LAUSR

Adsorption kinetics and conformational changes of a model protein, bovine serum albumin (BSA, 0.1, 0.5, or 1.0 g/L), on the surface of hematite (α-Fe2O3) particles in 39, 68, and 103 nm, respectively, were measured. As particle size increases, the amount of adsorbed BSA decreases, but the loss in the helical structure of adsorbed BSA is greater due to the stronger interaction forces between BSA and the larger particles. On 39 or 68 nm hematite particles, refolding of adsorbed BSA can be induced by protein-protein interactions, when protein surface coverage exceeds a critical value. 2D-COS results indicate that the increase in the amount of adsorbed BSA occurs prior to the loss in the BSA helical structure in the initial stage of adsorption processes, whereas an opposite sequence of the changes to BSA conformation and surface coverage is observed during the refolding processes. Desorption experiments show that replacing the protein solution with water can quench the refolding but not the unfolding of adsorbed BSA. A kinetic model was proposed to quantitatively describe the interplay of adsorption kinetics and conformational change, as well as effects of the studied factors on rate constants of elementary steps in protein adsorption onto mineral surface.