PT-141
PT-141 (bremelanotide) is a synthetic cyclic heptapeptide agonist of melanocortin receptors, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH.
- TypePeptide
- FormulaC50H68N14O10
- Average mass1025.16 g/mol
- CAS189691-06-3
- Vesta listings1
Reference page for laboratory use · updated 2026-10-30
Overview
PT-141 at a glance
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.
Structure
A lactam bridge between the side chains of aspartic acid and lysine closes the ring. The calculated formula with the lactam matches PubChem exactly.
Identity
Identity data
| Name | PT-141 |
|---|---|
| Also written as | Bremelanotide |
| Type | Peptide |
| Research area | Melanocortin peptides |
| Molecular formula | C50H68N14O10 |
| Monoisotopic mass | 1024.5243 Da |
| Average molecular weight | 1025.16 g/mol |
| CAS number | 189691-06-3 |
| Sequence | Ac-Nle-Asp-His-Phe-Arg-Trp-Lys |
| Ring structure | Cyclic: lactam bridge between the Asp and Lys side chains |
| PubChem record | CID 9941379 |
The formula was calculated independently from the written sequence and matches the PubChem record exactly. Reference data retrieved on 2026-10-30. Compare these values with the batch certificate of analysis, using the compound identity file template.
Expected values
Mass spectrometry reference
Ions calculated from the monoisotopic mass 1024.5243 Da. Use them to check an LC-MS result; for larger peptides the instrument usually reports a deconvoluted mass close to 1025.2 Da instead.
| Ion | m/z |
|---|---|
| [M+H]+ | 1025.5316 |
| [M+2H]2+ | 513.2694 |
| [M+Na]+ | 1047.5135 |
| [M+K]+ | 1063.4875 |
Read the guide to average and monoisotopic mass for how these values are calculated.
Quality
Analytical notes for batch documents
- 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.
- Mass shifts to look for in this sequence: tryptophan oxidation (+15.995 Da).
- The molecular weight of a vial of powder includes counter-ions and water; the share of the powder that is peptide is the net peptide content.
Terms used on this page: Deamidation, Lactam bridge.
Vesta listings
PT-141 formats and prices
| Product | Per vial | SKU | Price per kit | Price per vial |
|---|---|---|---|---|
| PT141 | 10 mg | p41 | $119.40 | $11.94 |
Prices are per kit of 10 vials in US dollars. Shipping is paid by the customer and is shown in the cart. Volume savings of 5 %, 8 % and 10 % apply from $350.00, $600.00 and $1,000.00. See the full price list.
Published literature
Selected scientific literature
Bibliographic details were read from PubMed on 2026-10-30. The papers are listed for scientific reference; Vesta makes no claim about the use of its research materials in people or animals.
- PT-141 PalatinHedlund P · Curr Opin Investig Drugs · 2004 · PMID 15134289
Questions
Frequently asked questions
What is PT-141?
PT-141 (bremelanotide) is a synthetic cyclic heptapeptide agonist of melanocortin receptors, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH.
What is the molecular weight of PT-141?
PT-141 has the formula C50H68N14O10, an average molecular weight of 1025.16 g/mol and a monoisotopic mass of 1024.5243 Da. A salt form, a different counter-ion or a metal complex changes the molecular weight printed on a certificate of analysis, so compare like with like.
How can I check the identity of a batch of PT-141?
Compare the intact mass measured by LC-MS with the expected values on this page, for example [M+2H]2+ at m/z 513.2694. Confirm that one main HPLC peak carries that mass and that the batch code on the report matches the vial. The guides on mass spectrometry and on certificates of analysis explain each step.
Which PT-141 products does Vesta list?
Vesta lists 1 product for PT-141: 10 mg per vial in kits of 10 vials. Prices are shown per kit in US dollars, and shipping is paid by the customer.