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Leech V, Kenny FN, Marcotti S, Shaw TJ, Stramer BM, Manhart A. Derivation and simulation of a computational model of active cell populations: How overlap avoidance, deformability, cell-cell junctions and cytoskeletal forces affect alignment. PLoS Comput Biol 2024; 20:e1011879. [PMID: 39074138 PMCID: PMC11309491 DOI: 10.1371/journal.pcbi.1011879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 08/08/2024] [Accepted: 07/13/2024] [Indexed: 07/31/2024] Open
Abstract
Collective alignment of cell populations is a commonly observed phenomena in biology. An important example are aligning fibroblasts in healthy or scar tissue. In this work we derive and simulate a mechanistic agent-based model of the collective behaviour of actively moving and interacting cells, with a focus on understanding collective alignment. The derivation strategy is based on energy minimisation. The model ingredients are motivated by data on the behaviour of different populations of aligning fibroblasts and include: Self-propulsion, overlap avoidance, deformability, cell-cell junctions and cytoskeletal forces. We find that there is an optimal ratio of self-propulsion speed and overlap avoidance that maximises collective alignment. Further we find that deformability aids alignment, and that cell-cell junctions by themselves hinder alignment. However, if cytoskeletal forces are transmitted via cell-cell junctions we observe strong collective alignment over large spatial scales.
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Affiliation(s)
- Vivienne Leech
- Department of Mathematics, University College London, London, United Kingdom
| | - Fiona N. Kenny
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
| | - Stefania Marcotti
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
| | - Tanya J. Shaw
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
| | - Brian M. Stramer
- Randall Centre for Cell and Molecular Biophysics, King’s College London, London, United Kingdom
| | - Angelika Manhart
- Department of Mathematics, University College London, London, United Kingdom
- Faculty of Mathematics, University of Vienna, Vienna, Austria
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2
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Tan F, Wang J, Yan R, Zhao N. Forced and spontaneous translocation dynamics of a semiflexible active polymer in two dimensions. SOFT MATTER 2024; 20:1120-1132. [PMID: 38224190 DOI: 10.1039/d3sm01409f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Polymer translocation is a fundamental topic in non-equilibrium physics and is crucially important to many biological processes in life. In the present work, we adopt two-dimensional Langevin dynamics simulations to study the forced and spontaneous translocation dynamics of an active filament. The influence of polymer stiffness on the underlying dynamics is explicitly analyzed. For the forced translocation, the results show a robust stiffness-induced inhibition, and the translocation time exhibits a dual-exponent scaling relationship with the bending modulus. Tension propagation (TP) is also examined, where we find prominent modifications in terms of both activity and stiffness. For spontaneous translocation into a pure solvent, the translocation time is almost independent of the polymer stiffness. However, when the polymer is translocated into a porous medium, an intriguing non-monotonic alteration of translocation time with increasing chain stiffness is demonstrated. The semiflexible chain is beneficial for translocation while the rigid chain is not conducive. Stiffness regulation on the diffusion dynamics of the polymer in porous media shows a consistent scenario. The interplay of activity, stiffness, and porous crowding provides a new mechanism for understanding the non-trivial translocation dynamics of an active filament in complex environments.
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Affiliation(s)
- Fei Tan
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Jingli Wang
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Ran Yan
- College of Chemistry, Sichuan University, Chengdu 610064, China.
| | - Nanrong Zhao
- College of Chemistry, Sichuan University, Chengdu 610064, China.
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3
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Zakharov A, Awan M, Cheng T, Gopinath A, Lee SJJ, Ramasubramanian AK, Dasbiswas K. Clots reveal anomalous elastic behavior of fiber networks. SCIENCE ADVANCES 2024; 10:eadh1265. [PMID: 38198546 PMCID: PMC10780871 DOI: 10.1126/sciadv.adh1265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 12/06/2023] [Indexed: 01/12/2024]
Abstract
The adaptive mechanical properties of soft and fibrous biological materials are relevant to their functionality. The emergence of the macroscopic response of these materials to external stress and intrinsic cell traction from local deformations of their structural components is not well understood. Here, we investigate the nonlinear elastic behavior of blood clots by combining microscopy, rheology, and an elastic network model that incorporates the stretching, bending, and buckling of constituent fibrin fibers. By inhibiting fibrin cross-linking in blood clots, we observe an anomalous softening regime in the macroscopic shear response as well as a reduction in platelet-induced clot contractility. Our model explains these observations from two independent macroscopic measurements in a unified manner, through a single mechanical parameter, the bending stiffness of individual fibers. Supported by experimental evidence, our mechanics-based model provides a framework for predicting and comprehending the nonlinear elastic behavior of blood clots and other active biopolymer networks in general.
