PT-141 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.

PT-141 and Melanotan II are easy to collapse into one "cyclic melanocortin" line. The residue order inside the ring matches. The C terminus does not. Melanotan II is the amide. PT-141 is the acid. That single difference changes the calculated mass, and it is why the catalogue uses two shop URLs. This page compares those records. For the linear-versus-cyclic page, which separates Melanotan I from Melanotan II, see Melanotan I versus Melanotan II. KPV is a third, shorter fragment and is not either vial. This page is not a protocol.

The same ring, a different terminus

Melanotan II is the cyclic lactam heptapeptide Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. 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 lactam bridge runs between the aspartate and lysine side chains. Seven residues, an N-terminal acetyl group, a norleucine, a D-phenylalanine, and a C-terminal amide are the identity marks this catalogue uses for that name. The linear 13-residue analogue associated with Melanotan I is a different mass. It is not reviewed again here.

PT-141, also called bremelanotide, is the same cyclic scaffold with a C-terminal carboxylic acid: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH. Molinoff and colleagues discussed that cyclic melanocortin ligand, as a relative of the Melanotan II amide, in the Annals of the New York Academy of Sciences in 2003 (PMID 12851303). This page cites the paper for the structural relationship. It does not restate the paper's title, and it does not copy assay endpoints onto a research vial. Amide versus acid is the catalogue difference. A remembered "Melanotan" label cannot choose between those two masses.

For the class note, see melanocortin ligands. For the glossary line, see melanocortin. For the PT-141 note, see PT-141. For the broader receptor overview, see Melanotan receptor research. Alpha-MSH remains the 13-residue reference peptide in that literature. Neither shop vial is that linear reference, and neither is KPV.

Two published rows, one for each C terminus

On the September 20, 2026 review, Melanotan II is published at the Melanotan II 10 mg certificate row. PT-141 has its own report on the PT-141 10 mg certificate. Neither report covers the other peptide. A Melanotan II, Melanotan I, or KPV report does not document a PT-141 vial. How to read a peptide COA still applies to the file that exists: area percent under the stated method, and observed mass against the amide you named. An acid and an amide will not share that mass. When you open the PT-141 report, check that the sample name and mass match the C-terminal acid. Certificate of Analysis and amino-acid residue are the glossary lines for that check.

Both listings are 10 mg. Shared fill size is not shared identity. Cyclization already separates this pair from Melanotan I. The terminus separates the two cyclic names from each other. Write the C-terminal form in the same sentence as the shop slug. "Cyclic melanocortin, 10 mg" fails that sentence.

Receiving and what not to merge

The solids are lyophilized. Open the parcel the day it arrives and store the sealed vial under the temperature on the product note. This page does not list a solvent volume. A cake that looks different after a cold Canada Post parcel is not an identity test. Do not heat a very cold vial. For the receiving note, see peptide storage for Canadian laboratories.

If the purchasing request names only the receptor, send it back for a slug. Sold-out status on either card is inventory. It does not convert the acid into the amide, and it does not create a backorder. Component language from a blend page does not belong here. These are single-sequence vials.

The practical line in the notebook is the C terminus, written out: acid for PT-141, amide for Melanotan II. Add the shop slug and the 10 mg fill. Then add the matching library URL: the Melanotan II 10 mg certificate for the amide, or the PT-141 10 mg certificate for the acid. Do not let a shared lactam drawing erase that last word. Melanotan I remains the linear chain on the other comparison. KPV remains Lys-Pro-Val. The desk is 4309 Canada Way, Burnaby, BC V5G 1J3. Labels use a Port Moody PO Box. Fulfilment can put both cyclic vials in one parcel. The masses still differ.

Canada fulfilment

Both cards sit on the cellular category hub beside matrix peptides. A melanocortin ligand is not a copper tripeptide and not a pentadecapeptide. Do not stretch a GHK-Cu or BPC-157 certificate across this pair. Payment is Interac e-Transfer. Parcels move on Canada Post Xpresspost inside Canada. For the operational page, see Canada laboratory procurement. Research use only. Not for human or veterinary use. This page is not a protocol.