Measurement of biomolecular association via static and dynamic light scattering

1.我们同时收集了非相互作用和相互作用蛋白质混合物的组合物依赖的静态和动态光散射数据，并开发了一个全球性的分析这两个数量的组合物依赖性。 与预期相反，添加动态光散射数据并没有提高仅使用静态光散射数据可获得的表征的分辨率。 这项工作的成果正在编写中，准备出版。 （B.（roso） 2.我们通过测量静态光散射的浓度依赖性，表征了无锌胰岛素在宽pH值范围内的自缔合平衡（A. Attri）。 在pH 1.6时，胰岛素在醋酸盐缓冲液中为非缔合单体，在HCl中为极弱的自缔合二聚体。 在pH值为3和8之间，散射的浓度依赖性定量占一个简单的等键不定缔合计划。 在pH值为10时，散射的浓度依赖性是定量占由一个修改的等键计划，其中的平衡缔合常数为单体单体的添加是约5倍小于平衡缔合常数为单体添加到所有更高的低聚物。 这项工作的报告已经发表（A。阿特里角费尔南德斯）。 3.我们的特点是在锌的存在下，胰岛素的自缔合平衡。 静态光散射的浓度依赖性分析表明，在研究的浓度范围内（0.3 - 5 mg/ml），胰岛素表现为六聚体经历等键不确定的自缔合。 动态光散射的浓度依赖性的分析证实了这一解释。 这项工作的报告已经发表（A。阿特里角费尔南德斯）。 4.我们已经表征了tau蛋白和7 K分子量级分的肝素（一种具有高负电荷密度的硫酸化多糖）之间的相互作用。 散射强度的组成依赖性很好地描述了一个简单的1：1的异缔合。 这是首次将组成梯度-静态光散射应用于两种不同类型大分子之间的缔合。 这项工作的报告已经发表（C。费尔南德斯，Y. Liang）。 5.我们已经测量了光散射的强度对蛋白质浓度的依赖性，在不同浓度的Mg++离子的存在下，在含有GTP的GTP再生系统或GPCPP，一种缓慢水解的GTP类似物的FtsZ溶液中。 观察到的依赖性的最简单的解释是，FtsZ-GTP或FtsZ-GPCPP的自缔合进行最初的线性增长，根据一个不确定的等键方案，然后通过合作形成一个稳定的寡聚体或窄的大小分布的寡聚体的大小30-40亚基，被认为是环状的。 这项工作正在编写出版（G。里瓦斯）。

1. We have simultaneously collected composition-dependent static and dynamic light scattering data on mixtures of non-interacting and interacting proteins, and developed a global analysis of the composition-dependence of both quantities. Contrary to expectation, addition of dynamic light scattering data did not enhance the resolution of characterization obtainable using static light scattering data only. Results of this work are being written up for publication. (B. Monterroso) 2. We have characterized the self-association equilibria of zinc-free insulin over a wide range of pH values, via measurement of the concentration dependence of static light scattering (A. Attri). At pH 1.6, insulin is a non-associating monomer in acetate buffer and a very weakly self-associating dimer in HCl. At pH values between 3 and 8, the concentration dependence of scattering is quantitatively accounted for by a simple isodesmic indefinite association scheme. At pH 10, the concentration dependence of scattering is quantitatively accounted for by a modified isodesmic scheme in which the equilibrium association constant for addition of monomer to monomer is about five times smaller than the equilibrium association constant for addition of monomer to all higher oligomers. A report of this work has been published (A. Attri, C. Fernandez). 3. We have characterized the self-association equilibria of insulin in the presence of zinc. Analysis of the concentration dependence of static light scattering indicates that over the concentration range studied (0.3 - 5 mg/ml), insulin behaves as a hexamer undergoing isodesmic indefinite self-association. Analysis of the concentration dependence of the dynamic light scattering confirms this interpretation. A report of this work has been published (A. Attri, C. Fernandez). 4. We have characterized the interaction between tau protein and a 7K molecular weight fraction of heparin, a sulfated polysaccharide with high negative charge density. The composition dependence of the scattering intensity is well described by a simple 1:1 heteroassociation. This is the first application of composition gradient - static light scattering to the association between two different types of macromolecule. A report of this work has been published (C. Fernandez, Y. Liang). 5. We have measured the dependence of the intensity of light scattering upon protein concentration in solutions of FtsZ containing either GTP an a GTP-regenerating system or GPCPP, a slowly hydrolyzable GTP analog, in the presence of varying concentrations of Mg++ ion. The simplest interpretation of the observed dependence is that self-association of either FtsZ-GTP or FtsZ-GPCPP proceeds initially by linear growtn according to an indefinite isodesmic scheme, followed by cooperative formation of a stable oligomer or narrow size distribution of oligomers of size 30-40 subunits that are thought to be cyclic. This work is being written up for publication (G. Rivas).