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Affiliation(s)
- Andrei Zakharov
- Department of Physics, University of California, Merced, Merced, CA 95343, USA
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Myra Awan
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Terrence Cheng
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, Merced, CA 95343, USA
| | - Sang-Joon John Lee
- Department of Mechanical Engineering, San José State University, San José, CA 95192, USA
| | - Anand K. Ramasubramanian
- Department of Chemical and Materials Engineering, San José State University, San José, CA 95192, USA
| | - Kinjal Dasbiswas
- Department of Physics, University of California, Merced, Merced, CA 95343, USA
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4
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Wang H, Chen W, Shen P, Feng Y, Shi D, Lu F. Follistatin (FST) is expressed in buffalo (Bubalus bubalis) ovarian follicles and promotes oocyte maturation and early embryonic development. Reprod Domest Anim 2023; 58:1718-1731. [PMID: 37917549 DOI: 10.1111/rda.14490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 09/29/2023] [Accepted: 10/02/2023] [Indexed: 11/04/2023]
Abstract
Follistatin (FST), a member of the transforming growth factor-β (TGF-β) superfamily, has been identified as an inhibitor of follicle-stimulating hormone. Previous studies showed that it plays an important role in animal reproduction. Therefore, this study aims to investigate its effect on the maturation of buffalo oocytes in vitro, and the underlying mechanism of FST affecting oocyte maturation was also explored in buffalo cumulus cells. Results showed that FST was enriched in the ovary and expressed at different stages of buffalo ovarian follicles as well as during oocyte maturation and early embryo development. The FST expression level was up-regulated in MII buffalo oocytes compared with the GV stage (p < .05). To study the effects of FST on buffalo oocytes' maturation and early embryonic development, we added the pcD3.1 skeleton vector and PCD3.1-EGFP-FST vector into the maturation fluid of buffalo oocytes, respectively. It was demonstrated that FST promoted the in vitro maturation rate of buffalo oocytes and the blastocyst rate of embryos cultured in vitro (p < .05). By interfering with FST expression, we discovered that FST in cumulus cells plays a crucial role in oocyte maturation. Interference with the FST expression during the buffalo oocyte maturation did not affect the first polar body rate of buffalo oocyte (p > .05). In contrast, the location of mitochondria in oocytes was abnormal, and the cumulus expansion area was reduced (p < .05). After parthenogenetic activation, the cleavage and blastocyst rates of the FST-interfered group were reduced (p < .05). Furthermore, RT-qPCR was performed to investigate further the underlying mechanism by which FST enhances oocyte maturation. We found that overexpression of FST could up-regulate the expression level of apoptosis suppressor gene Bcl-2 and TGF-β/SMAD pathway-related genes TGF-β, SMAD2, and SMAD3 (p < .05). In contrast, the expression levels of SMAD4 and pro-apoptotic gene BAX were significantly decreased (p < .05). The FST gene could affect buffalo oocyte maturation by regulating the oocyte mitochondria integrity, the cumulus expansion, cumulus cell apoptosis, and the expression levels of TGF-β/SMAD pathway-related genes.
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Affiliation(s)
- Haoxin Wang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
- College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, China
| | - Weili Chen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
| | - Penglei Shen
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
| | - Yun Feng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
| | - Deshun Shi
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
| | - Fenghua Lu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, Guangxi, China
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5
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Tan F, Yan R, Zhao C, Zhao N. Translocation Dynamics of an Active Filament through a Long-Length Scale Channel. J Phys Chem B 2023; 127:8603-8615. [PMID: 37782905 DOI: 10.1021/acs.jpcb.3c04250] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
Active filament translocation through a confined space is crucial for diverse biological processes. By using Langevin dynamics simulations, we investigate the translocation dynamics of an axially self-propelled chain through a channel. First, results show a suggestive reciprocal scaling of translocation time versus active force. Second, in the case of a long channel, we demonstrate a very intriguing nonmonotonic change of translocation time with increasing channel width. The driving force shows a similar trend, providing a consistent picture to understand the unexpected channel width effect. In particular, in a moderately broad channel, the disordered chain conformation results in a loss of driving force and thus inhibits translocation dynamics. Chain adsorption might occur in a wide channel, which accounts for a facilitated translocation. Lastly, we connect the translocation process to tension propagation (TP). A modified TP picture is proposed to interpret the waiting time distribution. Our work highlights the new phenomenology owing to the crucial interplay of activity and spacial confinement, which drives the translocation dynamics, going beyond the traditional entropic barrier scenario.
