水环境对GC和AT碱基对质子转移的影响

采用B3LYP/DZP++的方法研究了第一水化层作用和连续化处理的水溶剂作用对鸟嘌呤-胞嘧啶(GC)碱基对和腺嘌呤-胸腺嘧啶(AT)碱基对质子转移反应的影响. GC和AT碱基对在连续化水溶剂作用下，均发生单质子转移(SPT1)和分步的双质子转移(DPT)，而在第一水化层5 个水分子的作用下(GC·5H₂O，AT·5H₂O)或同时考虑第一水化层作用和连续化水溶剂作用(GC·5H₂O+PCM，AT·5H₂O+PCM)时，GC和AT碱基对的质子转移均只得到单质子转移反应(SPT1). 单质子转移过程中的活化能变化情况表明：第一水化层对GC和AT碱基对结构和质子转移影响较大，水环境对碱基对的作用主要发生在第一水化层.

Aqueous Solution Effects on the Proton-Transfer Processes of GC and AT Base Pairs

The effects of the first hydration shell and the bulk solvation effects on the proton-transfer processes of guanine-cytosine (GC) and adenine-thymine (AT) base pairs are studied based on density functional theory, using the B3LYP method and DZP++ basis set. The proton-transfer mechanisms of the GC and AT base pairs in bulk solvation are first single-proton transfer (SPT1) and stepwise double-proton transfer (DPT). When only the first hydration shell surrounded by five water molecules (GC ·5H₂O, AT· 5H₂O), or both the first hydration shell and bulk solvation effects through polarizable continuum model (PCM) (GC·5H₂O+PCM, AT·5H₂O+PCM) are considered, only the first single-proton-transfer mechanism (SPT1) is found. The proton- transfer activation energies of the GC and the AT base pairs show that the majority of the hydration effects come from the first hydration shell through hydrogen- bond interactions, therefore the first hydration shell greatly influences the base pair structures and proton-transfer mechanism.