Department of Chemistry and Biochemistry, Alberta RNA Research and Training Institute, University of Lethbridge, 4401 University Drive, Lethbridge, AB, T1K 3M4, Canada.
School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, 4072, Australia.
Eur Biophys J. 2019 Dec;48(8):781-787. doi: 10.1007/s00249-019-01404-0. Epub 2019 Oct 31.
This investigation examines the validity of employing single-solute theory to interpret SAXS measurements on buffered protein solutions-the current practice despite the necessity to regard the buffer components as additional non-scattering solutes rather than as part of the solvent. The present study of bovine serum albumin in phosphate-buffered saline supplemented with 20-100 g/L sucrose as small cosolute has certainly verified the prediction that the experimentally obtained second virial coefficient should contain protein-cosolute contributions. Nevertheless, the second virial coefficient determined for protein solutions supplemented with high cosolute concentrations on the basis of single-solute theory remains a valid means for identifying conditions conducive to protein crystallization, because the return of a slightly negative second virial coefficient based on single-solute theory [Formula: see text] still establishes the existence of slightly associative interactions between protein molecules, irrespective of the molecular source-protein self-interactions and/or protein-cosolute contributions.
本研究考察了在缓冲蛋白溶液的 SAXS 测量中应用单溶质理论的有效性——尽管需要将缓冲成分视为额外的非散射溶质，而不是溶剂的一部分，但目前仍在采用这种做法。本研究以牛血清白蛋白在磷酸盐缓冲盐水（添加 20-100g/L 蔗糖作为小共溶质）中的研究为例，肯定了实验获得的第二维里系数应包含蛋白质-共溶质贡献的预测。然而，基于单溶质理论确定的高共溶质浓度下补充蛋白质溶液的第二维里系数仍然是一种有效的方法，可以确定有利于蛋白质结晶的条件，因为基于单溶质理论[公式：见文本]返回的略微负的第二维里系数仍然表明蛋白质分子之间存在轻微的缔合相互作用，而不论分子来源是蛋白质自相互作用还是蛋白质-共溶质贡献。