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Affiliation(s)
- Fei Tan
- College of Chemistry, Sichuan University, Chengdu 610065, China
| | - Ran Yan
- College of Chemistry, Sichuan University, Chengdu 610065, China
| | - Chaonan Zhao
- College of Chemistry, Sichuan University, Chengdu 610065, China
| | - Nanrong Zhao
- College of Chemistry, Sichuan University, Chengdu 610065, China
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6
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Park J, Bird JE. The actin cytoskeleton in hair bundle development and hearing loss. Hear Res 2023; 436:108817. [PMID: 37300948 PMCID: PMC10408727 DOI: 10.1016/j.heares.2023.108817] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 05/18/2023] [Accepted: 05/25/2023] [Indexed: 06/12/2023]
Abstract
Inner ear hair cells assemble mechanosensitive hair bundles on their apical surface that transduce sounds and accelerations. Each hair bundle is comprised of ∼ 100 individual stereocilia that are arranged into rows of increasing height and width; their specific and precise architecture being necessary for mechanoelectrical transduction (MET). The actin cytoskeleton is fundamental to establishing this architecture, not only by forming the structural scaffold shaping each stereocilium, but also by composing rootlets and the cuticular plate that together provide a stable foundation supporting each stereocilium. In concert with the actin cytoskeleton, a large assortment of actin-binding proteins (ABPs) function to cross-link actin filaments into specific topologies, as well as control actin filament growth, severing, and capping. These processes are individually critical for sensory transduction and are all disrupted in hereditary forms of human hearing loss. In this review, we provide an overview of actin-based structures in the hair bundle and the molecules contributing to their assembly and functional properties. We also highlight recent advances in mechanisms driving stereocilia elongation and how these processes are tuned by MET.
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Affiliation(s)
- Jinho Park
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States
| | - Jonathan E Bird
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL 32610, United States; Myology Institute, University of Florida, Gainesville, FL 32610, United States.
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7
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Yan R, Tan F, Wang J, Zhao N. Conformation and dynamics of an active filament in crowded media. J Chem Phys 2023; 158:114905. [PMID: 36948796 DOI: 10.1063/5.0142559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023] Open
Abstract
The structural and dynamical properties of active filamentous objects under macromolecular crowding have a great relevance in biology. By means of Brownian dynamics simulations, we perform a comparative study for the conformational change and diffusion dynamics of an active chain in pure solvents and in crowded media. Our result shows a robust compaction-to-swelling conformational change with the augment of the Péclet number. The presence of crowding facilitates self-trapping of monomers and, thus, reinforces the activity mediated compaction. In addition, the efficient collisions between the self-propelled monomers and crowders induce a coil-to-globulelike transition, indicated by a marked change of the Flory scaling exponent of the gyration radius. Moreover, the diffusion dynamics of the active chain in crowded solutions demonstrates activity-enhanced subdiffusion. The center of mass diffusion manifests rather new scaling relations with respect to both the chain length and Péclet number. The interplay of chain activity and medium crowding provides a new mechanism to understand the non-trivial properties of active filaments in complex environments.
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Affiliation(s)
- Ran Yan
- College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Fei Tan
- College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Jingli Wang
- College of Chemistry, Sichuan University, Chengdu 610064, China
| | - Nanrong Zhao
- College of Chemistry, Sichuan University, Chengdu 610064, China
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8
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Zhang G, Chang Y, Fan N, Yan B, Li X, Yang Z, Yu Z. Study of the Effect of Cell Prestress on the Cell Membrane Penetration Behavior by Atomic Force Microscopy. MICROMACHINES 2023; 14:397. [PMID: 36838097 PMCID: PMC9961200 DOI: 10.3390/mi14020397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 06/18/2023]
Abstract
In recent years, atomic force microscopes have been used for cell transfection because of their high-precision micro-indentation mode; however, the insertion efficiency of the tip of AFM into cells is extremely low. In this study, NIH3T3 mouse fibroblast cells cultured on a flexible dish with micro-groove patterns were subjected to various substrate strains at 5%, 10%, 15%, and 20%. It was found that the cell stiffness depends on the prestress of the cell membrane, and that the insertion rate of AFM tips into the cell membrane is proportional to the stiffness through the AFM indentation experiment. The finite element analysis proves that prestress increases the bending stiffness of the cytoskeleton, allowing it to better support the cell membrane, which realizes the stress concentration in the contact area between the AFM tip and the cell membrane. The results indicate that the prestress contributes to the mechanical properties of the cell and suggest that the insertion efficiency could be greatly improved with an increase of the prestress of the cell membrane.
