Excess-Electron Transfer in DNA by a Fluctuation-Assisted Hopping Mechanism

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• 作者：Shih-Hsun Lin ; Mamoru Fujitsuka ; Tetsuro Majima
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：February 4, 2016
• 年：2016
• 卷：120
• 期：4
• 页码：660-666
• 全文大小：483K
• ISSN：1520-5207

文摘

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 10¹⁰–10¹¹ 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) × 10¹⁰ s^–1 in the DNA, which is consistent with the fluctuation frequency of the DNA sugar backbone and bases (3.3 × 10¹⁰ s^–1). Thus, we discuss the effect of structural fluctuations on the excess-electron hopping in DNA.