Studies On The Thermodynamics Of Interactions Of Amino Acids With Amides In Aqueous Solutions

Amino acids have been useful models for understanding the thermodynamic behavior of proteins, especially in determining functional group contributions to the biopolymers conformational stability. Investigations on the thermodynamic behavior of amino acids in aqueous solution would provide informations about mechanism of action of proteins in aqueous solution, however, most proteins exist in the complicated environment containing many organic substances, which leads to significant interests in investigation on the interaction in aqueous solutions between amino acids and organic molecules present in living organisms or possessing functional group identical.As a part of the project supported by National Natural Science Foundation (No.20273061), the present work consists of three parts.The first part summarizes the studies on the thermodynamic properties of systems containing protein model molecules.In the second part, the enthalpies of solution and the apparent molar volume of amino acids in aqueous solutions of urea, formamide and acetamide were determined at 298.15 K. Enthalpy and partial molar volume of transfer of amino acids from water to above mixed solvent were obtained and discussed in terms of solute-solute interaction between amino acids and amides, which also bring a new insight into the structure of the mixed solvent mentioned above.The results show that: (1) The difference in transfer properties of amino acids reflected the change in the structure interaction between solute and co-solvent molecules. The transfer enthalpy of amino acids from water to aqueous urea and formamide is negative, with the relative order of Z-serine