It is one of the most frequent chemical degradation pathways of peptides and proteins in solution. The asparagine side chain attacks the neighbouring peptide bond and forms a cyclic intermediate, succinimide, which opens to give aspartate or isoaspartate. The mass rises by about 1 Da and a new negative charge appears.
Its rate depends heavily on the sequence: it is especially fast when asparagine is followed by glycine (the Asn-Gly motif), because glycine offers no hindrance. It is also accelerated by neutral or alkaline pH and by temperature.
Like all reactions that need water, deamidation is minimal in the freeze-dried peptide and progresses once it is reconstituted, especially if the solution is not kept refrigerated.
Deamidation produces an impurity that HPLC can separate and mass spectrometry can detect by its +1 Da. Looking at the sequence makes it possible to anticipate which peptides are more sensitive and to be extra careful with storage.
Related terms
Learn it in depth at the Peptide University
- Chemical degradation: the weak points of the sequence · Module 11
- Related impurities and counterions · Module 7
- Lyophilization and excipients · Module 11
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).