of the human cathelicidin hCAP18 and the only cathelicidin-derived peptide in humans; it forms an amphipathic α-helix. The sequence is LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES. The literature covers its antimicrobial activity, supramolecular structure (including a published structure of the LL-37(17-29) fragment) and its binding to plasma proteins. It is a standard reference peptide in antimicrobial peptide and host-defence research. LL-37 is rich in lysine and arginine, which gives it a strong positive charge at neutral pH. The calculated formula from the sequence matches PubChem exactly. Analytical notes: - Highly charged peptides give high charge states in electrospray MS; the deconvoluted mass should be about 4493 Da. - Cationic amphipathic peptides adsorb to plastic and glass; low-bind labware is recommended in the laboratory. ## Mazdutide URL: https://vestapeptides.com/compounds/mazdutide/ Type: Peptide Also written as: IBI362, LY3305677 Formula: C207H317N45O65 Average molecular weight: 4475.99 g/mol Monoisotopic mass: 4473.2883 Da CAS: 2259884-03-0 Mazdutide (IBI362, LY3305677) is a synthetic peptide analogue of oxyntomodulin that acts on both the GLP-1 receptor and the glucagon receptor. Oxyntomodulin is a natural gut peptide that activates the GLP-1 and glucagon receptors. Mazdutide is an engineered analogue designed to give balanced dual activity, and its pharmacology is described in recent preclinical papers. It is used in research on dual GLP-1/glucagon receptor signalling and related metabolic models, and is supplied as a research material only. PubChem lists the molecule as a modified peptide of about 4.5 kDa. As with other engineered incretin analogues it contains non-standard components, so its mass is best confirmed on the intact molecule. Analytical notes: - Check that the COA gives an intact-mass result and that the main HPLC peak is integrated with a stated method. - Do not rely on a sequence-only calculation for the expected mass. ## Melanotan I URL: https://vestapeptides.com/compounds/melanotan-i/ Type: Peptide Also written as: Afamelanotide, NDP-MSH Formula: C78H111N21O19 Average molecular weight: 1646.85 g/mol Monoisotopic mass: 1645.8365 Da CAS: 75921-69-6 Melanotan I (afamelanotide) is a 13-residue linear analogue of α-melanocyte-stimulating hormone, [Nle4, D-Phe7]-α-MSH, with an N-terminal acetyl group and a C-terminal amide. Afamelanotide was made by replacing two residues of α-MSH to increase potency and stability. Its pharmacokinetics and pharmacodynamics are described in the clinical pharmacology literature. Vesta lists a single product named Melanotan I/II. Check the batch documents to confirm which of the two peptides the vial contains; their masses are very different. The sequence is Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. The calculated formula matches PubChem exactly. Analytical notes: - Melanotan I (about 1646.8 Da) and melanotan II (about 1024.2 Da) are easy to tell apart by mass. - Tryptophan is the main oxidation site. The methionine at position 4 of α-MSH was replaced by norleucine to remove an oxidation-prone residue. ## Melanotan II URL: https://vestapeptides.com/compounds/melanotan-ii/ Type: Peptide Also written as: MT-II Formula: C50H69N15O9 Average molecular weight: 1024.18 g/mol Monoisotopic mass: 1023.5403 Da CAS: 121062-08-6 Melanotan II is a synthetic cyclic heptapeptide analogue of α-MSH, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, that is a non-selective melanocortin receptor agonist. A lactam bridge closes the ring, and early formulation studies of melanotan II are documented in the pharmaceutical literature. More recent medicinal chemistry papers use it as a template to discover functionally selective melanocortin receptor agonists. Vesta lists a single product named Melanotan I/II, so the batch documents should be checked to confirm which peptide is supplied. It shares the cyclic core of PT-141 but ends in an amide instead of a free acid. The calculated formula matches PubChem exactly. Analytical notes: - The difference to PT-141 is only 0.984 Da (amide versus acid). A high-resolution mass is needed to separate them confidently. - Incomplete cyclisation gives a peak 18.011 Da heavier. ## MOTS-c URL: https://vestapeptides.com/compounds/mots-c/ Type: Peptide Also written as: Mitochondrial open reading frame of the 12S rRNA-c Formula: C101H152N28O22S2 Average molecular weight: 2174.59 g/mol Monoisotopic mass: 2173.1077 Da CAS: 1627580-64-6 MOTS-c is a 16-residue peptide (MRWQEMGYIFYPRKLR) encoded by a short open reading frame within the mitochondrial 12S rRNA gene. MOTS-c is one of the mitochondrial-derived peptides. The original paper (Cell Metabolism, 2015) described its metabolic effects in mice, and later work covers exercise-induced expression and an interaction with casein kinase 2. Because it is encoded by mitochondrial DNA, it is widely used in studies of mitochondria-to-nucleus signalling. The sequence contains two methionine residues (positions 1 and 5), a tryptophan and two tyrosines. The calculated formula matches PubChem exactly. Analytical notes: - Both methionines can oxidise, giving +15.995 Da and +31.990 Da species; a COA should list them if they exceed the reporting threshold. - Vesta lists MOTS-c at 10, 15, 20 and 40 mg per vial. ## NAD+ URL: https://vestapeptides.com/compounds/nad/ Type: Small molecule Also written as: Nicotinamide adenine dinucleotide, Diphosphopyridine nucleotide Formula: C21H27N7O14P2 Average molecular weight: 663.43 g/mol Monoisotopic mass: 663.1091 Da CAS: 53-84-9, 64417-72-7 NAD+ (nicotinamide adenine dinucleotide) is a small-molecule coenzyme found in all living cells; it carries electrons in redox reactions and is consumed by sirtuins, PARP enzymes and CD38. NAD+ is not a peptide. It is a dinucleotide made of nicotinamide and adenine linked through two phosphate groups, and its metabolism is covered by detailed reviews in Nature Reviews Molecular Cell Biology. In the laboratory it is used as a coenzyme or substrate in enzyme assays and in studies of NAD+ metabolism and consumption. The molecular formula is C21H27N7O14P2. PubChem gives the formula for the neutral form; commercial NAD+ may be supplied as the free acid or as a sodium salt, which have different molecular weights. Analytical notes: - NAD+ is analysed by HPLC with UV detection at 260 nm and by NMR or enzymatic assays, rather than by the peptide-style workflow of HPLC at 214 nm. - In solution NAD+ degrades, especially at alkaline pH; the COA should state the assay method, the water content and the form supplied. ## Oxytocin URL: https://vestapeptides.com/compounds/oxytocin/ Type: Peptide Formula: C43H66N12O12S2 Average molecular weight: 1007.19 g/mol Monoisotopic mass: 1006.4365 Da CAS: 50-56-6 Oxytocin is a nine-residue peptide hormone, Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2, with a disulfide bridge between the two cysteine residues. Oxytocin is made in the hypothalamus and has an extensive literature, including detailed reviews of the oxytocin receptor and its signalling pathways. In the laboratory it is a standard reference peptide for receptor pharmacology, and it is widely used as an analytical test compound because its mass and disulfide are well defined. The ring formed by the Cys1-Cys6 disulfide gives the molecule its characteristic shape. The C-terminus is an amide. Analytical notes: - The reduced form (open ring) is 2.016 Da heavier. A COA should show that the disulfide form is the main species. - Oxytocin is also sensitive to deamidation of the glutamine and asparagine residues (+0.984 Da). ## PE-22-28 URL: https://vestapeptides.com/compounds/pe-22-28/ Type: Peptide Also written as: Mini-spadin, Spadin analogue Formula: C35H55N11O9 Average molecular weight: 773.88 g/mol Monoisotopic mass: 773.4184 Da CAS: 1801959-12-5 PE-22-28 is a seven-residue peptide (Gly-Val-Ser-Trp-Gly-Leu-Arg) that is described as a short peptide related to spadin, a sortilin-derived peptide that blocks the TREK-1 potassium channel. Spadin was described in PLoS Biology in 2010 as a sortilin-derived peptide targeting TREK-1 channels. PE-22-28 is a shorter analogue based on the same region. The literature on this specific peptide is limited, so it should be verified by independent analysis. PubChem lists the peptide as glycyl-valyl-seryl-tryptophyl-glycyl-leucyl-arginine, and the calculated formula from that sequence matches the record. Analytical notes: - The tryptophan residue is the main oxidation site (+15.995 Da). - Expect [M+H]+ at m/z 774.43 and a weaker [M+2H]2+ at m/z 387.72. ## PT-141 URL: https://vestapeptides.com/compounds/pt-141/ Type: Peptide Also written as: Bremelanotide Formula: C50H68N14O10 Average molecular weight: 1025.16 g/mol Monoisotopic mass: 1024.5243 Da CAS: 189691-06-3 PT-141 (bremelanotide) is a synthetic cyclic heptapeptide agonist of melanocortin receptors, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH. It is the deamidated derivative of melanotan II, in which the C-terminal amide is replaced by a free carboxylic acid. Both peptides contain the His-Phe-Arg-Trp core sequence that is recognised by melanocortin receptors. The published research is largely clinical or regulatory in nature; for laboratory use it is a reference ligand for melanocortin receptor subtypes. A lactam bridge between the side chains of aspartic acid and lysine closes the ring. The calculated formula with the lactam matches PubChem exactly. Analytical notes: - The ring closure means the mass is 18.011 Da lower than the open-chain form; a COA showing the open-chain mass indicates an incomplete cyclisation. - PT-141 and melanotan II differ by 0.984 Da, so the mass spectrum must be read carefully. ## Retatrutide URL: https://vestapeptides.com/compounds/retatrutide/ Type: Peptide Also written as: LY3437943 Retatrutide (LY3437943) is a synthetic 39-residue peptide described in the literature as an agonist of the GIP, GLP-1 and glucagon receptors, often called a triple agonist. Retatrutide extends the dual-agonist concept by adding glucagon receptor activity to GIP and GLP-1 receptor activity. Published laboratory methods use it, for example, to measure lipolytic function in cultured human adipocytes. No PubChem compound record was available when this page was prepared, so the page does not state a formula or molecular weight. Use the batch documents for the exact mass of the supplied material. The FDA Global Substance Registration System lists a 39-residue backbone (UNII NOP2Y096GV). The registered record does not describe the non-standard residues and side-chain modifications, so Vesta does not derive a mass from it. Analytical notes: - No verified formula is published here on purpose. Compare the molecular weight on the batch COA with the manufacturer's stated value and with the intact mass measured by LC-MS. - For a lipidated multi-agonist peptide, ask whether the report shows an intact-mass spectrum and a chromatogram with the integration method. ## Selank URL: https://vestapeptides.com/compounds/selank/ Type: Peptide Also written as: TP-7 Formula: C33H57N11O9 Average molecular weight: 751.87 g/mol Monoisotopic mass: 751.4341 Da CAS: 129954-34-3 Selank is a synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) that is an analogue of the immunomodulatory peptide tuftsin. Tuftsin is Thr-Lys-Pro-Arg; Selank extends it with the stabilising Pro-Gly-Pro sequence. It was developed in Russia, and most of the published pharmacology is in rodent models. Vesta also lists a blend of Semax and Selank. Three proline residues make the molecule structurally rigid and resistant to some peptidases. The calculated formula matches PubChem exactly. Analytical notes: - The expected ion [M+H]+ is m/z 752.44. Doubly charged ions are also seen because of the two basic residues. - Proline-rich peptides can show split HPLC peaks caused by cis/trans proline isomers; this is not necessarily an impurity. ## Semaglutide URL: https://vestapeptides.com/compounds/semaglutide/ Type: Peptide Also written as: NN9535, Semaglutide acylated GLP-1 analogue Formula: C187H291N45O59 Average molecular weight: 4113.58 g/mol Monoisotopic mass: 4111.1154 Da CAS: 910463-68-2 Semaglutide is a synthetic 31-residue analogue of human glucagon-like peptide-1 (GLP-1) that carries a fatty diacid side chain on lysine 26 and an α-aminoisobutyric acid (Aib) residue at position 8. GLP-1 is an incretin hormone released from the gut that acts on the GLP-1 receptor. Semaglutide was designed by Novo Nordisk as a long-acting analogue, and the discovery work is described in the medicinal chemistry literature (J Med Chem, 2015). In research settings it is used as a GLP-1 receptor reference agonist in receptor pharmacology, signalling and animal-model studies. Vesta supplies it as a research material only; it is not the pharmaceutical product that is sold under similar names. The backbone follows GLP-1(7-37) with Aib at position 8 and arginine at position 34. The side chain on Lys26 is a C18 fatty diacid joined through a γ-glutamic acid and polyethylene-glycol-type spacer, which promotes binding to serum albumin. These non-standard parts mean the molecule cannot be described by a plain amino acid sequence alone. Analytical notes: - Because the lipid side chain and Aib are not standard residues, a useful COA reports the measured intact mass, not only a sequence-based expectation. - Large, lipidated peptides usually show a charge envelope (for example 3+ to 6+) in electrospray mass spectrometry; the intact mass is obtained by deconvolution. ## Semax URL: https://vestapeptides.com/compounds/semax/ Type: Peptide Also written as: ACTH(4-10)Pro-Gly-Pro Formula: C37H51N9O10S Average molecular weight: 813.92 g/mol Monoisotopic mass: 813.3480 Da CAS: 80714-61-0 Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) that is an analogue of the adrenocorticotropic hormone fragment ACTH(4-10) with a Pro-Gly-Pro tail. Semax was developed in Russia and is described in many publications in rodent and cell models, including studies of its binding sites in the brain and effects on monoaminergic systems. Like Selank, it uses the Pro-Gly-Pro tail to improve stability. The N-terminal methionine can oxidise to the sulfoxide. The calculated formula matches PubChem exactly. Analytical notes: - Methionine sulfoxide (+15.995 Da) is the most likely degradation product to check for. - Vesta lists Semax alone and in a blend with Selank. ## Sermorelin URL: https://vestapeptides.com/compounds/sermorelin/ Type: Peptide Also written as: GRF(1-29), GHRH(1-29)NH2 Formula: C149H246N44O42S Average molecular weight: 3357.88 g/mol Monoisotopic mass: 3355.8187 Da CAS: 86168-78-7 Sermorelin is the synthetic 29-residue N-terminal fragment of human growth hormone-releasing hormone (GHRH 1-29 amide), which retains activity at the GHRH receptor. Native GHRH has 44 residues. Experiments in the 1980s showed that the first 29 residues are enough to stimulate growth hormone release, and sermorelin is therefore described as GRF(1-29)-NH2 in the older literature. In research it is used as a reference GHRH-receptor agonist and as an analytical reference when developing detection methods for GHRH analogues. The sequence is YADAIFTNSYRKVLGQLSARKLLQDIMSR with a C-terminal amide. It contains a single methionine at position 27 and an asparagine at position 8. Analytical notes: - Methionine oxidation (+15.995 Da) and asparagine deamidation (+0.984 Da) are the typical modifications to look for in a GHRH-type peptide. - The calculated formula from the sequence matches the PubChem record, so the masses in the table can be used as the expected values. ## SLU-PP-332 URL: https://vestapeptides.com/compounds/slu-pp-332/ Type: Small molecule Also written as: ERR agonist SLU-PP-332 Formula: C18H14N2O2 Average molecular weight: 290.32 g/mol Monoisotopic mass: 290.1055 Da CAS: 303760-60-3 SLU-PP-332 is a synthetic small-molecule agonist of the estrogen-related receptors (ERRα, ERRβ and ERRγ), described in the literature as an exercise mimetic. The compound has the formula C18H14N2O2 and the systematic name 4-hydroxy-N-[(E)-naphthalen-2-ylmethylideneamino]benzamide. Published work covers metabolic-syndrome models, chemical optimisation and in-vitro metabolism. Recent analytical papers describe its in-vitro metabolites and LC-MS characterisation, which is a useful reference when verifying batch identity. The molecule is an acylhydrazone with an E-configured C=N bond between a 4-hydroxybenzoyl group and a naphthyl group. Analytical notes: - E/Z isomers of acylhydrazones may be separable by HPLC; the COA should show that the main peak is