L-苏氨酸在糖及维生素C水溶液中的体积性质

用精密数字密度计和粘度计测定了L-苏氨酸在不同质量分数的葡萄糖、蔗糖及维生素C水溶液中的密度和粘度，计算了L-苏氨酸的极限偏摩尔体积、迁移偏摩尔体积、理论水化数和粘度B系数，讨论了溶剂组成变化对L-苏氨酸迁移偏摩尔体积、粘度B系数和理论水化数的影响.结果表明，随混合溶剂中共溶质含量的增加，迁移偏摩尔体积、粘度B系数随之增加；而由于葡萄糖、蔗糖及维生素C分子与L-苏氨酸荷电中心的直接相互作用，削弱了两性离子带电中心对周围水分子的电致收缩效应，造成了理论水化数随其含量的增加而减小.

Volumetric Properties of L-threonine in Aqueous Glucose, Sucrose and L-ascorbic Acid Solutions

Amino acids and their derivatives are useful as models of specific aspects of more complex proteins in aqueous solution. In this paper, densities and viscosities of L threonine in glucose water, sucrose water and L ascorbic acid water mixed solvents have been measured at 298.15 K by an oscillating tube densimeter and a viscositymeter . Limiting partial molar volume, transfer partial molar volume, number of hydration and viscosity B coefficients of L threonine have been calculated. The viscosity B coefficients and the numbers of hydration of L threonine mixed solvent vary with mass concentration of sugar or L ascorbic acid. The transfer partial molar volumes from water to sugar water or L ascorbic acid water mixtures have been obtained and discussed in terms of the structural hydration interaction model. The results indicate that the transfer partial molar volumes and viscosity B coefficients of L threonine increase with increasing of the mass concentration of sugar or L ascorbic acid, and the hydration numbers of L threonine decrease owing to the interaction of sugar or L ascorbic acid with the zwitterionic groups. It is concluded that the degrees of the effect on volume and hydration number are related to the number of OH groups and the structure of mixture solvent.