Melanotan II
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.
- TypePeptide
- FormulaC50H69N15O9
- Average mass1024.18 g/mol
- CAS121062-08-6
- Vesta listings1
Reference page for laboratory use · updated 2026-10-30
Overview
Melanotan II at a glance
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.
Structure
It shares the cyclic core of PT-141 but ends in an amide instead of a free acid. The calculated formula matches PubChem exactly.
Identity
Identity data
| Name | Melanotan II |
|---|---|
| Also written as | MT-II |
| Type | Peptide |
| Research area | Melanocortin peptides |
| Molecular formula | C50H69N15O9 |
| Monoisotopic mass | 1023.5403 Da |
| Average molecular weight | 1024.18 g/mol |
| CAS number | 121062-08-6 |
| Sequence | Ac-Nle-Asp-His-Phe-Arg-Trp-Lys-NH2 |
| Ring structure | Cyclic: lactam bridge between the Asp and Lys side chains |
| PubChem record | CID 92432 |
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 1023.5403 Da. Use them to check an LC-MS result; for larger peptides the instrument usually reports a deconvoluted mass close to 1024.2 Da instead.
| Ion | m/z |
|---|---|
| [M+H]+ | 1024.5476 |
| [M+2H]2+ | 512.7774 |
| [M+Na]+ | 1046.5295 |
| [M+K]+ | 1062.5035 |
Read the guide to average and monoisotopic mass for how these values are calculated.
Quality
Analytical notes for batch documents
- 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.
- 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: Lactam bridge, Peptide.
Vesta listings
Melanotan II formats and prices
| Product | Per vial | SKU | Price per kit | Price per vial |
|---|---|---|---|---|
| Melanotan I/II | 10 mg | MT-1/MT-2 | $104.48 | $10.45 |
Vesta lists one product called Melanotan I/II. Confirm from the batch documents which of the two it contains.
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.
- Preformulation studies with melanotan-II: a potential skin cancer chemopreventive peptideLan EL, Ugwu SO, Blanchard J et al. · J Pharm Sci · 1994 · PMID 7983590
- CLIPSing Melanotan-II to Discover Multiple Functionally Selective hMCR AgonistsTomassi S, Dimmito MP, Cai M et al. · J Med Chem · 2022 · PMID 35188390
Questions
Frequently asked questions
What is Melanotan II?
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.
What is the molecular weight of Melanotan II?
Melanotan II has the formula C50H69N15O9, an average molecular weight of 1024.18 g/mol and a monoisotopic mass of 1023.5403 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 Melanotan II?
Compare the intact mass measured by LC-MS with the expected values on this page, for example [M+2H]2+ at m/z 512.7774. 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 Melanotan II products does Vesta list?
Vesta lists 1 product for Melanotan II: 10 mg per vial in kits of 10 vials. Prices are shown per kit in US dollars, and shipping is paid by the customer.