α-氨基酸-甲醇-水三元体系中分子间的异系焓相互作用

Heterotactic Enthalpic Interaction of α-Amino Acids-Methanol- Water Ternary Systems

探讨α 氨基酸 -甲醇 -水三元体系中溶质分子间相互作用机理 ,为揭示蛋白质的稳定机理、蛋白质变性的原因和生物大分子与小分子间的相互作用提供溶液热力学依据 .利用 2 2 77热活性检测仪的流动测量系统获得了 2 98.1 5K时甘氨酸、L 丙氨酸、和L 脯氨酸分别与甲醇在水溶液中的混合过程焓变以及各自的稀释焓 ,依据McMillan Mayer理论关联得到异系焓相互作用系数 ,讨论了不同氨基酸与甲醇分子的作用机理 .不同氨基酸与甲醇分子间的焓作用系数的大小主要取决于氨基酸分子结构的差异 ,氨基酸的不同侧基 (非极性或极性 )对焓作用系数有着不同的贡献 ,脯氨酸特殊的五元吡咯环结构对hxy 值有较大的正贡献 .

There is currently considerable interest in the thermodynamic properties of aqueous solutions and mixed aqueous solvents of various amino acids. The principle purpose for studying such systems is to obtain the information that contributes to the growing body of knowledge about solute solvation and solute interactions in aqueous media, and a better understanding of their role played in the conformational stability and unfolding behavior of proteins. Heterotactic enthalpies of mixing and dilution of aqueous methanol solutions and aqueous amino acids （glycine, L-alanine, L-proline） solutions have been determined at 298. 15 K by flow microcalorimetric system of 2277 Thermal Activity Monitor. The data have been analyzed according to the McMillan-Mayer theory to obtain the enthalpic interaction coefficients. The interaction of different amino acids and methanol molecules has been discussed. It is demonstrated that the hxy values between amino acids and the methanol depend on the structure of amino acids. The contributions of different side-groups of amino acids to hxy are different. The five-membered pyrrole ring of proline have larger effect on hxy.