title: DFT reinvestigation of DNA strand breaks induced by electron attachment.
abstract: The benchmark study of DFT methods on the activation energies of phosphodiester C3'-O and C5'-O bond ruptures and glycosidic C1'-N bond ruptures induced by electron attachment was performed. While conventional pure and hybrid functionals provide a relatively reasonable description for the C1'-N bond rupture, they significantly underestimate the energy barriers of the C-O bond ruptures. This is because the transition states of the later reactions, which are characterized by an electron distribution delocalized from the nucleobase to sugar-phosphate backbone, suffer from a severe self-interaction error in common DFT methods. CAM-B3LYP, M06-2X, and ωB97XD are the top three methods that emerged from the benchmark study; the mean absolute errors relative to the CCSD(T) values are 1.7, 1.9, and 2.2 kcal/mol, respectively. The C-O bond cleavages of 3'- and 5'-dXMP(•-), where X represents four nucleobases, were then recalculated at the M06-2X/6-31++G**//M06-2X/6-31+G* level, and it turned out that the C-O bond cleavages do not proceed as easily as previously predicted by the B3LYP calculations. Our calculations revealed that the C-O bonds of purine nucleotides are more susceptible than pyrimidine nucleotides to the electron attachment. The energies of electron attachment to nucleotides were calculated and discussed as well.
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 807, Taiwan.
authors.forename: Hsing-Yin
authors.initials: HY
authors.lastname: Chen
authors.forename: Po-Yu
authors.initials: PY
authors.lastname: Yang
authors.forename: Hui-Fen
authors.initials: HF
authors.lastname: Chen
authors.forename: Chai-Lin
authors.initials: CL
authors.lastname: Kao
authors.forename: Li-Wenm
authors.initials: LW
authors.lastname: Liao
mesh_terms: D004249:DNA Damage; D004583:Electrons