Melanotan I vs Melanotan II: Research Comparison

Research-use notice: This page records catalogue differences only: sequences, receptor classes, fill sizes, and Certificate of Analysis rows. It is not a protocol. It is not medical or veterinary advice, and it does not rank materials for personal use. BlueNex Labs materials are research use only. Research-use-only labelling is not a Health Canada authorization and it does not create a Drug Identification Number.

Melanotan I and Melanotan II are both synthetic analogues discussed against melanocortin receptors, and the shared nickname is why receiving logs collapse them. The molecules are not the same length, not the same shape, and not the same catalogue record. This page keeps the sequence, the receptor class named in the primary papers, and the BlueNex Labs lots apart. It does not rank the vials, and it does not describe either solid as a tanning product. For the longer receptor essay, see Melanotan receptor research. For the class note, see melanocortin ligands. For the glossary line, see melanocortin.

Sequence and shape

Alpha-melanocyte-stimulating hormone is the 13-residue reference peptide Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. Sawyer and colleagues, in Proceedings of the National Academy of Sciences in 1980, described the linear analogue with norleucine in place of methionine at position 4 and D-phenylalanine in place of phenylalanine at position 7 (PMID 6777774). That analogue, [Nle4, D-Phe7]-alpha-MSH, is the sequence literature associates with Melanotan I, also called afamelanotide in pharmaceutical naming. Thirteen residues, a linear chain, an N-terminal acetyl group, and a C-terminal amide are the structural facts this catalogue uses. The 1980 paper also reports bioassays. Those assay results stay in that paper. They are not a specification printed on a research vial.

Melanotan II is shorter and closed. Al-Obeidi and colleagues, in the Journal of Medicinal Chemistry in 1989, described cyclic lactam analogues of the alpha-MSH 4-10 region (PMID 2555512). The sequence associated with Melanotan II is the heptapeptide Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge between the aspartate and lysine side chains. Seven residues and a ring are not a trimmed copy of the 13-residue chain. Cyclization changes the calculated mass and the conformational ensemble a mass spectrometer and a chromatograph will see. A remembered "Melanotan" label cannot choose between those two masses.

Receptor class in the literature

Melanocortin receptors MC1R, MC3R, MC4R, and MC5R are G protein-coupled receptors. MC2R is the ACTH receptor and is not the usual frame for these two analogues. Papers that came after the receptor genes were cloned discuss the linear [Nle4, D-Phe7] analogue heavily in melanocyte-receptor models and discuss the cyclic heptapeptide across more than one melanocortin subtype, including MC1R, MC3R, MC4R, and MC5R. A subtype sentence in a paper is a description of that assay. It is not a second product name, and it is not a reason to substitute vials. This page does not translate a receptor panel into a consumer category.

Two neighbouring catalogue sequences are easy to paste onto the same line and should not be. PT-141 is a cyclic melanocortin ligand related to Melanotan II in the literature and sold here as its own 10 mg URL. Related is not identical. For the note, see PT-141. KPV is Lys-Pro-Val, three residues from the C terminus of alpha-MSH, with its own note. Three residues are not a 13-residue analogue and they are not the cyclic heptapeptide.

Catalogue sizes and lot files

Melanotan I is listed as a 10 mg vial at /shop/melanotan-i. Melanotan II is listed as a 10 mg vial at /shop/melanotan. Price and stock stay on those pages. This comparison does not set either one.

For the cyclic peptide's file, see the Melanotan II 10 mg certificate row. For the linear peptide's file, see the Melanotan I 10 mg certificate row. Janoshik task 225890, sample MT1, batch not stated, analysis conducted 28 Aug 2026, reports Melanotan 1 9.31 mg and purity 99.480%. That report has no endotoxin result. That Melanotan I file does not document Melanotan II, PT-141, or KPV. How to read a peptide COA still applies: area percent is purity under a stated method, and the observed mass is the identity check against the sequence you named. A cyclic amide and a linear chain will not share that mass.

What to write beside the vial

A complete line names the sequence, the shop slug, and the lot or the statement that no lot is published. "Melanotan" alone fails that line. "Melanocortin" alone fails it too. If the purchasing request says only the receptor subtype, send it back for a slug. The cellular category hub also lists matrix peptides. Shared navigation is not shared identity. Orders ship inside Canada after Interac e-Transfer, on Canada Post Xpresspost. For the operational note, see Canada laboratory procurement. This URL is not a city page. Research use only. Not for human or veterinary use.