Molecular structural effects produced in proteins by reaction with succinic anhydride.

Abstract The reaction of three proteins with succinic anhydride has been investigated. At pH 8 and 0°, the reagent attacks specifically and exhaustively at the free amino groups of the proteins, replacing a group which is positively charged near neutral pH with one which is negatively charged. These fully succinylated protein derivatives, near neutral pH, exhibit large increases in intrinsic viscosity and decreases in sedimentation constant, which indicate an unfolding or expansion of the protein molecules. This is attributed to the electrostatic repulsions produced by the large numbers of negative charges placed on the molecules.