Determination of free energy of protein folding on liquid-solid interface

Based on the fact that the stoichiometric displacement model for retention of solute and the total adsorption free energy of solute on a solid surface can be divided into two components, net adsorption and net desorbed energies, a new principle and an equation for calculating the free energy of protein folding, ΔΔG_F, on the solid surface are proposed. With high-performance hydrophobic interaction chromatography (HPHIC), an experimental method for determining the ΔΔG_F is established. Lysozyme and α-amylase have been selected as examples to test the new method, and their ΔΔG_F on the HPHIC stationary phase surface are found to be much higher than that reported from a solution. In addition, the ΔΔG_F of the two proteins are found to increase with the concentration of denaturing agent employed. The average standard deviations, ±4.7% for lysozyme and ±3.0% for α-amylase, indicate that the new method has a satisfactory reproducibility and reliability.