The effects of oxidation and protonation on the N-glycosidic bond stability of 8-oxo-2′-deoxyguanosine:: DFT study

This work is an attempt to evaluate the ability of protonation of 8-oxo-2'-deoxyguanosine (8-oxodG) and the effects of oxidation and protonation on its N-glycosidic bond stability by using the density functional theory B3LYP/6-31 ++ G(d,p) method. In all modified forms, the length of the N9-C1' bond increases as compared to the neutral system 8-oxodG. Especially, the changes are much more obvious for the di-cationic systems. The analysis for the ability of protonation indicates that for the mono-protonated systems, the 08 atom becomes the preferred protonation site in the gas phase. From the dissociation energies of the N-glycosidic bond, it has been found that the homolytic cleavage becomes more difficult upon introducing positive charge in the base ring. In contrast, these systems favor significantly the heterolytic cleavage, especially for the di-cationic systems in which the dissociation energy values are negative. The influence is most prominent with the mono-cation obtained by 08 protonation. (C) 2008 Elsevier B.V. All rights reserved.