title: Mechanism of charge separation in DNA by hole transfer through consecutive adenines.
abstract: To investigate the mechanism of charge separation in DNA with consecutive adenines adjacent to a photosensitizer (Sens), a series of naphthalimide (NI) and 5-bromouracil ((br)U)-modified DNAs were prepared, and the quantum yields of formation of the charge-separated states (Phi) upon photo-excitation of the Sens NI in DNA were measured. The Phi was modulated by the incorporation site of (br)U, which changes the oxidation potential of its complementary A through hydrogen bonding and the hole-transfer rates between adenines. The results were interpreted as charge separation by means of the initial charge transfer between NI in the singlet excited state and the second- and third-nearest adenine to the NI. In addition, the oxidation of the A nearest to NI leads to the rapid charge recombination within a contact ion pair. This suggests that the charge-separation process can be refined to maximize the Phi by putting a redox-inactive spacer base pair between a photosensitizer and an A-T stretch.
authors.affiliation: Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan. kiyohiko@sanken.osaka-u.ac.jp
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Kawai
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Osakada
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D000225:Adenine / Q000737:chemistry*; D001976:Bromouracil / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D053644:Naphthalimides / Q000737:chemistry*; D010782:Photolysis; D017319:Photosensitizing Agents / Q000737:chemistry*; D011789:Quantum Theory; D013997:Time Factors
chemical_list: D053644:Naphthalimides; D017319:Photosensitizing Agents; D001976:Bromouracil; D004247:DNA; D000225:Adenine