Role of hydration water in protein unfolding
Role of hydration water in protein unfolding
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DOI：
10.1016/s0006-3495(99)77162-6
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发表时间：
1999-12-01
影响因子：
3.4
通讯作者：
Cho, CH
中科院分区：
文献类型：
--
作者：
Robinson, GW;Cho, CH
本文通过对水的两态外邻混合键模型的研究，提出极性基团促进邻域中低密度冰i型键的形成，而非极性基团则倾向于促进高密度冰ii型结构的形成。在蛋白质中，由于大量暴露的极性和非极性基团，邻近的水结构会发生很大的变化。当然，这些变化取决于蛋白质是处于天然状态还是未折叠状态，这里将显示对蛋白质在高温和低温下展开的热力学有直接影响。例如，众所周知，极性水化熵随着温度的升高而迅速变得更负。这种非常不寻常的行为可能与在外部散装液体中促进更稳定的i型键而牺牲蛋白质极性基团的ii型键直接相关。相反，非极性基团对热力学有相反的影响。这种微妙的平衡是由这些外部水合作用、内部水合壳的普通热力学作用以及蛋白质分子本身的氢键和范德华力共同作用形成的，它负责蛋白质的热变性和冷变性。
In this paper, following our work on the two-state outer neighbor mixed bonding model of water, it is proposed that polar groups promote the formation of the low density ice Ih-type bonding in their neighborhood, whereas nonpolar groups tend to promote the higher density ice II-type structure. In a protein, because of the large numbers of exposed polar and nonpolar groups, large changes in the neighboring water structure can occur. These changes, of course, depend on whether the protein is in its native or its unfolded state and will be shown here to have a direct impact on the thermodynamics of protein unfolding at both high and low temperatures. For example, it is known that the polar hydration entropies become rapidly more negative with increasing temperature. This very unusual behavior can be directly related to the promotion in the outer bulk liquid of the more stable Ih-type bonding at the expense of II-type bonding by polar groups of the protein. In contrast, nonpolar groups have an opposite effect on the thermodynamics. It is the delicate balance created by these outer hydration contributions, mixed with ordinary thermodynamic contributions from the inner hydration shell and those from hydrogen-bond and van der Waals forces within the protein molecule itself that is responsible for both heat and cold denaturation of proteins.