the E isomer. - Expect [M+H]+ at m/z 291.11. The compound is not a peptide, so peptide-style ion series do not apply. ## SS-31 URL: https://vestapeptides.com/compounds/ss-31/ Type: Peptide Also written as: Elamipretide, MTP-131 Formula: C32H49N9O5 Average molecular weight: 639.79 g/mol Monoisotopic mass: 639.3857 Da CAS: 736992-21-5 SS-31 (elamipretide) is a synthetic tetrapeptide, D-Arg-Dmt-Lys-Phe-NH2, from the Szeto-Schiller peptide family that is designed to concentrate in mitochondria. Dmt stands for 2',6'-dimethyltyrosine. The peptides of this family have alternating aromatic and positively charged residues and interact with cardiolipin in the inner mitochondrial membrane, as set out in review articles on elamipretide's structure and mechanism. In research it is used in mitochondrial dysfunction models in cells and animals. The molecule contains a D-arginine, a non-natural dimethyltyrosine and a C-terminal amide. The sequence-based formula matches PubChem exactly. Analytical notes: - At 639.8 Da the main ion is [M+H]+ at m/z 640.39; because it has two basic side chains a [M+2H]2+ ion at m/z 320.70 is also strong. - D-amino acids do not change the mass, so enantiomeric purity is not shown by routine LC-MS. ## Survodutide URL: https://vestapeptides.com/compounds/survodutide/ Type: Peptide Also written as: BI 456906 Formula: C192H289N47O61 Average molecular weight: 4231.63 g/mol Monoisotopic mass: 4229.0957 Da CAS: 2805997-46-8 Survodutide (BI 456906) is a synthetic peptide that acts as a dual agonist of the glucagon receptor and the GLP-1 receptor. It was developed as a balanced glucagon/GLP-1 dual agonist, and its pharmacological profiling and central nervous system targets are described in published preclinical studies. Researchers use it to compare glucagon receptor activity with GLP-1 receptor activity in cell and animal models. It is provided here as a research material. PubChem gives a molecular formula of C192H289N47O61 for the compound. It is a modified peptide, so non-standard residues or side chains are part of the structure. Analytical notes: - Confirm identity by intact mass rather than by sequence letters alone. - Ask for the chromatogram and the integration parameters, not only a purity percentage. ## Tesamorelin URL: https://vestapeptides.com/compounds/tesamorelin/ Type: Peptide Also written as: TH9507 Formula: C221H366N72O67S Average molecular weight: 5135.78 g/mol Monoisotopic mass: 5132.7166 Da CAS: 218949-48-5, 804475-66-9 Tesamorelin is a synthetic 44-residue analogue of human GHRH (1-44) in which the N-terminus carries a trans-3-hexenoyl group. Tesamorelin keeps the full GHRH sequence and adds an N-terminal hexenoyl modification that changes its stability against enzymatic cleavage. Its chemistry and pharmacology are covered in drug-profile literature. Analytical chemistry groups have also published LC-MS/MS methods for detecting GHRH analogues, which are useful references for batch identity testing. Because of the N-terminal hexenoyl group and 44 residues, the molecule has a mass of more than 5 kDa and is usually observed as a series of multiply charged ions. Analytical notes: - Like other GHRH-type peptides it contains methionine, so a +15.995 Da oxidised variant is the first impurity to look for. - The Vesta listing also includes a blend of tesamorelin with ipamorelin. ## Thymalin URL: https://vestapeptides.com/compounds/thymalin/ Type: Peptide fraction (mixture) Also written as: Thymalin peptide complex, Thymic peptide fraction Components: not itemised by the manufacturer Thymalin is a peptide preparation obtained from thymus tissue. The supplier describes it as a bovine thymic peptide fraction with an average component size of about 500 Da, so it is a mixture and not a single defined molecule. Thymalin was developed in Russia from calf thymus and appears in the Russian-language literature from the 1980s. Recent papers from the Saint Petersburg Institute of Bioregulation and Gerontology describe it as a polypeptide extract of thymus and report the dipeptides Lys-Glu and Glu-Trp as active components. Thymalin should not be confused with two other thymic peptides. Thymosin alpha 1 is a defined 28-residue peptide, and thymulin is a defined nine-residue peptide that binds zinc. Thymalin is a mixture of short peptides and has neither a sequence nor a molecular weight of its own. Vesta lists one product called Thymalin/Thymulin, supplied as a kit of 10 vials at 10 mg per vial. The batch documents should say which of the two it contains. The thymulin page gives the verified data for the defined peptide. Analytical notes: - A mixture of peptides does not give one sharp HPLC peak or one intact mass. Identity is shown by a characteristic chromatographic profile compared with a reference batch, by the mass distribution, or by measuring marker peptides such as Lys-Glu and Glu-Trp. - An area-percentage purity figure does not mean the same thing for a mixture as for a single peptide. Ask what the percentage refers to and which peaks were counted. - The figure of about 500 Da is an average over many components. It is not a molecular weight and cannot be used to calculate the number of molecules in a vial. - If the vial contains thymulin instead, expect one main peak with the mass given on the thymulin page. The two outcomes are easy to tell apart by LC-MS. Q: What is Thymalin? A: Thymalin is a peptide preparation obtained from thymus tissue. The supplier describes it as a bovine thymic peptide fraction with an average component size of about 500 Da. It is a mixture and not a single molecule. Q: Is Thymalin the same as thymulin? A: No. Thymulin is a defined nine-residue peptide, pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, that binds zinc. Thymalin is a mixture of short peptides from thymus. Vesta lists one product under the combined name Thymalin/Thymulin, so confirm from the batch documents which one the vial contains. Q: Does Thymalin have a molecular weight? A: No single value applies. The supplier gives an average component size of about 500 Da, which describes the mixture and not one molecule. ## Thymosin alpha 1 URL: https://vestapeptides.com/compounds/thymosin-alpha-1/ Type: Peptide Also written as: Thymalfasin, Tα1 Formula: C129H215N33O55 Average molecular weight: 3108.28 g/mol Monoisotopic mass: 3106.5041 Da CAS: 62304-98-7, 69521-94-4, 1337515-90-8 Thymosin alpha 1 is a 28-residue, N-terminally acetylated peptide that was first isolated from the thymus; the synthetic form is also known as thymalfasin. The sequence is Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN. It is derived from the precursor prothymosin alpha, and its chemistry and pharmacology are covered in drug-profile and review literature. For analytical work, there is a published LC method that identifies and quantifies structurally related impurities in thymalfasin, which is a useful reference for what a thorough purity report should show. The N-terminus is acetylated, so there is no free N-terminal amine. The calculated formula from the sequence matches PubChem exactly. Analytical notes: - Truncated and deletion sequences are the main process-related impurities in a 28-residue synthetic peptide; ask whether they were separated and identified. - In electrospray MS expect a charge envelope from about 3+ to 5+; the deconvoluted mass should be close to the value in the table. ## Thymosin beta-4 (TB-500) URL: https://vestapeptides.com/compounds/thymosin-beta-4/ Type: Peptide Also written as: TB-500, TB500, Tβ4, Thymosin beta 4 Formula: C212H350N56O78S Average molecular weight: 4963.44 g/mol Monoisotopic mass: 4960.4863 Da Thymosin beta-4 is a 43-residue, N-terminally acetylated peptide and the main G-actin-sequestering peptide in many cells; "TB-500" is the name used by some suppliers for synthetic material related to it. Thymosin beta-4 has been studied for several decades, and the literature includes methods chapters, tissue-expression reviews and papers on how to quantify it in blood reliably. The name TB-500 is used in the market for a synthetic peptide derived from thymosin beta-4. Depending on the supplier it can mean the full-length 43-residue peptide or the shorter active-region fragment Ac-LKKTETQ (residues 17-23). The two have very different masses, so the batch documents must state which was supplied. Full-length thymosin beta-4 has the sequence Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES. The 17-23 fragment is a heptapeptide with an N-terminal acetyl group. Analytical notes: - Confirm identity by intact mass. The full-length peptide is about 4963 Da, the fragment about 889 Da. - It contains one methionine (position 6), so look for a sulfoxide at +15.995 Da. Q: Is TB-500 the same as thymosin beta-4? A: Not necessarily. TB-500 is a trade name used for synthetic material related to thymosin beta-4. Some suppliers use it for the full 43-residue peptide and others for the short fragment Ac-LKKTETQ. The molecular weight on the certificate of analysis shows which one it is: about 4963 Da for the full-length peptide and about 889 Da for the fragment. ## Thymulin URL: https://vestapeptides.com/compounds/thymulin/ Type: Peptide Also written as: Facteur thymique sérique, FTS, Zinc thymulin Formula: C33H54N12O15 Average molecular weight: 858.85 g/mol Monoisotopic mass: 858.3832 Da CAS: 78922-62-0 Thymulin is a nine-residue peptide, pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, produced by thymic epithelial cells. Its biological activity depends on binding zinc. Thymulin was first described as facteur thymique sérique (FTS), a circulating thymic factor, and the literature calls it a zinc-dependent hormone. Only the zinc-bound form is active in the classical assays, which is why papers discuss the peptide and its zinc complex separately. The peptide has an N-terminal pyroglutamic acid and a free C-terminus. The identity numbers on this page describe the peptide on its own. The zinc-bound form is heavier by roughly one zinc atom (about 65 Da) less any protons it displaces, and its spectra show the isotope pattern of zinc. Vesta lists one product under the combined name Thymalin/Thymulin. The batch documents should say whether the vial contains the defined peptide described here or the Thymalin peptide fraction described on its own page. The sequence is pyroglutamyl-alanyl-lysyl-seryl-glutaminyl-glycyl-glycyl-seryl-asparagine. The N-terminal residue is cyclised pyroglutamic acid, which has no free amine, and zinc binds to the peptide in a 1:1 ratio. Analytical notes: - Zinc has five stable isotopes (64Zn, 66Zn, 67Zn, 68Zn and 70Zn), so a zinc-containing species shows a wide isotope pattern. The peptide without zinc shows an ordinary pattern. - Ask whether the batch is the zinc complex or the peptide alone, and for the zinc content if it is the complex. The molecular weight on a certificate depends on the answer. - Asn and Gln can deamidate (+0.984 Da). A shoulder or a small peak at that mass difference is a common finding in an older sample. - The pyroglutamate N-terminus can form from glutamine during synthesis or storage. If a batch is supposed to start with pyroglutamate, an ion 17.027 Da heavier points to unconverted glutamine. Q: What is thymulin? A: Thymulin is a nonapeptide, pGlu-Ala-Lys-Ser-Gln-Gly-Gly-Ser-Asn, produced by thymic epithelial cells. It was first called facteur thymique sérique (FTS), and its activity depends on binding zinc. Q: Is thymulin the same as Thymalin? A: No. Thymulin is a single defined peptide. Thymalin is a mixture of short peptides extracted from thymus. Vesta lists one product called Thymalin/Thymulin, so check the batch documents. Q: Why does the molecular weight of thymulin depend on zinc? A: The peptide alone is C33H54N12O15, 858.85 g/mol. The active complex binds one zinc atom, which adds up to about 65 g/mol (one zinc atom, less any protons it displaces), so a certificate must state which form it reports. ## Tirzepatide URL: https://vestapeptides.com/compounds/tirzepatide/ Type: Peptide Also written as: LY3298176 Formula: C225H348N48O68 Average molecular weight: 4813.45 g/mol Monoisotopic mass: 4810.5249 Da CAS: 2023788-19-2 Tirzepatide is a synthetic 39-residue peptide based on the sequence of glucose-dependent insulinotropic polypeptide (GIP) that acts as an agonist at both the GIP receptor and the GLP-1 receptor. It is described in the literature as a dual GIP and GLP-1 receptor agonist, and its receptor pharmacology (including its biased and imbalanced signalling profile) is the subject of published in-vitro work. In research, it is used to study incretin receptor signalling, receptor selectivity and dual-agonist design. It is supplied here strictly as a research material. The peptide contains two α-aminoisobutyric acid residues, a C-terminal amide, and a C20 fatty diacid attached to a lysine side chain through a linker, which extends albumin binding. Analytical notes: - Tirzepatide is a modified peptide, so its mass should be confirmed from the intact molecule; a mass calculated only from the amino acid letters will not match. - Expect a multiply charged ion series in electrospray mass spectrometry and a deconvoluted mass close to the value in the table above. # Glossary - Peptide: A chain of amino acids joined by peptide bonds. By convention, chains of up to about 50 residues are called peptides and longer chains are called proteins, although the boundary is not strict. - Amino acid residue: The part of an amino acid that remains in a peptide chain after it loses a molecule of water during bond formation. Peptide masses are calculated by adding residue masses and then the mass of the two chain ends. - N-terminus: The end of a peptide chain that carries a free amino group (or a capping group such as acetyl or pyroglutamate). Peptide sequences are written from the N-terminus to the C-terminus. - C-terminus: The end of a peptide chain that carries a free carboxylic acid, or an amide if the peptide was synthesised with a C-terminal amide. The difference between an acid and an amide is 0.984 Da. - C-terminal amidation: Replacement of the C-terminal carboxylic acid by a carboxamide (-NH2). Many bioactive peptides, including ipamorelin, GHRP-2 and kisspeptin-10, are written with an amide and denoted with NH2 at the end of the sequence. - N-terminal acetylation: Capping of the N-terminal amino group with an acetyl group (+42.011 Da). Thymosin alpha 1, thymosin beta-4 and melanotan peptides are acetylated, so they have no free N-terminal amine. - D-amino acid: The mirror-image (enantiomer) form of an amino acid. D-amino acids have the same mass as L-amino acids, so routine mass spectrometry does not tell them apart; chiral chromatography or special methods are needed. - Non-proteinogenic amino acid: An amino acid that is not one of the 20 encoded by the standard genetic code, such as α-aminoisobutyric acid (Aib), norleucine (Nle), 2-naphthylalanine (2Nal) or 2',6'-dimethyltyrosine (Dmt). - Aib (α-aminoisobutyric acid): A non-proteinogenic amino acid with two methyl groups on the α-carbon. It promotes helical structure and protects the peptide bond from enzymatic cleavage, which is why it appears in semaglutide, tirzepatide and ipamorelin. - Disulfide bond: A covalent bond between the sulfur atoms of two cysteine residues. It lowers the mass by 2.016 Da compared with the two free thiols. Oxytocin, AOD9604, cagrilintide and IGF-1 LR3 contain disulfide bonds. - Lactam bridge: An amide bond formed between the side chains of an acidic residue (aspartic or glutamic acid) and a basic residue (lysine), which cyclises the peptide and removes a molecule of water (-18.011 Da). Melanotan II and PT-141 are closed this way. - Lipidation: Attachment of a fatty acid or fatty diacid to a peptide side chain, usually through a spacer, to promote binding to serum albumin. Semaglutide, liraglutide, tirzepatide and cagrilintide are lipidated. - Pyroglutamate: A cyclic form of N-terminal glutamine or glutamic acid, written pGlu or pE. It has no free amine and is found in gonadorelin and ARA290. It lowers the mass by 17.027 Da compared with glutamine. - Lyophilization: Freeze-drying: removal of water from a frozen sample under vacuum. Most research peptides are supplied as lyophilized powders because the dry form is more stable than a solution. - Counter-ion: The ion that balances the charge of a peptide in its solid form, usually trifluoroacetate (TFA) from synthesis and purification or acetate after exchange. The counter-ion is part of the powder mass but not of the peptide. - TFA salt: A peptide salt with trifluoroacetate as the counter-ion, the usual product of