Entropy-Enthalpy Compensation in Peptide Adsorption on Solid Surfaces: Dependence on Surface Hydration.

Although protein adsorption at the solid-water interface is of immense importance, understanding the crucial role of the water phase in mediating protein-surface interactions is lacking, particularly due to the lack of fundamental thermodynamic data. Herein, we have performed complicated free energy calculations and successfully extracted the entropy and enthalpy changes of molecular adsorption on solids. Using the gold and graphene as the surface models with distinct affinities to the water phase, we successfully unravel the sharply opposite manners of entropy-enthalpy compensation in driving water and tripeptide adsorptions on two surfaces. Though the thermodynamic features of water adsorption on surface are enthalpically dominated based on the positions of free energy barriers and minima, the favorable entropy term significantly decreases the free energy barrier and further stabilizes the adsorbate at the adsorption site on the graphene surface. For the peptide, the shape of the adsorption free energy profile is jointly determined by the enthalpy and entropy changes, which, however, alternatively act the driving force to promote the peptide adsorption on the Au surface and graphene surface. The distinct structural and dynamic properties of solid-liquid interfaces account for the special role of the interfacial water phase in regulating the competitive relationship between the entropy and enthalpy variations.