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Affiliation(s)
- Guocheng Zhang
- Department of Mechanical Engineering, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
| | - Yufang Chang
- School of Accountancy, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
| | - Na Fan
- School of Mechanical and Electrical Engineering, University of Electronic Science and Technology of China, 2006 Xiyuan Avenue, Hi-Tech West District, Chengdu 611731, China
| | - Bin Yan
- Department of Mechanical Engineering, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
| | - Xianmeng Li
- Department of Mechanical Engineering, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
| | - Zihan Yang
- Department of Mechanical Engineering, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
| | - Zhenyang Yu
- Department of Mechanical Engineering, Anyang Institute of Technology, Yellow River Avenue West, Anyang 455000, China
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9
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Wu S, Li JX, Lei QL. Facilitated dynamics of an active polymer in 2D crowded environments with obstacles. SOFT MATTER 2022; 18:9263-9272. [PMID: 36441607 DOI: 10.1039/d2sm00974a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Understanding the behaviors of a single active chain in complex environments is not only an interesting topic in non-equilibrium physics but also has applicative implications in biological/medical engineering. In this work, by using molecular simulations, we systematically study the dynamical and conformational behaviors of an active polymer in crowded environments, i.e., a single active chain confined in 2D space with randomly arranged obstacles. We found that the competition between the chain's activity and rigidity in the presence of obstacles leads to many interesting dynamical and conformational states, such as the diffusive expanded state, the diffusive collapsed state, and the localized collapsed state. Importantly, we found a counter-intuitive phenomenon, i.e., crowded environments facilitate the diffusion of the active polymer within a large parameter space. As the crowdedness (packing fraction of obstacles) increases, the parameter space in which crowding-enhanced diffusion occurs still remains. This abnormal dynamics is attributed to a structural reason that the obstacles prevent active chains from collapsing. Our findings capture some generic features of active polymers in complex environments and provide insights into the design of novel drug delivery systems.
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Affiliation(s)
- Song Wu
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Jia-Xiang Li
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
| | - Qun-Li Lei
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
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10
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Iqbal M, Abrar M, Iqbal T, Ahmed I, Sayed MA, El-Rehim AFA, Ali AM. Plasmonic-based Solar Cell: Geometrical Optimization of 1D-nanostructured Grating for Enhanced Efficiency. PLASMONICS 2022; 17:2491-2520. [DOI: 10.1007/s11468-022-01717-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 10/05/2022] [Indexed: 09/02/2023]
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11
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Pajic-Lijakovic I, Milivojevic M. Marangoni effect and cell spreading. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2022; 51:419-429. [PMID: 35930028 DOI: 10.1007/s00249-022-01612-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
Cells are very sensitive to the shear stress (SS). However, undesirable SS is generated during physiological process such as collective cell migration (CCM) and influences the biological processes such as morphogenesis, wound healing and cancer invasion. Despite extensive research devoted to study the SS generation caused by CCM, we still do not fully understand the main cause of SS appearance. An attempt is made here to offer some answers to these questions by considering the rearrangement of cell monolayers. The SS generation represents a consequence of natural and forced convection. While forced convection is dependent on cell speed, the natural convection is induced by the gradient of tissue surface tension. The phenomenon is known as the Marangoni effect. The gradient of tissue surface tension induces directed cell spreading from the regions of lower tissue surface tension to the regions of higher tissue surface tension and leads to the cell sorting. This directional cell migration is described by the Marangoni flux. The phenomenon has been recognized during the rearrangement of (1) epithelial cell monolayers and (2) mixed cell monolayers made by epithelial and mesenchymal cells. The consequence of the Marangoni effect is an intensive spreading of cancer cells through an epithelium. In this work, a review of existing literature about SS generation caused by CCM is given along with the assortment of published experimental findings, to invite experimentalists to test given theoretical considerations in multicellular systems.