reversed-phase purification with a trifluoroacetic acid mobile phase. Residual TFA can affect cell assays and adds substantial mass. - Acetate salt: A peptide salt with acetate as the counter-ion, often prepared by exchange from the TFA salt. Each acetate adds about 60.05 Da per charged site. - Net peptide content: The percentage of the powder mass that is peptide, excluding water and counter-ions. It is always lower than 100 % and is measured by amino acid analysis or quantitative NMR, not by HPLC purity. - Peptide purity: The proportion of the target peptide among all peptide-related species in a sample, usually reported as an HPLC area percentage. Purity says nothing about how much peptide is in the vial. - HPLC: High-performance liquid chromatography: a separation method that pushes a sample through a column under pressure. Peptide purity is normally measured by reversed-phase HPLC with UV detection at 214 nm. - Reversed-phase HPLC (RP-HPLC): HPLC with a non-polar stationary phase and a polar mobile phase whose organic content is increased during the run. Peptides elute in order of increasing hydrophobicity. - Retention time: The time between injection and the maximum of a chromatographic peak. It identifies a compound only when it is compared with a reference run under the same conditions. - Area percent: The area of the main peak divided by the total area of all integrated peaks, times 100. It depends on the detection wavelength and on how the baseline and small peaks were integrated. - Mass spectrometry (MS): A technique that measures the mass-to-charge ratio (m/z) of ions. For peptides, it confirms identity by comparing the measured mass with the expected mass. - Electrospray ionisation (ESI): A soft ionisation method that produces multiply charged ions from peptides and proteins in solution. It is the usual way to couple HPLC to a mass spectrometer. - m/z: Mass divided by the number of charges. A peptide of mass 1000 Da carrying two protons appears at m/z 501.01. - Monoisotopic mass: The mass of a molecule calculated from the lightest stable isotope of each element (12C, 1H, 14N, 16O, 32S). It is the value used in high-resolution mass spectrometry of small and medium peptides. - Average mass: The mass of a molecule calculated from the natural average atomic weight of each element. It is the value used for molecular weight and for large peptides, where the monoisotopic peak is too weak to see. - Charge state: The number of protons attached to a peptide ion in electrospray ionisation, written as [M+nH]n+. Larger peptides carry more charges, so their peaks appear at lower m/z. - Deconvolution: A calculation that converts a series of multiply charged ions into a single neutral mass. Reports for large peptides usually give the deconvoluted mass. - Adduct: An ion formed when a molecule picks up something other than a proton, most often sodium ([M+Na]+, +21.982 relative to [M+H]+) or potassium ([M+K]+, +37.956). Adducts are not impurities. - Methionine oxidation: Addition of one oxygen atom to the sulfur of methionine to give the sulfoxide (+15.995 Da). It is a common degradation product of peptides that contain methionine, such as Semax, MOTS-c and sermorelin. - Deamidation: Conversion of asparagine or glutamine to aspartic or glutamic acid, which adds 0.984 Da. It is a major non-enzymatic degradation pathway, especially for asparagine followed by glycine or serine. - Truncation and deletion sequences: Process-related impurities from solid-phase synthesis in which one or more amino acids are missing from the target peptide. They are the main impurities of long synthetic peptides. - Impurity profile: The list of related substances detected in a batch, with their approximate amounts and, where known, their identity. A good COA reports more than the main peak. - Certificate of analysis (COA): A document from the manufacturer or a testing laboratory that lists the tests performed on one batch, the methods used and the results obtained. - Batch (lot) number: An identifier that ties a vial, a COA and a manufacturing run together. A COA is only meaningful for the batch it names. - Batch traceability: The ability to follow a batch from supplier record through receiving, testing and use, using one stable identifier. - Identity test: A test that confirms that the material is the compound it is said to be, usually by mass spectrometry and, for peptides, by comparison with a reference standard. - Amino acid analysis (AAA): A method in which a peptide is hydrolysed to its amino acids, which are then quantified. It gives the amount of peptide in a sample and is the standard way to measure net peptide content. - Nuclear magnetic resonance (NMR): A technique that gives structural information about a molecule and, in its quantitative form, can measure content, including residual solvents and counter-ions such as TFA. - Karl Fischer titration: A titration method that measures the water content of a solid sample. Lyophilized peptides can contain several percent of water. - Reference standard: A well-characterised sample of a compound that is used as a comparator in identity and purity tests. - Stability-indicating method: An analytical method that can separate the intact compound from its degradation products, so a drop in purity can be detected. - Bacteriostatic water: Sterile water that contains a preservative, usually 0.9 % benzyl alcohol, which inhibits bacterial growth in a multi-use vial. For laboratory use, benzyl alcohol can interfere with some assays and with cell cultures. - Research use only (RUO): A label meaning that a material is intended for laboratory research, not for use in humans or animals, in diagnostics, or as a medicine, supplement, cosmetic or food. # Laboratory guides ## Average, Monoisotopic and Most Abundant Mass: Reading Peptide Mass Spectrometry Values URL: https://vestapeptides.com/resources/average-vs-monoisotopic-mass-peptides/ Updated: 2026-10-30 A peptide has two usual molecular weights. The monoisotopic mass uses the lightest isotope of every element and is the mass of the first peak in a high-resolution spectrum. The average mass uses the natural mix of isotopes and is the molecular weight printed in catalogues. Small peptides are checked against the monoisotopic mass, large peptides against the average mass, and the two differ by about 0.6 Da at 1 kDa and by about 2.4 Da at 4 kDa. - Monoisotopic mass is calculated from 12C, 1H, 14N, 16O and 32S; average mass is calculated from standard atomic weights. - For a peptide of about 1.4 kDa, such as BPC-157, the monoisotopic mass is 1418.704 and the average mass is 1419.54. - In electrospray ionisation a peptide appears as [M+nH]n+ ions, and the m/z of each ion is (M + n x 1.00728) / n. - Above about 3 kDa the monoisotopic peak is weak, so reports give the deconvoluted average mass instead. - Sodium and potassium adducts are +21.982 and +37.956 relative to the [M+H]+ ion and are not impurities. ### Why one peptide has more than one molecular weight Elements occur as mixtures of isotopes. Carbon is 98.93 % carbon-12 and 1.07 % carbon-13, and hydrogen, nitrogen, oxygen and sulfur have their own heavier isotopes. A single molecule is made of specific isotopes, so a mass spectrometer that resolves individual ions sees a group of peaks, each one a different isotopic composition of the same chemical formula. The molecular weight that appears in a catalogue is the average of all of them, weighted by natural abundance. The mass of the molecule made only of the lightest isotopes is the monoisotopic mass. Both numbers are correct; they answer different questions, and a COA should say which one it reports. ### Monoisotopic mass: the first peak The monoisotopic mass is the sum of the exact masses of the lightest isotope of each atom: 12.000000 for carbon, 1.007825 for hydrogen, 14.003074 for nitrogen, 15.994915 for oxygen and 31.972071 for sulfur. For BPC-157 (C62H98N16O22) it is 1418.7042. In a high-resolution instrument the first peak of the isotope pattern sits at this value, followed by peaks about 1.003 Da apart. Monoisotopic mass is the right number to compare for peptides up to about 2.5 to 3 kDa, where the first peak is still tall enough to see. ### Average mass: the catalogue molecular weight Average mass uses the standard atomic weights, such as 12.011 for carbon and 1.008 for hydrogen, which already include the isotope mixture. For BPC-157 it is 1419.54. Average mass is the number to use for weighing and for the molecular weight on a data sheet. It is also the number that a mass spectrometer reports when it cannot resolve the isotopes of a large molecule, and the peaks merge into one broad envelope. ### The most abundant mass and why it moves with size Every carbon has a 1.07 % chance of being carbon-13. A molecule with 62 carbons has roughly a 51 % chance of containing none, so the monoisotopic peak is the tallest. A molecule with 187 carbons, such as semaglutide, has only about a 13 % chance, and the tallest peak is one to two mass units above the monoisotopic one. This is why the exact mass listed by public databases for large peptides is often a little higher than a strict monoisotopic calculation. When two numbers differ by about 1 Da, the cause is usually which isotope peak was picked, not a different compound. ### Charge states: how to calculate the ions In electrospray ionisation, peptides pick up protons. An ion with n protons has m/z = (M + n x 1.007276) / n. For BPC-157 the [M+H]+ ion is at 1419.711, [M+2H]2+ at 710.359 and [M+3H]3+ at 473.909. For semaglutide, with a monoisotopic mass of 4111.115, the 3+ to 6+ ions fall at 1371.379, 1028.786, 823.230 and 686.193. Larger peptides and peptides with more basic residues carry more charges, which is why a 4 kDa peptide is observed at m/z values far below 4000. ### Deconvolution and adducts Software can convert a series of multiply charged ions into one neutral mass; this is called deconvolution. The result should agree with the expected value within the stated accuracy of the instrument, which is often 0.1 Da or better for a time-of-flight or Orbitrap system and 0.5 to 1 Da for a simple quadrupole. Extra peaks that are 21.982 or 37.956 above the [M+H]+ ion are sodium and potassium adducts. They indicate salts in the sample, not a second compound. ### Using this on a certificate of analysis Check three things. First, the COA names the expected mass and says whether it is monoisotopic or average. Second, the measured mass is given with a unit and a plausible accuracy. Third, the difference between expected and measured mass is small compared with the instrument's accuracy and is not explained by an adduct or an isotope peak. For modified peptides, such as those with a fatty acid side chain, the expected mass must come from the full molecular formula, not from the amino acid letters. The compound pages on this site list the formula, the monoisotopic and the average mass for each compound where a public record exists. Q: Which molecular weight should I use to weigh a peptide? A: Use the average molecular weight of the peptide, and remember that the powder also contains counter-ions and water, so the net peptide content is lower than the weighed mass. Q: Why does the mass on a COA differ from my calculation by about 1 Da? A: The usual reason is that the report gives the most abundant isotope peak or the average mass while you calculated the monoisotopic mass, or the other way round. Q: Does a matching mass prove that the peptide is pure? A: No. A matching mass supports identity. Purity is measured separately by chromatography, and content is measured by a quantitative method. ## Peptide Counter-Ions and Net Peptide Content: Why the Powder Weighs More Than the Peptide URL: https://vestapeptides.com/resources/peptide-counterions-net-peptide-content/ Updated: 2026-10-30 A lyophilized peptide powder is a salt. Every positively charged site is balanced by a counter-ion, usually trifluoroacetate (TFA) or acetate, and the powder also holds a few percent of water. The peptide itself is therefore only part of the weighed mass, called the net peptide content, which is often between 60 % and 90 %. HPLC purity does not measure it; amino acid analysis or quantitative NMR does. - Peptides purified by reversed-phase HPLC are normally TFA salts; acetate or hydrochloride salts are made by ion exchange. - One TFA adds 114.02 Da per charged site and one acetate adds 60.05 Da. - A 1000 Da peptide with two charged sites weighs 1228.05 Da as a TFA salt, so the peptide is 81.4 % of the salt before water is counted. - Net peptide content is measured by amino acid analysis or quantitative NMR, and water by Karl Fischer titration. - Residual TFA can interfere with cell-based assays; the counter-ion should therefore be stated on the COA. ### Why peptides are salts Peptides contain basic groups, such as the N-terminal amine and the side chains of lysine, arginine and histidine. During purification the mobile phase contains trifluoroacetic acid, which protonates these groups, and the trifluoroacetate anion stays with the peptide as it is dried. The powder is therefore a salt in which each charged site is paired with a counter-ion. If the TFA is exchanged for acetate or chloride, the peptide is delivered as an acetate or hydrochloride salt instead. ### A worked example Take a peptide with a molecular weight of 1000 Da and two basic sites. As a TFA salt, each site carries one trifluoroacetic acid (114.02 Da), so the salt weighs 1000 + 2 x 114.02 = 1228.05 Da and the peptide makes up 81.4 % of it. As an acetate salt, each site carries 60.05 Da, so the salt weighs 1120.10 Da and the peptide makes up 89.3 %. If the powder also contains 6 % water by weight, the TFA salt gives a net peptide content of 76.5 %. The same peptide therefore has different molecular weights and different net contents depending on the salt form. ### Net peptide content versus HPLC purity HPLC purity is the share of the main peptide peak among all peptide-related peaks. It ignores counter-ions, water and inorganic salts because they do not absorb at 214 nm. A peptide can be 99 % pure by HPLC and still contain only 70 % peptide by weight. The two numbers answer different questions and should never be multiplied or substituted for each other without a statement from the laboratory. ### How the content is measured Amino acid analysis hydrolyses the peptide and quantifies the released amino acids, which gives the amount of peptide present. Quantitative NMR can measure the peptide and the TFA together against an internal standard. Water is measured by Karl Fischer titration or by loss on drying. Ion chromatography and 19F NMR are used to quantify trifluoroacetate. A COA that reports a net peptide content should name the method. ### Why the counter-ion matters in an experiment Residual trifluoroacetate has been reported to affect cell proliferation assays, and methods for exchanging it for chloride or acetate are published. For experiments that are sensitive to acidity or to TFA, researchers either ask for an acetate or hydrochloride salt or measure the TFA content and correct for it. The salt form also matters for weighing, because the mass of powder needed to obtain a given amount of peptide depends on the net content. ### What to look for on the batch documents A useful set of documents states the counter-ion, the molecular weight of the salt (not only of the free peptide), the water content and the net peptide content, together with the methods. If only the free-peptide molecular weight and an HPLC purity are given, the amount of peptide in the vial remains unknown. Vesta lists some items explicitly as acetate salts, and the compound pages give the molecular weight of the free peptide so that it can be compared with the batch values. Q: Is an acetate salt better than a TFA salt? A: Neither is better in every case. Acetate is often preferred for biological assays because residual TFA can interfere with some cell systems, but the right choice depends on the experiment, the solubility of the peptide and the purification process. Q: Does the vial label amount refer to peptide or to powder? A: It depends on the supplier. Ask whether the labelled amount is the total powder mass or the net peptide content, and check the COA for the content value. Q: Can I calculate net peptide content from the molecular weights? A: Only as an estimate. The calculation needs the number of charged sites and the water content, and both vary between batches, so a measured value is preferable. ## Peptide Sequence Notation Explained: One-Letter Codes, D-Amino Acids and Terminal Groups