| Speaker: |
Prof. Paul Van Tassel Dept. of Chemical Engineering Yale University |
| Location: | URI University Club |
| Date/Time: | Thursday September 18, 1:00-2:00pm |
| Title: | Protein Adsorption: Kinetics and History Dependence |
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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. If you'd like to meet with Prof Van Tassel during his visit, please contact Patti Correia (x4-2656 or correia at egr.uri.edu). |
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