title: Excess-electron injection and transfer in terthiophene-modified DNA: terthiophene as a photosensitizing electron donor for thymine, cytosine, and adenine.
abstract: Excess-electron transfer (EET) in DNA has attracted wide attention owing to its close relation to DNA repair and nanowires. To clarify the dynamics of EET in DNA, a photosensitizing electron donor that can donate an excess electron to a variety of DNA sequences has to be developed. Herein, a terthiophene (3T) derivative was used as the photosensitizing electron donor. From the dyad systems in which 3T was connected to a single nucleobase, it was revealed that (1) 3T* donates an excess electron efficiently to thymine, cytosine, and adenine, despite adenine being a well-known hole conductor. The free-energy dependence of the electron-transfer rate was explained on the basis of the Marcus theory. From the DNA hairpins, it became clear that (1) 3T* can donate an excess electron not only to the adjacent nucleobase but also to the neighbor one nucleobase further along and so on. From the charge-injection rate, the possibilities of smaller β value and/or charge delocalization were discussed. In addition, EET through consecutive cytosine nucleobases was suggested.
authors.affiliation: The Institute of Scientific and Industrial, Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Man Jae
authors.initials: MJ
authors.lastname: Park
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Kawai
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima
mesh_terms: D000225:Adenine / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D004579:Electron Transport; D004583:Electrons; D008956:Models, Chemical; D015394:Molecular Structure; D017319:Photosensitizing Agents / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*; D013941:Thymine / Q000737:chemistry*
chemical_list: D017319:Photosensitizing Agents; D013876:Thiophenes; C019101:alpha-terthienyl; D003596:Cytosine; D004247:DNA; D000225:Adenine; D013941:Thymine