Abstract:To elucidate the mechanism of the nascent stage of DNA strand breakage by low-energy
electrons, theoretical investigations of electron attachment to nucleotides have been performed by the
reliably calibrated B3LYP/DZP++ approach ( Chem. Rev. 2002, 102, 231). The 2¡é-deoxycytidine-3¡é-
monophosphate (3¡é-dCMPH) and its phosphate-deprotonated anion (3¡é-dCMP-) have been selected herein
as models. This investigation reveals that 3¡é-dCMPH is able to capture near 0 eV electrons to form a
radical anion which has a lower energy than the corresponding neutral species in both the gas phase and
aqueous solution. The excess electron density is primarily located on the base of the nucleotide radical
anion. The electron detachment energy of this pyrimidine-based radical anion is high enough that subsequent
phosphate-sugar C-O ¨® bond breaking or glycosidic bond cleavage is feasible. Although the phosphatecentered
radical anion of 3¡é-dCMPH is not stable in the gas phase, it may be stable in aqueous solution.
However, an incident electron with kinetic energy less than 4 eV might not be able to effectively produce
the phosphate-centered radical anion either in solution or in the gas phase. This research also suggests
that the electron affinity of the nucleotides is independent of the counterion in aqueous solution.