中文摘要：

应用精密数字密度计测定了298．15K时甘氨酸、L-丙氨酸或L-缬氨酸与不同组成的木糖醇-水混合溶剂构成的三元系溶液的密度，计算了氨基酸的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积和水化数．根据结构水合作用模型讨论了迁移偏摩尔体积和水化数的变化规律．结果表明，氨基酸两性离子部分与木糖醇羟基间的相互作用占主导地位，且随木糖醇浓度的增大而增大．氨基酸在木糖醇水溶液中的迁移偏摩尔体积为正值，甘氨酸的迁移偏摩尔体积大于L-丙氨酸和L-缬氨酸的．氨基酸在木糖醇水溶液中的水化数随溶液中木糖醇浓度的增加而减小．

英文摘要：

Densities of glycine-, L-alanine- and L-valine-xylitol-water ternary solutions have been measured at 298.15 K by an oscillating-tube densimeter. Apparent molar volumes, limiting partial molar volumes, transfer partial molar volumes and hydration numbers for these three amino acids have been calculated. The transfer volumes and hydration numbers have been discussed in terms of a structural hydration interaction model, showing that the dominant interaction between OH group of xylitol and the zwitterionic group of amino acids gave a positive contribution to the transfer volumes. The transfer volumes △Vφ^0 of amino acids from water to xylitol-water mixed solvents are positive, and increase with increasing xylitol concentration; △Vφ^0 values of glycine are larger than those of L-alanine and L-valine over the whole range of composition of the mixed solvents studied; the hydration numbers decrease with increasing xylitol concentration.