EFFECT OF COMPOUNDS OF UREA-GUANIDINIUM CLASS ON ACTIVITY COEFFICIENT OF ACETYLTETRAGLYCINE ETHYL ESTER AND RELATED COMPOUNDS
EFFECT OF COMPOUNDS OF UREA-GUANIDINIUM CLASS ON ACTIVITY COEFFICIENT OF ACETYLTETRAGLYCINE ETHYL ESTER AND RELATED COMPOUNDS
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DOI：
10.1021/ja01089a028
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发表时间：
1965-01-01
影响因子：
15
通讯作者：
JENCKS, WP
中科院分区：
文献类型：
--
作者：
ROBINSON, DR;JENCKS, WP
几种蛋白质变性剂对乙酰四甘氨酸乙酯（ATGEE）、三种苯甲氧甘氨酸衍生物、甲苯和苯甲醇在水溶液中的活性系数的影响已通过溶解度测量确定。尿素 (8 M) 和 7 M 盐酸胍分别使 ATGEE（一种主要由酰胺基团组成的化合物）的溶解度增加 3.2 倍和 7.5 倍。这不是“疏水”效应，因为（z）脲和盐酸胍的烷基取代消除了它们溶解ATGEE的能力，但增加了它们溶解非极性化合物的能力；（z'z）非极性化合物的溶剂，例如乙醇和二恶烷，对ATGEE影响很小或没有；（iii）尿素对ATGEE的活度系数影响 与碳氢化合物相反，ATGEE 随着温度从 0 升高到 40 度而降低。未取代和烷基取代的脲和盐酸胍都会降低苯甲酰基甘酰胺的活度系数，这表明这些化合物的“疏水”和“非疏水”效果都很显着。尿素的活度系数效应对一系列短的碳苯氧基甘氨酸肽中的甘氨酸单元的数量表现出很小的敏感性，即，可能预期由非特异性溶剂效应产生的简单加和关系在这种情况下不成立。不同变性剂在降低 ATGEE 活性系数方面的相对有效性通常与它们在使牛血清白蛋白和一些其他蛋白质变性方面的有效性相似。结论是，脲-胍-类变性剂的“非疏水”作用通过降低变性蛋白质中暴露的酰胺和肽基团的活性系数，对其蛋白质变性效果做出了重大贡献。对于这些化合物对蛋白质的溶解度和解离成亚基的影响，得出了类似的结论。 “非疏水”效应的机制尚未确定，但结果与变性剂与 ATGEE 直接相互作用形成复合物一致，在 25 时尿素的缔合常数为 0.29，氯化胍的缔合常数为 0.90，尿素复合物的缔合热约为 2800 卡/摩尔。
The effects of several protein denaturingagents on the activity coefficients of acetyltetraglycine ethyl ester {ATGEE), three carbobenzoxyglycine derivatives, toluene, and benzyl alcohol in aqueous solution havebeen de-termined by solubility measurements. Urea {8 M) and 7 M guanidine hydrochloride cause a 3.2-and 7.5-fold increase in solubility, respectively, of ATGEE, a com-pound composed principally of amide groups. This is not a “hydrophobic” effect because (z) alkyl substitution of urea and guanidine hydrochloride eliminates their ability to solubilize ATGEE, but increases their ability to solubilize nonpolar compounds;(z'z) solvents for non-polar compounds, such as ethanol and dioxane, have little or no effect on ATGEE;{iii) the activity coefficient effect of urea on ATGEE, in contrast to that on hydro-carbons, decreases with increasing temperature from 0 to 40. The activity coefficients of carbobenzoxyglycineamides are decreased by both unsubstituted and alkyl-substituted ureas and guanidine hydrochlorides, which suggests that both “hydrophobic” and “nonhydrophobic” effects are significant with these compounds. The activity coefficient effect of urea displays little sensitivity to the number of glycine units in a series of short carbo-benzoxyglycine peptides, ie, a simple additivity relation, which might be expected to result from nonspecific solvent effects, does not hold in this case. The relative effectiveness of different denaturing agents in decreasing the activity coefficient of ATGEE generally parallels their effectiveness in denaturing bovine serum albumin and some other proteins. It is concluded that a “nonhydrophobic” effect of denaturing agents of the urea-guani-dinium class makes a major contribution to their de-naturing effectiveness toward proteins by decreasing the activity coefficients of exposed amide and peptide groups in the denatured protein. Similar conclusions are drawn for the effects of these compounds on the solubility and dissociation into subunits of proteins. The mech-anism of the “nonhydrophobic” effect has not been established, but the results are consistent with a direct interaction of the denaturing agent with ATGEE to form a complex, with an association constant of 0.29 for urea and 0.90 for guanidinium chloride at 25 and a heat of association on the order of—2800 cal./mole for the urea complex.