Quick answer
KPV is a three-residue peptide (Lys-Pro-Val, about 342 Da) matching the C-terminus of α-MSH; its small size makes synthesis simple but chromatography and quantitation unusually tricky.
- Identity: theoretical mass about 342 Da for the free tripeptide ([M+H]⁺ near 343.2 in positive-ion mode); terminally modified forms differ
- HPLC difficulty: small and polar, so it barely retains on standard C18 and can elute near the solvent front
- Detection: no aromatic residues, so UV detection relies on the peptide bond near 214 nm
- Content: counter-ions and water are a large share of a tripeptide powder, so net peptide content matters
- Product: the KPV 5 mg research vial is listed at ≥98% HPLC with sequence Lys-Pro-Val; see batch records
- Research use: For laboratory research use only; not for human consumption.
What is being tested
For laboratory research use only; not for human consumption.
KPV, lysyl-prolyl-valine, corresponds to residues 11–13 at the C-terminus of alpha-melanocyte-stimulating hormone (α-MSH, a 13-residue peptide). It lacks the central core sequence that the parent hormone uses to activate melanocortin receptors, which is part of why it is studied as a separate entity; the comparison is laid out in KPV vs. α-MSH, and background is in the KPV research overview.
KPV is only three residues long, and while its small size simplifies synthesis, confirming a lot's identity and purity remains standard practice before use in inflammation-model research. The smallness cuts both ways. There are few places for a synthesis error to hide, but the analytical methods built for 20- to 40-residue peptides do not transfer cleanly to a molecule this small.
| Property | KPV |
|---|---|
| Sequence | Lys-Pro-Val |
| Parent | C-terminal tripeptide (residues 11–13) of α-MSH |
| Approximate mass (free tripeptide) | About 342 Da |
| Aromatic residues | None (weak UV absorbance beyond the peptide bond) |
| Character | Small, polar, basic (free N-terminal amine plus lysine side chain) |
| Supplied form (V8 listing) | Lyophilized powder, 5 mg, ≥98% HPLC |
Reversed-phase HPLC
HPLC resolves the intended tripeptide from incomplete-coupling byproducts and other minor synthesis artifacts, with purity read per understanding HPLC purity.
Small, hydrophilic peptides present their own chromatographic difficulty: KPV is poorly retained on standard C18 columns and can elute close to the solvent front, where salts and other unretained material also appear. Methods therefore start at very low organic content with an ion-pairing acid, or use a polar-retentive column, to move the peak into a clean region of the trace. Common approaches include an aqueous-compatible C18 phase run from near-zero organic, a stronger ion-pairing agent such as trifluoroacetic acid, or hydrophilic-interaction chromatography (HILIC), which reverses the usual retention logic and holds polar peptides well.
Detection is a second constraint
KPV contains no tryptophan, tyrosine or phenylalanine, so there is no useful absorbance at 254 or 280 nm. Detection depends on the peptide bond near 214–220 nm, and a tripeptide has only two of them. The signal is therefore small compared with a longer peptide at the same mass load, and impurities that lack strong absorbance can be under-counted. A report that states the wavelength and sample load is more informative than one that gives a percentage alone.
Reading the KPV chromatogram
HPLC purity for KPV is reported as area percent: the main peak's share of all UV-absorbing material detected, normally at 214–220 nm. Three things make that number trustworthy:
- The method must be stated, including column chemistry, mobile phases, and gradient slope, because resolution determines what counts as a separate impurity.
- The trace should show a clean baseline and a main peak free of fronting, tailing, or shoulders that hint at co-eluting species.
- The integration table should account for every minor peak, so the percentage reflects the whole sample and not a selectively drawn window.
Because KPV elutes early, one further check is that the main peak is clearly separated from the solvent-front disturbance. A "pure" peak sitting inside the solvent front cannot be separated from salts, and the percentage is then close to meaningless.
Mass spectrometry for identity
Because KPV is so small, mass spectrometry confirmation is comparatively fast and unambiguous, distinguishing it cleanly from the larger parent sequence α-MSH or related fragments such as melanotan-II — see HPLC vs. mass spectrometry.
The theoretical mass of the free tripeptide is about 342 Da, against roughly 1665 Da for alpha-MSH and 1024 Da for melanotan-II. In positive-ion electrospray the protonated ion appears near m/z 343. Some KPV is supplied with an acetylated N-terminus or amidated C-terminus, which changes the expected value, so the certificate should state the form. Diastereomers containing a D-residue have identical mass and are assessed chromatographically.
| Species | Approximate neutral mass change vs. KPV | Detected by |
|---|---|---|
| Free tripeptide (target) | Reference, about 342 Da | MS, HPLC |
| N-acetylated form | About +42 Da | MS |
| C-terminal amide form | About −1 Da | MS (needs adequate resolution at this mass) |
| Deletion product (dipeptide, missing one residue) | Lower by the residue mass (Val 99, Pro 97, Lys 128 Da) | MS, HPLC |
| Epimer (D-residue substitution) | None | HPLC only |
Why simplicity doesn't remove the need for testing
KPV's research appeal is chemical simplicity paired with a defined activity profile (see its mechanism of action); skipping verification on a "simple" peptide still risks building results on material of unknown purity, the same risk that applies to any research peptide. A small peptide is also easier to confuse with look-alikes: a mislabeled vial of another short peptide would not show up on an HPLC trace alone, but would be obvious from the mass.
