298.15K甘氨酰二肽在乙酸钠水溶液中的体积性质

测定了298.15 K三种甘氨酰二肽(甘氨酰甘氨酸、甘氨酰-L-缬氨酸和甘氨酰-L-亮氨酸)在0.5, 1.0, 1.5和2.0 mol•kg－1乙酸钠水溶液中的密度, 计算了这些肽在乙酸钠水溶液中的表观摩尔体积, 标准偏摩尔体积, 标准偏摩尔转移体积, 理论水化数和体积相互作用参数. 结果表明: 甘氨酰二肽的标准偏摩尔体积和标准偏摩尔转移体积均随乙酸钠浓度的增加而增大, 溶液中离子与肽带电基团/甘氨酰基团(CH2CONH)之间的相互作用大于离子与肽的非极性基团间的相互作用, 乙酸钠和甘氨酰二肽之间主要是对相互作用. 利用共球交盖模型对所研究的肽与乙酸钠之间的体积相互作用进行了解释. 利用氨基酸的标准偏摩尔体积值, 对二肽的标准偏摩尔体积进行了估算, 发现计算值与实验值一致.

Volumetric Properties of Glycyl Dipeptides in Aqueous Sodium Acetate Solutions at 298.15 K

Densities have been measured for glycylglycine, glycyl-L-valine and glycyl-L-leucine in aqueous solutions of 0.5, 1.0, 1.5 and 2.0 mol•kg－1 sodium acetate at 298.15 K. The apparent molar volumes, standard partial molar volumes ( ), standard partial molar volumes of transfer for the dipeptide from water to aqueous sodium acetate solutions (DtV$), the hydration number and volumetric interaction coefficients have been calculated. Both the and DtV$ for the glycyl dipeptides increase with increasing molality of sodium acetate. The interactions between charged center or glycyl units of the peptide and ions dominate those between alkyl groups of the peptide and the ions. The interaction between the peptides and sodium acetate is mainly pairwise. The results were interpreted successfully by the cosphere overlap model. Using the values of the amino acids, the standard partial molar volumes of peptide were estimated. Excellent agreement between the calculated values and the experimental values of the peptides was observed.