Zou Q, Habermann-Rottinghaus S M, Murphy K P
Department of Biochemistry, University of Iowa College of Medicine, Iowa City 52242, USA.
Proteins. 1998 May 1;31(2):107-15.
The effects of urea on protein stability have been studied using a model system in which we have determined the energetics of dissolution of a homologous series of cyclic dipeptides into aqueous urea solutions of varying concentration at 25 degrees C using calorimetry. The data support a model in which urea denatures proteins by decreasing the hydrophobic effect and by directly binding to the amide units via hydrogen bonds. The data indicate also that the enthalpy of amide hydrogen bond formation in water is considerably higher than previously estimated. Previous estimates included the contribution of hydrophobic transfer of the alpha-carbon resulting in an overestimate of the binding between urea and the amide unit of the backbone and an underestimate of the binding enthalpy.
利用一个模型系统研究了尿素对蛋白质稳定性的影响。在该模型系统中，我们通过量热法测定了一系列环状二肽在25℃下溶解于不同浓度的尿素水溶液中的能量学。数据支持这样一个模型，即尿素通过降低疏水作用以及通过氢键直接与酰胺单元结合来使蛋白质变性。数据还表明，水中酰胺氢键形成的焓比先前估计的要高得多。先前的估计包括α-碳疏水转移的贡献，导致对尿素与主链酰胺单元之间结合的高估以及对结合焓的低估。
