ISOENTHALPIC AND ISOENTROPIC TEMPERATURES AND THE THERMODYNAMICS OF PROTEIN DENATURATION
ISOENTHALPIC AND ISOENTROPIC TEMPERATURES AND THE THERMODYNAMICS OF PROTEIN DENATURATION
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DOI：
10.1073/pnas.88.12.5154
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发表时间：
1991-06-01
影响因子：
11.1
通讯作者：
LEE, B
中科院分区：
文献类型：
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作者：
LEE, B
在给定温度下，小的非极性分子从非水相转移到水中时的标准焓变或熵变对于不同的溶质种类通常是不同的。然而，如果热容变化与温度无关，则存在一个温度，在该温度下，对于给定类别内的所有溶质物种，焓或熵变变得相同。类似地，蛋白质变性的焓变或熵变，当外推到高温时，假设热容量变化与温度无关，显示出其值对于许多不同的球状蛋白质在单位重量基础上变得相同的温度。它示出，这些温度的存在可以解释从一个共同的形式主义的基础上的热力学量和温度无关的分子性质，表征溶质或蛋白质之间的线性关系。对于小的非极性分子转移过程，该性质是与水接触的表面积或基团的数量。对于蛋白质变性，有人建议，这一性质的措施极性/非极性混合的内部相互作用内的蛋白质内部。在一定的假设下，该模型得出的结论是，蛋白质的非极性和极性基团对分子折叠状态的稳定性的贡献大致相等，并且变性形式的蛋白质的溶剂可及表面积不超过完全延伸形式的约三分之二。
The standard enthalpy or entropy change upon transfer of a small nonpolar molecule from a nonaqueous phase into water at a given temperature is generally different for different solute species. However, if the heat capacity change is independent of temperature, there exists a temperature at which the enthalpy or the entropy change becomes the same for all solute species within a given class. Similarly, the enthalpy or the entropy change of protein denaturation, when extrapolated to high temperature assuming a temperature-independent heat capacity change, shows a temperature at which its value becomes the same for many different globular proteins on a per weight basis. It is shown that the existence of these temperatures can be explained from a common formalism based on a linear relationship between the thermodynamic quantity and a temperature-independent molecular property that characterizes the solute or the protein. For the small nonpolar molecule transfer processes, this property is the surface area or the number of groups that are brought in contact with water. For protein denaturation, it is suggested that this property measures the polar/nonpolar mix of the internal interaction within the protein interior. Under a certain set of assumptions, this model leads to the conclusion that the nonpolar and the polar groups of the protein contribute roughly equally to the stability of the folded state of the molecule and that the solvent-accessible surface area of the denatured form of a protein is no more than about two-thirds that of the fully extended form.