1
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Nguyen AH, Kania S, Oztekin A, Webb EB. Predicting reaction behavior of tethered polymers in shear flow. J Chem Phys 2023; 159:174907. [PMID: 37929865 DOI: 10.1063/5.0168440] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 10/17/2023] [Indexed: 11/07/2023] Open
Abstract
Kinetics of force-mediated chemical reactions of end-tethered polymers with varying chain length N in varying shear rate flow γ̇ are explored via coarse-grained Brownian dynamics simulations. At fixed γ̇, force F along a polymer increases linearly with N as previously predicted; however, contrary to existing theory, the F(N) slope increases for N above a transition length that exhibits minimal dependence on γ̇. Force profiles are used in a stochastic model of a force-mediated reaction to compute the time for x percent of a polymer population to experience a reaction, tx. Observations are insensitive to the selected value of x in that tx data for varying N and γ̇ can be consistently collapsed onto a single curve via appropriate scaling, with one master curve for systems below the transition N (small N) and another for those above (large N). Different force scaling for small and large N results in orders of magnitude difference in force-mediated reaction kinetics as represented by the population response time. Data presented illustrate the possibility of designing mechano-reactive polymer populations with highly controlled response to flow across a range in γ̇.
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Affiliation(s)
- Anh Hung Nguyen
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Sagar Kania
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Alparslan Oztekin
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Edmund B Webb
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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2
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Chen H, Poitzsch ME. Dynamics of Polymers Flowing through Porous Media: Interplay of Solvent Properties, Flow Rates, and Wetting. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Hsieh Chen
- Aramco Americas: Aramco Research Center-Boston, Cambridge, Massachusetts02139, United States
| | - Martin E. Poitzsch
- Aramco Americas: Aramco Research Center-Boston, Cambridge, Massachusetts02139, United States
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3
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Conformation of von Willebrand factor in shear flow revealed with stroboscopic single-molecule imaging. Blood 2022; 140:2490-2499. [PMID: 36040485 PMCID: PMC9837445 DOI: 10.1182/blood.2022016969] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 08/02/2022] [Accepted: 08/16/2022] [Indexed: 01/21/2023] Open
Abstract
von Willebrand factor (VWF) is a multimeric blood protein that acts as a mechanical probe, responding to changes in flow to initiate platelet plug formation. Previously, our laboratory tests had shown that using single-molecule imaging that shear stress can extend surface-tethered VWF, but paradoxically, we found that the required shear stress was higher than reported for free-in-flow VWF, an observation inconsistent with basic physical principles. To resolve this inconsistency critical to VWF's molecular mechanism, we measured free-VWF extension in shear flow using pulsed laser stroboscopic imaging of single molecules. Here, laser pulses of different durations are used to capture multiple images of the same molecule within each frame, enabling accurate length measurements in the presence of motion blur. At high shear stresses, we observed a mean shift in VWF extension of <200 nm, much shorter than the multiple-micron extensions previously reported with no evidence for the predicted sharp globule-stretch conformational transition. Modeling VWF with a Brownian dynamics simulation, our results were consistent with VWF behaving as an uncollapsed polymer rather than the theorized compact ball. The muted response of free VWF to high shear rates implies that the tension experienced by free VWF in physiological shear flow is lower than indicated by previous reports and that tethering to platelets or the vessel wall is required to mechanically activate VWF adhesive function for primary hemostasis.
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4
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Nguyen AH, Kania S, Cheng X, Oztekin A, Zhang XF, Webb EB. Unraveling Kinetics of Collapsed Polymers in Extensional Flow. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00849] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Anh H. Nguyen
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Sagar Kania
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Xuanhong Cheng
- Department of Material Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Alparslan Oztekin
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - X. Frank Zhang
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
- Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Edmund B. Webb
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, United States
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5
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Abstract
Bottlebrush polymers (BBPs), composed of relatively short polymeric side chains densely grafted on a polymer backbone, exhibit many unique characteristics and hold promise for a variety of applications. This Perspective focuses on environmentally induced shape-changing behavior of BBPs at interface and in solution, particularly worm/star-globule shape transitions. While BBPs with a single type of homopolymer or random copolymer side chains have been shown to undergo pronounced worm-to-globule shape changes in response to external stimuli, the collapsed brushes are unstable and prone to aggregation. By introducing a second, solvophilic polymer into the side chains, either as a distinct type of side chain or as the outer block of block copolymer side chains, the collapsed brushes not only are stabilized but also create unimolecular micellar nanostructures, which can be used for, e.g., encapsulation and delivery of substances. The current challenges in the design, synthesis, and characterization of stimuli-responsive shape-changing BBPs are discussed.