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Affiliation(s)
- Ivana Pajic-Lijakovic
- Faculty of Technology and Metallurgy, Department of Chemical Engineering, University of Belgrade, Belgrade, Serbia.
| | - Milan Milivojevic
- Faculty of Technology and Metallurgy, Department of Chemical Engineering, University of Belgrade, Belgrade, Serbia
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12
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Mondal A, Morrison G. Compression-induced buckling of a semiflexible filament in two and three dimensions. J Chem Phys 2022; 157:104903. [DOI: 10.1063/5.0104910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ability of biomolecules to exert forces on their surroundings or resist compression from the environment is essential in a variety of biologically relevant contexts. For filaments in the low-temperature limit and under a constant compressive force, Euler buckling theory predicts a sudden transition from a compressed to a bent state in these slender rods. In this paper, we use a mean-field theory to show that if a semiflexible chain is compressed at a finite temperature with a fixed end-to-end distance (permitting fluctuations in the compressive forces), it exhibits a continuous phase transition to a buckled state at a critical level of compression. We determine a quantitatively accurate prediction of the transverse position distribution function of the midpoint of the chain that indicates this transition. We find the mean compressive forces are non-monotonic as the extension of the filament varies, consistent with the observation that strongly buckled filaments are less able to bear an external load. We also find that for the fixed extension (isometric) ensemble, the buckling transition does not coincide with the local minimum of the mean force (in contrast to Euler buckling). We also show the theory is highly sensitive to fluctuations in length in two dimensions, and that the buckling transition can still be accurately recovered by accounting for those fluctuations. These predictions may be useful in understanding the behavior of filamentous biomolecules compressed by fluctuating forces, relevant in a variety of biological contexts.
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Affiliation(s)
- Ananya Mondal
- Physics, University of Houston, United States of America
| | - Greg Morrison
- Physics, University of Houston, United States of America
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13
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Tauber J, van der Gucht J, Dussi S. Stretchy and disordered: Toward understanding fracture in soft network materials via mesoscopic computer simulations. J Chem Phys 2022; 156:160901. [PMID: 35490006 DOI: 10.1063/5.0081316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Soft network materials exist in numerous forms ranging from polymer networks, such as elastomers, to fiber networks, such as collagen. In addition, in colloidal gels, an underlying network structure can be identified, and several metamaterials and textiles can be considered network materials as well. Many of these materials share a highly disordered microstructure and can undergo large deformations before damage becomes visible at the macroscopic level. Despite their widespread presence, we still lack a clear picture of how the network structure controls the fracture processes of these soft materials. In this Perspective, we will focus on progress and open questions concerning fracture at the mesoscopic scale, in which the network architecture is clearly resolved, but neither the material-specific atomistic features nor the macroscopic sample geometries are considered. We will describe concepts regarding the network elastic response that have been established in recent years and turn out to be pre-requisites to understand the fracture response. We will mostly consider simulation studies, where the influence of specific network features on the material mechanics can be cleanly assessed. Rather than focusing on specific systems, we will discuss future challenges that should be addressed to gain new fundamental insights that would be relevant across several examples of soft network materials.
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Affiliation(s)
- Justin Tauber
- Physical Chemistry and Soft Matter, Wageningen University, Wageningen, The Netherlands
| | - Jasper van der Gucht
- Physical Chemistry and Soft Matter, Wageningen University, Wageningen, The Netherlands
| | - Simone Dussi
- Physical Chemistry and Soft Matter, Wageningen University, Wageningen, The Netherlands
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14
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Sherman WF, Asad M, Grosberg A. An Energetic Approach to Modeling Cytoskeletal Architecture in Maturing Cardiomyocytes. J Biomech Eng 2022; 144:021002. [PMID: 34382649 PMCID: PMC8547018 DOI: 10.1115/1.4052112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2021] [Revised: 07/28/2021] [Indexed: 02/03/2023]
Abstract
Through a variety of mechanisms, a healthy heart is able to regulate its structure and dynamics across multiple length scales. Disruption of these mechanisms can have a cascading effect, resulting in severe structural and/or functional changes that permeate across different length scales. Due to this hierarchical structure, there is interest in understanding how the components at the various scales coordinate and influence each other. However, much is unknown regarding how myofibril bundles are organized within a densely packed cell and the influence of the subcellular components on the architecture that is formed. To elucidate potential factors influencing cytoskeletal development, we proposed a computational model that integrated interactions at both the cellular and subcellular scale to predict the location of individual myofibril bundles that contributed to the formation of an energetically favorable cytoskeletal network. Our model was tested and validated using experimental metrics derived from analyzing single-cell cardiomyocytes. We demonstrated that our model-generated networks were capable of reproducing the variation observed in experimental cells at different length scales as a result of the stochasticity inherent in the different interactions between the various cellular components. Additionally, we showed that incorporating length-scale parameters resulted in physical constraints that directed cytoskeletal architecture toward a structurally consistent motif. Understanding the mechanisms guiding the formation and organization of the cytoskeleton in individual cardiomyocytes can aid tissue engineers toward developing functional cardiac tissue.
