Abstract
Electron spin resonance has been used for the study of the radicals in γ-irradiated single crystals of 5′-UMP (sodium salt). Six types of radicals have been identified at room temperature. They are formed by addition of H atoms to C5, C6, 02 and 04, and by an OH addition to C5 of the uracil ring. Five of these radicals have an appreciable spin density on C6. The radicals with the addition to C5 or C6 are less stable than the essentially planar radicals with the H addition to 02 and 04.