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Base Sequence and Higher-Order Structure Induce the Complex Excited-State Dynamics in DNA

Science  10 Oct 2008:
Vol. 322, Issue 5899, pp. 243-245
DOI: 10.1126/science.1161651

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Abstract

The high photostability of DNA is commonly attributed to efficient radiationless electronic relaxation processes. We used femtosecond time-resolved fluorescence spectroscopy to reveal that the ensuing dynamics are strongly dependent on base sequence and are also affected by higher-order structure. Excited electronic state lifetimes in dG-doped d(A)20 single-stranded DNA and dG·dC-doped d(A)20·d(T)20 double-stranded DNA decrease sharply with the substitution of only a few bases. In duplexes containing d(AGA)·d(TCT) or d(AG)·d(TC) repeats, deactivation of the fluorescing states occurs on the subpicosecond time scale, but the excited-state lifetimes increase again in extended d(G) runs. The results point at more complex and molecule-specific photodynamics in native DNA than may be evident in simpler model systems.

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