Radical transformation in irradiated DNA and its constituents

Electron spin resonance spectroscopy has been used to study transformation of radicals in DNA and a number of its constituents. It was found that in all the bases irradiated at 77°K, hydrogen-addition radicals were formed on warming. The following mechanism of radical transformation has been proposed: damaged species, probably ion-radicals, release hydrogen atoms on warming, which then add to the undamaged bases, preferentially thymine. Thymine need not be the place of the primary damage.