Amino Acids, Amides, Polyhydric Alcohol Compound Interaction Thermodynamic Study

Amino acids and amide, which have been used extensively as the most important biological model compounds, are not only the basic building blocks of proteins, but also the important active materials in living things. Sugars and polyols help in stabilizing the native conformation of globular proteins. There has been significant interest in the investigation on the interaction in aqueous solutions between amino acids and organic molecules present in living organisms or possessing functional group identical. The principle reasons for studying such systems are to obtain the information that contributes to the growing body of knowledge about solute solvation and solute-solute interactions in aqueous media, and a better understanding of their role played in the conformational stability and unfolding behavior of proteins.This paper mainly consists of the following five parts.The first part summarizes the general states of studies on the thermodynamic properties of systems containing protein model molecules.In the second part, enthalpies of mixing of aqueous amino acids solutions (glycine, L-alanine, L-serine, L-valine, L-proline, L-threonine) with aqueous polyols solutions (mannitol, manna saccharine) have been determined at 310.15K by 2277 flow micro calorimetric system. These results along with enthalpies of dilution of these aqueous solutions have been used to obtain the enthalpic interaction coefficients (h_xy, h_xxy, h_xyy) in terms of the McMillan-Mayer theory. The pairwise interactions between amino acids and polyols have been discussed by solute-solute interaction theory.In the third part, the enthalpic pairwise interactions between six kinds of amino acids and three N- ethane amides have been determined at 310.15K.In the forth part, the heterotactic enthalpic pairwise interaction coefficients between five amides and butanediol isomers (1,3-butanediol, 1,4-butanediol and 2,3-butanediol) at 310.15K are discussed. The change of temperature made remarkable effects on the values of h_xy.In the last part, the hydrogen bonding of 1:1 complexes formed between N-methyl amide and three kinds of isomers of butanediol have been completely investigated using B3LYP method at varied basis set levels from 6-31G to 6-31++G (d, p). The results show that the interaction energies of hydrogen bond complexes between amino acids and butanediol isomers have great effects on the values of hxy. The stronger the interaction energy is, the smaller is the value of hxy:...