A CRITICAL ANALYSIS OF THE USE OF RADIATION INACTIVATION TO MEASURE THE MASS OF PROTEIN

Measurements are presented of the radiation inactivation of four enzym es exposed to a 6 MeV proton beam. It has long been thought that the m easurement of the susceptibility of an enzyme to ionizing radiation ca n be used to determine its molecular mass. Results are frequently inte rpreted using the empirical analysis of Kempner and Macey (Biochim. Bi ophys. Acta 163, 188-203, 1963). We examine this analysis and discuss the validity and limitations of the assumptions on which it is based. Our results indicate that the specific biochemical properties of each enzyme make a significant contribution to its radiation sensitivity. ( C) 1995 by Radiation Research Society