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Affiliation(s)
- Bin Zhao
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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6
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Belyaev AV. Intradimer forces and their implication for conformations of von Willebrand factor multimers. Biophys J 2021; 120:899-911. [PMID: 33524374 DOI: 10.1016/j.bpj.2021.01.022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 12/31/2020] [Accepted: 01/19/2021] [Indexed: 10/22/2022] Open
Abstract
The largest blood glycoprotein von Willebrand factor (VWF) responds to hydrodynamic stresses in the bloodstream with abrupt conformation changes, thus increasing its adhesivity to platelets and collagen. Arterial and microvascular hemostasis relies on mechanical and physicochemical properties of this macromolecule. Recently, it was discovered that the mechanical properties of VWF are controlled by multiple pH-dependent interactions with opposite trends within dimeric subunits. In this work, computer simulations reveal the effect of these intradimer forces on the conformation of VWF multimers in various hydrodynamic conditions. A coarse-grained computer model of VWF has been proposed and parameterized to give a good agreement with experimental data. The simulations suggest that strong attraction between VWF D4 domains increases the resistance to elongation under shear stress, whereas even intermediate attraction between VWF C domains contributes to VWF compaction in nonsheared fluid. It is hypothesized that the detailed subdimer dynamics of VWF concatamers may be one of the biophysical regulators of initial hemostasis and arterial thrombosis.
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Affiliation(s)
- Aleksey V Belyaev
- Lomonosov Moscow State University, Faculty of Physics, Moscow, Russia; IRC Mathematical modelling in Biomedicine, S.M. Nikolskii Mathematical Institute, RUDN University, Moscow, Russia.
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7
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Dong C, Kania S, Morabito M, Zhang XF, Im W, Oztekin A, Cheng X, Webb EB. A mechano-reactive coarse-grained model of the blood-clotting agent von Willebrand factor. J Chem Phys 2019; 151:124905. [PMID: 31575216 DOI: 10.1063/1.5117154] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The von Willebrand Factor (vWF) is a large blood glycoprotein that aids in hemostasis. Within each vWF monomer, the A2 domain hosts a cleavage site for enzyme ADAMTS13, which regulates the size of vWF multimers. This cleavage site can only be exposed when an A2 domain unfolds, and the unfolding reaction energy landscape is highly sensitive to the force conditions on the domain. Based on previous optical tweezer experimental results, we advance here a new activated A2 monomer model (AA2MM) for coarse-grained modeling of vWF that accurately represents the force-based probabilistic change between the unfolded/refolded states. A system of springs is employed to mimic the complex mechanical response of vWF monomers subject to pulling forces. AA2MM was validated by comparing monomer scale simulation results to data from prior pulling experiments on vWF monomer fragments. The model was further validated by comparing multimer scale Brownian dynamics simulation results to experiments using microfluidic chamber microscopy to visualize tethered vWF proteins subject to flow. The A2 domain unfolding reaction was studied in bulk flow simulations (pure shear and elongation flow), giving evidence that elongational flow drives the vWF size regulation process in blood. The mechanoreactive, coarse-grained AA2MM accurately describes the complex mechanical coupling between human blood flow conditions and vWF protein reactivity.
