National Institute of Diabetes and Digestive and Kidney diseases, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, MD 20892, USA.
Biophys Chem. 2010 May;148(1-3):28-33. doi: 10.1016/j.bpc.2010.02.002. Epub 2010 Feb 8.
Insulin self-association at pH 1.85, 1.95, 3.0, 7.2, 8.0 and 10 was studied via composition gradient light scattering (CG-SLS). At pH 1.95 in acetic acid, insulin was found to exist as a monomer, and in pH 1.85 HCl as a dimer. At pH values of 3.0-8.0, the dependence of scattering intensity upon total insulin concentration at concentrations of up to 1.5mg/mL may be quantitatively accounted for by a simple isodesmic association equilibrium scheme requiring only a single association constant for addition of monomer to monomer or any oligomer. At pH 10, the association constant for addition of monomer to monomer was found to be smaller than the association constant for addition of monomer to all higher oligomers by a factor of approximately five. The isodesmic association scheme was also found to quantitatively account for the concentration dependence of the weight-average molecular weight derived from previously published sedimentation equilibrium measurements made at pH 7.0, and the best-fit value of the stepwise equilibrium constant obtained therefrom was in excellent agreement with that obtained from analysis of the light scattering data obtained at pH 7.2.
在 pH 值为 1.85、1.95、3.0、7.2、8.0 和 10 时，通过组成梯度光散射 (CG-SLS) 研究了胰岛素的自缔合。在 pH 值为 1.95 的乙酸中，胰岛素被发现以单体形式存在，而在 pH 值为 1.85 的 HCl 中以二聚体形式存在。在 pH 值为 3.0-8.0 时，在高达 1.5mg/mL 的浓度范围内，散射强度对总胰岛素浓度的依赖性可以通过简单的等摩尔缔合平衡方案进行定量解释，该方案仅需要一个单体与单体或任何低聚物的单体的单一缔合常数。在 pH 值为 10 时，发现单体与单体的加成的缔合常数比单体与所有更高低聚物的加成的缔合常数小约五倍。还发现，等摩尔缔合方案可以定量解释从先前在 pH 值为 7.0 时进行的沉降平衡测量中得出的重均分子量的浓度依赖性，并且从该处获得的逐步平衡常数的最佳拟合值与从在 pH 值为 7.2 时获得的光散射数据的分析获得的平衡常数非常吻合。
