KPV

KPV is a tripeptide corresponding to the C-terminal three residues of α-melanocyte-stimulating hormone. Reference suppliers catalogue it under the positional name α-MSH (11-13), which is the more precise designation and the one to use when reading a certificate.

A registry number to be careful about

CAS 67247-12-5 circulates widely for KPV and is wrong. That number belongs to Boc-Met-Leu-Phe-OH, an entirely unrelated protected tripeptide. The correct registry number for H-Lys-Pro-Val-OH is 67727-97-3.

The two numbers are visually similar, which is presumably how the error propagated. If a certificate of analysis quotes 67247-12-5, that certificate describes a different compound — and it is a reasonable prompt to ask what else on it was copied rather than measured.

Identity and classification

α-MSH is a 13-residue peptide. KPV is its last three residues, 11 through 13. No receptor target is assigned to the fragment in reference-supplier catalogue classification, and we make no claim about one.

As with TB-500, this is a compound whose name is a fragment designation, and the general rule applies: a fragment name without residue numbers is ambiguous. “α-MSH (11-13)” is unambiguous; “KPV” happens also to be unambiguous only because the three-letter sequence fully specifies it.

Structure

H-Lys-Pro-Val-OH. Three standard L-amino acids, free N-terminal amine, free C-terminal acid. No cyclisation, no disulfide, no amidation, no D-residues, no non-natural residues. There is essentially nothing structurally elaborate about it, which is worth saying plainly.

The lysine side-chain amine makes the peptide basic and freely water-soluble. The central proline restricts backbone flexibility and, as with any proline-containing peptide, introduces cis–trans isomerism.

Specification and characterisation

• No aromatic residues, so no 280 nm detection. Purity is assessed at 214 nm against the amide backbone. As with Selank and Epitalon, a 280 nm figure for this peptide would be meaningless.
• Poor reverse-phase retention. A basic tripeptide of 342 Da is small and polar and elutes very early on C18. Ion-pairing is essentially required, and as with Epitalon, an area-percent purity obtained near the void volume should be read alongside the method.
• Proline cis–trans isomerism can broaden the peak. Elevated column temperature sharpens it. Not an impurity.
• Mass confirmation against 342.4. Straightforward at this size.
• Amino acid analysis confirming 1:1:1 Lys:Pro:Val — a meaningful identity check on a peptide this short, where the composition fully determines the molecule.
• Counter-ion and net peptide content. Commonly supplied as the trifluoroacetate. On a 342 Da peptide with a free lysine, a single TFA counter-ion is roughly a quarter of the total mass again — so net peptide content is proportionally a much larger correction here than for the long peptides in this catalogue, and it is not a formality.

Handling and stability

Store sealed at 2–8 °C, dry, protected from light. Equilibrate in a desiccator before opening.

Chemically this is about as robust as a peptide gets: no cysteine, no methionine, no tryptophan, no asparagine, no aspartate-glycine motif. None of the degradation routes described elsewhere in this library apply. The practical risks are gravimetric — hygroscopicity and counter-ion mass — rather than chemical.

Related compounds in this library

Melanotan II and PT-141 derive from the same parent hormone, but from its central pharmacophore region rather than the C-terminus, and both are cyclic. KPV shares the parent and nothing else. Epitalon is the closest structural neighbour here — another very short, unmodified, standard-residue peptide — though basic where Epitalon is acidic.

References

Chemical, specification and analytical sources. This list is deliberately limited to chemistry and analytical references.

• Cayman Chemical, α-MSH (11-13) — formula, molecular weight, sequence, salt form
• Bachem, KPV product record — specification data
• ChemicalBook, CAS 67727-97-3 — registry confirmation
• Bachem, Handling and Storage Guidelines for Peptides — net peptide content, counter-ion, hygroscopicity

Cosmic Aminos supplies this material as a laboratory reagent for in-vitro research use only. It is not a drug, food, cosmetic or dietary supplement, is not approved by the Food and Drug Administration for any use, and is not for human or veterinary consumption. No dosing, administration or preparation guidance is provided.