Measurement of biomolecular interactions and association via light scattering

1.用动态光散射法研究了盐酸胍（GuHCl）和氧化三甲胺（TMAO）对四聚体氰化高铁血红蛋白（CNmetHb）平衡解离的影响。 该测量产生蛋白质的强度平均扩散系数，其随着蛋白质解离而增加。 结果表明，添加足够量的TMAO可以抑制添加盐酸胍增加CNmetHb解离的趋势。 TMAO的稳定作用主要归因于体积排阻（D. Wu）. 2.使用单角度和多角度静态光散射研究了在GTP或GTP类似物GMPCPP和500 mM钾的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。 结果表明，当蛋白质的浓度超过镁依赖的临界值，FtsZ进行协调的形成，类似于一个二阶相变的化学计量约100（GTP）或160（GMPCPP）的高分子量低聚物的窄分布。 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 effect of guanidine hydrochloride (GuHCl) and trimethyl-N-amine oxide (TMAO) upon the equilibrium dissociation of tetrameric to dimeric cyanmethemoglobin (CNmetHb) was studied by measurement of dynamic light scattering. This measurement yields the intensity average diffusion coefficient of the protein, which increases as the protein dissociates. The results showed that the increasing tendency of CNmetHb to dissociate with added GuHCl may be inhibited by addition of sufficient amounts of TMAO. The stabilizing effect of TMAO is attributed largely to volume exclusion (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 using single-angle and multi-angle static light scattering. The results reveal that when the concentration of protein exceeds a Mg-dependent critical value, FtsZ 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 100 (GTP) or 160 (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).