Deamidation

[1] In the deamidation of an asparagine residue under physiological conditions, the side chain is attacked by the nitrogen atom of the following peptide group (in black at top right of Figure), forming an asymmetric succinimide intermediate (in red).

Recently reported novel ERLIC-MS/MS method would enhance the separation of deamidated and non-deamidated peptides with increased identification and quantitation quantification.

[4] Mass spectrometry is commonly used to characterize deamidation states of proteins, including therapeutic monoclonal antibodies.

This can prove problematic in the case of therapeutic proteins which can be mischaracterized in QC protocols if a large percentage of detected deamidation is due to artifacts.

[1] Deamidation proceeds much more quickly if the susceptible amino acid is followed by a small, flexible residue such as glycine whose low steric hindrance leaves the peptide group open for attack.