Schwalb Nina K, Temps Friedrich
Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany.
Science. 2008 Oct 10;322(5899):243-5. doi: 10.1126/science.1161651.
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.
DNA的高光稳定性通常归因于高效的无辐射电子弛豫过程。我们使用飞秒时间分辨荧光光谱法来揭示随后的动力学强烈依赖于碱基序列，并且还受到高级结构的影响。在仅替换少数几个碱基时，掺杂dG的d(A)20单链DNA和掺杂dG·dC的d(A)20·d(T)20双链DNA中的激发电子态寿命会急剧下降。在含有d(AGA)·d(TCT)或d(AG)·d(TC)重复序列的双链体中，荧光态的失活发生在亚皮秒时间尺度上，但在延伸的d(G)序列中激发态寿命又会增加。结果表明，天然DNA中的光动力学比简单模型系统中可能更复杂且具有分子特异性。
