Concentration effects on adsorption of bacteriophage T4 lysozyme stability variants to silica

The adsorption kinetics and dodeceyltrimethylammonium bromide-mediated elution of the wild type and two structural stability mutants of bacteriophage T4 lysozyme were recorded in situ, at silica surfaces. Experiments were performed at different solution concentrations, ranging from 0.01 to 1.0 mg/ml. Plateau values of adsorbed mass generally increased with increasing solution concentration, with the adsorbed layer being only partially eluted by buffer. Treatment with surfactant removed more of the adsorbed protein in each case, with the remaining adsorbed mass varying little with concentration. Comparison of the data to an adsorption mechanism allowing for three adsorbed states, distinguished by binding strength, showed that the fraction of adsorbed molecules present in the most tightly bound state (state 3) decreased as adsorption occurred from solutions of increasing concentration. However, the absolute amounts of state 3 molecules present in each case were less dependent on solution concentration. Adsorption of T4 lysozyme into state 3 is suggested to occur early in the adsorption process and continue until some critical surface concentration is reached. Beyond this critical value of adsorbed mass, adsorption is suggested to progress with adoption of more loosely bound states.