脲-二酮哌嗪相互作用：蛋白质尿素诱导变性的模型

Urea-diketopiperazine interactions: a model for urea induced denaturation of proteins.

作者信息

Sijpkes A H, van de Kleut G J, Gill S C

机构信息

Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309-0215.

出版信息

Biophys Chem. 1993 Apr;46(2):171-7. doi: 10.1016/0301-4622(93)85024-c.

DOI:10.1016/0301-4622(93)85024-c

PMID:8513118

Abstract

The solubility of diketopiperazine (DKP) in aqueous urea (U) solutions with molalities ranging from 0 to 16 mol kg-1 (corresponding to urea activities ranging from 0 to 10 mol kg-1) has been measured as a function of the urea activity at 298.15 K. In accordance with a previous study the solubility of diketopiperazine increases with increasing urea activity but drops sharply at a urea activity of 5.7 +/- 0.2 mol kg-1. This drop in solubility can be attributed to the formation of a DKP.U2 cocrystal. The solubility data were fitted to a simple model based on the stoichiometry of the DKP.U2 to yield an intrinsic equilibrium constant kappa describing the interactions occurring between a urea molecule and a peptide group of diketopiperazine in aqueous solution, its value being kappa = 0.0447 +/- 0.0007 kg mol-1. When the activity of water is taken into account, kappa has a lower value of 0.0398 +/- 0.0007 kg mol-1.

摘要

在298.15 K下，已测量了二酮哌嗪（DKP）在质量摩尔浓度范围为0至16 mol kg⁻¹（对应尿素活度范围为0至10 mol kg⁻¹）的尿素（U）水溶液中的溶解度，并将其作为尿素活度的函数。与先前的研究一致，二酮哌嗪的溶解度随尿素活度的增加而增加，但在尿素活度为5.7±0.2 mol kg⁻¹时急剧下降。溶解度的这种下降可归因于DKP·U₂共晶的形成。根据DKP·U₂的化学计量比，将溶解度数据拟合到一个简单模型中，以得出一个描述尿素分子与二酮哌嗪的肽基团在水溶液中相互作用的固有平衡常数κ，其值为κ = 0.0447±0.0007 kg mol⁻¹。当考虑水的活度时，κ的值较低，为0.0398±0.0007 kg mol⁻¹。