KPV: structure and analysis

What it is

KPV is a tripeptide with the sequence lysine-proline-valine, corresponding to the C-terminal fragment of alpha-melanocyte-stimulating hormone. Three residues makes it, with GHK, the shortest compound in this catalogue.

Its relationship to α-MSH is structural: it is a fragment of that hormone's sequence, which is why it groups with the melanocortin peptides despite bearing no resemblance to the cyclic heptapeptides in that class.

The proline in the middle position imposes a conformational constraint that a more flexible residue would not.

How it is produced

Assembled by solid-phase peptide synthesis: the chain is built one residue at a time on an insoluble resin support, then cleaved from the resin, deprotected and purified — most commonly by reversed-phase high-performance liquid chromatography. The purified material is lyophilized to a dry solid.

The impurity profile that appears on a certificate is a record of where that process was imperfect: deletion sequences from an incomplete coupling, truncated chains, and species retaining a protecting group.

Confirming identity

Mass spectrometry confirms a three-residue composition. At this size the measurement is very precise in absolute terms, and any deviation from the expected mass is proportionally large.

Analytical considerations

The dominant analytical challenge is retention rather than resolution. A charged tripeptide is barely retained on a reversed-phase column under conditions suitable for longer sequences: it elutes close to the injection front, where it can be poorly separated from small-molecule reagent residues.

A purity method for KPV therefore has to be built for a small, basic, polar analyte. A figure produced by a generic gradient is not a reliable one, which is a good illustration of why a certificate states its method rather than only its result.

What its certificate reports

A certificate for a lot of this material names the lot, names the issuing laboratory, and states for each parameter both the method used and the specification the result was measured against. Identity and purity are the two core results; net peptide content states how much of the fill weight is actually peptide.

A certificate belongs to a lot, not to a product line. When a new lot is released it is tested again, and the certificate published against it is that lot's certificate — a previous lot's result is never carried forward.

Research use only

This page describes structure and analysis. It makes no claim about what this compound does, and none should be inferred from it. Material is supplied for laboratory research use only: it is not a drug, food, dietary supplement, cosmetic or medical device, it is not for human or veterinary consumption, and no dosing, administration or reconstitution guidance is provided for any such use.