Enthalpy and entropy contributions to the pressure dependence of hydrophobic interactions
Enthalpy and entropy contributions to the pressure dependence of hydrophobic interactions
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DOI：
10.1063/1.1431582
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发表时间：
2002-02-08
影响因子：
4.4
通讯作者：
Garde, S
中科院分区：
文献类型：
--
作者：
Ghosh, T;García, AE;Garde, S
我们用长分子动力学方法模拟了甲烷分子在三种不同温度、压力分别为1和4000大气压的显性水中，计算了甲烷-甲烷缔合自由能的熵和热焓贡献。与以前的模拟研究结果一致，我们发现接触极小值主要由熵决定，而溶剂分离极小值则由有利的缔合焓稳定。接触极小处的熵和热焓随压力的增加变化不大，导致接触极小构型的相对压力不敏感。相反，我们发现溶剂分离的构型在更高的压力下越来越稳定，这是因为自由能的焓贡献超过了略微不利的熵贡献。去溶势垒主要由甲烷之间维持干体积的不利热能所控制。然而，退溶势垒的高度随着压力的增加而增加，这是由于势垒构型处的熵变化所致。对缔合热的进一步解析表明，水-水相互作用和使甲烷分离r所需的机械功(PDeltaV)的变化是对缔合热的主要贡献。通过计算甲烷-甲烷-水氧三重态关联函数，将这些热力学特征与水结构的潜在变化联系起来。(C)2002年美国物理研究所。
We use long molecular dynamics simulations of methane molecules in explicit water at three different temperatures at pressures of 1 and 4000 atm to calculate entropic and enthalpic contributions to the free energy of methane-methane association. In agreement with previous simulation studies, we find that the contact minimum is dominated by entropy whereas the solvent-separated minimum is stabilized by favorable enthalpy of association. Both the entropy and enthalpy at the contact minimum change negligibly with increasing pressure leading to the relative pressure insensitivity of the contact minimum configurations. In contrast, we find that the solvent-separated configurations are increasingly stabilized at higher pressures by enthalpic contributions that prevail over the slightly unfavorable entropic contributions to the free energy. The desolvation barrier is dominated by unfavorable enthalpy of maintaining a dry volume between methanes. However, the increasing height of the desolvation barrier with increasing pressures results from entropy changes at the barrier configurations. Further resolution of the enthalpy of association shows that major contributions to the enthalpy arise from changes in water-water interactions and the mechanical work (PDeltaV) expended in bringing the methanes to a separation of r. A connection of these thermodynamic features with the underlying changes in water structure is made by calculating methane-methane-water oxygen triplet correlation functions. (C) 2002 American Institute of Physics.