Thermodynamic origin of hofmeister ion effects.
Thermodynamic origin of hofmeister ion effects.
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DOI：
10.1021/jp800816a
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发表时间：
2008-08-07
期刊：
影响因子：
--
通讯作者：
Record MT Jr
中科院分区：
文献类型：
--
作者：
Pegram LM;Record MT Jr
定量解释和预测霍夫迈斯特离子对蛋白质过程的影响，包括折叠和结晶，一直是一个世纪以来难以实现的研究目标。在这里，一个定量的热力学分析，被用来处理溶质与生物聚合物表面的非库仑相互作用，最近扩展到分析Hofmeister盐对水的表面张力的影响，被应用于文献中关于小分子烃和模型肽的溶解度数据。这一分析使我们能够获得碳氢化合物表面水化b1(H2Oä−2)的最小估计值和表征该水化水和散装水之间的盐和盐离子分布的分配系数Kp。假设从碳氢表面的水合水中完全排除Na~+和Na_2SO_4离子(这种盐使碳氢化合物的溶解度降低最大，表面张力增加最大)，我们得到与空气-水表面相同的b1(∼0.18H2O？−2)。对于蛋白质过程，非极性表面的阳离子和阴离子分配系数的级数遵循Hofmeister级数，但对于排除方向(优先水化)的阳离子，它们的秩次被强烈抵消。假设水可达表面积(ASA)粗粒分解为非极性、极性酰胺和其他极性ASA，并假设相同的水化b1来解释多肽的溶解度增量，我们确定了酰胺表面的盐分配系数。根据观察到的Cl-−和Na+(也包括K+)在蛋白质过程的阴离子和阳离子霍夫迈斯特系列的中间占据中性位置，这些分配系数被分离为单离子贡献。不考虑这一指定，我们发现所有被研究的阳离子都强烈地聚集在酰胺表面，而大多数阴离子被排除在外。离子效应是独立的和相加的，允许根据结构信息(ASA)成功地预测霍夫迈斯特盐对胶束形成和其他过程的影响。
Quantitative interpretation and prediction of Hofmeister ion effects on protein processes, including folding and crystallization, have been elusive goals of a century of research. Here, a quantitative thermodynamic analysis, developed to treat noncoulombic interactions of solutes with biopolymer surface and recently extended to analyze the effects of Hofmeister salts on the surface tension of water, is applied to literature solubility data for small hydrocarbons and model peptides. This analysis allows us to obtain a minimum estimate of the hydration b1 (H2O Å−2) of hydrocarbon surface and partition coefficients Kp characterizing the distribution of salts and salt ions between this hydration water and bulk water. Assuming that Na+ and ions of Na2SO4 (the salt giving the largest reduction in hydrocarbon solubility as well as the largest increase in surface tension) are fully excluded from the hydration water at the hydrocarbon surface, we obtain the same b1 as for air-water surface (∼0.18 H2O Å−2). Rank orders of cation and anion partition coefficients for nonpolar surface follow the Hofmeister series for protein processes, but are strongly offset for cations in the direction of exclusion (preferential hydration). Assuming a coarse-grained decomposition of water accessible surface area (ASA) into nonpolar, polar amide, and other polar ASA and the same hydration b1 to interpret peptide solubility increments, we determine salt partition coefficients for amide surface. These partition coefficients are separated into single-ion contributions based on the observation that both Cl− and Na+ (also K+) occupy neutral positions in the middle of the anion and cation Hofmeister series for protein processes. Independent of this assignment, we find that all cations investigated are strongly accumulated at amide surface while most anions are excluded. Ion effects are independent and additive, allowing successful prediction of Hofmeister salt effects on micelle formation and other processes from structural information (ASA).
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影响因子：
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通讯作者：
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