Baldwin R L
Proc Natl Acad Sci U S A. 1986 Nov;83(21):8069-72. doi: 10.1073/pnas.83.21.8069.
Accurate calorimetric data for the thermodynamics of transfer of six liquid hydrocarbons to water have been combined with solubility data to provide a model for the temperature dependence of the hydrophobic interaction in protein folding. The model applies at temperatures for which the change in heat capacity (delta Cp) is constant. The extrapolated value of the temperature (Ts) at which the entropy of transfer (delta S degrees) reaches zero is strikingly similar (Ts = 112.8 degrees C +/- 2.2 degrees C) for the six hydrocarbons. This finding provides an interpretation for the empirical relation discovered by Sturtevant: the ratio delta S degrees/delta Cp measured at 25 degrees C is constant for the transfer of nonpolar substances from nonaqueous media to water. Constancy of this ratio is equivalent to Ts = constant. When applied to protein folding, the hydrocarbon model gives estimates of the contributions of the hydrophobic interaction to the entropy and enthalpy changes on unfolding and, by difference, estimates of the residual contributions from other sources. The major share of the large enthalpy change observed on unfolding at high temperatures comes from the hydrophobic interaction. The hydrophobic interaction changes from being entropy-driven at 22 degrees C to being enthalpy-driven at 113 degrees C. Finally, the hydrocarbon model predicts that plots of the specific entropy change on unfolding versus temperature should nearly intersect close to 113 degrees C, as observed by Privalov.
已将六种液态烃转移至水的热力学精确量热数据与溶解度数据相结合，以提供一个关于蛋白质折叠中疏水相互作用温度依赖性的模型。该模型适用于热容变化（ΔCp）为常数的温度范围。对于这六种烃而言，转移熵（ΔS°）达到零时的外推温度（Ts）惊人地相似（Ts = 112.8℃±2.2℃）。这一发现为斯特蒂文特发现的经验关系提供了解释：对于非极性物质从非水介质转移至水的过程，在25℃下测得的ΔS°/ΔCp比值是恒定的。该比值的恒定等同于Ts = 常数。当应用于蛋白质折叠时，烃模型给出了疏水相互作用对去折叠时熵变和焓变贡献的估计值，并且通过差值给出了其他来源的残余贡献估计值。在高温下去折叠时观察到的大焓变的主要部分来自疏水相互作用。疏水相互作用从22℃时的熵驱动转变为113℃时的焓驱动。最后，烃模型预测，去折叠时比熵变与温度的关系图应如普里瓦洛夫所观察到的那样，在接近113℃处几乎相交。
