Shen Liang, Ji Hong-Fang, Zhang Hong-Yu
Shandong Provincial Research Center for Bioinformatic Engineering and Technique, Center for Advanced Study, Shandong University of Technology, Zibo, PR China.
Photochem Photobiol. 2006 May-Jun;82(3):798-800. doi: 10.1562/2005-10-20-RN-723.
In this paper, the solvent-dependent photosensitive behaviors of fullerene (C(60)) were investigated in polar and nonpolar solvents by time-dependent density functional theory (TD-DFT) calculation. Based on the calculated physicochemical parameters on triplet state, it is revealed that excited-state C(60) only generates (1)O(2) via energy transfer in benzene, but can give birth to O(2)(.-) and (1)O(2) in water via energy transfer and electron transfer, respectively. Considering the fact that electron transfer is more favorable compared with energy transfer in polar biological systems, especially with the presence of electron donors, the O(2)(.-)-generating process will get predominant in physiological systems. These results account well for the experimental observations that O(2)(.-) and (.)OH are primarily responsible for the photoinduced DNA cleavage by C(60) under physiological conditions, whereas (1)O(2) plays a critical role in nonpolar solvents.
本文采用含时密度泛函理论（TD-DFT）计算方法，研究了富勒烯（C(60)）在极性和非极性溶剂中依赖于溶剂的光敏行为。基于对三重态计算得到的物理化学参数，结果表明，激发态的C(60)在苯中仅通过能量转移生成单线态氧((1)O(2))，而在水中则分别通过能量转移和电子转移生成超氧阴离子自由基(O(2)(.-))和单线态氧((1)O(2))。考虑到在极性生物体系中，尤其是存在电子供体时，电子转移比能量转移更有利，因此在生理体系中，生成O(2)(.-)的过程将占主导地位。这些结果很好地解释了实验观察到的现象：在生理条件下，O(2)(.-)和羟基自由基(.)OH是C(60)光诱导DNA裂解的主要原因，而(1)O(2)在非极性溶剂中起关键作用。
