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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Eletrostatics for Exploring Hydration Patterns of Molecules,3.Uracil
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Eletrostatics for Exploring Hydration Patterns of Molecules,3.Uracil

机译：探索分子水化形式的静电学，3。尿嘧啶

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A systematic investigation of the stepwise hydration of uracil has been carried out.The rich molecular electrostatic potential (MESP) topographical features of uracil provide clues on the probable water binding sites.The most noteworthy among these are the MESP minima due to carbonyl oxygens where the MESP value is negative as well as those over the uracil ring at which the MESP value is positive.Hydrated structures of uracil have been obtained employing an electrostatics-based model,EPIC (Electrostatic potential for Intermolecular Complexation) followed by ab initio optimization at the HF/6-31G(d,p) levels.Further geometry optimizations carried out at the HF/6-31+G(2d,p) and B3LYP/6-31+G(2d,p) levels,for smaller clusters,lead to trends in interaction energies which are in general agreement with those observed at the HF/6-31G-(d,p) level.These structures incorporate squares and cubes of water as the dominant building blocks.An analysis of the difference in interaction energies (#DELTA#E_(rel)) of U..n(H_2O)_n clusters is seen to provide valuable information regarding hydration shells.This #DELTA#E_(rel) stabilizes to -7 to -8 kcal mol~(-1) for n> 9 and this value of n may correspond to the number of water molecules that make up the first solvation shell of uracil,based on a criterion of the interaction energy.
机译：对尿嘧啶的逐步水合进行了系统的研究。尿嘧啶的丰富分子静电势（MESP）形貌特征为可能的水结合位点提供了线索，其中最值得注意的是羰基氧引起的MESP最小值。 MESP值是负值，而在尿嘧啶环上是MESP值的正值。已使用基于静电的模型，EPIC（分子间络合的静电势），然后在HF处从头开始优化，获得了尿嘧啶的水合结构。 / 6-31G（d，p）级别。对于较小的群集，在HF / 6-31 + G（2d，p）和B3LYP / 6-31 + G（2d，p）级别上进行了进一步的几何优化相互作用能的趋势与在HF / 6-31G-（d，p）水平上观察到的趋势基本一致。这些结构以水的正方形和立方体为主要构造基块。相互作用能差异的分析（＃三角洲＃ U..n（H_2O）_n簇的E_（rel））提供了有关水化壳的有价值的信息。对于n>，此＃DELTA＃E_（rel）稳定在-7至-8 kcal mol〜（-1）根据相互作用能的标准，图9中的n和n的值可以对应于组成尿嘧啶的第一溶剂化壳的水分子的数量。

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