ELUTION OF PROTEINS FROM SILANIZED SILICA SURFACES BY SODIUM DODECYL-SULFATE AND DODECYLTRIMETHYLAMMONIUM BROMIDE

Adsorption kinetic data recorded for alpha-lactalbumin, beta-casein, b eta-lactoglobulin, bovine serum albumin, and lysozyme at silanized sil ica surfaces of low and high hydrophobicity, along with a simple model for adsorption and surfactant-mediated elution of protein, were used to analyze the removal of each protein by sodium dodecylsulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) at each surface. The model relates resistance to surfactant elution to two rate constants: one g overning conversion of removable protein to a nonremovable form (s(i)) and one governing removal of protein by the surfactant (k(s)). Elutio n of each protein from hydrophobic silica with SDS was interpreted as providing information relevant to protein-surface binding strength, or s(1); i.e., protein-specific differences in removal were a result of SDS adsorption to the surface and displacement of surface-bound protei n, as opposed to solubilization driven by SDS binding to the protein. SDS-mediated removal of protein from surfaces of lower hydrophobicity were interpreted as generally proceeding according to a similar, displ acement mechanism. The model indicated that data recorded for DTAB-med iated elution at each surface were generally less representative of pr otein surface behavior, and more a function of k(s), where differences in surfactant attachment to protein and solubilization appeared to pl ay an important role in protein removal. Under controlled conditions u se of the model would allow identification of cases where k(s) is part icularly protein-specific, and illustrates the point that in such case s surfactant-mediated elution of a protein may reveal little about its surface behavior. (C) 1995 Academic Press, Inc.