Department of Physical and Quantum Chemistry, Wroclaw University of Science and Technology, Faculty of Chemistry, Wybrzeże Wyspiańskiego 27, 50-370, Wrocław, Poland.
Chem Commun (Camb). 2019 Dec 19;56(2):201-204. doi: 10.1039/c9cc06180k.
Dark nπ* states were shown to have substantial contribution to the destructive photochemistry of pyrimidine nucleobases. Based on quantum-chemical calculations, we demonstrate that the characteristic hydrogen bonding pattern of the GC base pair could facilitate the formation of a wobble excited-state charge-transfer complex. This entails a barrierless electron-driven proton transfer (EDPT) process which enables damageless photodeactivation of the base pair. These photostabilizing properties are retained even when guanine is exchanged to hypoxanthine. The inaccessibility of this process in the AT base pair sheds further light on the reasons why cytosine is less susceptible to the formation of photodimers in double-stranded DNA.
研究表明，暗 nπ* 态对嘧啶核苷酸碱基的破坏性光化学反应有很大贡献。基于量子化学计算，我们证明 GC 碱基对的特征氢键模式可以促进摆动激发态电荷转移配合物的形成。这需要一个无势垒的电子驱动质子转移（EDPT）过程，从而使碱基对能够无损地光失活。即使将鸟嘌呤交换为次黄嘌呤，这些光稳定性质也得以保留。在 AT 碱基对中，这个过程无法进行，这进一步说明了为什么在双链 DNA 中胞嘧啶不太容易形成光二聚体的原因。