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Affiliation(s)
- Chuqiao Dong
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Sagar Kania
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Michael Morabito
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Wonpil Im
- Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Alparslan Oztekin
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Xuanhong Cheng
- Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA
| | - Edmund B Webb
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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8
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Wei W, Dong C, Morabito M, Cheng X, Zhang XF, Webb EB, Oztekin A. Coarse-Grain Modeling of Shear-Induced Binding between von Willebrand Factor and Collagen. Biophys J 2019; 114:1816-1829. [PMID: 29694861 DOI: 10.1016/j.bpj.2018.02.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 02/01/2018] [Accepted: 02/12/2018] [Indexed: 12/11/2022] Open
Abstract
Von Willebrand factor (VWF) is a large multimeric protein that aids in blood clotting. Near injury sites, hydrodynamic force from increased blood flow elongates VWF, exposing binding sites for platelets and collagen. To investigate VWF binding to collagen that is exposed on injured arterial surfaces, Brownian dynamics simulations are performed with a coarse-grain molecular model. Accounting for hydrodynamic interactions in the presence of a stationary surface, shear flow conditions are modeled. Binding between beads in coarse-grain VWF and collagen sites on the surface is described via reversible ligand-receptor-type bond formation, which is governed via Bell model kinetics. For conditions in which binding is energetically favored, the model predicts a high probability for binding at low shear conditions; this is counter to experimental observations but in agreement with what prior modeling studies have revealed. To address this discrepancy, an additional binding criterion that depends on the conformation of a submonomer feature in the model local to a given VWF binding site is implemented. The modified model predicts shear-induced binding, in very good agreement with experimental observations; this is true even for conditions in which binding is significantly favored energetically. Biological implications of the model modification are discussed in terms of mechanisms of VWF activity.
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Affiliation(s)
- Wei Wei
- Department of Mechanical Engineering and Mechanics
| | - Chuqiao Dong
- Department of Mechanical Engineering and Mechanics
| | | | - Xuanhong Cheng
- Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania; Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics; Department of Bioengineering, Lehigh University, Bethlehem, Pennsylvania
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9
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Jiang Y, Fu H, Springer TA, Wong WP. Electrostatic Steering Enables Flow-Activated Von Willebrand Factor to Bind Platelet Glycoprotein, Revealed by Single-Molecule Stretching and Imaging. J Mol Biol 2019; 431:1380-1396. [PMID: 30797858 DOI: 10.1016/j.jmb.2019.02.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/21/2019] [Accepted: 02/14/2019] [Indexed: 01/13/2023]
Abstract
Von Willebrand factor (VWF), a large multimeric blood protein, senses changes in shear stress during bleeding and responds by binding platelets to plug ruptures in the vessel wall. Molecular mechanisms underlying this dynamic process are difficult to uncover using standard approaches due to the challenge of applying mechanical forces while monitoring structure and activity. By combining single-molecule fluorescence imaging with high-pressure, rapidly switching microfluidics, we reveal the key role of electrostatic steering in accelerating the binding between flow-activated VWF and GPIbα, and in rapidly immobilizing platelets under flow. We measure the elongation and tension-dependent activation of individual VWF multimers under a range of ionic strengths and pH levels, and find that the association rate is enhanced by 4 orders of magnitude by electrostatic steering. Under supraphysiologic salt concentrations, strong electrostatic screening dramatically decreases platelet binding to VWF in flow, revealing the critical role of electrostatic attraction in VWF-platelet binding during bleeding.
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Affiliation(s)
- Yan Jiang
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Hongxia Fu
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Division of Hematology, Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, WA 98109, USA
| | - Timothy A Springer
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
| | - Wesley P Wong
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA 02115, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA.
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10
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Dong C, Lee J, Kim S, Lai W, Webb EB, Oztekin A, Zhang XF, Im W. Long-ranged Protein-glycan Interactions Stabilize von Willebrand Factor A2 Domain from Mechanical Unfolding. Sci Rep 2018; 8:16017. [PMID: 30375453 PMCID: PMC6207679 DOI: 10.1038/s41598-018-34374-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 10/15/2018] [Indexed: 12/14/2022] Open
Abstract
von Willebrand Factor (vWF) is a large multimeric protein that binds to platelets and collagen in blood clotting. vWF A2 domain hosts a proteolytic site for ADAMTS13 (A Disintegrin and Metalloprotease with a ThromboSpondin type 1 motif, member 13) to regulate the size of vWF multimers. This regulation process is highly sensitive to force conditions and protein-glycan interactions as the process occurs in flowing blood. There are two sites on A2 domain (N1515 and N1574) bearing various N-linked glycan structures. In this study, we used molecular dynamics (MD) simulation to study the force-induced unfolding of A2 domain with and without a single N-linked glycan type on each site. The sequential pullout of β-strands was used to represent a characteristic unfolding sequence of A2. This unfolding sequence varied due to protein-glycan interactions. The force-extension and total energy-extension profiles also show differences in magnitude but similar characteristic shapes between the systems with and without glycans. Systems with N-linked glycans encountered higher energy barriers for full unfolding and even for unfolding up to the point of ADAMTS13 cleavage site exposure. Interestingly, there is not much difference observed for A2 domain structure itself with and without glycans from standard MD simulations, suggesting roles of N-glycans in A2 unfolding through long-ranged protein-glycan interactions.
