Neely Robert K, Jones Anita C
School of Chemistry and the Collaborative Optical Spectroscopy, Micromanipulation and Imaging Centre (COSMIC), The University of Edinburgh, Edinburgh EH9 3JJ, UK.
J Am Chem Soc. 2006 Dec 20;128(50):15952-3. doi: 10.1021/ja064390m.
Time-resolved fluorescence of 2-aminopurine-labeled DNA duplexes at 77 K reveals the relationship between base dynamics and the conformational heterogeneity that results in the well-known multiexponential fluorescence decay at room temperature. The conformation that exhibits rapid interbase charge transfer at room temperature is not populated in the frozen duplex at 77 K; this geometry is accessed by thermal motion of the bases, it is not a minimum energy structure of the duplex. Three photophysically distinct conformational states persist in the frozen duplex; these are minimum energy structures and do not interconvert at room temperature on the time scale of the 2-aminopurine excited-state lifetime.
77K下2-氨基嘌呤标记的DNA双链体的时间分辨荧光揭示了碱基动力学与构象异质性之间的关系，这种构象异质性导致了室温下众所周知的多指数荧光衰减。在室温下表现出快速碱基间电荷转移的构象在77K的冷冻双链体中不存在；这种几何结构是通过碱基的热运动获得的，它不是双链体的最低能量结构。三种光物理上不同的构象状态在冷冻双链体中持续存在；这些是最低能量结构，在室温下2-氨基嘌呤激发态寿命的时间尺度上不会相互转化。
