脂肪族α-氨基酸疏水自缔合作用的流动微量热法研究

Study on Hydrophobic Self-association of Aliphatic α-amino Acids by Flow Microcalorimetry

建立了水溶液中脂肪族α-氨基酸疏水自缔合相互作用的化学模型,根据模型方程对由精密流动微量热法测得的α-氨基酸水溶液的稀释焓数据进行回归分析,得到等步自缔合作用的平衡常数(K)、焓变(ΔHm)和熵变(ΔSm)等热力学参数,发现焓、熵之间存在很好的补偿关系.同时计算了溶液中水的偏摩尔过量熵(SE1),并根据脂肪族α-氨基酸的水化模型对结果进行了讨论.建立的化学模型参数能在一定程度上解释McMillan-Mayer模型中的同系焓作用系数的物理意义.

A chemical interaction model has been established for the hydrophobic self-association of aliphatic α- amino acids in aqueous solutions, In order to obtain the parameters of the model equation, dilution enthalpies of 5 aliphatic α-amino acids aqueous solutions have been measured at 298.15 K by flow microcalorimetry. The equilibrium constants （K）, enthalpy change （AHm） and entropy change （ASm） have been determined for the equal-step association, It was found that between enthalpy and entropy exists a good compensation relationship. In addition, partial molar excess entropies of water in solutions （S1^E） were calculated, and were discussed according to the hydration model for aliphatic α-amino acids. Noteworthily, the parameters in the model equation can be used to explain the homogeneous enthalpic interaction coefficients in McMillan-Mayer model to some extent.