COLL 487 |
| Paul R. Van Tassel, Department of Chemical Engineering, Department of Chemical Engineering, Yale University, P. O. Box 208286, New Haven, CT 06520 |
| The adsorption of protein and other macromolecular species is often strongly history dependent owing to the slow relaxation of non-equilibrium structures. The rate at which molecules adsorb is exquisitely sensitive to, and thus a sensitive measure of, interfacial structure; adsorption kinetics may therefore serve both to identify and quantify history dependence. Optical waveguide lightmode spectroscopy (OWLS) in multi-step mode, where an adsorbing surface is alternately exposed to a protein solution and one free of protein, enables the comparison of adsorption rates onto interfacial layers of identical composition but different formation histories. Contributions to the overall kinetics from the apparent adsorption rate constant, the desorption rate constants of molecules in different adsorbed states, and the interfacial one-body cavity function (a measure of the probability of a “cavity” on the surface free of protein) may be isolated from OWLS kinetic data. We find the rate of adsorption and the corresponding cavity function to increase significantly – for systems of fibronectin, cytochrome c, and lysozyme adsorbing onto Si(Ti)O2 – from a first to a subsequent adsorption step and attribute this to a clustering transition among adsorbed protein molecules. From the kinetic data, we determine important structural and temporal information on this event. |
|
Symposium in Memory of Arthur W. Adamson
8:30 AM-11:50 AM, Thursday, April 1, 2004 Marriott -- Orange County 4, Oral
Division of Colloid and Surface Chemistry |