URL: https://vestapeptides.com/resources/peptide-sequence-notation-guide/ Updated: 2026-10-30 Peptide sequences are written from the N-terminus to the C-terminus, using one-letter or three-letter codes. Prefixes such as Ac- describe an N-terminal modification, suffixes such as -NH2 describe a C-terminal amide, lower-case or D- marks a D-amino acid, and brackets or cyclo[...] describe unusual residues and rings. Each of these features changes the mass, so a notation has to be read in full before an expected molecular weight is calculated. - The sequence is always written from the free amino end (N-terminus) to the carboxyl end (C-terminus). - A C-terminal amide (-NH2) is 0.984 Da lighter than a free acid, and an N-terminal acetyl (Ac-) adds 42.011 Da. - D-amino acids have the same mass as L-amino acids, so they are invisible in a standard mass spectrum. - Lactam and disulfide rings remove 18.011 Da and 2.016 Da respectively. - Non-standard residues such as Aib, Nle, 2Nal and Dmt need their own residue masses. ### One-letter and three-letter codes The 20 standard amino acids have a three-letter code (Gly, Ala, Lys) and a one-letter code (G, A, K). Short peptides are often written with hyphens between three-letter codes, as in Gly-His-Lys, while longer peptides are written as strings of one-letter codes, as in YADAIFTNSYRKVLGQLSARKLLQDIMSR. Both notations describe the same chain; the string always starts at the N-terminus. ### Terminal groups: free, acetylated, amidated Unless stated otherwise, a peptide has a free amino group at the N-terminus and a free carboxylic acid at the C-terminus. Ac- in front of the sequence means that the N-terminus is acetylated, as in thymosin alpha 1 and Melanotan I. -NH2 after the sequence means that the C-terminus is an amide, as in ipamorelin, kisspeptin-10 and sermorelin. An amide is 0.984 Da lighter than the acid, so two peptides with the same letters can differ by that amount. ### D-amino acids and mixed chirality Most natural peptides are built from L-amino acids. Synthetic peptides often include D-amino acids to resist enzymes: ipamorelin contains D-2-naphthylalanine and D-phenylalanine, GHRP-6 contains D-tryptophan and D-phenylalanine, and SS-31 contains D-arginine. In notation, D- precedes the residue or a lower-case letter is used. Because a D-amino acid has the same mass as its L-form, mass spectrometry cannot see the difference; chiral chromatography or derivatisation methods can. ### Non-standard residues Several common research peptides use residues outside the standard 20. Aib is α-aminoisobutyric acid and appears in semaglutide, tirzepatide and ipamorelin. Nle is norleucine, a non-oxidisable replacement for methionine used in the melanotans. 2Nal is 2-naphthylalanine, Dmt is 2',6'-dimethyltyrosine, and pGlu is pyroglutamate. Each has its own residue mass, and a calculation that treats them as their closest standard letter will not match the measured mass. ### Rings and cross-links A disulfide bond joins two cysteines and is often written as a line or as 'cyclo' in the name; it removes two hydrogen atoms (2.016 Da). A lactam bridge joins an acidic and a basic side chain, as in cyclo[Asp-His-D-Phe-Arg-Trp-Lys], and removes a molecule of water (18.011 Da). Oxytocin, AOD9604 and cagrilintide use disulfides; Melanotan II and PT-141 use a lactam. ### Side-chain modifications Lipidated peptides carry a fatty acid on a lysine side chain through a spacer. This is written in parentheses after the lysine, for example Lys(γGlu-C18 diacid). The attached group adds several hundred daltons, so the mass of semaglutide or liraglutide is much higher than that of the unmodified backbone. For these compounds, the formula published in a chemical database is the reliable source for the expected mass, and the sequence letters alone are not. ### A worked reading Melanotan II is written Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. Read from the left: an acetylated N-terminus (+42.011), a norleucine, then a ring through the side chains of Asp and Lys (-18.011) containing His, D-Phe, Arg and Trp, and finally a C-terminal amide. The calculated formula is C50H69N15O9 and the monoisotopic mass is 1023.540 Da, which agrees with the public record. Q: Why does a lower-case letter sometimes appear in a sequence? A: Many authors use lower-case letters for D-amino acids, so f means D-phenylalanine. Always check the key that comes with the sequence. Q: What does the number in a name such as GRF(1-29) mean? A: It gives the residues of the parent protein that are included. GRF(1-29) is the first 29 amino acids of growth hormone-releasing factor. Q: How do I know if a peptide is cyclic from its name? A: Look for the words cyclo, a bracket that encloses part of the sequence, or a statement of a disulfide or lactam bond. Without them the peptide is assumed to be linear. ## Lyophilized Peptides Explained: What Freeze-Drying Does and What It Does Not Guarantee URL: https://vestapeptides.com/resources/lyophilized-peptides-explained/ Updated: 2026-10-30 Lyophilization removes water from a frozen peptide solution under vacuum, leaving a dry, porous powder called a cake. Dry peptides are more stable than peptides in solution because water drives hydrolysis, deamidation and other degradation. But freeze-drying does not purify the material and does not guarantee a particular amount of peptide, so identity, purity, content and moisture still have to be measured and recorded for each batch. - Lyophilization has three stages: freezing, primary drying by sublimation and secondary drying to remove bound water. - The result is a porous cake whose appearance can vary from batch to batch without a change in quality. - Residual moisture is measured by Karl Fischer titration and is typically a few percent for peptides. - Peptide powders are hygroscopic, so exposure to humid air raises the moisture content. - A lyophilized appearance says nothing about purity, content or identity. ### Why peptides are freeze-dried Most degradation reactions of peptides need water: hydrolysis of peptide bonds, deamidation of asparagine and glutamine, oxidation reactions that are driven by dissolved oxygen, and aggregation. Removing water slows these reactions substantially. After synthesis and purification, the peptide is in a mixture of water and acetonitrile, and lyophilization is the gentle way of turning it into a solid without heating it. ### The three stages In the first stage the solution is frozen so that water becomes ice. In primary drying the pressure is lowered and the ice sublimes directly to vapour, which removes most of the water while the product stays frozen. In secondary drying the temperature is raised a little under vacuum to desorb water that is bound to the solid. The process is controlled so that the cake does not melt or collapse. ### What the cake looks like and what it means A lyophilized peptide is often a white, fluffy or compact cake. Its volume and texture depend on the concentration, the vial, the excipients and the drying cycle. A small cake or a powder that has broken into pieces is not by itself a sign of poor quality. A collapsed, shrunken or yellowed cake can indicate that moisture entered or that the peptide has degraded, so the appearance on arrival should be recorded together with the batch information. ### Residual moisture and hygroscopicity Even after drying, peptide powders contain some water, and many take up moisture from the air quickly, especially salts with acidic or basic side chains. Residual moisture is measured by Karl Fischer titration and is part of the net peptide content calculation. A vial that is opened in humid air before it has reached room temperature can pick up water, which is one reason why the handling conditions should be written into the laboratory record. ### What lyophilization does not tell you A freeze-dried powder can be impure, can contain the wrong peptide or can contain a lower amount of peptide than the label states. It does not remove impurities, counter-ions or salts. Identity (by mass spectrometry), purity (by HPLC) and content (by amino acid analysis or NMR) must be established separately, and a certificate of analysis for that batch should state them. ### Documenting a lyophilized batch in the laboratory On receipt, record the batch number, the appearance of the cake, the condition of the seal and the date. Follow the product-specific storage information supplied with the batch, because a generic temperature rule cannot replace compound-specific stability data. Record any excursions from the intended conditions and keep the vial closed until it has equilibrated to room temperature. The guide on documenting storage conditions on this site gives a template. Q: Does lyophilization sterilise a peptide? A: No. Freeze-drying removes water but does not kill or remove microorganisms or endotoxin. Sterility is a separate property that has to be tested. Q: Is a lyophilized peptide stable indefinitely? A: No. Dry peptides are much more stable than solutions, but they still degrade slowly, and the rate depends on the sequence, the moisture, the temperature and the counter-ion. Q: Why is there so little powder in a vial? A: A few milligrams of peptide form a very small cake. The vial size is chosen for handling, not to match the volume of the powder. ## Common Peptide Degradation Products and the Mass Shifts That Reveal Them URL: https://vestapeptides.com/resources/peptide-degradation-products-mass-shifts/ Updated: 2026-10-30 Most peptide degradation products differ from the intact peptide by a small, fixed mass: +15.995 Da for one oxidation, +0.984 Da for deamidation, +2.016 Da for a reduced disulfide, -17.027 Da for pyroglutamate from glutamine, -18.011 Da for loss of water and +21.982 Da for a sodium adduct. Knowing these values lets a reader decide whether a minor peak in a mass spectrum is an impurity, a degradation product or just an adduct. - Methionine oxidation to the sulfoxide adds 15.995 Da; a second oxidation adds another 15.995 Da. - Deamidation of asparagine or glutamine adds 0.984 Da, which is close to the spacing of isotope peaks and needs a high-resolution instrument to see. - Reduction of a disulfide bond adds 2.016 Da; a disulfide-linked dimer weighs 2M - 2.016. - N-terminal glutamine cyclises to pyroglutamate with a loss of 17.027 Da, and glutamic acid does so with a loss of 18.011 Da. - Sodium and potassium adducts are +21.982 and +37.956 relative to [M+H]+ and are artefacts of the sample, not degradation. ### Why mass shifts matter A purity percentage tells you how much of the sample is the main peak. It does not tell you what the minor peaks are. Mass spectrometry connects each peak to a mass, and a list of well-known mass shifts then gives a first explanation. A minor species that is 15.995 Da heavier than the main peak is almost certainly an oxidised form; one that is 0.984 Da heavier is probably deamidated; one that is 2.016 Da heavier may be a reduced disulfide. The explanation is a hypothesis to test, but it points the investigation in the right direction. ### Oxidation of methionine, tryptophan and cysteine Methionine is the most easily oxidised residue and converts to methionine sulfoxide (+15.995 Da); stronger oxidation gives the sulfone (+31.990 Da). Peptides such as Semax, MOTS-c, sermorelin, tesamorelin and thymosin beta-4 contain methionine. Tryptophan also oxidises, giving +15.995, +31.990 and related products, and cysteine can form sulfenic, sulfinic or sulfonic acids. Oxidation is accelerated by light, metal ions and peroxides in solvents and excipients. ### Deamidation and aspartate isomerisation Asparagine and glutamine side chains lose ammonia and gain water to become aspartic and glutamic acid (+0.984 Da). The reaction passes through a cyclic imide intermediate that can open to the normal or to the iso form, so the same mass can correspond to two different species that elute at different retention times. Asparagine followed by glycine or serine deamidates fastest. The imide itself is 17.027 Da lighter than the intact peptide. ### Disulfide bonds: reduced, scrambled and dimerised Each intramolecular disulfide bond lowers the mass by 2.016 Da compared with the two free thiols. An open (reduced) form is therefore 2.016 Da heavier than the intact peptide, as is the case for oxytocin, AOD9604 and cagrilintide. Peptides with several disulfides, such as IGF-1 LR3, can also form wrongly paired isomers that have the same mass as the correct molecule and differ only in retention time. Free thiols can combine to form dimers with a mass of 2M - 2.016. ### Pyroglutamate and loss of water An N-terminal glutamine cyclises to pyroglutamate with a loss of ammonia (-17.027 Da), and an N-terminal glutamic acid does the same with a loss of water (-18.011 Da). Gonadorelin and ARA290 are written with pyroglutamate on purpose. Elsewhere in a sequence, a loss of 18.011 Da can indicate dehydration of aspartic acid to an anhydride or imide, or incomplete ring closure in a cyclic peptide that is expected to be lactamised. ### Adducts and other artefacts of the measurement Sodium and potassium ions from glassware or buffers form [M+Na]+ and [M+K]+ ions, which sit 21.982 and 37.956 Da above [M+H]+. Formic acid in the mobile phase can add a formyl group (+27.995). Trifluoroacetate can appear as an adduct of the protonated peptide. These species come from the way the sample was measured and do not indicate degradation. ### Truncation, deletion and insertion Solid-phase synthesis can produce peptides in which one amino acid is missing (deletion) or an extra amino acid is added. The mass shift equals the residue mass of the amino acid involved: 57.021 for glycine, 71.037 for alanine, 99.068 for valine and 128.095 for lysine. These impurities are often close to the main peak in a chromatogram, so a stability-indicating, high-resolution HPLC method is needed to separate them. Q: Is a small oxidised peak a reason to reject a batch? A: That depends on the specification and the experiment. A COA should report such species above a stated threshold, and the researcher decides whether the level is acceptable for the intended use. Q: Can mass spectrometry distinguish asparagine from aspartic acid? A: Only with a high-resolution instrument, because the difference is 0.984 Da and overlaps with isotope peaks. Chromatography usually shows the two forms at different retention times. Q: Do D-amino acids show up as a mass shift? A: No. A D-amino acid has the same mass as the L-form, so epimerisation does not change the mass. ## How to Build a Compound Identity File for Incoming Research Peptides URL: https://vestapeptides.com/resources/compound-identity-file-template/ Updated: 2026-10-30 A compound identity file is a single record that ties one batch of a research peptide to its expected identity, the supplier's analytical evidence, your own measurements and the decision you made about it. It should contain the product and batch codes, the expected formula and mass from a public reference, the COA values, any in-house results, the storage record and an accept or reject decision with a date. - The file is organised around one stable batch identifier that appears on the vial, the COA and the internal record. - Expected values should come from an independent public source such as PubChem, not from the supplier's own page. - The measured intact mass is compared with the expected mass in the same units, monoisotopic or average. - Mismatches, deviations and decisions are written down with a date and a name. - The file is kept for as long as the material or data derived from it are in use. ### Section 1: what was ordered Record the product name and SKU exactly as listed by the supplier, the strength per vial, the number of vials, the order reference and the date. Add the compound name in the form used by public databases, so that it can be matched to a reference record. For a blend, list every component and its amount. This section answers the question: what did we think we were buying? ### Section 2: what arrived On receipt record the date, the condition of the shipping package, the labels on the vial (name, strength, batch), the appearance of the powder and the seal. Photograph the labels. Compare the batch code on the vial with the batch code on the COA and write down whether they match. Any discrepancy is logged immediately and the material is set aside until it has been resolved with the supplier. ### Section 3: the expected identity Write the molecular formula, the monoisotopic mass, the average mass and the sequence or structure from an independent public reference, with