Melanotan II
A ring rather than a chain. Seven residues closed head to tail through a lactam bridge, with a D-amino acid inside the ring and both termini capped — four separate departures from an ordinary peptide.
- Class
- Synthetic cyclic heptapeptide, N-terminally acetylated and C-terminally amidated
- Also written
- MT-II; MT2
- Molecular formula
- C50H69N15O9
- Molecular weight
- 1024.2 g/mol
- CAS number
- 121062-08-6
- Appearance
- White lyophilised powder
- Purity specification
- 99%+ by HPLC
- Vial size stocked
- 10 mg
Sequence
Ac – Nle – cyclo[ Asp – His – D-Phe – Arg – Trp – Lys ] – NH2
Acetyl-norleucine, then a six-residue ring closed by a lactam bond between the aspartate side chain and the lysine side chain, ending in a C-terminal amide. Three of the features here are non-standard: norleucine in place of the parent hormone's methionine, D-phenylalanine rather than the L-form, and the side-chain-to-side-chain cyclisation itself. The single tryptophan gives the molecule an ultraviolet absorbance at 280 nm.
Origin
Melanotan II was developed at the University of Arizona in the 1980s as an analogue of α-melanocyte-stimulating hormone, a thirteen-residue peptide. The core His-Phe-Arg-Trp motif is drawn from that hormone; the norleucine substitution, the D-configuration and the ring are all designed. KPV, elsewhere in this catalog, comes from the same parent hormone by an entirely different route.
Solubility
Soluble in water and in aqueous buffers. The lactam ring makes this a more conformationally constrained — and correspondingly more robust — molecule than a linear peptide of the same length. Both termini are capped, so it lacks the free amine and free acid that give most peptides their pH sensitivity; the arginine and histidine still carry charge.
Storage and handling
- Lyophilised powder: store at −20 °C, protected from light and moisture.
- Protect from light in particular. The tryptophan is photosensitive.
- In solution: refrigerate, protect from light, and treat the working life as far shorter than that of the powder.
- Avoid repeated freeze-thaw cycles; aliquot first if the solution will be drawn on more than once.
- Label every reconstituted vial with compound, lot, concentration and date.
How your lot is verified
An independent third-party laboratory tests the material first, then we test it again in-house when it arrives — purity by HPLC, identity by mass spectrometry — and only then does it ship. On a cyclic peptide the mass is the tell for the ring: an uncyclised chain weighs eighteen daltons more than the closed form, because closing the lactam expels a molecule of water. How we verify.
Supplied for laboratory research use only. Not for human or veterinary use. No statement on this page has been evaluated by the Food and Drug Administration, and nothing here is intended to diagnose, treat, cure, or prevent any disease. Alpha Aminos is a chemical supplier and does not provide guidance on the use of any compound.