Radiation target analysis of enzymes with stable free radicals

Irradiation of ribonucleotide reductase yielded a functional target size of the entire tetramer. The free radical-containing R2 subunit target size fo r activity was much larger than the physical structure while that for loss of structure was similar to the monomer. This indicates that indirect effec ts of ionizing radiation removed the free radical in the isolated R2 withou t substantial structural damage. Preliminary results of galactose oxidase i ndicate a target mass equal to the monomer size. No indirect effects were o bserved on the free radical which is not accessible to the solvent. Publish ed by Elsevier Science Ltd.