THE BEHAVIOR OF SOME MODEL PROTEINS AT SOLID LIQUID INTERFACES .2. SEQUENTIAL AND COMPETITIVE ADSORPTION

The proteins used in this study, lysozyme, ribonuclease, myoglobin and α-lactalbumin, have similar molecular masses (ca 15 000 dalton) and similar dimensions, but they differ with respect to isoelectric point and structure stability. Sequential and competitive adsorption experiments have been performed in a systematic way using sorbent surfaces of varying hydrophobicity and charge density. Adsorbed and desorbed amounts were calculated from changes in the protein solution concentrations as determined by FPLC. In addition, electrophoretic mobilities of bare and protein-covered sorbent particles were measured. Sequential and competitive adsorption of lysozyme, ribonuclease and myoglobin are primarily influenced by electrostatic interactions. With α-lactalbumin an extra factor, related to the low structure stability of this protein, contributes to preferential adsorption. As a rule, displacement of pre-adsorbed protein by a secondly supplied different protein is facilitated by the hydrophilicity of the sorbent surface. © 1990.