Melanotan-1 vs melanotan-2: selectivity is the difference
Melanotan-1 is comparatively selective for the melanocortin-1 receptor. Melanotan-2 is a cyclic lactam analogue that retains affinity across several melanocortin receptors, including MC3R and MC4R. That difference decides which one a design can attribute an effect to.
| Melanotan-1 | Melanotan-2 | |
|---|---|---|
| Receptor preference | MC1R-selective | MC1R, MC3R, MC4R, MC5R |
| Structure | Linear 13-residue analogue | Cyclic lactam heptapeptide |
| Length | 13 residues | 7 residues |
| Molecular weight | 1646.8 g/mol | 1024.2 g/mol |
| CAS | 75921-69-6 | 121062-08-6 |
| Best suited to | MC1R and pigmentation assays | Receptor-selectivity mapping |
Why does selectivity decide the experiment?
An effect observed with melanotan-2 could come from any of four receptors without further controls. The same effect with melanotan-1 narrows to MC1R. Non-selectivity is useful for mapping and a liability for attribution.
How does PT-141 relate to these?
PT-141 is a metabolite of melanotan-2 with the C-terminal amide replaced, which shifts activity away from MC1R toward MC3R and MC4R. It is listed separately in this catalogue.
Are either the same as alpha-MSH?
Neither. Both are analogues of alpha-melanocyte-stimulating hormone carrying substitutions that resist degradation; the native hormone is a different molecule.
Common questions
Which is the cyclic one?
Melanotan-2. The cyclic lactam structure is what retains affinity across the melanocortin receptor family.
Does melanotan-1 have another name?
Afamelanotide. Both names refer to the same MC1R-selective analogue.
Where to go next
For laboratory research use only. Clinical trial results are cited as context and do not describe use of the material sold here.
