α-MSH and KPV compared

KPV is the C-terminal tripeptide of α-MSH, residues 11–13, with free termini where α-MSH is amidated and its N-terminus acetylated.

Sequences side by side

KPV is a continuous stretch of α-MSH: 3 residues in common, aligned below by α-MSH's numbering. In each column the upper residue is α-MSH's and the lower is KPV's. Positions outside the shorter sequence are dimmed.

Termini and bridges also differ: N-terminus: α-MSH N-acetyl, KPV free amine; C-terminus: α-MSH amide, KPV free acid.

Calculated properties

Calculated from each structure

Property	α-MSH	KPV	Difference (KPV − α-MSH)
Residues	13	3	−10
Molecular formula	C77H109N21O19S	C16H30N4O4
Monoisotopic mass (Da)	1,663.7929	342.2267	−1,321.5662
Average mass (g/mol)	1,664.91	342.44	−1,322.47
Net charge at pH 7	1.2	1.0	−0.3
Isoelectric point	10.44	9.70	−0.74
Hydropathy (GRAVY)	-0.92	-0.43	+0.49
ε280 (M−1 cm−1)	6,990	0

Telling them apart by mass spectrometry

The monoisotopic masses differ by 1,321.5662 Da, which any routine mass spectrometer resolves.

Expected protonated ions (monoisotopic m/z)

Ion	α-MSH	KPV
[M+H]+	1,664.8002	343.2340
[M+2H]2+	832.9037	172.1206
[M+3H]3+	555.6049	115.0828

Telling them apart by HPLC

They differ greatly in size (13 and 3 residues), so their reversed-phase retention cannot be estimated from average hydropathy; size, charge and the residues at the ends all contribute. They are usually well separated. Retention depends on the whole molecule and on the method, so the order is confirmed by running both, or by mass spectrometry of each peak.

Analytical variants each can form

The sequence-specific variants from each entry. A variant only one of them can form is a quick way to tell which is which, and a reminder of what to look for in each.

Sequence-specific variants

Variant	Mass change	α-MSH	KPV
Methionine oxidation	+15.995 Da per oxidized residue	Yes	No
Tryptophan oxidation	+15.995 or +31.990 Da	Yes	No
C-terminal amide	free-acid variant +0.984 Da	Yes	No

Full details, with isotope patterns and fragment ions, are on each entry: α-MSH and KPV. Both are compared with the rest of their family on the family page.

Sources & Further Reading

1. Prohaska T, Irrgeher J, Benefield J, Böhlke JK, Chesson LA, Coplen TB, et al. Standard atomic weights of the elements 2021 (IUPAC Technical Report). Pure and Applied Chemistry 2022;94(5):573–600. doi:10.1515/pac-2019-0603
2. Wang M, Huang WJ, Kondev FG, Audi G, Naimi S. The AME 2020 atomic mass evaluation (II). Tables, graphs and references. Chinese Physics C 2021;45(3):030003. doi:10.1088/1674-1137/abddaf
3. Rice P, Longden I, Bleasby A. EMBOSS: the European Molecular Biology Open Software Suite. Trends in Genetics 2000;16(6):276–277. doi:10.1016/S0168-9525(00)02024-2
4. Pace CN, Vajdos F, Fee L, Grimsley G, Gray T. How to measure and predict the molar absorption coefficient of a protein. Protein Science 1995;4(11):2411–2423. doi:10.1002/pro.5560041120
5. Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. Journal of Molecular Biology 1982;157(1):105–132. doi:10.1016/0022-2836(82)90515-0
6. Meija J, Coplen TB, Berglund M, Brand WA, De Bièvre P, Gröning M, et al. Isotopic compositions of the elements 2013 (IUPAC Technical Report). Pure and Applied Chemistry 2016;88(3):293–306. doi:10.1515/pac-2015-0503
7. Roepstorff P, Fohlman J. Letter to the editors: proposal for a common nomenclature for sequence ions in mass spectra of peptides. Biomedical Mass Spectrometry 1984;11(11):601. doi:10.1002/bms.1200111109
8. Biemann K. Contributions of mass spectrometry to peptide and protein structure. Biomedical and Environmental Mass Spectrometry 1988;16(1–12):99–111. doi:10.1002/bms.1200160119
9. Geiger T, Clarke S. Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation. Journal of Biological Chemistry 1987;262(2):785–794. doi:10.1016/S0021-9258(19)75855-4
10. Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 2010;27(4):544–575. doi:10.1007/s11095-009-0045-6
11. D'Hondt M, Bracke N, Taevernier L, Gevaert B, Verbeke F, Wynendaele E, et al. Related impurities in peptide medicines. Journal of Pharmaceutical and Biomedical Analysis 2014;101:2–30. doi:10.1016/j.jpba.2014.06.012

Cosmic Peptides. (2026, October 25). α-MSH and KPV compared. Cosmic Peptides Research Library. Retrieved October 26, 2026, from https://cosmicpeptides.com/research/peptides/compare/alpha-msh-vs-kpv

@misc{cosmicpeptides_research_peptides_compare_alpha_msh_vs_kpv,
  author       = {{Cosmic Peptides}},
  title        = {α-MSH and KPV compared},
  howpublished = {Cosmic Peptides Research Library},
  year         = {2026},
  month        = oct,
  url          = {https://cosmicpeptides.com/research/peptides/compare/alpha-msh-vs-kpv},
  urldate      = {2026-10-26},
  note         = {Last reviewed 2026-10-25}
}

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