PEPTIDE-UREA INTERACTION - HEATS OF MIXING OF CYCLIC DIPEPTIDES WITH UREA

Abstract

The excess enthalpies of the ternary aqueous solutions containing urea and the glycyl-glycine, glycyl-L-alanine, L-alanyl-L-alanine and sarcosyl-sarcosine diketopiperazines respectively were determined. A weak but favorable enthalpic contribution to the interaction between these solutes is found. The difference between strong and weak interactions in aqueous solutions of non-electrolytes is stressed and the role of water in the weak, non-specific interactions, is discussed. The consequence of the weakness of the urea-peptide interactions on the binding of urea to the proteins is also briefly discussed.