The mixing enthalpies of N,N'-hexamethylenebisacetamide (HMBA) and N-methylformamide (NMF) with glycine, L-alanine, L-serine, and L-valine in aqueous sucrose solutions have been determined by using mixing-flow isothermal microcalorimetry at the temperature of 298.15 K along with their dilution enthalpies, respectively. Based on the obtained results, the heterotactic enthalpic interaction coefficients (h(xy), h(xxy), and h(xyy)) have been obtained according to McMillan-Mayer's theory with the sucrose molality from 0 to 1.5 mol . kg (1). The fitted results indicate that the values of hxy between HMBA or NMF and the four investigated amino acids in aqueous sucrose solutions are all positive. Meanwhile, the values of hxy reach the corresponding maximum at different sucrose molalities except that the values of hxy between NMF and glycine decrease monotonically with the increasing molality of sucrose. Furthermore, the order for the value of h(xy) of the four amino acids with HMBA or NMF are h(xy) (L-valine) > h(xy) (L-alanine) > h(xy) (L-serine) > h(xy) (glycine) in pure water or in aqueous solution with the same molality of sucrose. The values of h(xy) between HMBA and the four amino acids are much larger than that between NMF and the same amino acids with the same molality of sucrose. All the variations of the heterotactic enthalpic pairwise interaction coefficients in the quaternary systems can be interpreted with the help of the solute-solute and solute-solvent interactions theory. (C) 2011 Elsevier Ltd. All rights reserved.