THE LIQUID AMIDE TRANSFER MODEL AND THE UNFOLDING THERMODYNAMICS OF SMALL GLOBULAR-PROTEINS

In this paper, the solid cyclic dipeptide model developed by Murphy an d Gill is analysed in order to point out that, apart from general ther modynamic features shown by well-characterized small globular proteins , only the polar and apolar contributions to the net denaturation heat capacity change are necessary to calculate the so-called protein stab ility curve, Delta(d)G degrees versus temperature. We propose that the se specific heat capacity contributions can be determined in a reliabl e manner by a group additivity analysis of the transfer process of liq uid amides from pure liquid phase into water. This suggests that the u nfolding process, thought of as the transfer of amino acid residues fr om the protein 'core' to contact with water molecules, can be modelled based on the transfer process of organic amides. The reliability of t he model is tested in comparison with literature data.