中文摘要：

应用量子力学（QM）与ABEEM浮动电荷力场（ABEEM/MM）相结合的方法研究了抗癌药物NAMI-A在水溶液中的结构性质.所有的结构优化都是在DFT的B3LYP方法下采用6-31G（d,p）和LanL2DZ基组完成的,没有加入任何限制性条件.结果表明,优化得到的NAMI-A构型受不同环境及方法的影响均有变化.与气相中得到的构型相比,QM/MM迭代优化得到构型要比PCM的构型变化更明显.QM/MM（ABEEM/MM）迭代优化得到的NAMI-A构型比QM/MM（OPLS-AA）的变化要小.总之,溶剂通过极化效应对NAMI-A结构、电荷分布及径向分布函数等性质均有影响,客观地处理极化效应才能正确地反映QM区的性质.

英文摘要：

Since 1970s carried out by Warshel et al. QM/MM method has been successfully applied to a wide range of reac- tions in solution, enzyme and proteins. Up to now, QM has been combined with some popular force fields, like OPLS-AA, Amber or CHARMM. In this work, QM has been combined with ABEEM fluctuating charge force field （ABEEM/MM）. ABEEM/MM is a polarizable force field in which the ABEEMcrzr method has been fused. ABEEMoTv method, the atom-bond electronegativity equalization method, was proposed and developed by Yang et al. based on electronegativity equalization principle in density functional theory （DFT）. In order to further improve the feasibility of combining QM with ABEEM/MM, the properties of anticancer drug imidazolium [trans-tetrachloro（DMSO）（imidazole）ruthenate（III）]（NAMI-A） in aqueous solution have been investigated, such as structures, polarization energies, charge distributions and radial distribution func- tions. All the configurations were optimized at B3LYP/6-31G（d,p）//LanL2DZ （for Ru） level by using the Gaussian 03 pro- gram. The isoelectric focusing polarized continuum model （IEF-PCM） with UAHF atomic radii was employed for PCM model, and the dielectric constant of water @=78.39） was used to approximate the effect of aqueous solution. In QM/MM method, QM and MM regions were optimized by using different methods. The convergence criteria that the maximum gradi- ent of energy is less than 5 X 10-4 a.u. in QM region and the RMS gradient is less than 1 X 10 3 kcal~mol-l.A-i in MM re- gion was adopted for the iterative optimization. After MM minimization, MM region participated as point charges to impact the optimization of QM. No cutoff was introduced to QM and MM interactions. Iterative optimizations have accomplished until reaching the convergence criteria. All the MD simulations were performed by using the modified Tinker program in the NVT ensemble at 298 K with Berendsen thermostats, the velocity Verlet integrator, and a time step of 1 fs. To prepare a rea-