What is Melanotan-1?
The molecular reference lists the synonym [Nle4-D-Phe7]-alpha-MSH, which describes the molecule precisely: the parent hormone sequence with methionine at position four replaced by norleucine, and phenylalanine at position seven inverted to the D configuration. The first removes the only oxidation prone residue in the parent, and the second stabilises the turn the receptor binding core adopts. No full sequence is recorded, so none is reproduced here, and the average mass of 1646.85 anchors identity testing.
Melanotan-1 is linear, which distinguishes it structurally from the cyclic analogue in the same family. In the published literature it is an agonist across melanocortin receptor subtypes with notable activity at MC1R, the receptor driving eumelanin synthesis in melanocytes. Cell culture studies use it to stimulate tyrosinase expression and melanin production in melanocyte lines, and rodent pigmentation models have studied MC1R signalling in the animals used.
What is not settled is the relative contribution of the several receptor subtypes to observations in whole animal models, and how receptor polymorphisms alter the response, since MC1R is among the most variable receptors in vertebrate genetics.
Reconstitution & handling
Sterile or bacteriostatic water is added slowly down the inner wall and swirled gently until the cake clears. The peptide is moderately soluble in neutral water, and where dissolution is slow the cake is wetted with a little dilute acetic acid before making up to volume. Vortexing is avoided. Concentration is arithmetic, so 1 mL added to a 10 mg vial gives 10 mg per millilitre.
Storage & stability
Sealed lyophilized vials are stored at -20 °C, protected from light and moisture, and equilibrated to room temperature before opening. Melanocortin analogues are light sensitive, so reconstituted solution is kept in amber or foil wrapped vials at 2 to 8 °C, aliquoted for single use, and protected from repeated freezing and thawing. Replacing the parent methionine with norleucine removes the principal oxidation liability, which is one reason this analogue holds up better in solution than the native hormone.
How it's tested
Each lot is analysed by reversed phase HPLC at 214 and 220 nm and reported at 99 percent or greater, with aromatic residues giving a confirmatory signal at 280 nm. Mass spectrometry confirms identity against the theoretical average mass of 1646.85 calculated from C78H111N21O19. Because the D configured phenylalanine has the same mass as its L counterpart, chromatographic resolution rather than mass is what excludes the epimer.