its source and the date on which it was read. For peptides, record the terminal groups, any D-amino acids or non-standard residues, and the salt form that the supplier states. The compound pages on this site list the formula and masses together with the PubChem record, and the guide on average and monoisotopic mass explains which number to use. ### Section 4: the supplier's analytical evidence Copy the key values from the COA: the issuing laboratory, the report number, the test date, the methods (HPLC conditions, mass spectrometer type), the measured mass, the HPLC purity with the detection wavelength, the water content, the net peptide content and the counter-ion. Mark which values are given and which are missing. Record whether the report can be verified with the issuing laboratory. ### Section 5: your own results If you measure the material yourself, record the method, the instrument, the sample preparation, the measured intact mass, and the difference to the expected mass in daltons. Note any additional peaks and the mass shifts that you assigned to them, for example +15.995 for an oxidised form. Keep the raw data files and give them names that include the batch code. ### Section 6: storage record and disposition Write down where and under what conditions the material is kept, when it was opened, and any excursions from the intended storage. Finally, record the decision: accepted, accepted with a deviation, or rejected, with the reason, the date and the name of the person who decided. This is what makes the file useful to someone who reads it a year later. ### A worked example line for BPC-157 Expected: C62H98N16O22, monoisotopic 1418.704, average 1419.54, sequence GEPPPGKPADDAGLV, free N-terminus and free acid, per PubChem. Measured by LC-MS: [M+H]+ at 1419.711, which matches the expected 1419.711. HPLC: one main peak at 98.3 % (214 nm). Counter-ion: acetate, net peptide content 82 % from amino acid analysis. Decision: accepted. The numbers in this example are illustrative; the point is that each statement is paired with a source. Q: Do I need to do my own mass spectrometry on every batch? A: That depends on how critical the material is. At a minimum, the identity file should hold the supplier's evidence and your assessment of it. For critical work, an independent intact-mass measurement is the most informative single test. Q: What should I do if the measured mass does not match? A: Check the units and the isotope convention first, then look for adducts and common mass shifts. If the difference remains, log a deviation, contact the supplier with the data, and do not use the batch for critical work until it is resolved. Q: Which public source should I use for expected values? A: PubChem is a convenient source of formulas and masses. For compounds that are not listed, use the structure given in the primary literature and write the source in the file. ## Peptide Analytical Methods Compared: HPLC, LC-MS, Amino Acid Analysis, NMR and Karl Fischer URL: https://vestapeptides.com/resources/peptide-analytical-methods-compared/ Updated: 2026-10-30 No single test describes a peptide. HPLC with UV detection measures purity, mass spectrometry confirms identity, amino acid analysis or quantitative NMR measures how much peptide is present, Karl Fischer titration measures water, and ion chromatography or 19F NMR measures trifluoroacetate. Chiral methods check stereochemistry, and microbiological tests check sterility and endotoxin. A complete certificate of analysis combines several of them for one batch. - HPLC purity is usually read at 214 nm, where the peptide bond absorbs. - LC-MS adds a mass to each peak and is the standard identity test for peptides. - Amino acid analysis and quantitative NMR measure peptide content; HPLC does not. - Karl Fischer titration measures water; ion chromatography or 19F NMR measures TFA. - Chiral chromatography is needed for enantiomeric purity because D- and L-forms have the same mass. ### Reversed-phase HPLC with UV detection: purity A peptide is injected onto a reversed-phase column and eluted with a gradient of increasing organic solvent. The detector, usually set at 214 nm, records the absorbance of the peptide bond. The area of the main peak divided by the total area gives the HPLC purity. The result depends on the column, the gradient, the wavelength and the integration, so a report should give the method. It cannot see compounds that do not absorb at 214 nm and does not show the amount of peptide in the vial. ### LC-MS: identity and impurity assignment Coupling the HPLC to a mass spectrometer assigns a mass to each peak. The main peak should have the expected mass, and minor peaks can be explained with known mass shifts such as oxidation or deamidation. High-resolution instruments allow the exact mass to be compared with the calculated one. LC-MS is the single most informative test for peptide identity, but it is not a content assay and does not distinguish D- from L-amino acids. ### Amino acid analysis: content In amino acid analysis the peptide is hydrolysed to free amino acids, which are separated and quantified against standards. The amounts of the amino acids, compared with the known composition, give the amount of peptide present. It is the traditional method for net peptide content and also verifies the amino acid composition. Some residues, such as tryptophan and cysteine, are partly destroyed during hydrolysis and need special treatment. ### Quantitative NMR Quantitative NMR compares the signals of the peptide with those of an internal standard of known purity and can measure peptide content, residual solvents and counter-ions such as trifluoroacetate in a single experiment. It needs more material and a specialised laboratory than HPLC, and it works best for peptides that give resolved signals. ### Karl Fischer titration and loss on drying: water Water is part of the powder but not of the peptide. Karl Fischer titration measures it selectively and precisely, and loss on drying measures all volatile components. Water content is needed to calculate net peptide content and changes when the material takes up moisture from the air. ### Counter-ions, stereochemistry and sterility Ion chromatography and 19F NMR quantify trifluoroacetate, and ion chromatography also measures acetate and chloride. Enantiomeric purity is determined by hydrolysing the peptide and analysing the amino acids with a chiral column or a derivatising agent, or by direct chiral chromatography of the intact peptide. Sterility and bacterial endotoxin are determined by microbiological tests and are relevant for products that are labelled sterile. ### Putting it together A COA that reports only HPLC purity answers one of at least four questions. For a given use, decide which properties matter: identity is almost always essential, purity matters for most work, content matters when the concentration of a solution has to be known, and counter-ion and water matter when comparing the amounts of different batches. The compound pages on this site list the expected mass of each compound so that the identity question can be checked quickly. Q: Is a 99 % HPLC purity result enough to use a peptide? A: It shows that the main peak dominates the chromatogram under that method. It does not confirm identity, content, counter-ion, water or stereochemistry. Q: Which single test would you ask for if you could only have one? A: LC-MS, because it reports both an HPLC profile and the mass of each peak, so it addresses purity and identity together. Q: Why do two laboratories report different purity for the same peptide? A: Different columns, gradients, wavelengths and integration rules give different values. The method should be stated and, ideally, the chromatogram included. ## Laboratory Water and Diluents: Sterile Water, Bacteriostatic Water and Acetic Acid Solution URL: https://vestapeptides.com/resources/laboratory-water-and-diluents/ Updated: 2026-10-30 Sterile water is water that has been sterilised and contains nothing else. Bacteriostatic water is sterile water with a preservative, normally 0.9 % benzyl alcohol, which prevents bacterial growth in a vial that is opened more than once. Dilute acetic acid is an acidic solvent that helps basic peptides dissolve. All three are laboratory reagents; the choice depends on the peptide's charge and on whether the preservative or the pH interferes with the assay. They are sold by Vesta for laboratory use only. - Sterile water has no preservative and is intended for single use once opened. - Bacteriostatic water usually contains 0.9 % benzyl alcohol, which inhibits bacterial growth but can interfere with cell cultures and some assays. - Dilute acetic acid is used to dissolve basic, hydrophobic peptides that do not dissolve well in neutral water. - A peptide's net charge at the working pH predicts its solubility; acidic peptides dissolve better in dilute base and basic peptides in dilute acid. - These reagents are for laboratory use only and must not be used with humans or animals. ### Three reagents, three purposes Sterile water is the simplest: water that has been sterilised, with no added substances. Bacteriostatic water is the same water with a preservative that stops bacteria multiplying, so it can be used from a vial several times. Dilute acetic acid is a solvent with a low pH that is used when a peptide will not dissolve in neutral water. Each choice carries consequences for the experiment, which is why the identity and the lot of the reagent should be recorded. ### What bacteriostatic water contains and why it matters The usual preservative is benzyl alcohol at 0.9 %. It prevents growth of many bacteria but does not kill all organisms and does not make the water sterile after contamination. In a laboratory, benzyl alcohol can affect cell viability, enzyme activity and some analytical methods, so a preserved diluent is not appropriate for every experiment. If a protocol does not call for a preservative, use sterile water. ### Sterile water: what sterile does and does not mean A sterile product has been treated so that viable microorganisms are absent when the container is closed. Once opened, it can be contaminated, and without a preservative it should be used promptly. Sterility is not the same as low endotoxin or purity; if an assay is sensitive to endotoxin, check that the lot is tested for it. ### Dilute acetic acid and peptide solubility Whether a peptide dissolves depends on its sequence and net charge. Peptides with many basic residues (lysine, arginine, histidine) carry a positive charge in acid and dissolve more easily in dilute acetic acid than in neutral water. Peptides with many acidic residues behave the other way. Hydrophobic peptides may need a small amount of organic solvent. The concentration of the acetic acid solution supplied by Vesta is given in the batch documents and should be checked with support before it is used for a particular peptide. ### Compatibility with the assay A low pH may change the structure of a protein target, a preservative may inhibit a cell line, and either may change the retention of a peptide on an HPLC column. Before using a diluent in a new assay, run a vehicle control containing the diluent alone and compare it with the assay buffer. Record the lot number of the diluent together with the lot number of the peptide. ### Record keeping and laboratory-only use Record the product, the strength, the lot, the date opened and the date discarded. Discard diluents according to the laboratory's policy once the expiry or in-use period has passed. The products described here are laboratory reagents and are not intended for use in humans or animals; no dosing or administration guidance is given on this site. Q: Can I use bacteriostatic water for cell culture? A: Usually not, because benzyl alcohol can be toxic to cells. Use sterile water or a medium prepared for the cell line, and check the protocol. Q: How do I know which solvent a peptide needs? A: Calculate the net charge of the sequence at neutral pH and test a small amount first. Basic peptides generally dissolve in dilute acid, acidic peptides in dilute base, and hydrophobic peptides may need an organic co-solvent. Q: Does a diluent have an expiry? A: Yes. The batch documents give the information for each lot, and an opened multi-use vial has a shorter in-use period than an unopened one. ## How to Check a Multi-Component Research Blend URL: https://vestapeptides.com/resources/multi-component-blends-quality-control/ Updated: 2026-10-30 A multi-component blend cannot be described by one purity figure or one molecular weight. Each component needs its own identity evidence (for a peptide, its expected ions in an LC-MS run), its own declared and measured amount, and a method that can detect it. For a peptide blend, expect one chromatographic peak per component. For a mixed formulation of small molecules, enzymes or phospholipids, ask which detector and assay were used for each ingredient. - A blend has no single molecular weight; each defined component has its own. - The total mass per vial is the sum of the declared component masses, not the amount of any one of them. - Peptide blends should show one HPLC peak and one set of expected ions for each peptide. - UV detection at 220 nm suits peptides but not ingredients without a chromophore, such as inositol and choline. - Enzymes are quantified by activity and phospholipid mixtures by composition, not by molecular weight. - Keep a formulation sheet with the certificate so that every ingredient is covered by the batch record. ### Why a blend is a different analytical problem A single research peptide has one sequence, one formula and one set of expected ions. A blend has several of each, and the properties that make a single compound easy to check, such as one main peak, one intact mass and one amount, are replaced by a list. The record for a blend is correspondingly longer, and a general statement such as high purity says very little about whether every declared component is present at the declared level. ### Two kinds of blend The first kind is a peptide blend, in which every component is a defined peptide with its own formula and mass. Examples on the Vesta site are the GLOW and Klow blends and the BPC-157 plus TB-500 kits. Each component can be identified by LC-MS and has a reference page with expected values. The second kind is a mixed formulation, in which the ingredients are small molecules, enzymes or phospholipid mixtures. The Lipo-C products and Lemon Bottle are of this kind. These need different detectors and assays, and some ingredients are mixtures themselves. ### Identity: expected ions for every component For a peptide blend, work out the expected ions for each component before looking at the data. In a blend of a tripeptide of 340.19 Da, a 15-residue peptide of 1418.70 Da and a 43-residue peptide of 4960.49 Da, the tripeptide appears mainly at m/z 341.19 ([M+H]+), the middle peptide at m/z 710.36 ([M+2H]2+) and the large peptide as a series at charge states from 3+ to 6+, for example m/z 993.10 for [M+5H]5+. Each of these should be found at the retention time of its own chromatographic peak. Finding all three masses in one averaged spectrum, without separating the peaks, does not show which peak carries which mass. - List each component with its formula and monoisotopic mass. - Calculate [M+H]+ and the main multiply charged ions. - Extract those masses from the LC-MS run and check that each belongs to its own peak. - Check for near-isobaric neighbours: a pair of tripeptides that differ by 2.04 Da overlap in their isotope envelopes and need retention time to be told apart. ### Purity: one peak, several peaks, and area percent The chromatogram of a correct peptide blend has several main peaks, one for each peptide. A purity figure for the whole chromatogram has no clear meaning, because the largest peak may simply belong to the component present in the largest amount. A better record reports the purity of each component peak, or reports related-substance peaks for each. Also remember that area percent depends on detector response, which differs between peptides, so the area ratio of two peaks is not their mass ratio. ### Amount: declared, assayed and net Component amounts are normally declared masses, for example 10 mg of a peptide per vial. These are not measurements of the batch. The peptide content of a declared mass is lower than the mass itself, because each powder holds counter-ions and water, as explained in the guide to counter-ions and net peptide content. A component such as a copper peptide has an additional