In oriented DNA, ESR studies have been performed on the decay of the primary anionic base free radicals, γ-induced at 77 K, and the formation of the secondary hydrogen addition free radicals on the thymine base at different elevated temperatures. Quantitatively and kinetically there is a close correspondence between these two processes, thus confirming the reaction pattern$\dot{{\rm T}}^{-}+{\rm XH}^{+}\rightarrow \dot{{\rm T}}{\rm H}+{\rm X}$, where$\dot{{\rm T}}^{-}$ is the anionic and ṪH the hydrogen addition free radical on thymine, and X indicates that the source of hydrogen ions is not known. The kinetics of the free radical conversion can be described by a model in terms of a fractional first (or pseudo-first)-order reaction between spatially correlated pairs of$\dot{{\rm T}}^{-}$ and${\rm XH}^{+}$ with a distribution of activation energies.

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