Shear-Activated Molecular Glue

William Marsh Rice University, Houston TX

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0907676 PI: Kiang, Ching-Hwa ORG: Rice University Title: Title: Shear Activated Molecular Glue INTELLECTUAL MERIT: This research will focus on single-molecule manipulation techniques to study multimeric materials that are activated by shear stress. The structure-function relationships will be determined for the macromolecules and biopolymers in their active form. In particular, the research will focus on the activation of adhesion in von Willebrand factor (VWF), the largest multimeric adhesion ligand circulating in blood, which is activated by shear stress to function as a molecular glue to bind platelets. The objectives of the research are to: (1) Characterize mechanical resistance to domain unfolding of VWF. The PI will determine whether disufide bonds are responsible for the lateral association, hence the fiber formation, of ultra large VWF and sheared VWF. The focus here will be on the mechanical resistance of VWF unfolding to external stretching force. (2) Quantify platelet binding kinetics. Through a single-molecule AFM pulling experiment, the PI will determine the kinetic rate and free energy of plasma VWF binding with glycoprotein (GP) Ib-alpha before and after shear exposure and under flow conditions. These data will quantify activation of the molecular glue by shear. (3) Investigate the viscoelastic and free energies of mesoscopic VWF fibers. We will use thermal fluctuations and dynamically imposed oscillations in the pulling schedule to measure the viscoelastic properties and free energies of VWF, sheared VWF, and ultra large VWF. BROADER IMPACTS: The proposed research will advance knowledge on the mechanism of activation of VWF, a shear-activated molecular glue important in blood clotting. The lessons learned from nature may help to derive strategies for synthesis of functional smart biopolymers. For the broad society, understanding the blood clotting mechanism, which plays an important role in the blood interactions with biomaterials surfaces, may help people with synthetic devices such as heart valve implants, people with bleeding disorders, and thrombic wound treatment. Experimental findings will be incorporated into the PI?s new undergraduate level course, Introduction to Biological Physics, and a graduate level course, Topics in Biological Physics. Students and postdoctoral associates will have the opportunity to use the state-of-the art instrument for biological physics research. A computer program developed in this project will be used to advance the usefulness of AFM instrumentation. Outreach activities include serving as mentor for the Rice Research Experience for Undergraduates (REU) program through the Rice Quantum Institute (RQI), for the Keck Undergraduate Research Training Program (URTP) through the W. M. Keck Center for Computational and Structural Biology, and for participants in the summer undergraduate research program in HHMI Bionanotechnology at Rice University. Students are recruited from physics, chemistry, mathematics and engineering disciplines that have interests in moving into biologically-oriented research. In addition the PI will serve as mentor for high school students from the Harmony Science Academy, through a collaboration between the Rice Institute of Biosciences and Bioengineering, and the predominantly Hispanic Science Academy of South Texas as well as inner-city schools in Houston.