What mass should a KPV COA show?

KPV, as Lys-Pro-Val, is C16H30N4O4 with an average mass of 342.43 g/mol and a monoisotopic mass of 342.23 Da in PubChem. A certificate should show the expected and measured values and say which kind of mass it used. An expected value near 192 means the reference came from an unrelated PubChem entry returned by a search for the name KPV.

How do I know if my KPV is real?

Test a sample from your own vial. Mass spectrometry should find 342.43 g/mol, HPLC gives purity, and an amount test reports milligrams of peptide. Because KPV is so small, also ask for counter-ion content, which can be a large share of the powder. A label, a seller's word or a certificate for another batch cannot confirm any of this.

Is Ac-KPV-NH2 the same as KPV?

No. Ac-KPV-NH2 carries an acetyl group at the N-terminus and an amide at the C-terminus, so its formula and mass differ from the free tripeptide. Both appear in published research. If your label says KPV, a test should find 342.43 g/mol; a capped version shows a different mass, which means the vial holds a different molecule.

Why could my KPV vial contain much less peptide than the label?

Partly because of salt. KPV has two basic sites that pair with counter-ions such as trifluoroacetate, and on a peptide this light those ions add a lot of weight per molecule. If the vial was filled by weighing the salt, peptide content will be well below the label. Underfilling is the other explanation, and an amount test with counter-ion data separates the two.

One of the 30 compound testing profiles

KPV

KPV is a 3-amino-acid peptide, Lys-Pro-Val (C16H30N4O4, average mass 342.43 g/mol); a test should confirm that mass, rule out capped or substituted versions of the tripeptide, and report the peptide content, because on a molecule this small the salt can be a large share of the powder.

KPV (lysyl-prolyl-valine) is the C-terminal tripeptide of alpha-melanocyte-stimulating hormone (Brzoska et al., Endocrine Reviews, 2008), and the US FDA states it has identified no human exposure data on drug products containing it (FDA, bulk substances with safety risks).

Test your KPV

Identity card

Formula: C16H30N4O4
Average mass: 342.43 g/mol
Monoisotopic mass: 342.23 Da
Length: 3 residues
Modifications: None: free N-terminal amine and free C-terminal acid (H-Lys-Pro-Val-OH)
Also sold as: Lys-Pro-Val, Lysyl-prolyl-valine, alpha-MSH (11-13)
Sequence: KPV
Note: PubChem CID 125672 is titled Msh (11-13), with synonyms Lys-Pro-Val and L-lysyl-L-prolyl-L-valine. It gives an average mass of 342.43 g/mol and a monoisotopic mass of 342.22670545 Da, recorded as 342.23. A PubChem name search for "KPV" returns CID 13294447, 2-oxo-5-phenylpentanoic acid (C11H12O3), an unrelated compound.

Source: PubChem CID 125672, Msh (11-13), Lys-Pro-Val, PubChem CID 13294447, 2-oxo-5-phenylpentanoic acid (returned for the name KPV).

Compare the mass printed on a certificate with the values above. The mass checker explains charge states and which mass a lab usually reports.

What usually goes wrong with KPV. Documented failure modes, with sources.

A reference mass taken from the wrong database entry

A PubChem name search for "KPV" returns 2-oxo-5-phenylpentanoic acid, C11H12O3 at 192.21 g/mol (PubChem CID 13294447), not the tripeptide, which is filed as Lys-Pro-Val at 342.43 g/mol (PubChem CID 125672). A certificate built from the first hit compares the sample against the wrong mass. A KPV certificate should print the formula or sequence of the reference it used; an expected mass near 192 means the wrong record.

Capped and substituted versions of the tripeptide

Research on KPV does not always use the free tripeptide: one study worked with Ac-KPV-NH2, acetylated at the N-terminus and amidated at the C-terminus (Songok et al., PLoS One, 2018), and a related tripeptide, KdPT, is described alongside KPV in the alpha-MSH literature (Brzoska et al., 2008). Capping and residue swaps change the formula, so mass spectrometry separates them. An L- to D-proline switch keeps the mass, and racemisation during synthesis is a recognised source of such diastereomers (D'Hondt et al., 2014), so only chromatography shows it.

