Electron attachment to the DNA bases adenine and guanine and dehydrogenation of their anionic derivatives: Density functional study

摘要

Density functional theory (DFT) calculations have been used to explore electron attachment to the purines adenine and guanine and their hydrogen atom loss. Calculations show that the dehydrogenation at the N9 site in the adenine and guan: ne transient anions is the lowest-cost channel of hydrogen loss, and the N9-H bond scission has Gibbs free energies of dissociation Delta H degrees of 8.8 kcal mol(-1) for the anionic adenine and 13.9 kcal mol(-1) for the anionic guanine. The relatively high feasibility of low-energy electron (LEE)-induced N9-H bond cleavage in the purine nucleobases arises from high electron affinities of their H-deleted counterparts. Unlike adenine, other N-H bond dissociations are competitive with the N9-H bond fission in the anionic guanine. The replacement of hydrogen in the ring of purine has a significant effect on the N9-H bond fragmentation. (c) 2006 Wiley Periodicals, Inc.