MECHANISM OF PROTEIN SALTING IN AND SALTING OUT BY DIVALENT-CATION SALTS - BALANCE BETWEEN HYDRATION AND SALT BINDING
MECHANISM OF PROTEIN SALTING IN AND SALTING OUT BY DIVALENT-CATION SALTS - BALANCE BETWEEN HYDRATION AND SALT BINDING
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DOI：
10.1021/bi00320a004
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发表时间：
1984-01-01
期刊：
影响因子：
2.9
通讯作者：
TIMASHEFF, SN
中科院分区：
文献类型：
--
作者：
ARAKAWA, T;TIMASHEFF, SN
本文研究了Mg ~（2+）、Ba ~（2+）、Ca ~（2+）、Mn ~（2+）和Ni ~（2+）的硫酸盐、乙酸盐和氯化物[CaSO_4、BaSO_4、Mn-（OAc）_2和Ni（OAc）_2除外]的浓水溶液中蛋白质与溶剂组分的优先相互作用，并与Na ~+盐的结果进行了比较。对于所有的盐，优先水化的顺序为Cl- <CH 3-COO- <SO 4 2-，与阴离子溶致系列一致，而相同的参数表现出的顺序为Mn 2+，Ni 2 + <Ca 2+，Ba 2 + <Mg 2 + < Na+。盐的盐析和稳定或盐在和不稳定的有效性解释所观察到的优先相互作用。盐的表面张力增量与二价阳离子盐的表面张力增量没有相关性，而表面张力增量是导致Na+盐优先相互作用的主要因素。二价阳离子与蛋白质的结合克服了由于表面张力增加而导致的盐排斥，从而导致优先水合的减少。与此机制相一致，MgCl 2的优先相互作用具有强烈的pH依赖性，这是由于Mg 2+对蛋白质的亲和力依赖于蛋白质的电荷，而NaCl的优先相互作用则不依赖于pH。所提出的机制得到了支持之间的强相关性的优先相互作用的结果和这些盐与模型肽化合物乙酰基四甘氨酸乙酯，所描述的罗宾逊和Jencks的相互作用。
The preferential interactions of proteins with solvent components were studied in concentrated aqueous solutions of the sulfate, acetate and chloride salts of Mg2+, Ba2+, Ca2+, Mn2 + and Ni2+ [except for CaSO4, BaSO4, Mn-(OAc)2 and Ni(OAc)2], and results were compared with those of the Na+ salts. For all the salts, the preferential hydration increased in the order of Cl- < CH3-COO- < SO42- regardless of the cationic species used, in agreement with the anionic lyotropic series, and the same parameter exhibited a tendency to increase in the order of Mn2+, Ni2+ < Ca2+, Ba2+ < Mg2+ < Na+. The salting-out and stabilizing or salting-in and destabilizing effectiveness of the salts were interpreted in terms of the observed preferential interactions. The surface tension increment of salts, which is a major factor responsible for the preferential interactions of the Na+ salts, had no correlation with those of the divalent cation salts. The binding of divalent cations to the proteins overcomes the salt exclusion due to the surface tension increase, leading to a decrease in the preferential hydration. In conformity with this mechanism, the preferential interaction of MgCl2 was strongly pH dependent, because of the protein charge-dependent affinity of Mg2+ for prot eins, while NaCl showed no pH dependence of the preferential interaction. The proposed mechanism was supported by a strong correlation between the preferential interaction results and the interaction of these salts with the model peptide compound acetyltetraglycine ethyl ester, described by Robinson and Jencks.