Water inside a hydrophobic cavitand molecule
Water inside a hydrophobic cavitand molecule
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DOI：
10.1021/jp804429n
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发表时间：
2008-08-21
影响因子：
3.3
通讯作者：
Rick, Steven W.
中科院分区：
文献类型：
--
作者：
Ewell, Jeffrey;Gibb, Bruce C.;Rick, Steven W.
利用分子动力学计算机模拟研究了水溶性碗状空腔和内部疏水分子中水的结构和动力学。模拟发现，内部水分子的数量约为4.5个，但在几十纳秒的时间尺度上，它会从完全空到满波动。从空到满的过渡在能量上是有利的，在熵上是不利的。内部水分子的氢键比整体水分子少，相互作用一般也较弱；较低的能量来自于与腔体原子和腔体入口处的水分子的最近邻相互作用，这种相互作用在脱湿时丢失。对平移和旋转运动的分析表明，水分子内部较低的熵是由于平移熵的减少，其作用大于取向熵的增加。空腔分子作为宿主结合疏水客体，在入口上方约3埃处存在疏水客体分子可诱导脱湿。在这个位置，客体取代了水分子，使内部的水分子和空腔稳定下来，变得比满腔更稳定。
The structure and dynamics of water inside a water-soluble, bowl-shaped cavitand molecule with a hydrophobic interior are studied using molecular dynamics computer simulations. The simulations find that the number of inside water molecules is about 4.5, but it fluctuates from being completely empty to full on a time scale of tens of nanoseconds. The transition from empty to full is energetically favorable and entropically unfavorable. The water molecules inside have fewer hydrogen bonds than the bulk and in general weaker interactions; the lower energy results from the nearest- neighbor interactions with the cavitand atoms and the water molecules at the entrance of the cavitand, interactions that are lost upon dewetting. An analysis of translational and rotational motion suggests that the lower entropy of the inside water molecules is due to decreased translational entropy, which outweighs an increased orientational entropy. The cavitand molecule acts as a host binding hydrophobic guests, and dewetting can be induced by the presence of a hydrophobic guest molecule about 3 angstrom above the entrance. At this position, the guest displaces the water molecules which stabilize the inside water molecules and the empty cavitand becomes more stable than the full.