Effect of solute size and solute-water attractive interactions on hydration water structure around hydrophobic solutes
Effect of solute size and solute-water attractive interactions on hydration water structure around hydrophobic solutes
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DOI：
10.1021/ja016324k
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发表时间：
2001-10-31
影响因子：
15
通讯作者：
Paulaitis, ME
中科院分区：
文献类型：
--
作者：
Ashbaugh, HS;Paulaitis, ME
使用Monte Carlo模拟，我们研究了溶质的大小和溶质-水的吸引力的相互作用对水合水结构周围的球形集群的1，13，57，135，和305六方密堆积甲烷和单硬球（HS）溶质类似物这些集群的影响。我们得到的HS半径为3.25和16.45埃之间的溶质大小的函数与HS溶质接触的水分子的密度的定量结果。基于标度颗粒理论对这些结果进行分析，得出水合自由能/表面积系数等于139 cal/（mol Angstrom（2）），与溶质尺寸无关，当该系数相对于溶质的货车德瓦尔斯表面定义时。对于HS半径小于10埃，相对于溶剂可接近表面定义的相同系数随着溶质尺寸的减小而减小。我们还发现，溶质-水的吸引相互作用在甲烷团簇的水合中起着重要的作用。三个最大团簇的第一水化壳层中的水密度均大于体积水密度，且对团簇尺寸不敏感。与此相反，这些集群的HS类似物的接触水密度随着溶质的大小而降低，低于水的体积密度的两个最大的溶质。因此，大的HS溶质去湿，而相同大小的甲烷团簇不。
Using Monte Carlo simulations, we investigated the influence of solute size and solute-water attractive interactions on hydration water structure around spherical clusters of 1, 13, 57, 135, and 305 hexagonally close-packed methanes and the single hard-sphere (HS) solute analogues of these clusters. We obtain quantitative results on the density of water molecules in contact with the HS solutes as a function of solute size for HS radii between 3.25 and 16.45 Angstrom. Analysis of these results based on scaled-particle theory yields a hydration free energy/surface area coefficient equal to 139 cal/(mol Angstrom (2)), independent of solute size, when this, coefficient is defined with respect to the van der Waals surface of the solute. The same coefficient defined with respect to the solvent-accessible surface decreases with decreasing solute size for HS radii less than similar to 10 Angstrom. We also find that solute-water attractive interactions play an important role in the hydration of the methane clusters. Water densities in the first hydration shell of the three largest clusters are greater than bulk water density and are insensitive to the cluster size. In contrast, contact water densities for the HS analogues of these clusters decrease with solute size, falling below the bulk density of water for the two largest solutes. Thus, the large HS solutes dewet, while methane clusters of the same size do not.