question: whether the declared mass refers to the peptide or to the copper complex. A complete record states the basis of each declared amount and whether any component was assayed. ### Mixed formulations: choose the detector for the ingredient UV detection near 220 nm works for peptides because the peptide bond absorbs there. It does not work for every ingredient. Inositol and choline have no useful UV absorbance, and methionine absorbs weakly, so a UV purity figure says little about them. Light-scattering and charged-aerosol detectors, refractive-index detection, mass spectrometry and NMR are used for such ingredients. Vitamin B12 is the opposite case: cyanocobalamin absorbs strongly near 361 and 550 nm and is easily quantified by UV-visible spectroscopy. Ask which detector produced each value. ### Ingredients that are mixtures Enzymes such as bromelain are quantified by activity, with a defined substrate and unit, and not by milligrams of protein. Lecithin is a mixture of phospholipids, and its specification is the content of phosphatidylcholine, measured by HPLC with light-scattering detection or by 31P NMR. For both, the batch will differ slightly from the last, and the document to request is the specification with the assay method. An enzyme that cleaves peptides should not be placed in a peptide solution in vitro unless digestion is the aim. ### What to request and file Ask for the formulation sheet with every ingredient, its grade and its declared amount; for each peptide, the intact-mass LC-MS result and the chromatogram with the peaks labelled; for each other ingredient, the assay method; and the batch code on every document. File these with the vial photographs and the receiving record using the compound identity file template, and add a line for each component so that none is left without evidence. Q: Can one HPLC purity value describe a blend? A: Not on its own. A blend has several peaks, and the percentage depends on how the peaks are counted and on the response of each component at the detection wavelength. Ask for per-component results. Q: Does the total mass on the label equal the amount of each component? A: No. It is the sum of the declared component masses. Each component's own amount is stated separately, and the peptide share of each is lower than its declared mass. Q: Why might two components of a blend be hard to separate by mass spectrometry? A: If their masses are close, their isotope envelopes overlap. Two tripeptides that differ by about 2 Da are an example. Use retention time together with accurate mass. Q: What if the manufacturer does not list the ingredients of a mixed formulation? A: Ask for the formulation sheet before buying. Without the ingredient list and the amount of each, identity and quantity cannot be checked. ## How to Read a Peptide Certificate of Analysis (COA) URL: https://vestapeptides.com/resources/how-to-read-peptide-certificate-of-analysis/ Updated: 2026-10-30 A useful peptide COA should connect one identifiable batch to reproducible analytical evidence. Check the sample or batch identifier first, then separate identity evidence from purity and content measurements. Confirm the laboratory, test date, analytical methods, numerical results, and any public verification key. A purity percentage alone does not establish molecular identity or the amount of peptide in a vial. - Identity, purity and content answer different questions and should not be treated as interchangeable. - The batch or sample identifier on the report should match the material being supplied. - A public verification key is useful only when the laboratory record matches the unedited report. - Method details such as detector wavelength, column and gradient show whether a result fits its stated purpose. - A mass result is only meaningful when the report states the charge state, the ion type and the expected value it was compared with. - A COA is one part of supplier qualification, not a substitute for traceability and receiving controls. ### Start with report identity and traceability Before reading any number, establish what the report describes. A certificate that cannot be tied to a specific batch is a statement about a product type, not evidence about the vial on the bench. Preserve the original file, because changing the client, manufacturer, QR code, signature, result or verification text breaks the link to the laboratory record. - The issuing laboratory and its contact details - A task, report or sample number, and any verification key or QR destination - The client and manufacturer names as they appear on the laboratory record - The product name, the batch identifier and the testing and release dates - The signature or approval of a named person If the supplied vial carries a different batch code, the report may still describe the same compound, but it is not batch-specific evidence for that vial. The guide to batch-specific verification explains how to document this link. ### Separate identity, purity and content Three questions are often collapsed into one number. Identity asks whether the main substance is the expected molecule. Purity asks what share of the detected signal belongs to the main peak. Content asks how much target material is in the vial. A report can show high chromatographic purity while the measured content differs from the label, so each result should be reviewed on its own. Question | Typical test | What it cannot tell you Is it the right molecule? | Mass spectrometry, sometimes MS/MS or amino acid analysis | How much of the powder is that molecule How pure is the main peak? | RP-HPLC with UV detection | Identity, and anything that does not absorb at the chosen wavelength How much peptide is in the vial? | Amino acid analysis, quantitative NMR or a validated content assay | Whether the peptide is the right sequence How much water and counter-ion? | Karl Fischer titration; ion chromatography or 19F NMR for TFA | Peptide purity ### Read the HPLC result in context Do not stop at the printed purity percentage. Review the chromatogram itself, the detector and its wavelength, the column, the mobile phases, the gradient, the run time, the retention time of the main peak and the way peaks were integrated. Peptides are normally detected at 214 or 220 nm, where the peptide bond absorbs, and area normalization compares integrated responses at that wavelength only. Impurities that do not absorb there are invisible, and impurities that co-elute with the main peak are counted as part of it. - A baseline blank run shows which peaks belong to the system rather than the sample. - A visible shoulder on the main peak suggests a closely related impurity that the integration may have merged. - The integration threshold decides which small peaks are counted at all. - The same sample can give different percentages with different gradients. The guide to reading an HPLC chromatogram goes through these points with examples. ### Review the mass-spectrometry evidence Check whether the report gives the expected formula or mass, the observed ions, their charge states and a calculated or deconvoluted mass. Peptides usually carry several charges, so a raw mass-to-charge value is not the intact mass. For a 1,000 Da peptide, the singly charged ion appears near m/z 1001 and the doubly charged ion near m/z 501. The observed result should be explained by the expected molecule, the ionization mode, the salt form and any adducts. Agreement within a few tenths of a dalton is typical for a low-resolution instrument, and within a few parts per million for a high-resolution one. Compare the numbers with the reference values on the compound page for the product. If the report compares an observed mass with an expected value, the expected value should be stated on the report, along with whether it is monoisotopic or average. ### Look for content, water and counter-ion data A lyophilized peptide is a salt. The powder holds counter-ions such as trifluoroacetate or acetate and a few percent of water, so the peptide is only part of the weighed mass. A report that gives net peptide content, water content and counter-ion information lets a laboratory work out how much peptide a vial contains. A report that gives only a purity percentage leaves that question open. ### Recognise common warning signs Some features do not prove a problem but justify a question to the supplier before the material is accepted. - Only a purity percentage, with no chromatogram - No batch identifier, or an identifier that differs from the vial - A chromatogram cropped so that the baseline and early or late peaks are not visible - A mass listed without a charge state, an ion type or an expected value - Identical-looking reports for different compounds, with only the name changed - A verification key or QR code that opens a page that does not match the printed report ### Use a repeatable acceptance checklist A receiving laboratory can document five decisions: the report is authentic, the material and the report are traceably linked, the methods are appropriate, the results meet internal specifications, and any discrepancy has been resolved before release. Keep the report, the verification evidence, the purchase record, photographs of the received batch and the internal decision together. The compound identity file template gives a layout for this record. Q: Does 99% HPLC purity mean the vial contains 99% of the labeled amount? A: No. HPLC area purity and measured vial content are different measurements. A separate quantitative assay or content test is needed to evaluate the amount present. Q: Can a supplier rename the client on a third-party COA after rebranding? A: The original laboratory report should remain unedited. A supplier can add a separate rebranding note, but an amended client or manufacturer field should come from the issuing laboratory. Q: Is one analytical technique enough for peptide verification? A: It depends on the claim and method, but orthogonal evidence is stronger. Chromatography can support purity assessment while mass spectrometry can support molecular identity. Q: What mass difference between observed and expected is acceptable? A: That depends on the instrument and the laboratory's own specification. As a rule of thumb, a low-resolution instrument agrees within a few tenths of a dalton and a high-resolution one within a few parts per million. State the tolerance in advance and apply it to the deconvoluted or monoisotopic mass, not to a single raw m/z value. Q: Should a COA include the chromatogram? A: Yes. The percentage is a summary of the chromatogram, and the trace shows whether the main peak is symmetric, whether there are shoulders and how the baseline looks. A report without the trace cannot be reviewed. Q: What should I do if the batch code on the report does not match the vial? A: Quarantine the material and ask the supplier in writing for the report that matches the vial. Do not release the batch on the basis of a report for another lot. ## How to Read an HPLC Chromatogram for Peptide Purity URL: https://vestapeptides.com/resources/how-to-read-hplc-chromatogram-peptide-purity/ Updated: 2026-10-30 An HPLC chromatogram plots detector response against time after a sample passes through a chromatographic system. For a peptide purity review, identify the principal peak, inspect secondary peaks, check how peaks were integrated, and read the reported area percentage together with the method conditions. The largest peak is not proof of molecular identity, and area percentage is not the same as vial content. - Peptide purity by HPLC is the area of the main peak divided by the total integrated area, under one method and one wavelength. - The largest peak is not proof of identity; a mass measurement or another orthogonal method is needed. - Peptides are normally detected at 214 to 220 nm, so impurities that do not absorb there are not counted. - Integration settings, baseline and the gradient can change the percentage for the same sample. - Area percentage is not vial content and is not the same as net peptide content. ### What a peptide HPLC trace shows Reversed-phase HPLC separates peptides mainly by hydrophobicity. A sample is injected into a stream of aqueous solvent and flows through a C18 or similar column. An organic solvent, usually acetonitrile with 0.1 % trifluoroacetic acid, is raised gradually, and peptides leave the column in order of increasing hydrophobicity. A detector records the signal as a function of time, and the result is a chromatogram: signal on the vertical axis, retention time on the horizontal axis. Each peak is a population of molecules that left the column together. ### How to find the main peak The main peak is normally the tallest and largest, but that is only an assumption. Note its retention time and compare it with a reference lot or with an earlier batch of the same compound. A shift of a few tenths of a minute between runs can be normal when the system differs, but the elution order of the main peak and its neighbours should be stable. A main peak at a very different retention time from earlier batches deserves a question, because a different molecule may elute elsewhere. ### Reading secondary peaks Small peaks near the main peak are usually related substances: truncated or deleted sequences from synthesis, oxidized forms, deamidated forms or peptides with a protecting group still attached. Peaks that appear before the main peak are more polar, and peaks after it are more hydrophobic. A peak at the very start of the run is typically unretained material such as salts, and a peak at the end can come from the gradient washout. - Compare the chromatogram with a blank run, which shows system peaks that are not from the sample. - A broad, humped peak suggests a mixture of closely related molecules. - A shoulder on the main peak suggests co-eluting impurity that the integration may have merged. ### How the percentage is calculated Area normalization takes the area of the main peak and divides it by the sum of all integrated peak areas. The result depends on three choices: the wavelength, the integration threshold and the baseline. Because it uses detector response and not mass, it assumes every component responds equally at the chosen wavelength. Components with a low response, such as peptides without aromatic residues or compounds without a chromophore, are under-represented. Components that do not elute during the run, or that co-elute with the main peak, are not counted separately. ### Method conditions that matter The same sample can give different purity values under different methods. Ask for or look for the column chemistry and dimensions, the mobile phases, the gradient, the flow rate, the column temperature, the detection wavelength and the injection amount. A steeper gradient compresses peaks and can hide neighbours, and a shallower one resolves them. A method used for release testing should be described in a way that allows another laboratory to reproduce it, as the validation guidelines for analytical procedures expect. ### What HPLC does not tell you A single HPLC trace does not establish identity, because many different peptides can give a single clean peak. It does not measure how much peptide is in the vial, how much water or counter-ion the powder holds, or whether the amino acids are the L-isomers. It also cannot show impurities that do not absorb at the detection wavelength. For these questions, mass spectrometry, amino acid analysis, Karl Fischer titration and chiral methods are used; the guide to comparing analytical methods lists them side by side. ### A short review routine Look at the trace first, then the table. Find the main peak and its retention time. Read the baseline for noise and drift. Count the secondary peaks and note any shoulders. Check the integration marks. Read the stated purity and see whether the trace supports it. Finally, link the HPLC result to a mass result for the same batch. If the report offers only the percentage, the review cannot be completed. Q: Does a single sharp peak prove the peptide is pure? A: No. A single peak shows that one population eluted under that method. Impurities that co-elute, or that do not absorb at the detection wavelength, are not visible. An orthogonal method such as mass spectrometry or a second HPLC condition is needed. Q: Why is 214 or 220 nm used for peptides? A: The peptide bond absorbs strongly in this range, so almost every peptide gives a signal. Detection at 280 nm sees only residues with aromatic side chains and would miss many peptides. Q: Is a purity of 98% better than 95%? A: Only if both numbers come