Ready separation of proteins from nucleoprotein complexes by reversible modification of lysine residues.

Modification of proteins with citraconic anhydride altered the electrostatic relationship between cationic epsilon-NH3+ groups of lysine residues of proteins and anionic phosphate groups of nucleic acids, thereby destabilizing the nucleoprotein complex. This procedure facilitated the separation of proteins from nucleic acids at pH4-4.2. The modifying groups were then deacylated from the proteins under acidic conditions (pH3-6) at 30 degrees C.