Cu^(2+)对腺嘧啶-胸腺嘧啶碱基对阴离子质子转移的影响

Effects of Cu^(2+) on Proton Transfer Processes in an Adenine-Thymine Anion Base Pair

采用B3LYP/DZP++方法研究了腺嘌呤-胸腺嘧啶(A-T)碱基对阴离子(AT)-的单质子转移机理以及金属离子Cu2+对(AT)-碱基对质子转移的影响.(AT)-碱基对的单质子转移路径是由胸腺嘧啶N25位上的质子H26沿分子间的氢键N25-H26…N10转移到腺嘌呤的N10位.金属Cu2+可通过络合作用分别吸附在(AT)-碱基对O24、O28、N4、N13上,从而影响(AT)-碱基对中质子转移过程.Cu2+络合作用在胸腺嘧啶(T)的O24、O28上时,发生了从胸腺嘧啶到腺嘌呤方向上的单质子转移反应;而作用在腺嘌呤(A)的N4、N13上时,得到了双质子转移的稳定产物.

The proton-transfer processes of the adenine-thymine （A-T） base pair anion （AT）- and the Cu2＋ cationized （A-T） base pair anion were investigated using the B3LYP/DZP＋＋ method. A single proton- transfer process was found for the （A-T） base pair anion in which proton H28 at the N2, site of thymine transferred to the N10 site of adenine. The metal cation Cu2＋ can coordinate to the N4 and N13 sites of adenine as well as the 024 and 028 sites of thymine in （AT）- by coordination interactions. For Cu2＋ coordinated to the 024 and 028 sites of thymine the single proton transfer from thymine to adenine is possible. However, when Cu2＋ interacts with the N40r N13 of adenine the double proton-transferred product was found to be stable.