THE BEHAVIOR OF SOME MODEL PROTEINS AT SOLID LIQUID INTERFACES .1. ADSORPTION FROM SINGLE PROTEIN SOLUTIONS

The adsorption of proteins of similar molecular size and shape on various well-defined surfaces is discussed. The hydrophobicity and the electrical charge density of both the protein molecule and the sorbent surface as well as the structure stability of the protein molecule were taken as the experimental variables. The adsorption process was studied by determining adsorption isotherms and by measuring electrophoretic mobilities and heats of adsorption at varying degrees of coverage of the sorbent surface by the protein. It appeared that proteins of which the structure is stabilized by a large Gibbs energy behave like hard particles: they adsorb on hydrophobic interfaces under all conditions of charge interaction and on hydrophilic surfaces only if electrostatically attracted. Soft proteins, i.e., proteins characterized by a lower structure stability, adsorb on hydrophobic and hydrophilic surfaces under attractive and repulsive electrostatic conditions. These proteins contain an extra driving force for adsorption, related to structure rearrangements in the molecule, that outweighs the unfavorable contributions form hydrophilic dehydration and electrostatic repulsion. © 1990.