title: Excess-Electron Transfer in DNA by a Fluctuation-Assisted Hopping Mechanism.
abstract: The dynamics of excess-electron transfer in DNA has attracted the attention of scientists from all kinds of research fields because of its importance in biological processes. To date, several studies on excess-electron transfer in consecutive adenine (A):thymine (T) sequences in donor-DNA-acceptor systems have been published. However, the reported excess-electron transfer rate constants for consecutive T's are in the range of 10(10)-10(11) s(-1) depending on the photosensitizing electron donor, which provides various driving forces for excess-electron injection into DNA. In this study, we employed a strongly electron-donating photosensitizer, a dimer of 3,4-ethylenedioxythiophene (2E), and an electron acceptor, diphenylacetylene (DPA), to synthesize a series of modified DNA oligomers (2-Tn, n = 3-6) in order to investigate the excess-electron transfer dynamics in these donor-DNA-acceptor systems using femtosecond laser flash photolysis. The relation between the free energy change for charge injection and the excess-electron transfer rate among consecutive T's provided an intrinsic excess-electron hopping rate constant of (3.8 ± 1.5) × 10(10) s(-1) in the DNA, which is consistent with the fluctuation frequency of the DNA sugar backbone and bases (3.3 × 10(10) s(-1)). Thus, we discuss the effect of structural fluctuations on the excess-electron hopping in DNA.
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Shih-Hsun
authors.initials: SH
authors.lastname: Lin
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D004583:Electrons; D007700:Kinetics; D017319:Photosensitizing Agents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017319:Photosensitizing Agents; D004247:DNA