Shear-Activated Molecular Glue

ID: MPS/DMR/BMAT(7623) 0907676皮：江，清华ORG：莱斯大学标题：剪切活化分子胶智力优势：本研究将集中于单分子操作技术来研究剪切应力活化的多聚体材料。将确定活性形态下的大分子和生物聚合物的结构-功能关系。特别是，研究将重点放在von Willebrand factor （VWF）的粘附激活上，VWF是血液中循环的最大的多聚体粘附配体，它被剪切应力激活，作为结合血小板的分子胶。研究的目的是：(1)表征VWF对区域展开的机械阻力。PI将决定是否分散键负责横向结合，从而形成纤维，超大VWF和剪切VWF。本文的重点将放在VWF展开对外部拉伸力的机械阻力上。(2)量化血小板结合动力学。通过单分子AFM拉扯实验，PI将确定剪切暴露前后和流动条件下等离子体VWF与糖蛋白（GP） ib - α结合的动力学速率和自由能。这些数据将量化剪切作用下分子胶的活化。(3)研究了细观VWF纤维的粘弹性和自由能。我们将使用拉拔计划中的热波动和动态施加的振荡来测量VWF、剪切VWF和超大型VWF的粘弹性和自由能。更广泛的影响：拟议的研究将推进对VWF活化机制的认识，VWF是一种剪切激活的分子胶，在血液凝固中很重要。从自然界中吸取的经验教训可能有助于得出合成功能性智能生物聚合物的策略。对于整个社会来说，了解血液与生物材料表面相互作用中起重要作用的凝血机制，可能有助于心脏瓣膜植入等人工合成装置的患者、出血性疾病患者和血栓性伤口治疗。实验结果将被纳入PI？他的新本科课程《生物物理学导论》和研究生课程《生物物理学专题》。学生和博士后将有机会使用最先进的仪器进行生物物理研究。本项目开发的计算机程序将用于提高原子力显微镜仪器的实用性。外展活动包括通过赖斯量子研究所（RQI）担任赖斯本科生研究经验（REU）计划的导师，通过W. M.凯克计算和结构生物学中心担任凯克本科生研究培训计划（URTP）的导师，以及莱斯大学HHMI生物纳米技术暑期本科生研究计划的参与者。招收的学生来自物理、化学、数学和工程学科，他们有兴趣进入以生物为导向的研究。此外，PI还将通过赖斯生物科学与生物工程研究所、以西班牙裔为主的南德克萨斯州科学院以及休斯顿市内学校之间的合作，为和谐科学院的高中生担任导师。

ID: MPS/DMR/BMAT(7623) 0907676 PI: Kiang, Ching-Hwa ORG: Rice UniversityTitle: Title: Shear Activated Molecular GlueINTELLECTUAL 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.