Elution of Proteins from Silanized Silica Surfaces by Sodium Dodecylsulfate and Dodecyltrimethylammonium Bromide

Abstract

Adsorption kinetic data recorded for α-lactalbumin, β-casein, β-lactoglobulin, bovine serum albumin, and lysozyme at silanized silica 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 governing conversion of removable protein to a nonremovable form (s1) and one governing removal of protein by the surfactant (ks). Elution of each protein from hydrophobic silica with SDS was interpreted as providing information relevant to protein-surface binding strength, or s1 ; i.e., protein-specific differences in removal were a result of SDS adsorption to the surface and displacement of surface-bound protein, 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, displacement mechanism. The model indicated that data recorded for DTAB-mediated elution at each surface were generally less representative of protein surface behavior, and more a function of ks, where differences in surfactant attachment to protein and solubilization appeared to play an important role in protein removal. Under controlled conditions use of the model would allow identification of cases where ks is particularly proteinspecific, and illustrates the point that in such cases surfactantmediated elution of a protein may reveal little about its surface behavior.