水溶液中八种氨基酸与尿素的焓相互作用

用LKB-2277精密微热量计测定了298.15K时甘氨酸、L-丙氨酸、L-丝氨酸、L-脯氨酸、L-羟脯氨酸、L-蛋氨酸、L-苏氨酸和L-缬氨酸分别与尿素在水溶液中的混合过程焓变，根据McMillan-Mayer理论关联得到各组焓作用系数，并运用基团贡献法探讨了不同氨基酸与尿素分子的相互作用机制。结果表明，氨基酸的两性离子部分及α-碳上的非极性脂肪侧基、极性的羟基侧基和五元吡咯环侧基等对焓对作用系数具有不同的贡献。

The enthalpic interactions between eight kinds of amino acid and urea in aqueous solutions at 298.15K

The enthalpies of mixing of aqueous urea solutions and eight kinds of aqueous amino acid solutions (glycine, L - alanine, L - serine, L - proline, L - hydroxproline, L - methionine, L - threonine and L -valine) have been determined at 298.15K by LKB-2277 flow microcalorimetric system.The data have been analyzed in terms of the McMillan - Mayer formalism to obtain the enthalpic virial coefficients for heterotactic interactions. The pairwise interactions between amino acids and urea have been studied by a group contribution additivity approach. The results show that the zwitterionic groups and different side - groups of the amino acids, such as non - polar alkyl groups, hydroxy group and five - membered pyrolidine ring, make their different contributions to enthalpic pair interactions.