National Center for Macromolecular Hydrodynamics, School of Biosciences, University of Nottingham, Sutton Bonington, UK.
Anal Biochem. 2013 Apr 15;435(2):159-65. doi: 10.1016/j.ab.2012.12.014. Epub 2013 Jan 10.
Theoretical consideration is given to the effect of cosolutes (including buffer and electrolyte components) on the determination of second virial coefficients for proteins by small-angle X-ray scattering (SAXS)-a factor overlooked in current analyses in terms of expressions for a two-component system. A potential deficiency of existing practices is illustrated by reassessment of published results on the effect of polyethylene glycol concentration on the second virial coefficient for urate oxidase. This error reflects the substitution of I(0,c3,0), the scattering intensity in the limit of zero scattering angle and solute concentration, for I(0,0,0), the corresponding parameter in the limit of zero cosolute concentration (c3) as well. Published static light scattering results on the dependence of the apparent molecular weight of ovalbumin on buffer concentration are extrapolated to zero concentration to obtain the true value (M2) and thereby establish the feasibility of obtaining the analogous SAXS parameter, I(0,0,0), experimentally.
理论上考虑了共溶剂（包括缓冲剂和电解质成分）对小角 X 射线散射（SAXS）测定蛋白质第二维里系数的影响——这是当前分析中在双组分系统的表达式方面被忽视的一个因素。通过重新评估关于聚乙二醇浓度对尿酸氧化酶第二维里系数影响的已发表结果，说明了现有实践中存在的潜在缺陷。这种错误反映了用 I(0,c3,0)（在零散射角和溶质浓度极限下的散射强度）代替 I(0,0,0)（在零共溶剂浓度（c3）极限下的相应参数）。已发表的关于卵清蛋白表观分子量对缓冲液浓度依赖性的静态光散射结果被外推到零浓度以获得真实值（M2），从而从实验上确定获得类似的 SAXS 参数 I(0,0,0)的可行性。
