2015 — 2018 |
Oztekin, Alparslan (co-PI) [⬀] Cheng, Xuanhong Zhang, Xiaohui Webb Iii, Edmund |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mechano-Biologically Informed Molecular Models of Flow Sensitive Biopolymers
In human bodies, bleeding is stopped by forming a clot at the site of vascular damage. Under rapid blood flow conditions associated with injury, the plasma protein von Willebrand Factor (vWF) plays an indispensable role in sticking to both platelets and collagen on damaged vessel walls, allowing the formation of platelet plugs. vWF effectively senses blood flow, changing conformation in high flow from a compact globule to an elongated shape; this reveals binding sites on vWF for platelets and collagen. Abnormalities in vWF adhesion are involved in the pathogenesis of many cardiovascular diseases, such as von Willebrand disease (affecting 1 to 2% of world's population), thrombosis and arteriosclerosis. Although basic biological properties of vWF have been elucidated, little is known about the detailed biomechanical properties of vWF and how these properties dictate its structure and function in varying flow environments. Such information can abet not only better understanding of vWF; it can provide insight for the design of synthetic molecules in pursuit of targeted drug therapies, advancing federal interests in health and medicine.
This project will establish, for the first time, a generalized experimental and theoretical platform to investigate the mechanical properties of complicated, multi-domain molecules such as vWF. The platform advanced will provide transformative predictive capability for how flow sensitive biopolymers behave in specific vascular flow scenarios and how that behavior depends on molecular architecture and biological surface chemistry. A single-molecule force spectroscopy will be implemented to systematically probe the mechanical response of vWF monomer fragments, monomers, and multimers; data so obtained will be used to optimize new coarse grain molecular models that predict vWF mechanical behavior with unprecedented quantitative accuracy. The model's predictive capabilities will be further enhanced via fluorescence microscopy analysis of vWF in microfluidic flow chambers with systematically functionalized surfaces. The optimized model will be used to explore how changes to molecular architecture influence biological functionality in varying flow conditions. This work will enable a detailed understanding of the molecular mechanisms underlying conformational changes of vWF and lay crucial groundwork toward biologically inspired materials design and the development of biomimetic devices that resemble the functionality of known biopolymers. In addition, the study will fill the long-standing knowledge gap on the mechanobiology of vWF, and potentially offer new therapeutic approaches to treat von Willebrand disease. This project will educate both undergraduate and graduate STEM students in experimental and theoretical aspects of biomolecular investigation, emphasizing the need for multi-disciplinary, diverse collaborations between practitioners of experiment, computation, and theory. Such immersive STEM educational experiences will best prepare students to confront technological challenges of the future. Through associated outreach efforts, this work will showcase for both technical and non-technical societal audiences the power of high performance computing in exploring complex molecular behavior and advancing new solutions in human health and wellness.
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0.961 |
2018 |
Jagota, Anand (co-PI) [⬀] Zhang, Xiaohui |
R15Activity Code Description: Supports small-scale research projects at educational institutions that provide baccalaureate or advanced degrees for a significant number of the Nation’s research scientists but that have not been major recipients of NIH support. The goals of the program are to (1) support meritorious research, (2) expose students to research, and (3) strengthen the research environment of the institution. Awards provide limited Direct Costs, plus applicable F&A costs, for periods not to exceed 36 months. This activity code uses multi-year funding authority; however, OER approval is NOT needed prior to an IC using this activity code. |
Biomechanics of Tim Protein-Mediated Ebola Virus-Host Cell Adhesion
The most recent outbreak of the Ebola virus (EBOV) epidemic posed a major threat to the world. Because the mechanisms of EBOV infection remain obscure, there is still no specific treatment or vaccine for EBOV disease. While EBOV-host cell attachment has been shown to depend critically on the molecular biomechanics of interaction between receptors on the cell surface and the outer coat of the virus, the quantitative understanding essential for guiding the development of therapies is completely lacking. Recent work has established the importance of TIM family proteins and the geometry and mechanical properties of its mucin-like stalk domain (MLD). However, further progress building on these recent findings requires expertise in experimental and theoretical molecular biomechanics, different than that which has advanced our knowledge so far. This proposal takes advantage of the PIs? capabilities in single-molecule force spectroscopy (Zhang) and computational molecular adhesion mechanics (Jagota) to address the problem of establishing quantitative understanding of the molecular, cellular, and biomechanical mechanisms of EBOV attachment to a host cell. We hypothesize that quantitative knowledge about the biomechanical properties of the stalk presenting the ligand binding IgV domain, i.e., the length, rigidity and charge of the MLD of TIM, can be used to predict conditions for EBOV attachment. Aim 1 will utilize single-molecular force spectroscopy to characterize experimentally how TIM family proteins interact with EBOV in a rate- and force- dependent fashion, and how the interaction is influenced by the length, rigidity and charge of MLD. Aim 2 will test the hypothesis by developing biomechanical models that show how single-molecule biomechanical properties, and how the properties of the MLD, such as its length, rigidity, and charge density, control TIM mediated cellular/viral membrane adhesion and engulfment. Model development will be calibrated and validated through single-molecule measurements. The study will elucidate quantitatively?for the first time?the biomechanical mechanism of EBOV?host cell interaction, providing potential new targets for antiviral drug development.
