Department of Chemistry, University of Wisconsin, Madison WI 53706, USA.
Faraday Discuss. 2013;160:9-44; discussion 103-20. doi: 10.1039/c2fd20128c.
Understanding how Hofmeister salt ions and other solutes interact with proteins, nucleic acids, other biopolymers and water and thereby affect protein and nucleic acid processes as well as model processes (e.g. solubility of model compounds) in aqueous solution is a longstanding goal of biophysical research. Empirical Hofmeister salt and solute "m-values" (derivatives of the observed standard free energy change for a model or biopolymer process with respect to solute or salt concentration m3) are equal to differences in chemical potential derivatives: m-value = delta(dmu2/dm3) = delta mu23, which quantify the preferential interactions of the solute or salt with the surface of the biopolymer or model system (component 2) exposed or buried in the process. Using the solute partitioning model (SPM), we dissect mu23 values for interactions of a solute or Hofmeister salt with a set of model compounds displaying the key functional groups of biopolymers to obtain interaction potentials (called alpha-values) that quantify the interaction of the solute or salt per unit area of each functional group or type of surface. Interpreted using the SPM, these alpha-values provide quantitative information about both the hydration of functional groups and the competitive interaction of water and the solute or salt with functional groups. The analysis corroborates and quantifies previous proposals that the Hofmeister anion and cation series for biopolymer processes are determined by ion-specific, mostly unfavorable interactions with hydrocarbon surfaces; the balance between these unfavorable nonpolar interactions and often-favorable interactions of ions with polar functional groups determine the series null points. The placement of urea and glycine betaine (GB) at opposite ends of the corresponding series of nonelectrolytes results from the favorable interactions of urea, and unfavorable interactions of GB, with many (but not all) biopolymer functional groups. Interaction potentials and local-bulk partition coefficients quantifying the distribution of solutes (e.g. urea, glycine betaine) and Hofmeister salt ions in the vicinity of each functional group make good chemical sense when interpreted in terms of competitive noncovalent interactions. These interaction potentials allow solute and Hofmeister (noncoulombic) salt effects on protein and nucleic acid processes to be interpreted or predicted, and allow the use of solutes and salts as probes of
了解霍夫迈斯特盐离子和其他溶质如何与蛋白质、核酸、其他生物聚合物以及水相互作用，从而影响蛋白质和核酸的过程以及水溶液中的模型过程（例如模型化合物的溶解度），这是生物物理研究的一个长期目标。经验霍夫迈斯特盐和溶质的“m 值”（观察到的标准自由能变化的衍生物，相对于溶质或盐浓度 m3，用于模型或生物聚合物过程）等于化学势衍生物的差异：m 值= delta(dmu2/dm3)= delta mu23，它量化了溶质或盐与暴露或埋藏在该过程中的生物聚合物或模型系统（组分 2）表面的优先相互作用。使用溶质分配模型（SPM），我们剖析了溶质或霍夫迈斯特盐与一组显示生物聚合物关键官能团的模型化合物相互作用的 mu23 值，以获得相互作用势（称为 alpha 值），该值量化了每个官能团或类型表面的单位面积上溶质或盐的相互作用。使用 SPM 进行解释，这些 alpha 值提供了有关官能团水合作用以及水和溶质或盐与官能团竞争相互作用的定量信息。该分析证实并量化了先前的提议，即生物聚合物过程的霍夫迈斯特阴离子和阳离子系列是由离子特异性、主要是与烃表面的不利相互作用决定的；这些不利的非极性相互作用与离子与极性官能团的有利相互作用之间的平衡决定了系列的零点。尿素和甘氨酸甜菜碱（GB）在非电解质相应系列的相对两端的位置是由于尿素的有利相互作用以及 GB 与许多（但不是全部）生物聚合物官能团的不利相互作用所致。量化溶质（例如尿素、甘氨酸甜菜碱）和霍夫迈斯特盐离子在每个官能团附近分布的相互作用势和局部-整体分配系数，当根据竞争非共价相互作用进行解释时，具有很好的化学意义。这些相互作用势允许解释或预测溶质和霍夫迈斯特（非库仑）盐对蛋白质和核酸过程的影响，并允许将溶质和盐用作
