Carpenter J F, Crowe J H
Department of Zoology, University of California, Davis, 95616.
Cryobiology. 1988 Jun;25(3):244-55. doi: 10.1016/0011-2240(88)90032-6.
We have tested the capacity of 28 different compounds to protect lactate dehydrogenase from damage during freeze-thawing. These solutes come from very dissimilar chemical classes including sugars, polyols, amino acids, methylamines, and lyotropic salts. All the compounds tested, except NaCl, protected the enzyme, to varying degrees, from inactivation. The only characteristic that these compounds have in common, as a group, is that they have all been shown to be preferentially excluded from contact with the surface of proteins in aqueous solution. It has been demonstrated previously (via thermodynamic arguments) that this interaction of solutes with proteins leads to the stabilization of proteins in nonfrozen, aqueous systems. Conversely, those solutes, e.g., urea and guanidine HCl, that bind to proteins destabilize proteins in solution, and we have found that they also enhanced the inactivation of lactate dehydrogenase during freeze-thawing. Based on the results of our freeze-thawing experiments and a review of the theory of protein stabilization in nonfrozen, aqueous solution we propose that the cryoprotection afforded to isolated proteins by solutes can be accounted for by the fact that these solutes are preferentially excluded from contact with the protein's surface.
我们测试了28种不同化合物在冻融过程中保护乳酸脱氢酶免受损伤的能力。这些溶质来自非常不同的化学类别，包括糖类、多元醇、氨基酸、甲胺和离液盐。除氯化钠外，所有测试的化合物都不同程度地保护了该酶不被灭活。作为一个整体，这些化合物唯一的共同特征是，它们都已被证明在水溶液中优先被排除在与蛋白质表面接触之外。先前已经证明（通过热力学论证），溶质与蛋白质的这种相互作用导致蛋白质在非冷冻的水性系统中稳定。相反，那些与蛋白质结合的溶质，例如尿素和盐酸胍，会使溶液中的蛋白质不稳定，并且我们发现它们还会增强冻融过程中乳酸脱氢酶的失活。基于我们的冻融实验结果以及对非冷冻水性溶液中蛋白质稳定化理论的综述，我们提出溶质对分离蛋白质的冷冻保护作用可以通过这些溶质优先被排除在与蛋白质表面接触之外这一事实来解释。
