Studies of molecular crowding

1.通过荧光去偏振法研究了尿素和三甲基N-胺氧化物(TMAO)对α-胰凝乳蛋白酶(CHY)和大豆胰蛋白酶抑制剂(STI)异位缔合的影响。用Alexa-488标记STI，用Chy滴定。标记的STI的转动弛豫时间与添加的CHY的浓度的依赖关系可以在一个模型的背景下解释，在该模型中，CHY可以以近似相等的亲和力结合到STI上的两个独立的位置。在不同添加浓度的尿素和TMAO存在下进行滴定，发现添加尿素倾向于抑制CHY和STI的缔合，而TMAO增强了缔合。对结果与添加尿素和TMAO浓度的相关性分析表明，这两种影响虽然方向相反，但是相加的。(吴东升) 2.将浓缩剂对稀相反应物自缔合模型的总体影响分析为排挤体积效应和聚集剂与反应物物种间吸引作用的影响之和。(A·明顿)

1. The effect of urea and trimethyl-N-amine oxide (TMAO) upon the heteroassociation of alpha-chymotrypsin (chy) and soybean trypsin inhibitor (STI) was studied by measurement of fluorescence depolarization. STI was labeled with Alexa-488 and titrated with chy. The dependence of the rotational relaxation time of labeled STI upon the concentration of added chy was interpreted in the context of a model in which chy could bind to two independent sites on STI with approximately equal affinity. Titrations were conducted in the presence of various added concentrations of urea and TMAO, and it was found that while added urea tended to inhibit the association of chy and STI, TMAO enhanced the association. Analysis of the dependence of results upon the concentrations of added urea and TMAO showed that the two effects, although in opposite directions, were additive. (D. Wu) 2. The overall effect of a concentrated crowding agent upon a model for self-association of a dilute reactant was analyzed as the sum of the effects of both excluded volume and attractive interactions between the crowding agent and the reactant species. (A. Minton)