Effect of Ionizing Radiation on Protein Denaturation

Abstract

IT has long been known that the stability of proteins with respect to denaturation (as defined by aggregation) is lowered upon treatment with ionizing radiation¹. Detailed studies are lacking, however. We have found that the denaturation of solutions of egg albumin and hæmoglobin subjected to X-rays (the denaturation kinetics of which in the intact state is known²) can be defined quantitatively by the usual coagulation method, its validity being established by order of reaction studies on dilutions of the complex irradiated systems. By this procedure it was found that the heterogeneous protein material of these systems was (at ordinary pH) initially undenatured and contained relatively large quantities of species of decreased thermal stability, characterized by much reduced values of both the Arrhenius frequency factor (ν) and the energy of activation (E) of their first-order denaturation velocity-constants.