Molecular solutes are known to have a strong effect on the structural and dynamical properties of the surrounding water. In our recent study (PNAS, 114, 322 (2017)) we have identified the presence of strengthened water hydrogen bonds near hydrophobic solutes by using both IR spectroscopy and ab-initio molecular dynamics simulations. The water molecules involved in the enhanced hydrogen bonding have been shown to display extensive structural ordering and restricted mobility. We observed that an individual pair of water molecules can make stronger hydrogen bond to each other if it is not surrounded by intercalating water molecules. Here we present compelling simulation results which unravel a simple mechanistic picture of the emergence of the hydrogen bond (HB) strengthening around solvated methane. We show explicitly that actual absence of water molecules within the excluded volume due to the hydrophobic molecule assures smaller residual torque on neighboring water molecules enabling the formation of stronger HBs between them.

中文翻译：

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为什么小的疏水性溶质周围的水分子形成的氢键比大分子中的强？

已知分子溶质对周围水的结构和动力学性质有很大影响。在我们最近的研究中（PNAS，114，322（2017）），我们已经通过使用红外光谱和从头算分子动力学模拟确定了疏水溶质附近水氢键的增强。已显示出参与增强氢键的水分子显示出广泛的结构有序性和受限的迁移性。我们观察到，如果一对水分子没有被插入的水分子包围，则它们彼此之间会形成更强的氢键。在这里，我们提出了令人信服的模拟结果，这些结果揭示了溶剂化甲烷周围氢键（HB）增强的简单机理图。