Excess-electron injection and transfer in terthiophene-modified DNA: terthiophene as a photosensitizing electron donor for thymine, cytosine, and adenine.

Man Jae Park, Mamoru Fujitsuka, Kiyohiko Kawai, Tetsuro Majima

Index: Chemistry 18(7) , 2056-62, (2012)

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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.Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.