ENTHALPIES OF SOLUTION OF N-ACETYLAMINO ACID-AMIDES IN AQUEOUS-SOLUTIONS OF ELECTROLYTES AT THE TEMPERATURE 298.15 K

The standard molar enthalpies of solution at infinite dilution Delta(s ol)H(m)(infinity) of N-acetylglycinamide, N-acetyl-L-alaninamide, N-ac etyl-N'-methylglycinamide, and N-acetyl-N'-methyl-L-alaninamide in aqu eous solutions of sodium chloride, potassium chloride, and sodium iodi de have been determined by calorimetry. The results obtained were used to calculate the heterotactic enthalpic interaction coefficients h(xy ) and h(xyy) of peptides with the three salts. The effects of the ion type, of the structure of the amino acid chain, and of methylation of the acid amide group on the magnitude and sign of the enthalpic intera ction coefficients are discussed. (C) 1997 Academic Press Limited.