from the same method with the same integration rules. A higher number from a method that hides impurities is less informative than a lower number from a stricter method. Q: What causes a peak after the main peak? A: Peaks that elute later are more hydrophobic than the main peptide. Typical causes are sequences that retain a protecting group, aggregated material and, for lipidated peptides, related lipid-containing species. ## Mass Spectrometry for Peptide Identity: A Practical Guide URL: https://vestapeptides.com/resources/mass-spectrometry-peptide-identity-guide/ Updated: 2026-10-30 Peptide mass spectrometry supports identity by testing whether observed ions are consistent with the expected molecular composition. Because peptides often carry more than one charge, the instrument may show several mass-to-charge peaks for one molecule. A report should connect those ions to an expected neutral or deconvoluted mass and explain relevant adducts, salt forms, or modifications. - Mass spectrometry tests whether the observed mass is consistent with the expected composition; it does not give purity. - Peptides in electrospray ionization carry several charges, so one molecule produces a series of m/z peaks. - The intact mass is calculated from the series (deconvolution) and compared with a stated expected value. - Sodium and potassium adducts, oxidation and deamidation each shift the mass by known amounts. - High-resolution data allow the monoisotopic mass to be read; low-resolution data often give an average mass. ### What the instrument measures A mass spectrometer measures mass-to-charge ratio, written m/z. In electrospray ionization the peptide acquires protons in solution, so an ion with mass M and z protons has m/z = (M + z × 1.00728) / z. A small peptide such as a tripeptide mostly appears with one charge. A peptide of 3 to 4 kDa often carries three to six charges. The instrument therefore reports several peaks for one molecule, each corresponding to a different charge state. ### From m/z values to a molecular mass To reach the intact mass, take two neighbouring peaks of the series, solve for their charges and compute the mass. Software does this routinely and is called deconvolution. A worked example: peaks at m/z 1001.0 and 501.0 are consistent with a mass of about 1000.0 Da, since 1001.0 × 1 − 1.007 ≈ 1000.0 and 501.0 × 2 − 2.015 ≈ 1000.0. The deconvoluted mass is what is compared with the expected mass, and the report should show both the raw ions and the result. ### Monoisotopic and average mass Every element has natural isotopes, so a peptide is a family of molecules of slightly different mass. The monoisotopic mass uses the lightest isotope of each element. The average mass weights all isotopes by abundance. High-resolution instruments resolve the isotope peaks and report the monoisotopic mass, which is the first peak for small peptides. For larger peptides the first peak is weak, and the instrument reports an average or most abundant mass. The two differ by about 1 Da at 1 kDa and about 2 Da at 4 kDa. The guide to average and monoisotopic mass explains how to calculate each. ### Adducts, oxidation and other shifts Not every peak is the intact peptide. Sodium and potassium from glassware and buffers produce adducts at +21.982 Da and +37.956 Da relative to the protonated ion. Methionine and tryptophan oxidize (+15.995 Da), asparagine and glutamine deamidate (+0.984 Da), and a reduced disulfide is 2.016 Da heavier than the oxidized form. Recognising these steps lets a reader decide whether a minor peak is a degradation product, an impurity or an artefact. The guide to degradation products and mass shifts lists them with examples. - +21.982 Da: sodium adduct (replaces H with Na) - +37.956 Da: potassium adduct - +15.995 Da: one oxidation - +0.984 Da: deamidation - −18.011 Da: loss of water ### What a good report shows A report that supports identity gives the expected formula and mass, the instrument type and ionization mode, the observed ions and their charge states, the deconvoluted mass and the difference from the expected value. It states whether the mass is monoisotopic or average. It also links the spectrum to the main HPLC peak, ideally by showing that the mass belongs to the retention time of the main component, so that the identity is not that of a minor impurity. ### What mass spectrometry does not show Two peptides with the same composition but a different sequence have the same mass, so an intact mass cannot tell them apart. Fragmentation (MS/MS) or amino acid analysis is needed for that. Mass spectrometry also does not measure how much peptide is present, and the signal strength of an ion depends on how well the molecule ionizes, so peak heights in a spectrum are not a purity measure. Q: Why does a mass spectrum of one peptide show several peaks? A: In electrospray ionization the peptide picks up a variable number of protons. Each charge state appears at a different m/z, so one molecule produces a series of peaks that deconvolution combines into one mass. Q: Which mass should I compare, monoisotopic or average? A: Compare like with like. Use the monoisotopic mass for high-resolution data on smaller peptides and the average mass for larger peptides or low-resolution data. The report should state which one it uses. Q: Can mass spectrometry measure purity? A: Not reliably. Ionization efficiency differs between molecules, so peak heights in a spectrum do not reflect amounts. Purity is assessed by chromatography. Q: What does a peak 22 Da above the expected ion mean? A: It is most likely a sodium adduct, which sits 21.982 Da above the protonated ion. A peak 38 Da above suggests potassium. ## Peptide Purity vs Vial Content: Why the Numbers Differ URL: https://vestapeptides.com/resources/peptide-purity-vs-vial-content/ Updated: 2026-10-30 Peptide purity and vial content are not the same measurement. Chromatographic purity usually describes the relative detector area assigned to the principal peak. Vial content estimates how much target peptide is present. The total lyophilized mass may also include water, counterions, salts, or formulation components, so it should not be substituted for either purity or peptide content. - Purity is a share of detector signal; content is an amount of peptide. - A lyophilized powder contains counter-ions and water as well as peptide, so its weight is not the peptide weight. - Net peptide content is often between 60 % and 90 % of the powder and is measured by amino acid analysis or quantitative NMR. - A vial labelled 10 mg may hold about 6 to 9 mg of peptide even when HPLC purity is above 95 %. - Use net peptide content, not the label weight, to calculate molar amounts. ### Two different questions Peptide purity and vial content are often confused because both are reported as numbers and both appear on a certificate of analysis. Chromatographic purity describes the relative detector area assigned to the principal peak among the peaks that were detected. Vial content estimates how much target peptide is present. The total lyophilized mass may also include water, counter-ions, salts or formulation components, so it should not be substituted for either purity or peptide content. ### Why the powder is not all peptide A synthetic peptide is purified by reversed-phase HPLC in an acidic solvent, normally with trifluoroacetic acid. Every positively charged site on the peptide (the N-terminal amine and the side chains of lysine, arginine and histidine) takes up an acid anion as a counter-ion. After freeze-drying, the powder contains the peptide, those counter-ions and residual water. A peptide with four basic sites can therefore carry four trifluoroacetate ions, and these can account for a fifth or more of the weighed mass. ### A worked example Take a peptide of average molecular weight 1,500 g/mol with three basic sites. Three trifluoroacetate counter-ions (114.02 g/mol each) add about 342 g/mol, so the salt weighs about 1,842 g/mol and the peptide is 81 % of the salt. If the powder also holds 6 % water, the peptide is about 76 % of the weighed powder. A vial labelled 10 mg then contains about 7.6 mg of peptide, even though the HPLC purity of the main peak could be 98 %. Item | Value Peptide average mass | 1,500 g/mol Three TFA counter-ions | +342 g/mol Peptide share of the salt | 81 % Water in the powder | 6 % Peptide share of the weighed powder | about 76 % Peptide in a vial labelled 10 mg | about 7.6 mg ### How content is measured Net peptide content is measured by methods that count peptide molecules rather than detector response. Amino acid analysis hydrolyses the peptide and quantifies the released amino acids against standards. Quantitative NMR compares peptide signals with an internal standard of known amount. Karl Fischer titration measures water, and ion chromatography or 19F NMR measures trifluoroacetate. Together these account for the whole powder. A certificate that gives only a purity percentage cannot answer how much peptide is in the vial. ### What to do with the numbers For experiments in which the molar amount matters, use the net peptide content, not the label weight. Divide the weighed mass by the peptide's molecular weight after multiplying by the net content fraction. If the certificate does not give net peptide content, treat the label weight as an upper bound, ask the supplier for a content assay, or measure it in house. Keep the figure in the compound identity file so that every later calculation uses the same value. ### Where purity and content come together A good batch record has both: a chromatogram that shows the main peak is dominant, and a content result that says how much of the powder is peptide. Together with mass spectrometry for identity, these answer the three basic questions about a research peptide. The guide to reading a certificate of analysis shows how the pieces fit; the guide to counter-ions and net peptide content goes deeper into the content calculation. Q: Is a 10 mg vial really 10 mg of peptide? A: Usually not. The label weight is the weight of the powder or a nominal amount, and the powder also contains counter-ions and water. The peptide content is often 60 % to 90 % of the powder weight. Q: Does higher purity mean higher content? A: No. Purity is a ratio among detected peaks; content is an absolute share of the powder. A very pure peptide can still have a low net content if it holds a lot of counter-ion or water. Q: What is the difference between acetate and TFA salts? A: They add different masses per basic site (acetic acid 60.05 g/mol, trifluoroacetic acid 114.02 g/mol), so the same peptide has a different salt molecular weight and net content. Acetate is often chosen for biological assays because trifluoroacetate can interfere with cells. Q: Which test shows how much peptide is in a vial? A: Amino acid analysis or quantitative NMR gives net peptide content. HPLC purity does not. ## Batch-Specific COA Verification and Research Material Traceability URL: https://vestapeptides.com/resources/batch-specific-coa-verification-traceability/ Updated: 2026-10-30 Batch-specific traceability means a laboratory can demonstrate which material was ordered, which container was received, which sample was tested, which report applies, and who accepted or rejected it. The key is a stable identifier carried across the supplier record, vial label, COA, verification page, receiving log, and internal disposition. - Traceability is the ability to show which material was ordered, received, tested and accepted. - A stable identifier must follow the batch from the supplier record to the vial label, the report and the receiving log. - A report for another batch of the same compound is not evidence for the batch in hand. - Verification means checking the report against the issuing laboratory's own record, not only reading the PDF. - Every discrepancy should be written down, resolved and kept with the batch file. ### What batch-specific means A batch, or lot, is material made in one run under the same conditions and tested as one unit. Batch-specific traceability means a laboratory can demonstrate which material was ordered, which container was received, which sample was tested, which report applies and who accepted or rejected the material. The key is a stable identifier carried across the supplier record, the vial label, the certificate of analysis, the verification page, the receiving log and the internal disposition. ### Build the chain link by link Each link in the chain should be a record that anyone can inspect later. - Order record: product, SKU, quantity, order number and date - Packing list or invoice: the batch code the supplier assigned - Container label: the batch code printed on the vial, checked on arrival - Certificate of analysis: the same code, the testing laboratory and the date - Verification record: confirmation from the issuing laboratory that the report is genuine - Receiving log: who checked the shipment, what was found and where it was stored - Disposition: accepted, rejected or held, with a signature and a date ### Common ways the chain breaks Most failures are mundane. A supplier may re-use one report for several lots of the same compound. A batch code on the label may differ from the one on the report by a character, or a report may carry a product name without any lot at all. A vial may be re-labelled in transit. Reports can also be edited after issue, so that the visible text no longer matches the laboratory record. A single mismatch does not prove misconduct, but it means the chain cannot be closed until it is resolved. ### How to verify a report Compare the task or report number, the verification key and the date on the report with the issuing laboratory's own record where one is offered. Check that the QR code or link goes to a page on the laboratory's domain and that the page shows the same sample, client and results. Keep the original file unchanged and add your own notes in a separate record. The guide to verifying a third-party report lists the fields to compare. ### What to do with a mismatch Quarantine the affected material and write down what was found: the two codes, the dates and photographs of the label and the report. Ask the supplier in writing for the matching report, and keep the reply. If the supplier states that two codes describe the same lot, ask for the explanation on letterhead or in a signed note. Release the material only when the chain is complete or when your own testing provides the evidence that was missing. ### Keep a batch file A batch file brings the pieces together: the order, the invoice, the report, the verification, photographs of the label, the receiving record, storage conditions, any in-house results and the disposition. The compound identity file template gives a layout that is easy to audit and easy to hand to a colleague. Q: Is a COA for the same compound but a different lot acceptable? A: It can be useful context, but it is not batch-specific evidence. Treat it as supporting information and ask for the report that matches the lot you received. Q: What if the supplier uses an internal batch code and the laboratory uses another? A: That is acceptable only when the supplier provides a documented cross-reference that links both codes to the same material. Keep that cross-reference with the batch file. Q: How long should batch records be kept? A: Keep them at least as long as the material or any data produced with it is in use, and longer if your quality system or funder requires it. Q: Can a photograph of the label serve as evidence? A: Yes, as one link in the chain. Photograph the label together with the container and a note of the date, and store it with the receiving log. ## Research Peptide Supplier Qualification Checklist URL: https://vestapeptides.com/resources/research-peptide-supplier-qualification-checklist/ Updated: 2026-10-30 Supplier qualification should evaluate evidence and operations, not a purity slogan. Confirm business identity, product and batch traceability, original analytical reports, test-method context, warehouse and shipping controls, issue-resolution procedures, research-use restrictions, and the ability to answer a batch-specific question before purchase. - Qualify a supplier on evidence and operations, not on a purity slogan. - Ask a batch-specific question before purchase; the quality of the answer is information. - Original analytical reports, method context and traceability are the core documents. - Research-use restrictions and clear labelling show whether a supplier understands its market. - Write down the decision and the date so that it can be