Wills P R, Nichol L W, Siezen R J
Biophys Chem. 1980 Feb;11(1):71-82. doi: 10.1016/0301-4622(80)85009-5.
An improved iterative method for computing association constants from sedimentation equilibrium results obtained with self-interacting protein systems is presented which accounts for the composition-dependence of the activity coefficients of all oligomeric species. The method is based on the calculation of viral coefficients from covolume and charge considerations, the statistical mechanical basis of which is discussed in relation to the DLVO theory. The method is applied to results obtained with lysozyme in diethylbarbiturate buffer of pH 8.0 and ionic strength 0.15 at 15 degrees C. It is shown that these results, encompassing a range of total solute concentration up to 19.7 g/liter are consistent with self-association patterns comprising either a monomer--dimer--trimer system or an isodesmic indefinite self-association of the monomer, the latter being favored. A firmer distinction between these possibilities is sought on the basis of the dependence of the weight-average partition coefficient, determined by frontal gel chromatography, on total solute concentration (up to 56.6/liter). This analysis accounts for the composition-dependence of the ratio of the activity coefficients of partitioning monomer in mobile and stationary phases. It is concluded that all results are consistent with an indefinite self-association of lysozyme governed by a single association constant of 4.61 x 10(2) liter/mole.
本文提出了一种改进的迭代方法，用于从自相互作用蛋白质系统的沉降平衡结果计算缔合常数，该方法考虑了所有寡聚体物种活度系数的组成依赖性。该方法基于从共体积和电荷考虑计算维里系数，并讨论了其统计力学基础与DLVO理论的关系。该方法应用于在15℃下pH 8.0和离子强度0.15的二乙巴比妥酸盐缓冲液中溶菌酶的实验结果。结果表明，这些涵盖总溶质浓度高达19.7 g/升范围的结果与包含单体 - 二聚体 - 三聚体系统或单体的等键不定自缔合的自缔合模式一致，后者更受青睐。基于前沿凝胶色谱法测定的重均分配系数对总溶质浓度（高达56.6 /升）的依赖性，寻求对这些可能性进行更明确的区分。该分析考虑了流动相和固定相中分配单体的活度系数之比的组成依赖性。得出的结论是，所有结果都与溶菌酶由单一缔合常数4.61×10²升/摩尔控制的不定自缔合一致。
