Spolar R S, Ha J H, Record M T
Department of Chemistry, University of Wisconsin, Madison 53706.
Proc Natl Acad Sci U S A. 1989 Nov;86(21):8382-5. doi: 10.1073/pnas.86.21.8382.
Large negative standard heat capacity changes (delta CP degree much less than 0) are the hallmark of processes that remove nonpolar surface from water, including the transfer of nonpolar solutes from water to a nonaqueous phase and the folding, aggregation/association, and ligand-binding reactions of proteins [Sturtevant, J. M. (1977) Proc. Natl. Acad. Sci. USA 74, 2236-2240]. More recently, Baldwin [Baldwin, R. L. (1986) Proc. Natl. Acad. Sci. USA 83, 8069-8072] proposed that the delta CP degree of protein folding could be used to quantify the contribution of the burial of nonpolar surface (the hydrophobic effect) to the stability of a globular protein. We demonstrate that identical correlations between the delta CP degree and the change in water-accessible nonpolar surface area (delta Anp) are obtained for both the transfer of nonpolar solutes from water to the pure liquid phase and the folding of small globular proteins: delta CP degree/delta Anp = -(0.28 +/- 0.05) (where delta Anp is expressed in A2 and delta CP degree is expressed in cal.mol-1.K-1; 1 cal = 4.184 J). The fact that these correlations are identical validates the proposals by both Sturtevant and Baldwin that the hydrophobic effect is in general the dominant contributor to delta CP degree and provides a straightforward means of estimating the contribution of the hydrophobic driving force (delta Ghyd degree) to the standard free energy change of a noncovalent process characterized by a large negative delta CP degree in the physiological temperature range: delta Ghyd degree congruent to (80 +/- 10)delta CP degree.
大的负标准热容变化（ΔCP°远小于0）是从水中去除非极性表面的过程的标志，包括非极性溶质从水相转移到非水相以及蛋白质的折叠、聚集/缔合和配体结合反应[斯特蒂文特，J. M.（1977年）《美国国家科学院院刊》74，2236 - 2240]。最近，鲍德温[鲍德温，R. L.（1986年）《美国国家科学院院刊》83，8069 - 8072]提出，蛋白质折叠的ΔCP°可用于量化非极性表面埋藏（疏水效应）对球状蛋白质稳定性的贡献。我们证明，对于非极性溶质从水相转移到纯液相以及小的球状蛋白质的折叠，在ΔCP°与水可及非极性表面积变化（ΔAnp）之间获得了相同的相关性：ΔCP°/ΔAnp = -（0.28 ± 0.05）（其中ΔAnp以Ų表示，ΔCP°以cal·mol⁻¹·K⁻¹表示；1 cal = 4.184 J）。这些相关性相同这一事实验证了斯特蒂文特和鲍德温的提议，即疏水效应通常是ΔCP°的主要贡献因素，并提供了一种直接的方法来估计疏水驱动力（ΔGhyd°）对生理温度范围内具有大的负ΔCP°的非共价过程的标准自由能变化的贡献：ΔGhyd° ≈ （80 ± 10）ΔCP°。
