Carboxyl group on Glutamate and Aspartate resides on a protein

GEE labeling of OCP under dark and light conditions to track the protein conformational changes

Primary amine groups of N-terminus and Lysine residues on proteins

The kinetics of primary modification by acylating reagents is strongly pH dependent: A pH of 8.5 to 9.5 is usually optimal for modifying lysine residues, in contrast to the amino group at a protein’s N-terminus that usually has a pKa of ~7. Succinimidyl esters are mostly used and reliable reagents for amine modification because the amide bonds they form are as stable as peptide bonds. More readings,