Melanotan II, written MT-II in most of the older literature, is the cyclic lactam peptide that came out of Mac Hadley and Victor Hruby's group at the University of Arizona in the mid-1980s. The brief at the time was unromantic: design a melanocortin agonist stable enough to survive in plasma, so it could be tested as a non-UV route to skin pigmentation and, in theory, reduce melanoma risk. The molecule they ended up with is a seven-residue ring closed through a lactam bridge between the side chains of Asp5 and Lys10. That ring is the reason MT-II behaves the way it does in receptor assays.

Why the ring matters at the bench

Native alpha-MSH is a thirteen-residue linear peptide and falls apart fast. Closing the active core into a constrained ring kept the pharmacophore in place and pushed potency up by a couple of log units against the cloned melanocortin receptors. MT-II is non-selective on purpose: it activates MC1R, MC3R, MC4R and MC5R. For receptor-pharmacology work, that breadth is the feature, not the bug. It is the standard reference agonist when a lab needs a peptide that lights up the whole melanocortin family in a single assay, before narrowing in with a more selective tool.

The lineage that gets cited everywhere

MT-II is the structural parent of PT-141 (Bremelanotide). The Palatin team took the cyclic core, cleaved the C-terminal amide back to a carboxylic acid, and got a molecule that retained MC3R and MC4R activity while dropping the pigment-driving MC1R response. If you are running a comparative receptor study or writing a chapter on melanocortin medicinal chemistry, the MT-II to Bremelanotide arc is the worked example most reviews use. Worth having the parent compound on the bench rather than relying on the metabolite alone.

Provenance of the powder

Lyophilised MT-II at 10 mg per glass vial, sealed under inert atmosphere
Purity 98 percent or higher by reverse-phase HPLC, identity confirmed by ESI-MS
Synthesised at a UK or EU contract peptide house we have audited in person
Lot-specific Certificate of Analysis with the actual chromatogram and MS trace, not a generic template

We do not list MT-II from unverified Asian re-packers. The recurring failure mode on this peptide is not gross purity, it is acetate counter-ion drift and trace TFA carry-over, both of which quietly skew MC1R EC50 numbers in functional assays. If a batch you receive does not match its CoA, refund. That rule applies across the catalogue.

Holding it stable

Lyophilised MT-II is tolerant for shipping but should move to minus 20 C on arrival for any storage past a few weeks. Once reconstituted in bacteriostatic water or sterile saline, refrigerate and treat the solution as short-lived for assay work where receptor data has to stand up to review. The acetate salt is mildly hygroscopic, so cap tightly between uses.

Stock is held in the UK and roughly nine in ten UK orders are with the courier inside 48 hours. If you need ten vials or more for a longer protocol, message support rather than clicking add-to-cart ten times. Bulk pricing is set by a quick conversation, not a calculator. Live chat is staffed during UK hours by people who actually handle the orders, so questions about reconstitution volume or a CoA peak get a real answer.

Sold strictly for in vitro laboratory research. Not for human or veterinary use. UK 18+.

Tanning

Melanotan II