Melanotan 1 vs Melanotan II: structural differences
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Melanotan 1 is a linear peptide of 13 amino acids, while Melanotan II is a cyclic peptide of seven. Both are synthetic analogues of alpha-melanocyte-stimulating hormone, and they carry different CAS numbers. This guide compares their identifiers and structure, which is what distinguishes the two materials on paper.
Melanotan 1 and Melanotan II at a glance
| Melanotan 1 | Melanotan II | |
|---|---|---|
| CAS number | 75921-69-6 | 121062-08-6 |
| Synonyms | MT-1, Afamelanotide, Melanotan-1, NDP-MSH | MT-II, MT2, Melanotan-2 |
| Structure | Linear tridecapeptide (13 amino acids) | Cyclic heptapeptide (7 amino acids) |
| Parent | Analogue of alpha-melanocyte-stimulating hormone | Analogue of alpha-melanocyte-stimulating hormone |
| Supplied form | White lyophilised powder | White lyophilised powder |
| Vial size | 10mg | 10mg |
What is the difference between linear and cyclic?
A linear peptide is an open chain with a free amino end and a free carboxyl end. A cyclic peptide has a ring formed by an extra bond between two parts of the chain. Ring closure changes the shape and the mass of a molecule, so the two forms cannot be confused on a mass spectrometry trace.
Length is the other obvious difference. Thirteen residues against seven means a clearly different molecular mass for each material. Our listings do not state a formula or molecular weight for either, so expected values should be taken from the batch certificate of analysis.
Why do the CAS numbers matter?
The names are close enough to be mistaken for one another, and abbreviations such as MT-1 and MT-II differ by a single character. The CAS numbers, 75921-69-6 and 121062-08-6, are the reliable way to tell which material a label or document refers to. The method is explained in what is a CAS number.
Which listings contain each compound?
| Listing | Format |
|---|---|
| Melanotan 1 10mg | One vial, 10mg |
| Melanotan II 10mg | One vial, 10mg |
Each is a separate single-compound listing. For other analogues in the catalogue see peptide analogues.
What should the documentation show?
- The compound name, abbreviation and CAS number match the listing.
- An HPLC purity figure for the batch.
- A mass result consistent with a linear 13-residue or cyclic 7-residue structure, as applicable.
- Appearance recorded as a white lyophilised powder.
Batch documents are on the COAs page. The general method is in how to read a peptide certificate of analysis.
Frequently asked questions
What is the CAS number for Melanotan 1?
The CAS number listed for Melanotan 1 is 75921-69-6.
What is the CAS number for Melanotan II?
The CAS number listed for Melanotan II is 121062-08-6.
Is Melanotan 1 linear or cyclic?
Linear. It is listed as a tridecapeptide, a chain of 13 amino acids.
Is Melanotan II linear or cyclic?
Cyclic. It is listed as a cyclic heptapeptide of seven amino acids.
Do the two share any synonyms?
No. Melanotan 1 is listed with the synonyms MT-1, Afamelanotide and NDP-MSH, while Melanotan II is listed as MT-II, MT2 and Melanotan-2.
All Ascend Research products are sold strictly for laboratory research use only. They are not for human or animal use, and nothing in this article is medical advice.
The Ascend Research team
