DNA constituents are effectively decomposed via dissociative electron attachment (DEA). However, the DEA contribution to radiation damage in living tissues is a subject of ongoing discussion. We address an essential question, how aqueous environment influences the DEA to DNA. In particular, we report experimental fragmentation patterns for DEA to microhydrated 2-deoxycytidine 5-monophosphate (dCMP). Isolated dCMP was previously set as a model to describe mechanisms of DNA-strand breaks induced by secondary electrons and decomposes primarily by dissociation of the C-O phosphoester bond. We show that hydrated molecules decompose via dissociation of the C-N glycosidic bond followed by dissociation of the P-O bond. This significant change of the proposed mechanism can be interpreted by a reactive role of water in the postattachment dynamics. Comparison of the fragmentation with previous macroscopic irradiation studies suggests that the actual contribution of DEA to DNA radiation damage in living tissue is rather small.

Deptartment of Nuclear Chemistry Faculty of Nuclear Sciences and Physical Engineering Czech Technical University Prague Brehová 7 115 19 Prague Czech Republic

J Heyrovský Institute of Physical Chemistry v v i The Czech Academy of Sciences Dolejškova 3 18223 Prague Czech Republic

Normandie Univ ENSICAEN UNICAEN CEA CNRS CIMAP 14000 Caen France

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