Two peptides with the same amino acids in a different order are different molecules with different properties. That is why the sequence is the central datum of any technical data sheet: the molecular formula, the molecular weight and the mass that should appear in the analysis are all derived from it.
Short sequences are written out in full: KPV is Lys-Pro-Val; Epitalon is Ala-Glu-Asp-Gly. For longer peptides the one-letter code is used and modifications are flagged: non-natural amino acids, amidated ends, fatty-acid chains or internal bridges.
The sequence gives rise to the secondary structure (helices and sheets), the tertiary structure (the full fold) and, in proteins made of several chains, the quaternary structure. In short peptides the primary structure usually explains almost all of their behaviour.
Confirming the identity of a batch means checking that the measured mass matches the mass calculated from the sequence. A single amino acid substitution changes the mass and can completely change the activity.
Related terms
Learn it in depth at the Peptide University
- Chemical modifications: from the natural sequence to the analog · Module 1
- Levels of structure and structure-activity relationship · Module 1
- Mass spectrometry and identity · Module 7
- Classification and solid-phase synthesis · Module 1
- Half-life engineering · Module 2
Related catalogue compounds
Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).