Enthalpy of solution of glycine, L-alanine or L-serine in water and aqueous solutions of dimethyl sulfoxide (DMSO) was measured at 298.15 K. Transfer enthalpy, D_trH, of aminoacids from water to aqueous solutions of DMSO was derived, interpreted qualitatively with cosphere overlap model and compared with the values from water to aqueous solutions of urea in our previous work. The results show that the contribution to the transfer enthalpy of electrostatic interaction and hydrophilic-hydrophilic type structure interaction between solute and cosolvent molecule was negative, while that of hydrophilic-hydrophobic and hydrophobic-hydrophobic type structure interaction was positive. Different from the fact that the absolute value of transfer enthalpy of aminoacids from water to aqueous solutions of urea was overall increased with the concentration increase of urea with regular breaks, the results for water-DMSO mixtures were linearly increased with the increased content of cosolvent. The behavior of D_trH-composition profile could characterize the structure feature of solvent, providing thermodynamic evidence of the self-association of urea in aqueous solution.

Key words: aminoacid, dimethyl sulfoxide, transfer enthalpy