Department of Physics, and Program of Biophysics, The Ohio State University, Columbus, Ohio 43210, USA.
J Am Chem Soc. 2012 Jan 25;134(3):1501-3. doi: 10.1021/ja2112788. Epub 2012 Jan 12.
To mimic photolyase for efficient repair of UV-damaged DNA, numerous biomimetic systems have been synthesized, but all show low repair efficiency. The molecular mechanism of this low-efficiency process is still poorly understood. Here we report our direct mapping of the repair processes of a flavin-thymine dimer adduct with femtosecond resolution. We followed the entire dynamic evolution and observed direct electron transfer (ET) from the excited flavin to the thymine dimer in 79 ps. We further observed two competitive pathways, productive dimer ring splitting within 435 ps and futile back-ET in 95 ps. Our observations reveal that the underlying mechanism for the low repair quantum yield of flavin-thymine dimer adducts is the short-lived excited flavin moiety and the fast dynamics of futile back-ET without repair.
为了模拟光解酶以有效修复紫外线损伤的 DNA，人们合成了许多仿生系统，但所有这些系统的修复效率都很低。这一低效率过程的分子机制仍知之甚少。在这里，我们报告了我们使用飞秒分辨率直接绘制黄素-胸腺嘧啶二聚体加合物修复过程的结果。我们跟踪了整个动态演变过程，并在 79 皮秒时观察到从激发态黄素到胸腺嘧啶二聚体的直接电子转移（ET）。我们还观察到两种竞争途径，435 皮秒内有产生活性二聚体环分裂，95 皮秒内有无效的反向 ET。我们的观察结果表明，导致黄素-胸腺嘧啶二聚体加合物修复量子产率低的根本原因是短暂存在的激发态黄素部分和没有修复的无效反向 ET 的快速动力学。
