Shukla M K, Leszczynski Jerzy
Computational Centre for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, Jackson, MS 39217, USA.
J Phys Chem B. 2005 Sep 15;109(36):17333-9. doi: 10.1021/jp0520751.
An ab-initio computational study was performed to investigate the effect of explicit hydration on the ground and lowest singlet PiPi* excited-state geometry and on the selected stretching vibrational frequencies corresponding to the different NH sites of the guanine acting as hydrogen-bond donors. The studied systems consisted of guanine interacting with one, three, five, six, and seven water molecules. Ground-state geometries were optimized at the HF level, while excited-state geometries were optimized at the CIS level. The 6-311G(d,p) basis set was used in all calculations. The nature of potential energy surfaces was ascertained via the harmonic vibrational frequency analysis; all structures were found minima at the respective potential energy surfaces. The changes in the geometry and the stretching vibrational frequencies of hydrogen-bond-donating sites of the guanine in the ground and excited state consequent to the hydration are discussed. It was found that the first solvation shell of the guanine can accommodate up to six water molecules. The addition of the another water molecule distorts the hydrogen-bonding network by displacing other neighboring water molecules away from the guanine plane.
进行了一项从头算计算研究，以探究显式水合作用对鸟嘌呤基态和最低单重态ππ*激发态几何结构以及对应于作为氢键供体的鸟嘌呤不同NH位点的选定伸缩振动频率的影响。所研究的体系由与一、三、五、六和七个水分子相互作用的鸟嘌呤组成。基态几何结构在HF水平上进行优化，而激发态几何结构在CIS水平上进行优化。所有计算均使用6-311G(d,p)基组。通过谐波振动频率分析确定势能面的性质；所有结构在各自的势能面上均为极小值。讨论了水合作用导致的鸟嘌呤基态和激发态中氢键供体位点的几何结构和伸缩振动频率的变化。发现鸟嘌呤的第一溶剂化壳最多可容纳六个水分子。再添加一个水分子会通过将其他相邻水分子从鸟嘌呤平面移开来扭曲氢键网络。
