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A Comprehensive Study of Sugar Radicals in Irradiated DNA

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journal contribution
posted on 10.09.1998 by Stacey D. Wetmore, Russell J. Boyd, Leif A. Eriksson
Density functional theory is used to study the energetics, geometries, and hyperfine couplings in sugar radicals which are generated through irradiation of DNA. The C4‘−S and the C3‘−S radicals are determined to be the lowest lying species of the radicals formed through abstraction of a hydrogen or a hydroxyl group from a model of the sugar present in DNA, respectively. The C2‘ radical has the highest energy and the smallest degree of ring puckering of all possible carbon-centered radicals formed via hydrogen abstraction. In addition to the possible dehydrogenated and dehydroxylated products, various radicals which lead to substantial ring alterations, such as ring breaks or flattening of the ring, are also studied. In most cases, the calculated hyperfine coupling constants directly support the assignment of the experimentally observed couplings to the specific radicals. The effects of rotation about the C5‘C4‘ bond on the HFCCs in the C5‘ and O5‘ radicals are examined in order to compare the experimental and theoretical results. In cases where experiment and theory differ, the calculated results facilitate the assignment of the experimental couplings to alternative radicals.