title: Ultrafast repair of irradiated DNA: nonadiabatic ab initio simulations of the guanine-cytosine photocycle.
abstract: Nonadiabatic first-principles molecular dynamics simulations have been performed of the photoexcited Watson-Crick guanine-cytosine (GC) DNA base pair in the gas phase and in aqueous solution. An excited state coupled proton-electron transfer (CPET) from G to C along the central hydrogen bond is observed upon excitation of the pipi* state initially localized on G. In the resulting charge transfer state a conical intersection between the excited state and the ground state is easily accessible. Therefore radiationless decay is fast, of the order of 100 fs, followed by a rapid CPET back reaction retrieving the initial Watson-Crick structure. A detailed analysis of the mechanism of nonradiative decay suggests a biexponential behavior in which out-of-plane motion plays a special role for the longer decay component.
authors.affiliation: Institut de Biologie Structurale J.-P. Ebel, 41 Rue Jules Horowitz, 38027 Grenoble Cedex, France.
authors.forename: Phineus R L
authors.initials: PR
authors.lastname: Markwick
authors.forename: Nikos L
authors.initials: NL
authors.lastname: Doltsinis
mesh_terms: D020029:Base Pairing; D001692:Biological Transport; D003198:Computer Simulation; D003596:Cytosine / Q000737:chemistry*; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair / Q000502:physiology*; D004579:Electron Transport; D006147:Guanine / Q000737:chemistry*; D011522:Protons
chemical_list: D011522:Protons; D006147:Guanine; D003596:Cytosine