Makhatadze G I, Privalov P L
Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
Biophys Chem. 1994 Aug;51(2-3):291-304; discussion 304-9. doi: 10.1016/0301-4622(94)00050-6.
The enthalpies and entropies of hydration of polar, aromatic and aliphatic groups upon unfolding of nine different globular proteins were calculated over a broad temperature range using information on the three-dimensional structures of the native states of these proteins and thermodynamic data on the transfer of various low molecular compounds modeling protein groups from the gaseous phase to water. Exclusion of these hydration effects from the calorimetrically determined enthalpy and entropy of unfolding of these proteins permitted us to estimate the energy of interactions between groups packed in the interior of the native protein, and also the entropy effects associated with the increase of configurational freedom of the backbone polypeptide chain and side chains. It is shown that the compact native state of a protein is stabilized by the enthalpic interactions between internal groups while the hydration effects of all the groups, except the aliphatic ones, which are exposed upon unfolding destabilize this state.
利用这九种不同球状蛋白质天然态的三维结构信息以及各种模拟蛋白质基团的低分子化合物从气相转移到水中的热力学数据，在很宽的温度范围内计算了这九种球状蛋白质展开时极性、芳香族和脂肪族基团的水合焓和水合熵。从量热法测定的这些蛋白质展开焓和熵中排除这些水合效应，使我们能够估算天然蛋白质内部堆积基团之间的相互作用能，以及与主链多肽链和侧链构象自由度增加相关的熵效应。结果表明，蛋白质紧密的天然态通过内部基团之间的焓相互作用得以稳定，而除脂肪族基团外，所有在展开时暴露的基团的水合效应都会使该状态不稳定。
