Chalikian Tigran V
Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 19 Russell St., Toronto, Ontario M5S 2S2, Canada.
Biopolymers. 2003 Dec;70(4):492-6. doi: 10.1002/bip.10538.
Proteins and nucleic acids are able to adopt their native conformation and perform their biological role only in the presence of water with which they actively interact in a mutually modifying way. Traditionally, hydrophobic effect has been considered to be the major factor stabilizing biopolymeric structures. However, solvent reorganization around polar groups is an event thermodynamically more unfavorable than solvent reorganization around nonpolar groups. Consequently, burial of polar groups with formation of complementary solute-solute hydrogen bonds out of contact with water is an energetically favorable process that also provides a major force driving macromolecular association and folding. In contrast to nonpolar groups, polar groups may form their complementary intra- or intersolute hydrogen bonds out of contact with water only provided that an appropriate solute structure has been formed with properly positioned hydrogen bond donors and acceptors. Formation of such structures is disfavored entropically and may not be possible due to steric reasons. However, the interior of a folded protein, alpha-helices and beta-sheets, double helical nucleic acid structures, and protein-ligand interfaces all provide rigid matrices where polar groups may form their complementary hydrogen bonds. For these structures, the inward drive of polar groups represents a considerable stabilizing factor.
蛋白质和核酸只有在有水存在的情况下才能呈现其天然构象并发挥生物学作用，它们与水以相互修饰的方式积极相互作用。传统上，疏水作用被认为是稳定生物聚合物结构的主要因素。然而，极性基团周围的溶剂重组在热力学上比非极性基团周围的溶剂重组更不利。因此，极性基团通过形成互补的溶质-溶质氢键而被掩埋，使其与水不接触，这是一个能量上有利的过程，同时也提供了驱动大分子缔合和折叠的主要力量。与非极性基团不同，极性基团只有在形成了具有适当定位的氢键供体和受体的合适溶质结构时，才可能在与水不接触的情况下形成其互补的溶质内或溶质间氢键。这种结构的形成在熵上是不利的，并且由于空间位阻原因可能无法实现。然而，折叠蛋白的内部、α-螺旋和β-折叠、双螺旋核酸结构以及蛋白质-配体界面都提供了刚性基质，极性基团可以在其中形成其互补的氢键。对于这些结构，极性基团的向内驱动力是一个相当大的稳定因素。