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Affiliation(s)
- Chuqiao Dong
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, United States
| | - Jumin Lee
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, 18015, United States
| | - Seonghoon Kim
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, 18015, United States
| | - Whitney Lai
- Department of Bioengineering, Lehigh University, Bethlehem, PA, 18015, United States
| | - Edmund B Webb
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, United States
| | - Alparslan Oztekin
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, United States
| | - X Frank Zhang
- Department of Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, PA, 18015, United States
- Department of Bioengineering, Lehigh University, Bethlehem, PA, 18015, United States
| | - Wonpil Im
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, 18015, United States.
- Department of Bioengineering, Lehigh University, Bethlehem, PA, 18015, United States.
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11
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Henn DM, Holmes JA, Kent EW, Zhao B. Worm-to-Sphere Shape Transition of Thermoresponsive Linear Molecular Bottlebrushes in Moderately Concentrated Aqueous Solution. J Phys Chem B 2018; 122:7015-7025. [DOI: 10.1021/acs.jpcb.8b04767] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel M. Henn
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jessica A. Holmes
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Ethan W. Kent
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Bin Zhao
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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12
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Nir G, Chetrit E, Vivante A, Garini Y, Berkovich R. The role of near-wall drag effects in the dynamics of tethered DNA under shear flow. SOFT MATTER 2018; 14:2219-2226. [PMID: 29451293 DOI: 10.1039/c7sm01328k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We utilized single-molecule tethered particle motion (TPM) tracking, optimized for studying the behavior of short (0.922 μm) dsDNA molecules under shear flow conditions, in the proximity of a wall (surface). These experiments track the individual trajectories through a gold nanobead (40 nm in radius), attached to the loose end of the DNA molecules. Under such circumstances, local interactions with the wall become more pronounced, manifested through hydrodynamic interactions. To elucidate the mechanical mechanism that affects the statistics of the molecular trajectories of the tethered molecules, we estimate the resting diffusion coefficient of our system. Using this value and our measured data, we calculate the orthogonal distance of the extended DNA molecules from the surface. This calculation considers the hydrodynamic drag effect that emerges from the proximity of the molecule to the surface, using the Faxén correction factors. Our finding enables the construction of a scenario according to which the tension along the chain builds up with the applied shear force, driving the loose end of the DNA molecule away from the wall. With the extension from the wall, the characteristic times of the system decrease by three orders of magnitude, while the drag coefficients decay to a plateau value that indicates that the molecule still experiences hydrodynamic effects due to its proximity to the wall.
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Affiliation(s)
- Guy Nir
- Dep. of Genetics, Harvard Medical School, Boston, MA 02115, USA. and Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Einat Chetrit
- Department of Chemical-Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
| | - Anat Vivante
- Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Yuval Garini
- Department of Physics and Institute of Nanotechnology, Bar Ilan University, Ramat Gan 52900, Israel
| | - Ronen Berkovich
- Department of Chemical-Engineering, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel. and The Ilze Katz Institute for Nanoscience and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
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13
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Hoore M, Rack K, Fedosov DA, Gompper G. Flow-induced adhesion of shear-activated polymers to a substrate. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:064001. [PMID: 29297854 DOI: 10.1088/1361-648x/aaa4d5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Adhesion of polymers and proteins to substrates plays a crucial role in many technological applications and biological processes. A prominent example is the von Willebrand factor (VWF) protein, which is essential in blood clotting as it mediates adhesion of blood platelets to the site of injury at high shear rates. VWF is activated by flow and is able to bind efficiently to damaged vessel walls even under extreme flow-stress conditions; however, its adhesion is reversible when the flow strength is significantly reduced or the flow is ceased. Motivated by the properties and behavior of VWF in flow, we investigate adhesion of shear-activated polymers to a planar wall in flow and whether the adhesion is reversible under flow stasis. The main ingredients of the polymer model are cohesive inter-monomer interactions, a catch bond with the adhesive surface, and the shear activation/deactivation of polymer adhesion correlated with its stretching in flow. The cohesive interactions within the polymer maintain a globular conformation under low shear stresses and allow polymer stretching if a critical shear rate is exceeded, which is directly associated with its activation for adhesion. Our results show that polymer adhesion at high shear rates is significantly stabilized by catch bonds, while at the same time they also permit polymer dissociation from a surface at low or no flow stresses. In addition, the activation/deactivation mechanism for adhesion plays a crucial role in the reversibility of its adhesion. These observations help us better understand the adhesive behavior of VWF in flow and interpret its adhesion malfunctioning in VWF-related diseases.
