Theoretical studies of uracil-(H2O)(n) (n=1-7) clusters by ab initio and ABEEM sigma pi/MM fluctuating charge model

摘要

Uracil-(H2O)(n) (n = 1-7) clusters were systemically investigated by ab initio methods and the newly constructed ABEEM sigma pi/MM fluctuating charge model. Water molecules have been gradually placed in an average plane containing uracil. The geometries of 38 uracil-water complexes were obtained using. B3LYP/6-311++G** level optimizations, and the energies were determined at the MP2/6-311++G** level with BSSE corrections. The ABEEM sigma pi/MM potential model gives reasonable properties of these clusters when comparing with the present ab initio data. For interaction energies, the root mean square deviation is 0.96 kcal/mol, and the linear coefficient reaches 0.997, Furthermore, the ABEEM sigma pi charges changed when H2O interacted with the uracil molecule, especially at the sites where the hydrogen bond form. These results show that the ABEEM sigma pi/MM model is fine giving the overall characteristic hydration properties of uracil-water systems in good agreement with the high-level ab initio calculations.