School of Physical Science and Technology, Southwest Jiaotong University, Chengdu 610031, P. R. China.
J Phys Chem B. 2012 Aug 2;116(30):8908-15. doi: 10.1021/jp3048746. Epub 2012 Jul 23.
The double-proton transfer reactions in Watson-Crick guanine-cytosine (GC) base pairs after hydrogen atom addition are studied theoretically. The structural changes and energy differences among the structures are compared to explore the double-proton transfer mechanisms, concerted and stepwise. The concerted mechanism is found in all five radicals (GC+H)(•) considered, while the stepwise mechanism is predicted only for structures G-H(•)C(C6) and H(•)G(N7)-C. The geometrical features have been found to change regularly in the concerted double-proton transfer. This is different from the single-proton transfer, for which the structural perturbations are dispersed throughout the GC base pair. The energy analyses demonstrate that the concerted double-proton transfer mechanism is more favorable in the gas phase, while the stepwise mechanism dominates in water. The structures of proton transfer products become less favored energetically.
沃森-克里克鸟嘌呤-胞嘧啶（GC）碱基对中氢原子加成后的双质子转移反应进行了理论研究。比较了结构变化和结构之间的能量差异，以探讨协同和逐步的双质子转移机制。在所考虑的所有五个自由基（GC+H）（•）中都发现了协同机制，而仅预测了结构 G-H（•）C（C6）和 H（•）G（N7）-C 存在逐步机制。在协同双质子转移中发现了几何特征的有规律变化。这与单质子转移不同，单质子转移的结构扰动分散在整个 GC 碱基对中。能量分析表明，协同双质子转移机制在气相中更有利，而逐步机制在水中占主导地位。质子转移产物的结构在能量上变得不那么有利。
