ENERGY AND ENTROPY OF PROTEIN ADSORPTION

Protein adsorption data, in particular adsorption isotherms and calorimetric results, are interpreted using thermodynamic arguments. Energetic and entropic contributions from the major factors that constitute the overall process are presented. With respect to the adsorption behavior the protein molecules may be classified as "rigid" or "soft". With rigid proteins structural rearrangements do not contribute to the adsorption process. They adsorb on hydrophobic surfaces and on hydrophilic surfaces only if electrostatically attracted. Soft proteins show a stronger affinity for surfaces, so that they even may adsorb under the adverse conditions of a hydrophilic, electrostatically repelling surface. With these proteins there is a significant driving force for adsorption resulting from intramolecular structural rearrangements.