Measurement of biomolecular interactions and association via light scattering

1.四种蛋白质，BSA，卵清蛋白，卵类粘蛋白和大豆胰蛋白酶抑制剂，浓度高达2毫克/毫升，和一个小分子，蔗糖，浓度高达200克/升的混合物的光散射强度的组合物依赖性进行测量，使用本实验室开发的技术和仪器，并在以前的报告中描述。 使用本实验室开发的适合于非缔合溶质的二元混合物在高浓度下表现出排斥性的自我和异源相互作用的形式主义的结果进行了分析。 结果可以定量占的半经验模型，根据该模型的蛋白质和蔗糖表示为等效的球形颗粒，其有效体积取决于自我和异源相互作用。 结果表明，蔗糖与自身和蛋白质的相互作用是通过空间排斥和弱吸引的组合，部分补偿了空间排斥。 蔗糖和蛋白质之间的相互吸引作用的大小因蛋白质而异，并且对于大豆胰蛋白酶抑制剂最大，而对于卵清蛋白最小（D. Wu）. 2.研究了在GTP或GTP类似物GMPCPP和500 mM钾存在下细菌分隔蛋白FtsZ的自缔合作为蛋白质和Mg浓度的函数。 从几个生物物理测量，包括静态和动态光散射，沉降速度，和荧光相关光谱获得的数据显示，随着浓度的增加，蛋白质经历了一致的形成，类似于一个二阶相变到窄分布的高分子量低聚物与化学计量约80（GTP）或120（GMPCPP）。 在过渡浓度以上，低聚物的量而不是大小增加，而低分子量物质的量大致保持不变（Riskroso，里瓦斯）。 从几种类型的测量中获得的所有数据可以在模型的背景下半定量地解释，根据该模型，稳定的寡聚体是环状物质，其大小反映了蛋白质原纤维在不同浓度的Mg和存在的特定鸟嘌呤核苷酸的存在下在溶液中弯曲或弯曲的趋势（B.阿克罗索湾里瓦斯，CIB）。

1. The composition dependence of the light scattering intensity of mixtures of each of four proteins, BSA, ovalbumin, ovomucoid, and soybean trypsin inhibitor, at concentrations up to 2 mg/ml, and a small molecule, sucrose, at concentrations of up to 200 g/l was measured using a technique and instrumentation developed in this laboratory and described in previous reports. The results were analyzed using formalism developed in this laboratory appropriate for binary mixtures of non-associating solutes exhibiting repulsive self- and hetero-interaction at high concentration. The results could be quantitatively accounted for by a semiempirical model, according to which the protein and sucrose are represented as equivalent spherical particles, the effective volume of which depends upon self- and hetero-interactions. The results indicate that sucrose interacts with itself and with proteins through a combination of steric repulsion and weak attraction that partially compensates for the steric repulsion. The magnitude of the attractive interaction between sucrose and protein varies between proteins, and is greatest for soybean trypsin inhibitor and smallest for ovalbumin (D. Wu). 2. The self-association of the bacterial septation protein FtsZ in the presence of GTP or a GTP analogue, GMPCPP, and 500 mM potassium was studied as a function of protein and Mg concentration. Data obtained from several biophysical measurements, including static and dynamic light scattering, sedimentation velocity, and fluorescence correlation spectroscopy reveal that with increasing concentration, the protein undergoes a concerted formation, akin to a second-order phase transition to a narrow distribution of high molecular weight oligomers with a stoichiometry of ca 80 (GTP) or 120 (GMPCPP). Above the transition concentration, the amount, but not the size, of oligomer increases, while that of low molecular weight species remains roughly constant (Monterroso, Rivas). All of the data obtained from the several types of measurements may be accounted for semiquantitatively in the context of a model, according to which the stable oligomer is a cyclic species, the size of which reflects the tendency of the protein fibrils to flex or curve in solution in the presence of different concentrations of Mg and the particular guanine nucleotide present (B. Monterroso, G. Rivas, CIB).