RADIATION EFFECTS ON THE NATIVE STRUCTURE OF PROTEINS - FRAGMENTATIONWITHOUT DISSOCIATION

Several proteins (avidin, carboxypeptidase B, glucose-8-phosphate dehy drogenase, glutamate dehydrogenase, maltase, and peroxidase) composed of one to six subunits were irradiated in the frozen state. Each irrad iated protein was examined by size-exclusion chromatography (SEC) and by denaturing gel electrophoresis (SDS-PAGE). All these proteins elute d from SEC as a single peak even though SDS-PAGE showed cleavage of th e polypeptide backbone of the monomers. Thus, fragmentation of the sub units did not result in dissociation of the oligomeric structure.