溶液中Zn2+与腺嘌呤异构体间相互作用的理论研究

用B3LYP/6-311++G**方法和PCM及Onsager模型研究了Zn2+与腺嘌呤异构体在溶液中的11种较为稳定配合物. 结果显示, 这些配合物在溶液中的稳定性顺序与气相中明显不同, 其结合位点表现出如下的规律性, 在亚氨基类配合物中, Zn2+与腺嘌呤的N7、N6位结合比与N1、N6位结合形成的配合物更稳定; 氨基类配合物中, Zn2+以"双齿"形式与腺嘌呤异构体上的氮结合时的优先顺序为(N3和N9)>(N7和N6)>(N1和N6). 研究表明, 不论气相还是溶液相, 孤立的腺嘌呤分子内的质子转移较困难, 结合Zn2+后也不能明显降低关键步骤的活化能; 结合Cu2+却能明显地降低气相中关键步骤的活化能, 但溶剂效应却不利于Cu2+引发腺嘌呤分子内的质子转移.

Theoretical Study on the Interactions between Zn2+ and Adenine Isomers in Aqueous Phase

Eleven stable adenine-Zn2+ isomers in aqueous phase were investigated at B3LYP/6-311++G** level in combination with the PCMand Onsager models. Different from those in gas phase, the stabilization ordering of these adenine-Zn2+ isomers in the aqueous phase changed and the binding sites of Zn2+ showed obvious regularity. In the adenine-Zn2+ isomerswith imine group, the complexeswith the combination between Zn2+ and (N7 andN6 ) sitesweremore stable than those with the combination between the Zn2+ and (N1 and N6) sites. In those isomers with amido groups, the preferred ordering of double nitrogen sites for Zn2+ combination was (N3 and N9)>(N7 and N6)>(N1 and N6). Activation energy calculations indicated that the intramolecular proton transfer (i.e., (N6)Ha→Ha(N1) in a9=>a9→a19l) was difficult for an isolated adenine (a9). Moreover, Zn2+ could hardly induce the decrease of activation energy of intramolecular proton transfer both in the gas and aqueous phases, whereas the Cu2+ could and the effect was obvious.