Counter-ions on a very small peptide

KPV has two basic sites, the N-terminal amine and the lysine side chain. In synthetic peptides the number of trifluoroacetate counter-ions follows the number of positive charges, and trifluoroacetate reached up to 35% of total weight in the peptide salts studied in one paper (Erckes et al., Pharmaceuticals, 2025). On a 342 g/mol peptide, two counter-ions per molecule are a large share of the powder, so a vial filled by weighing the salt holds less KPV than its label.

Truncated and cyclised by-products

Peptide impurities include deletion sequences from incomplete synthesis steps and degradation products such as diketopiperazines (D'Hondt et al., 2014). For a tripeptide, a deletion leaves a dipeptide, Lys-Pro or Pro-Val, which mass spectrometry separates easily. A by-product that co-elutes with the main peak can still inflate a UV purity figure unless a mass detector checks the peak.

Which tests matter most

LC-MSConfirms 342.43 g/mol for Lys-Pro-Val and separates capped forms such as Ac-KPV-NH2 and dipeptide by-products by mass.
HPLC-UVGives purity and is needed to see same-mass forms such as a D-proline diastereomer.
Amino acid analysisChecks that lysine, proline and valine are present in equal proportion and gives peptide content regardless of the salt.
Counter-ion contentSeparates salt from peptide, which matters more on a 342 g/mol molecule with two basic sites than on a large peptide.

Reading KPV results

No common label amounts are listed because Tested.ph has not yet recorded KPV listings. Whatever the label says, the useful result is milligrams of KPV peptide measured against a characterised reference, with the counter-ion content stated. The net peptide content lesson explains why a genuine vial can hold less peptide than its label, and the content calculator estimates how much of a label amount is the target peptide.

Public Tested.ph results

No public KPV records yet

Each public KPV record will appear here with its identity, HPLC purity and measured amount against the label, once the first vial is tested.

FIG 13Amount against the label

Questions about testing KPV

What mass should a KPV COA show?: KPV, as Lys-Pro-Val, is C16H30N4O4 with an average mass of 342.43 g/mol and a monoisotopic mass of 342.23 Da in PubChem. A certificate should show the expected and measured values and say which kind of mass it used. An expected value near 192 means the reference came from an unrelated PubChem entry returned by a search for the name KPV.
How do I know if my KPV is real?: Test a sample from your own vial. Mass spectrometry should find 342.43 g/mol, HPLC gives purity, and an amount test reports milligrams of peptide. Because KPV is so small, also ask for counter-ion content, which can be a large share of the powder. A label, a seller's word or a certificate for another batch cannot confirm any of this.
Is Ac-KPV-NH2 the same as KPV?: No. Ac-KPV-NH2 carries an acetyl group at the N-terminus and an amide at the C-terminus, so its formula and mass differ from the free tripeptide. Both appear in published research. If your label says KPV, a test should find 342.43 g/mol; a capped version shows a different mass, which means the vial holds a different molecule.
Why could my KPV vial contain much less peptide than the label?: Partly because of salt. KPV has two basic sites that pair with counter-ions such as trifluoroacetate, and on a peptide this light those ions add a lot of weight per molecule. If the vial was filled by weighing the salt, peptide content will be well below the label. Underfilling is the other explanation, and an amount test with counter-ion data separates the two.

Sources

Brzoska T et al. Alpha-melanocyte-stimulating hormone and related tripeptides: biochemistry and future perspectives. Endocr Rev. 2008;29(5):581-602, PubMed
Certain bulk drug substances for use in compounding that may present significant safety risks, US Food and Drug Administration
PubChem CID 125672, Msh (11-13), Lys-Pro-Val, National Library of Medicine
PubChem CID 13294447, 2-oxo-5-phenylpentanoic acid, National Library of Medicine
Songok AC et al. Structural modification of the tripeptide KPV by reductive glycoalkylation of the lysine residue. PLoS One. 2018;13(6):e0199686, PLoS One (PMC)
D'Hondt M et al. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014;101:2-30, PubMed
Erckes V et al. Towards a Consensus for the Analysis and Exchange of TFA as a Counterion in Synthetic Peptides. Pharmaceuticals. 2025;18(8):1163, Pharmaceuticals (PMC)

Last reviewed 6 Oct 2026.