(37d) An Investigation of Protein Adsorption on Zinc Oxide

The adsorptive behavior of BSA and Urease onto a zinc oxide adsorbent was investigated. The dependence of protein surface concentration on pH was studied. Isotherm measurements indicated that protein adsorption significantly varied with pH. Protein adsorption was essentially non-existent at elevated pH, however, the surface concentration of protein steadily increased when the acidity level of the buffer was raised. At a pH value of 5, multilayer protein adsorption was observed for BSA. Zeta potential measurements indicated that the protein and the zinc adsorbent each possessed a strong negative potential at high pH, however, the magnitude of negative potential was reduced at lower pH. As the solution became more acidic, the driving forces associated with hydrogen bonding and hydrophobic interactions appeared to overcome the repulsive forces arising from the negative potential on the protein and the zinc oxide adsorbent. Urease was also adsorbed onto the surface of zinc oxide. The impact of immobilization on Urease will be tested by studying the enzymes ability to degrade urea. The urea degradation kinetics of adsorbed Urease will be compared to the degradtion kinetics of unbound Urease in solution.