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Affiliation(s)
- Masoud Hoore
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
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14
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Margination and stretching of von Willebrand factor in the blood stream enable adhesion. Sci Rep 2017; 7:14278. [PMID: 29079767 PMCID: PMC5660260 DOI: 10.1038/s41598-017-14346-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 10/10/2017] [Indexed: 12/22/2022] Open
Abstract
The protein von Willebrand factor (VWF) is essential in primary hemostasis, as it mediates platelet adhesion to vessel walls. VWF retains its compact (globule-like) shape in equilibrium due to internal molecular associations, but is able to stretch when a high enough shear stress is applied. Even though the shear-flow sensitivity of VWF conformation is well accepted, the behavior of VWF under realistic blood flow conditions remains poorly understood. We perform mesoscopic numerical simulations together with microfluidic experiments in order to characterize VWF behavior in blood flow for a wide range of flow-rate and hematocrit conditions. In particular, our results demonstrate that the compact shape of VWF is important for its migration (or margination) toward vessel walls and that VWF stretches primarily in a near-wall region in blood flow making its adhesion possible. Our results show that VWF is a highly optimized protein in terms of its size and internal associations which are necessary to achieve its vital function. A better understanding of the relevant mechanisms for VWF behavior in microcirculation provides a further step toward the elucidation of the role of mutations in various VWF-related diseases.
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15
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Miao L, Young CD, Sing CE. An iterative method for hydrodynamic interactions in Brownian dynamics simulations of polymer dynamics. J Chem Phys 2017; 147:024904. [DOI: 10.1063/1.4993218] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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16
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Henn DM, Fu W, Mei S, Li CY, Zhao B. Temperature-Induced Shape Changing of Thermosensitive Binary Heterografted Linear Molecular Brushes between Extended Wormlike and Stable Globular Conformations. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b00150] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Daniel M. Henn
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Wenxin Fu
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Shan Mei
- Department
of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Christopher Y. Li
- Department
of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Bin Zhao
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
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17
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Henn DM, Lau CM, Li CY, Zhao B. Light-triggered unfolding of single linear molecular bottlebrushes from compact globular to wormlike nano-objects in water. Polym Chem 2017. [DOI: 10.1039/c7py00279c] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The photocleavage of o-nitrobenzyl moieties drives shape transitions from globular to wormlike in stimuli-responsive homografted and binary heterografted molecular bottlebrushes.
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Affiliation(s)
- Daniel M. Henn
- Department of Chemistry
- University of Tennessee
- Knoxville
- USA
| | - C. Maggie Lau
- Department of Chemistry
- University of Tennessee
- Knoxville
- USA
| | - Christopher Y. Li
- Department of Materials Science and Engineering
- Drexel University
- Philadelphia
- USA
| | - Bin Zhao
- Department of Chemistry
- University of Tennessee
- Knoxville
- USA
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18
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Ouyang W, Teng C, Wang Y, Li Y. Characteristics of von Willebrand Factor multimer adhesion and its bio-inspired applications. MOLECULAR SIMULATION 2016. [DOI: 10.1080/08927022.2016.1261290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Wenli Ouyang
- AVIC China Aero-Polytechology Establishment, Aviation Industry of China, Beijing, P.R. China
| | - Chunyu Teng
- AVIC China Aero-Polytechology Establishment, Aviation Industry of China, Beijing, P.R. China
| | - Yun Wang
- AVIC China Aero-Polytechology Establishment, Aviation Industry of China, Beijing, P.R. China
| | - Yonghong Li
- AVIC China Aero-Polytechology Establishment, Aviation Industry of China, Beijing, P.R. China
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19
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Heidari M, Mehrbod M, Ejtehadi MR, Mofrad MRK. Cooperation within von Willebrand factors enhances adsorption mechanism. J R Soc Interface 2016; 12:20150334. [PMID: 26179989 DOI: 10.1098/rsif.2015.0334] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
von Willebrand factor (VWF) is a naturally collapsed protein that participates in primary haemostasis and coagulation events. The clotting process is triggered by the adsorption and conformational changes of the plasma VWFs localized to the collagen fibres found near the site of injury. We develop coarse-grained models to simulate the adsorption dynamics of VWF flowing near the adhesive collagen fibres at different shear rates and investigate the effect of factors such as interaction and cooperativity of VWFs on the success of adsorption events. The adsorption probability of a flowing VWF confined to the receptor field is enhanced when it encounters an adhered VWF in proximity to the collagen receptors. This enhancement is observed within a wide range of shear rates and is mostly controlled by the attractive van der Waals interactions rather than the hydrodynamic interactions among VWF monomers. The cooperativity between the VWFs acts as an effective mechanism for enhancing VWF adsorption to the collagen fibres. Additionally, this implies that the adsorption of such molecules is nonlinearly dependent on the density of flowing VWFs. These findings are important for studies of primary haemostasis as well as general adsorption dynamics processes in polymer physics.