There is also a quantitative point. With so little mass per molecule, counter-ions and moisture make up a larger share of a tripeptide powder than of a long peptide. A trifluoroacetate counter-ion weighs about 114 Da and KPV has two basic sites, so a salt form can plausibly carry a substantial fraction of the weighed mass as non-peptide material. Net peptide content is therefore especially relevant for KPV when preparing solutions for cell-culture assays of NF-kB or cytokine signaling, where the working concentration is the variable under study.
What an HPLC percentage leaves out
Two quantities are easy to confuse: purity and content. Purity is the proportion of UV-absorbing peptide that is the target molecule. Content is the proportion of the dry powder that is peptide at all, once counter-ions and residual water are subtracted. A lot can be very pure and still carry a meaningful salt and moisture fraction, which matters when preparing standards by mass. The peptide calculator is a convenient way to plan reconstitution volumes and resulting concentrations; if the certificate reports a net peptide content, apply it as a correction factor to the labeled vial mass before calculating.
Documentation to expect
A lot-specific certificate of analysis with HPLC purity and mass-spec identity — see how to read a CoA. A useful KPV certificate is specific and traceable. It should show:
- The lot number, linking the document to a physical vial
- Chromatographic purity with the underlying trace and method
- Mass-spectrometric identity, with theoretical and measured values side by side
- The exact form (free, acetylated or amidated)
- Who ran the tests and when
Lot-level documents are available from the CoA library. For the supplied KPV vial, the product page states the sequence as Lys-Pro-Val and a refrigerated storage condition, so the certificate should be consistent with those.
KPV inside other products
KPV also appears as a motif in combined research materials, and each has its own verification considerations. In GHK-KPV, the two tripeptide units are joined in one sequence, so the mass is a sum of the parts rather than a KPV mass. In the KLOW stack, KPV is one component of a blend, which means the blend's certificate must account for each constituent separately. A KPV-only report cannot be borrowed for either product.
Keeping a verified lot verified
Verified purity is not permanent. KPV stored as dry powder in cold, dark conditions holds its profile far longer than material kept in solution, where hydrolysis, oxidation, and adsorption to container surfaces proceed more quickly. The product page gives the supplied storage guidance: refrigerate at 2–8 °C, or at −20 °C for long-term storage, protected from heat, moisture and light. Recording reconstitution dates, minimizing freeze-thaw cycles, and keeping a retained aliquot for re-analysis gives a lab a way to rule material degradation in or out when a result looks anomalous. General storage principles are in storing research peptides.
Frequently asked questions
What mass confirms KPV identity?
About 342 Da for the unmodified tripeptide, seen as an ion near m/z 343 in positive-ion mode. Terminally modified versions differ, so the certificate of analysis should name the exact form and its theoretical mass.
Why is KPV harder to analyze by HPLC than larger peptides?
Its small size and polarity give it little affinity for a reversed-phase column. Without a suitably adapted method it elutes too early for impurities to be separated and measured reliably.
Why is UV detection weak for KPV?
It has no aromatic residues, so it does not absorb at 254 or 280 nm. Detection relies on the peptide bond near 214 nm, and a tripeptide has only two of those bonds.
Can mass spectrometry detect a D-valine or D-proline impurity?
No. A diastereomer has the same mass as the target. It must be resolved chromatographically, usually as a separate or shouldered peak.
Does ≥98% purity mean 98% of the powder is KPV?
No. Purity is a ratio of UV-absorbing species. Counter-ions and water also contribute to the weighed mass, and for a tripeptide that share can be large.
Is KPV used in joined or blended research peptides?
Yes. It is one motif in GHK-KPV and a component of the KLOW stack, each of which has its own verification considerations.
Where do I find the batch record for my vial?
On the CoA page, matched by lot number. If you are comparing sources first, where to buy KPV lists what to look for.
Research Use Only. For laboratory research use only; not for human consumption. Supplied strictly for laboratory research and development, not for human or veterinary use, and not for diagnostic purposes. This article is research education, not usage guidance.
References
- KPV research overview (V8 Peptides)
- What is KPV peptide (V8 Peptides)
- Understanding HPLC purity (V8 Peptides)
- HPLC vs. mass spectrometry (V8 Peptides)
- How to read a CoA (V8 Peptides)
- KPV product specification (V8 Peptides)