Mechanism
and Dynamics of Electron Injection and Charge Recombination in DNA.
Dependence on Neighboring Pyrimidines
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Abstract
The
mechanism and dynamics of photoinduced electron injection and charge
recombination have been investigated for several series of DNA hairpins.
The hairpins possess a stilbenediether linker, which serves as an
electron donor and base pair stems that possess different pyrimidine
bases adjacent to the linker. Hairpins with adjacent thymine-adenine
(T-A) base pairs undergo fast electron injection and relatively slow
charge recombination with rate constants that are not strongly dependent
upon the following base pair. Hairpins with adjacent cytosine-guanine
(C-G) base pairs undergo reversible electron injection and much faster
charge recombination than those with adjacent T-A base pairs. Hairpins
with 5-fluorouracil or other halogenated pyrimidines in their first
and second base pair undergo fast electron injection and multiexponential
charge recombination. The difference in kinetic behavior for the different
series of hairpins and its implications for the formation of long-lived
charge-separated states are discussed and compared to results reported
previously for other electron-donor chromophores