Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
J Chem Phys. 2010 Jun 14;132(22):225103. doi: 10.1063/1.3453713.
Molecular dynamics simulations of chymotrypsin inhibitor 2 in different polyols (glycerol, xylitol, sorbitol, trehalose, and sucrose) at 363 K were performed to probe the molecular basis of the stabilizing effect, and the data in water, ethanol, and glycol were compared. It is found that protein protection by polyols is positively correlated with both the molecular volume and the fractional polar surface area, and the former contributes more significantly to the protein's stability. Polyol molecules have only a few direct hydrogen bonds with the protein, and the number of hydrogen bonds between a polyol and the protein is similar for different polyols. Thus, it is concluded that the direct interactions contribute little to the stabilizing effect. It is clarified that the preferential exclusion of the polyols is the origin of their protective effects, and it increases with increasing polyol size. Namely, there is preferential hydration on the protein surface (2 A), and polyol molecules cluster around the protein at a distance of about 4 A. The preferential exclusion of polyols leads to indirect interactions that prevent the protein from thermal unfolding. The water structure becomes more ordered with increasing the polyol size. So, the entropy of water in the first hydration shell decreases, and a larger extent of decrease is observed with increasing polyol size, leading to larger transfer free energy. The findings suggest that polyols protect the protein from thermal unfolding via indirect interactions. The work has thus elucidated the molecular mechanism of structural stability of the protein in polyol solutions.
在 363 K 下对糜蛋白酶抑制剂 2 在不同多元醇（甘油、木糖醇、山梨醇、海藻糖和蔗糖）中的分子动力学模拟，以探究稳定化效应的分子基础，并将水、乙醇和乙二醇中的数据进行比较。结果发现，多元醇对蛋白质的保护作用与分子体积和分数极性表面积呈正相关，前者对蛋白质的稳定性贡献更为显著。多元醇分子与蛋白质只有少数直接氢键，并且不同多元醇之间与蛋白质形成氢键的数量相似。因此，可以得出结论，直接相互作用对稳定化效应的贡献不大。澄清的是，多元醇的优先排斥是其保护作用的起源，并且随着多元醇尺寸的增加而增加。也就是说，在蛋白质表面存在优先水合（2 A），并且多元醇分子在距蛋白质约 4 A 的位置聚集。多元醇的优先排斥导致间接相互作用，从而防止蛋白质热解折叠。随着多元醇尺寸的增加，水的结构变得更加有序。因此，第一水合壳层中水的熵降低，并且随着多元醇尺寸的增加观察到更大程度的降低，导致更大的转移自由能。研究结果表明，多元醇通过间接相互作用保护蛋白质免受热解折叠。因此，该工作阐明了蛋白质在多元醇溶液中结构稳定性的分子机制。