reviewed. ### Why qualify a supplier A supplier qualification is a documented decision that a source of materials is fit for a laboratory's purpose. For research peptides the risk is not only whether a vial contains the labelled compound but also whether the supplier can show it, repeat it and explain it. Qualification should therefore evaluate evidence and operations, not a purity slogan or a price. ### Business identity and contact Confirm who the supplier is and how to reach them. Look for a named company, a registered address or jurisdiction, a working email address and a response time you can test. If the supplier states a company, check that the name matches its terms, invoices and payment details. A supplier that is still being formed should say so plainly instead of implying a registered entity. ### Product and batch traceability Ask whether each product has a batch code, whether the code is printed on the vial, and whether the certificate of analysis carries the same code. A supplier that can show the chain from batch to report to label is easier to qualify than one that offers a general sample report. The guide to batch-specific verification describes the chain. ### Analytical evidence Request an original report for a recent batch of a compound you intend to buy and review it with the guide to reading a certificate of analysis. Check that the identity is supported by a mass result, that the purity is supported by a chromatogram, and that the method is described. If an independent laboratory issued the report, verify it with that laboratory. Ask what is tested on every batch and what is tested only on selected batches, because a clear answer matters more than a favourable one. ### Operations and handling Ask how the material is stored before dispatch, how it is packed and what the stated temperature conditions are. Ask who ships it, how the parcel is tracked and what the supplier does if the package is damaged or delayed. A supplier does not need to be large, but it needs a described process that can be audited after a problem. ### Research-use position and documentation A supplier of research materials should label them clearly as for laboratory research and state that they are not for human or veterinary use. Product pages that describe use, dosing or effects in people point away from that position. Terms, returns and privacy policies should be readable and consistent with each other. ### Run a pre-purchase test Before placing an order, send a specific question about one batch and see what comes back: the report, the code, the method, the date and an honest statement of what is not known. Score the answer against a short rubric and write down the result. The same rubric can be reused for each new supplier and for periodic review of existing ones. Q: How many suppliers should a laboratory qualify? A: At least two for materials that are critical to a study, so that a delay or a failed batch does not stop the work. Qualify each one separately. Q: Is a third-party report enough to qualify a supplier? A: No. It shows one sample was tested. Qualification also covers traceability, handling and the supplier's response to questions. Q: How often should a supplier be reviewed? A: At least once a year, and after any incident such as a failed batch, a changed address or a new manufacturing source. Q: What if a supplier will not answer batch-specific questions? A: Treat it as a finding. Record it and either qualify another supplier or base acceptance on your own testing. ## Laboratory Receiving Inspection for Lyophilized Research Peptides URL: https://vestapeptides.com/resources/laboratory-receiving-inspection-lyophilized-peptides/ Updated: 2026-10-30 A receiving inspection should confirm that the shipment, labels, batch documentation, container count, seals, and visible condition agree with the order before material is released to inventory. Record the condition on arrival, photograph labels and packaging, link the batch to its COA, and quarantine any discrepancy for supplier review. - Receiving inspection confirms that what arrived matches what was ordered and documented. - Record the condition on arrival with photographs before anything is opened or moved. - Link each container to its batch and its certificate of analysis. - Quarantine any discrepancy and tell the supplier in writing. - Release to inventory is a decision with a name and a date. ### Why inspect on arrival A receiving inspection is the first point at which a laboratory can catch a problem and the last point at which the evidence is still intact. It confirms that the shipment, labels, batch documentation, container count, seals and visible condition agree with the order before material is released to inventory. It also fixes the time and condition of receipt, which matters if there is later a dispute about transport. ### Before the parcel is opened Photograph the outer packaging, the shipping label and any seals or tape. Note the date and time, the carrier and the tracking number, and whether the parcel is intact, wet or damaged. Record any temperature indicator if one was included. Do not discard packaging until the inspection is closed, because it may be needed for a carrier claim. ### Check the contents against the paperwork Open the parcel in a clean area and compare the contents with the packing list and the order. - Product names and SKUs - Quantity of vials and kits - Batch or lot codes on each container - Seals, caps and crimps intact - Label legibility and agreement with the packing list - Any documents enclosed, such as certificates of analysis ### Look at the material Inspect each vial for the state of the lyophilized cake. A cake is normally a white or off-white, porous solid. Collapse, discolouration, wet patches or loose powder in the cap suggest moisture or an excursion in transit and should be recorded. Do not open sealed vials for this check; view them through the glass and photograph them. Copper-containing peptides are blue in colour, and some small molecules are coloured or are supplied as liquids, so compare with the product documentation. ### Link the batch to its documents Match the batch code on each container with the certificate of analysis you hold and with the supplier's packing list. If the batch code is missing or differs from the document, treat the material as unreleased. The guide to batch-specific verification describes how to close the chain. ### Decide and record Record the disposition: accept, accept with comment or quarantine. Sign and date the entry, and store it with the batch file. A quarantine entry should state the discrepancy, the photographs taken and the person informed. Quarantined material should be physically separated from released stock and labelled so that no one uses it by mistake. ### Store immediately Move accepted material to its documented storage condition without delay and record the time. Lyophilized peptides are normally kept cold and dry, but the product documentation governs. The guide to documenting storage conditions describes what to record. Q: Should vials be opened during receiving inspection? A: No. Inspect through the glass and keep the seal intact. Opening a vial exposes the material to moisture and creates a record problem. Q: What if the parcel arrived warm? A: Record the condition, photograph the packaging and any indicator, and quarantine the material until the supplier's documentation supports a decision. Do not assume that a warm parcel means damaged material; ask for the stability information. Q: How should discrepancies be reported? A: In writing, with the order number, photographs and a precise description. Keep the reply with the batch file. Q: Who should do the inspection? A: Someone trained in the receiving procedure who is not the only person to benefit from a quick release, so that the check is independent where possible. ## Documenting Storage Conditions for Lyophilized Peptide Research Materials URL: https://vestapeptides.com/resources/documenting-storage-conditions-lyophilized-peptides/ Updated: 2026-10-30 A laboratory should store lyophilized peptide research material according to product-specific documentation and record the actual conditions, location, dates, and excursions. A generic temperature recommendation cannot replace compound- and formulation-specific stability data. When an excursion occurs, quarantine the affected material until a documented assessment supports its disposition. - Follow product-specific storage documentation and record the actual conditions. - A generic temperature recommendation cannot replace compound-specific stability data. - Record location, dates, temperature monitoring and every excursion. - Quarantine material after an excursion until a documented assessment supports its use. - Moisture is the main enemy of a lyophilized peptide; keep containers sealed and let them warm before opening. ### What a storage record should show A laboratory should store lyophilized peptide research material according to product-specific documentation and record the actual conditions, location, dates and excursions. The record should let a colleague who was not there answer four questions: where was the material, at what temperature, for how long, and did anything unusual happen. ### Why peptides are stored dry and cold In a dry state (see lyophilized peptides explained), water-driven reactions such as hydrolysis and deamidation are slow, and the powder is more stable than a solution. Lower temperature slows the remaining reactions. Oxidation of methionine, cysteine and tryptophan is affected by oxygen and light, and some peptides absorb water from the air because the powder is hygroscopic. A closed, dry, cold and dark container therefore protects the material. The exact temperature depends on the compound and the formulation, and the supplier's documentation should say what it is. ### Record the essentials A simple log is enough if it is consistent. - Product name, batch code and container identifier - Date received and date moved to storage - Storage location (freezer, shelf, box) and the stated condition - Temperature monitoring: logger or thermometer identifier and readings or alarm history - Each time the container was removed, by whom and for how long - Any excursion: start, end, temperature reached and the action taken - Disposition after each excursion ### Handling before opening A cold vial opened in a warm room draws moisture onto the powder. Let the sealed vial reach room temperature before opening, work quickly, and close the container promptly. Avoid repeated freeze-thaw cycles for material that has been dissolved, and record the date a vial was first opened. Do not store opened vials in the same place as unopened stock without clear labelling. ### Handling an excursion An excursion is any departure from the stated condition: a power failure, a door left open, a delayed courier or a freezer alarm. Quarantine the affected material, write down what happened and for how long, and look for stability data that covers the departure. If the supplier or the literature does not cover it, the options are to test the material or to retire it. Record the decision and who made it. ### Reviewing storage records Review the records on a schedule, not only after a problem. Check that monitoring devices are calibrated, that alarm contacts are current and that stock past its retest or expiry date is identified. Link the storage record to the compound identity file so that a result can always be traced back to how the material was kept. Q: Is a household freezer acceptable for storing peptides? A: That depends on the laboratory's quality system. A monitored laboratory freezer is easier to document. A household freezer cycles in temperature, so if one is used, add a logger and record its readings. Q: How long can a lyophilized peptide be stored? A: There is no general figure. It depends on the sequence, the form and the conditions. Use the supplier's stability data or your own testing, and set a retest date. Q: Does reconstituted peptide need the same records? A: Yes, and more often. Record the solvent, concentration, date prepared, storage temperature and number of freeze-thaw cycles. Q: What if I cannot find stability data for a compound? A: Treat the material conservatively: keep it dry, cold and dark, limit handling, set a short retest interval and test a sample periodically. ## How to Verify a Third-Party Peptide Test Report Without Altering It URL: https://vestapeptides.com/resources/verify-third-party-peptide-test-report/ Updated: 2026-10-30 Verify a third-party peptide report against the issuing laboratory's own record. Compare the task number, verification key or QR destination, client, manufacturer, sample, dates, methods, results, and signature. Keep the original file unchanged. If a supplier has rebranded, document the brand relationship separately instead of editing historical laboratory fields. - Verify a report against the issuing laboratory's own record, not only against the PDF. - Compare the task number, verification key, client, manufacturer, sample, dates, methods, results and signature. - Keep the original file unchanged; make notes in a separate record. - A rebranded supplier should document the brand relationship separately instead of editing laboratory fields. - A report verifies one sample on one date; it does not certify every later batch. ### What third-party means and why it is checked A third-party report is issued by a laboratory that is independent of the supplier. Its value comes from that independence, which is lost if the document can be altered. Verification therefore means comparing the report with the issuing laboratory's own record, so that the numbers a reader sees are the numbers the laboratory produced. ### Fields to compare Read every field on the report and compare it with what you expect. - Task, report or sample number - Verification key or the destination of the QR code - Client and manufacturer names - Sample name and any batch code - Dates of receipt, testing and issue - Methods used for identity, purity and content - Numerical results and units - Signature or approval and the laboratory's name ### Use the laboratory's own verification route Where the laboratory offers an online lookup by task number or key, use it and compare the page with the PDF line by line. The address should belong to the laboratory's own domain. If the page shows different results, a different client or a different date from the PDF, treat the report as unverified. If no verification route exists, ask the laboratory directly and keep the reply. ### Check that the report is about this material A genuine report can still describe another product. Compare the sample name and any batch code with the vial, as described in the guide to batch-specific verification. Check that the compound identity matches the product, for example that the stated mass belongs to the compound you ordered. A report for a different product, a different strength or a different lot is context at best. ### Keep the original, document the rest Do not edit, crop or annotate the original file. If a supplier has rebranded or changed its company name since the report was issued, the supplier should document the brand relationship in a separate statement. Changes to the client or manufacturer field should be made only by the issuing laboratory, because those fields are part of what is verified. ### Know what a report does not cover A third-party report describes a sample taken on a certain date. It does not by itself show that other batches are the same, that the material has been stored well since or that every batch is tested. Ask the supplier what share of batches are tested by an independent laboratory and how selected batches are chosen, and treat the answer as part of the supplier file. Q: What if the verification page does not load? A: Try again later, then contact the laboratory directly with the task number. Record the attempt. Do not treat a failed lookup as a pass. Q: Can a supplier edit the client name on a third-party report? A: No. If the client or manufacturer changed, the issuing laboratory should reissue the report. The supplier can add a separate note explaining the relationship. Q: Is a QR code enough? A: Only if it opens a page on the laboratory's own domain that shows the same data as the PDF. A QR code on a copied report can point anywhere. Q: How often should a supplier provide new third-party reports? A: There is no standard. Ask how often it happens and which batches are covered, and decide whether that fits the importance of your work.