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0.961 |
2020 — 2023 |
Cheng, Xuanhong Zhang, Xiaohui |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Bioinspired, Single-Molecule Based Shear Switchable Nanomaterials
Nontechnical Summary: Shear flow is widely present in physiological environments and contributes significantly to various normal and pathological processes, especially in the circulatory system. Consequently, biomaterials with structure and function tunable by shear represent powerful tools to detect and rectify pathological processes induced by abnormal flows in the body. For the past few decades, shear-responsive hydrogels and molecular assemblies have been widely explored. However, single-biomolecule based shear responders remains a poorly-tapped subject, despite such materials could better mimic natural functions in circulation, delivering more accurate spatial and temporal responses with function reversibility. This project will design and characterize novel Single-MOlecule based materials with switchable structures and functions REsponsive to Shear flows (SMORES). Owing to the modular design, the material concept can be generalized to other constructs capable of responding to abnormal flows in the circulatory system towards novel diagnostics and therapeutics for cardiovascular diseases in the long term. This project will provide fundamental insights into biomechanics of polymer devices under the influence of ligands and the flow environment, perspectives that have not been studied in depth before. Rational design of biomaterials containing both bio- and nonbio- functionalities to achieve predictable flow responses will advance the fields of materials science, biomechanics, bio-conjugation, molecular engineering and bio-transport. Knowledge from this work will enable new diagnostics and theranostics for hemostatic applications, advancing the national health. The PIs will actively recruit underrepresented students to their research and disseminated discoveries from the research broadly to the general public through various K12 outreach programs.
Technical Summary: The design is inspired by a coagulation molecule in circulation, the von Willebrand Factor (vWF), which executes its function of crosslinking platelets to damaged blood vessel wall at shear rates > 5,000 per sec. The function is switched on by conformational changes under high shear and is enabled by an extremely complicated molecular structure: vWF is comprised of tens to hundreds of monomer units, each of which contains more than ten domains. To demonstrate that an artificial material of modular design could achieve a similar function to vWF, i.e. binding cells at high shear, we propose the construction SMORES to inhibit or promote the cell binding activity of the vWF?s platelet binding domain under shear control. Shear dependent cell binding to the proposed material will be characterized and correlated with molecular conformations studied by single-molecular force spectroscopy, microfluidic imaging experiments and computer modeling. Besides demonstrating the material design concept, the proposed work will emphasize fundamental studies of single-molecule biomechanical behaviors in different biochemical environment, especially the presence and absence of ligands.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
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0.961 |
2020 — 2021 |
Zhang, Xiaohui |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Single-Cell Analysis of Endothelial Mechanotransduction Mediated by Endothelial Surface Glycocalyx
Endothelial surface glycocalyx (ESG) is a carbohydrate-rich layer found on vascular endothelium. ESG is composed of membrane glycoproteins, glycosaminoglycans and proteoglycans, forming a bulky, matrix-like structure that serves critical functions in mechanotransduction of blood flow, maintenance of the endothelial permeability, and the control of leukocyte adhesion and inflammation. One of the most important normal physiological functions of ESG is to mediate mechanotransduction that leads to the intake of calcium ions and the production of Nitric Oxide (NO) in response to blood flow. Dysfunctional ESG mechanotransduction has been found in cardiovascular diseases such as sepsis, ischemia-reperfusion, hypertension, and diabetes. While the critical involvement of ESG in cardiovascular diseases has been established, its biomechanical properties, as well as the mechanisms underlying its normal mechanotransduction, have resisted elucidation. This lack of progress is due in large part to the fact that mechanical forces and responses that occur at the molecular and sub-cellular levels are transient, minute and therefore difficult to trace and measure. The goal of the current proposal is to develop new research tools and model systems, and use them to uncover the biomechanical and mechanotranduction properties of ESG. We will characterize mechanisms underlying ESG-mediated mechanotransduction on a single-cell level using a novel Atomic Force microscopy (AFM)-fluorescence microscopy approach. The proposed study will achieve a clearer understanding of ESG-mediated mechanotransductory function, with important implications for ESG-related diseases, such as sepsis, ischemiareperfusion, diabetes and hypertension, and their therapeutics.
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0.961 |