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Affiliation(s)
- Maziar Heidari
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
| | - Mehrdad Mehrbod
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
| | - Mohammad Reza Ejtehadi
- Department of Physics and Center of Excellence in Complex Systems and Condensed Matter, Sharif University of Technology, Tehran, Iran
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, CA 94720, USA
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Radtke M, Lippok S, Rädler JO, Netz RR. Internal tension in a collapsed polymer under shear flow and the connection to enzymatic cleavage of von Willebrand factor. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:32. [PMID: 26993993 DOI: 10.1140/epje/i2016-16032-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/01/2016] [Indexed: 06/05/2023]
Abstract
By means of Brownian hydrodynamics simulations we show that the tension distribution along the contour of a single collapsed polymer in shear flow is inhomogeneous and above a threshold shear rate exhibits a double-peak structure when hydrodynamic interactions are taken into account. We argue that the tension maxima close to the termini of the polymer chain reflect the presence of polymeric protrusions. We establish the connection to shear-induced globule unfolding and determine the scaling behavior of the maximal tensile forces and the average protrusion length as a function of shear rate, globule size, and cohesive strength. A quasi-equilibrium theory is employed in order to describe the simulation results. Our results are used to explain experimental data for the shear-sensitive enzymatic degradation of von Willebrand factor.
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Affiliation(s)
- Matthias Radtke
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
| | - Svenja Lippok
- Fakultät für Physik, der Ludwig-Maximilians-Universität München, Schellingstraße 4, 80799, München, Germany
| | - Joachim O Rädler
- Fakultät für Physik, der Ludwig-Maximilians-Universität München, Schellingstraße 4, 80799, München, Germany
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
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Force sensing by the vascular protein von Willebrand factor is tuned by a strong intermonomer interaction. Proc Natl Acad Sci U S A 2016; 113:1208-13. [PMID: 26787887 DOI: 10.1073/pnas.1516214113] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The large plasma glycoprotein von Willebrand factor (VWF) senses hydrodynamic forces in the bloodstream and responds to elevated forces with abrupt elongation, thereby increasing its adhesiveness to platelets and collagen. Remarkably, forces on VWF are elevated at sites of vascular injury, where VWF's hemostatic potential is important to mediate platelet aggregation and to recruit platelets to the subendothelial layer. Adversely, elevated forces in stenosed vessels lead to an increased risk of VWF-mediated thrombosis. To dissect the remarkable force-sensing ability of VWF, we have performed atomic force microscopy (AFM)-based single-molecule force measurements on dimers, the smallest repeating subunits of VWF multimers. We have identified a strong intermonomer interaction that involves the D4 domain and critically depends on the presence of divalent ions, consistent with results from small-angle X-ray scattering (SAXS). Dissociation of this strong interaction occurred at forces above [Formula: see text]50 pN and provided [Formula: see text]80 nm of additional length to the elongation of dimers. Corroborated by the static conformation of VWF, visualized by AFM imaging, we estimate that in VWF multimers approximately one-half of the constituent dimers are firmly closed via the strong intermonomer interaction. As firmly closed dimers markedly shorten VWF's effective length contributing to force sensing, they can be expected to tune VWF's sensitivity to hydrodynamic flow in the blood and to thereby significantly affect VWF's function in hemostasis and thrombosis.
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