Melanotan II Explained: the Cyclic α-MSH Analogue and How to Verify a Batch
Melanotan II is a synthetic cyclic analog of the hormone α-MSH, with seven amino acids and a molecular mass of 1,024.18 Da. It binds to several melanocortin receptors. This guide explains its structure, how it differs from Melanotan I and PT-141, and how to verify a batch.
Key facts
- Type: Synthetic cyclic heptapeptide (seven amino acids); analog of α-MSH
- Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
- Molecular formula: C50H69N15O9
- Molecular mass: 1,024.18 Da
- CAS number: 121062-08-6
- Supplied as: lyophilized powder in a sealed vial
What is Melanotan II
Melanotan II was designed at the University of Arizona in the 1980s as a shortened, more stable version of α-MSH. Its ring is closed by a lactam bond between the side chains of aspartic acid and lysine. It contains two residues not found in natural proteins: norleucine and D-phenylalanine. The peptide is a non-selective agonist of the melanocortin receptors MC1, MC3, MC4 and MC5.
What the scientific literature covers
Published work was carried out in cell cultures, animal models and early clinical studies. Laboratory topics include:
- Binding to the melanocortin receptors MC1, MC3, MC4 and MC5
- Melanin production in pigment cells and animal models
- Feeding behavior and energy balance in rodents through MC4
- Structure–activity studies of cyclic α-MSH analogs
These are laboratory findings. CellMind supplies Melanotan II for research purposes only, not for human use.
How identity and purity are verified
The lactam ring is what a Melanotan II report has to confirm. HPLC separates the cyclic peptide from the open, linear form and from shortened sequences. Mass spectrometry confirms 1,024.18 Da. PT-141 (bremelanotide) has the same ring but ends in a free acid instead of an amide and is only about 1 Da heavier, so an accurate mass and the HPLC retention time are both needed to tell them apart. Both results must appear on the certificate of analysis (CoA) for the specific batch. Our CoA guide explains how to read one.
Checklist before buying Melanotan II
- A CoA for the specific batch
- HPLC purity stated as a number, above 99%
- Mass of 1,024.18 Da confirmed on the report
- A clearly stated amount per vial (10 mg)
- A batch number on the vial that matches the report
Common questions about Melanotan II
How is Melanotan II different from Melanotan I?
Melanotan I (afamelanotide) is a linear peptide of 13 amino acids with a mass of about 1,646.9 Da. Melanotan II is a cyclic peptide of seven amino acids with a mass of 1,024.18 Da.
How is Melanotan II different from PT-141?
PT-141 (bremelanotide) has the same ring and sequence, but its last residue ends in a free acid instead of an amide. Its mass is about 1,025.2 Da, roughly 1 Da more than Melanotan II.
What does cyclic mean for this peptide?
The side chains of aspartic acid and lysine are joined by a lactam bond, which closes six of the residues into a ring. The linear form has the same amino acids but is a different compound.
Storage and handling
Keep lyophilized vials in a cool, dark place. After reconstitution the solution should be refrigerated and used within the planned study period. Avoid repeated temperature changes: they are the most common cause of degradation that nobody notices until results stop matching.
CellMind Melanotan II 10mg
- 10 mg of lyophilized powder per vial, sealed under inert conditions
- HPLC-tested by Janoshik Analytical, purity above 99%
- A CoA for the specific batch with every order
Product page for US orders: Melanotan II 10mg. Ordering and delivery: Where to buy Melanotan II. Reports for current batches: Lab reports and CoA.
Sources
- Al-Obeidi F. et al. Journal of Medicinal Chemistry. 1989;32(12):2555–2561.
Research purposes only.