PT-141 10mg

What PT-141 is

PT-141 is a development code for the cyclic heptapeptide Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, whose International Nonproprietary Name is bremelanotide. The N-terminal norleucine is acetylated and sits outside a six-residue ring formed by a lactam bond between the Asp and Lys side chains. The phenylalanine is the D-enantiomer, and the molecule finishes in a free carboxylic acid rather than an amide.

That free acid is the defining detail. Melanotan 2 has the identical ring, tail and residues but ends in a C-terminal amide, so the two formulas differ only by an O swapped for an NH (C50H68N14O10 against C50H69N15O9) and the average masses by roughly 1 Da. The linear thirteen-residue Melanotan 1 is related by descent from the same parent sequence but is far heavier and simple to distinguish.

PT-141 10mg specification

How PT-141 is analyzed

PT-141 combines a hydrophobic face (Nle, D-Phe, Trp) with basic arginine and histidine, so it is retained well on C18 under ion-paired acidic conditions and elutes mid-gradient, clear of the solvent front. Unlike the amide analog, it also carries an ionizable C-terminal carboxyl, which means its retention relative to Melanotan 2 can move with mobile-phase pH and additive; the two may swap order between methods. Tryptophan gives a strong 280 nm signal, yet a purity figure read only there would miss non-aromatic impurities, so integration near 214 nm is the more honest number. The deconvoluted mass should land close to 1025.2, and reporting it to one decimal place is what separates the acid from a mislabeled amide. A peak 18 Da above the target suggests linear material in which the lactam never formed.

The published reverse-phase HPLC result on this page applies to PT-141. The vials are unmarked by batch or lot codes, and the crimp and cap color is how a vial is matched to that result.

Research contexts for PT-141

• In-vitro melanocortin receptor pharmacology, profiling binding across the MC1R to MC5R subtypes in transfected cell membranes
• Comparative ligand studies of a free-acid cyclic peptide against its C-terminal amide counterpart
• cAMP accumulation and reporter-gene assays in recombinant receptor cell lines
• High-resolution mass spectrometry method validation for 1 Da terminal differences

PT-141 is provided as a reference compound for bench-top in-vitro study and is not meant for people or animals in any form.

PT-141 questions

Are PT-141 and bremelanotide the same molecule?

Yes. PT-141 is the development code and bremelanotide is the nonproprietary name; both refer to the free-acid cyclic heptapeptide described above.

What mass should the spectrum show for PT-141?

About 1025.2 g/mol for the neutral peptide. A reading near 1024.2 would be consistent with the Melanotan 2 amide instead, which is why a whole-number result is weak evidence here.

Why does the C-terminal acid change retention?

A carboxyl group can be charged or neutral depending on pH, while an amide cannot. That makes PT-141’s retention more sensitive to mobile-phase conditions than its amide neighbor.