Mg^(2+)/Ca^(2+)与DNA碱基和水相互作用的量子化学研究

Quantum chemical studies on the interactions of Mg^(2+)/Ca^(2+) with DNA bases and H_2O

采用高水平量子化学方法,MP2/6-311G(d,p),对气相中的Mg2+/Ca2+与DNA碱基和水的相互作用进行了研究,优化base-M-(H2O)n(M=Mg2+/Ca2+,n=1~2)的几何结构,计算其结合能和电荷分布等性质.结果表明,Mg2+与配体碱基及水的距离要比Ca2+与其配体距离更近,Mg2+与其配体的平均距离要比Ca2+小0.03nm左右.Mg2+与其配体的结合能要比Ca2+的大60~70kcal/mol左右,随着水数目的增加,离子与配体的结合能力逐渐减弱,Mg2+/Ca2+到水和碱基的平均距离越来越大,但变化幅度较小.金属离子的电荷主要转移到水中.

By applying a high-level quantum chemistry （QM） method,the interactions between Mg^2＋/ Ca^2＋ with DNA bases and water in gas-phase were investigated. The structures,binding energies and charge distributions of base-M-（H2O）n, （M = Mg^2＋/Ca^2＋ , n = 1 - 2） were studied. Results show that the distances of Mg2＋-base and Mg2＋-water are smaller than those of Ca^2＋ , and the distances from the Mg^2＋ to H2O are 0.03 nm smaller than those of Ca2＋-H2O; the binding energies between Mg2＋ and its ligands are 60-70 kcal/mol larger than those of Ca^2＋. With the increasing number of water molecules,the interactions between cation and its ligands reduce gradually, the average distances from Mg^2＋/Ca^2＋to water and base enlarge gradually and insignificantly,and the positive charges of Mg^2＋/ Ca^2＋ mainly transfer to water.