甘氨酸、L-丙氨酸和L-丝氨酸在尿素水溶液中的体积性质

蛋白质的折叠与解折叠、稳定性、变性行为和酶的活性等都受到环境中其它各种物质影响.作为蛋白质模型分子,氨基酸在混合溶液中的热力学研究近年来引起了广泛重视.尿素在生物体系中的独特地位主要表现在:它是水结构的破坏者,同时又是许多球状蛋白的变性剂.然而,尿素对球状蛋白的变性作用尚未达成共识.

Volumetric Properties of Glycine, L-Alanine and L-Serine in Aqueous Urea Solutions at 298.15 K

Densities of glycine, L-alanine, L-serine in various aqueous urea solutions were measured at 298. 15 K with an Anton Paar Model 55 densimeter. From these densities, apparent molar volumes and limited partial molar volumes were calculated, transfer volumes from water to aqueous urea solutions and substituent contributions to the transfer volumes have been obtained. Furthermore, the hydration numbers and volumetric interaction coefficients for the three amino acids were evaluated. Solvent and substituent effects are discussed in detail. The results show that all of the transfer volumes are positive, except alanine in rich-water region, and increase with increasing urea concentration; the side-chain contributions to the transfer volumes are highly related to the nature of side-chain groups; the hydration numbers for the three amino acids in solutions decrease with increasing urea concentration.