Enthalpic Interaction Of Several Simple Amide Molecules

The protein occupies the special position in the living creature body, and is the material foundation that the morphosis and the life activities of the organism depend on. 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 alcohol help in stabilizing the native conformation of globular proteins. The organic solvent has great affects on the solubility, duration, folding and unfolding of proteins and enzyme activity. 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 four parts.The first part summarizes the general statement of studies on the thermodynamic properties of systems containing protein model molecules.In the second part, enthalpies of mixing of aqueous amide solutions with aqueous alcohol solutions (memanol,ethanol,propanol,butanol) 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 amide and alcohol have been discussed by solute-solute interaction theory.In the third part, the enthalpic pairwise interactions between five kinds of amides and two Sugars have been determined at 310.15K.The forth part consists of the following two sections.(1) Enthalpies of mixing of aqueous acetamide solutions with aqueous picolines solutions (2-picoline, 3-picoline,4-picoline) have been determined at 298.15K by 2277 flow microcalorimetric 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.(2) The hydrogen bonding of 1:1 complexes formed between acetamide and three kinds of isomers of picolines have been completely investigated using B3LYP method at various basis set levels from 6-31G to 6-31+G(d) and 6-31++G(d,p). The results show that the interaction energies of hydrogen bond complexes between acetamide and picoline isomers have great effects on the values of h_xy. The stronger the interaction energy is, the smaller the value of h_xy is.