AVS 52nd International Symposium
    Biomaterial Interfaces Friday Sessions
       Session BI+SS-FrM

Paper BI+SS-FrM10
Protein-Solvent Interactions in Surface-Grafted ELPs Measured by Single Molecule Force Spectroscopy

Friday, November 4, 2005, 11:20 am, Room 311

Session: Biomaterials Surface Characterization
Presenter: A. Valiaev, Duke University
Authors: A. Valiaev, Duke University
D.W. Lim, Duke University
S. Schmidler, Duke University
A. Chilkoti, Duke University
S. Zauscher, Duke University
Correspondent: Click to Email
Stimulus-responsive biomolecules attract significant research interest due to their potential applications in areas such as drug delivery, molecular motors and nanoscale sensors. Here we present our results of the conformational and hydration behavior of surface grafted elastin-like polypeptides (ELPs), measured by single molecule force spectroscopy. ELPs are stimulus-responsive polypeptides that contain repeats of the five amino acids Val-Pro-Gly-Xaa-Gly (VPGXG), where Xaa is a guest residue, and undergo an inverse phase transition in response to an environmental stimulus, such as a change in temperature. Our results suggest that single-molecule force spectroscopy can be used to quantify the effect of the type of guest residue, pH or ionic strength on molecular conformation and elasticity. By fitting ELP force-extension data to a freely jointed chain model, using our newly developed data analysis approach, we showed that we can resolve differences in Kuhn segment lengths as small as 0.03 nm; i.e., differences that are about an order of magnitude smaller than those previously reported. The observed force-extension behavior at intermediate and large extensions supports a phenomenological model that describes ELPs as kinetically mobile and disordered macromolecules. Importantly we find that molecular elasticity upon extension arises both from a deformation of the polypeptide backbone and from hydrophobic polymer-solvent interactions. Our observations here agree with recent MD simulations which suggest that hydrophobic hydration of side-chains plays an important role for elasticity and provides the molecular basis for the inverse temperature transition behavior.