Radiation Effects on the Native Structure of Proteins: Fragmentation without Dissociation

Several proteins (avidin, carboxypeptidase B, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, maltase, and peroxidase) composed of one to six subunits were irradiated in the frozen state. Each irradiated protein was examined by size-exclusion chromatography (SEC) and by denaturing gel electrophoresis (SDS–PAGE). All these proteins eluted from SEC as a single peak even though SDS–PAGE showed cleavage of the polypeptide backbone of the monomers. Thus, fragmentation of the subunits did not result in dissociation of the oligomeric structure.