The change in Gibbs free energy for hydrophobic association: Derivation and evaluation by means of inverse temperature transitions

The change in Gibbs free energy resulting from changes in the temperature (Tt) and heat (ΔHt) of an inverse temperature transition (ITT) of hydrophobic association is derived and utilized to develop a hydrophobicity scale for amino acid residues within an elastic model protein, (GVGVP)n. On raising the temperature, hydrophobic residues go from water to hydrophobic association. Using Tt and ΔHt of the ITT, the change in Gibbs free energy for hydrophobic association, Δ G HA 0 , in kcal/mol-(GXGVP) where X is the guest amino acid residue, was calculated for the naturally occurring amino acid residues in PBS. Δ G HA 0 varies by more than 10 kcal/mol-(GXGVP) from the most hydrophobic tryptophan residue to the most hydrophilic glutamate residue.