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Affiliation(s)
- William F. Sherman
- Center for Complex Biological Systems, Edwards Lifesciences Center for Advanced Cardiovascular Technology, University of California, Irvine, CA 92697
| | - Mira Asad
- Edwards Lifesciences Center for Advanced Cardiovascular Technology, Department of Biomedical Engineering, University of California, Irvine, CA 92697
| | - Anna Grosberg
- Edwards Lifesciences Center for Advanced Cardiovascular Technology, Department of Biomedical Engineering, NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, CA 92697; Department of Chemical and Biomolecular Engineering, Center for Complex Biological Systems, University of California, Irvine, CA 92697
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15
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Khan MI, Gilpin K, Hasan F, Mahmud KAHA, Adnan A. Effect of Strain Rate on Single Tau, Dimerized Tau and Tau-Microtubule Interface: A Molecular Dynamics Simulation Study. Biomolecules 2021; 11:1308. [PMID: 34572521 PMCID: PMC8472149 DOI: 10.3390/biom11091308] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 08/30/2021] [Accepted: 09/02/2021] [Indexed: 01/24/2023] Open
Abstract
Microtubule-associated protein (MAP) tau is a cross-linking molecule that provides structural stability to axonal microtubules (MT). It is considered a potential biomarker for Alzheimer's disease (AD), dementia, and other neurological disorders. It is also a signature protein for Traumatic Brain Injury (TBI) assessment. In the case of TBI, extreme dynamic mechanical energies can be felt by the axonal cytoskeletal members. As such, fundamental understandings of the responses of single tau protein, polymerized tau protein, and tau-microtubule interfaces under high-rate mechanical forces are important. This study attempts to determine the high-strain rate mechanical behavior of single tau, dimerized tau, and tau-MT interface using molecular dynamics (MD) simulation. The results show that a single tau protein is a highly stretchable soft polymer. During deformation, first, it significantly unfolds against van der Waals and electrostatic bonds. Then it stretches against strong covalent bonds. We found that tau acts as a viscoelastic material, and its stiffness increases with the strain rate. The unfolding stiffness can be ~50-500 MPa, while pure stretching stiffness can be >2 GPa. The dimerized tau model exhibits similar behavior under similar strain rates, and tau sliding from another tau is not observed until it is stretched to >7 times of original length, depending on the strain rate. The tau-MT interface simulations show that very high strain and strain rates are required to separate tau from MT suggesting Tau-MT bonding is stronger than MT subunit bonding between themselves. The dimerized tau-MT interface simulations suggest that tau-tau bonding is stronger than tau-MT bonding. In summary, this study focuses on the structural response of individual cytoskeletal components, namely microtubule (MT) and tau protein. Furthermore, we consider not only the individual response of a component, but also their interaction with each other (such as tau with tau or tau with MT). This study will eventually pave the way to build a bottom-up multiscale brain model and analyze TBI more comprehensively.
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Affiliation(s)
- Md Ishak Khan
- Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, TX 76019, USA; (M.I.K.); (F.H.); (K.A.H.A.M.)
| | - Kathleen Gilpin
- Academic Partnership and Engagement Experiment (APEX), Wright State Applied Research Corporation, Beavercreek, OH 45431, USA;
| | - Fuad Hasan
- Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, TX 76019, USA; (M.I.K.); (F.H.); (K.A.H.A.M.)
| | - Khandakar Abu Hasan Al Mahmud
- Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, TX 76019, USA; (M.I.K.); (F.H.); (K.A.H.A.M.)
| | - Ashfaq Adnan
- Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington, TX 76019, USA; (M.I.K.); (F.H.); (K.A.H.A.M.)
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16
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Liu N, Chavoshnejad P, Li S, Razavi MJ, Liu T, Pidaparti R, Wang X. Geometrical nonlinear elasticity of axon under tension: A coarse-grained computational study. Biophys J 2021; 120:3697-3708. [PMID: 34310941 DOI: 10.1016/j.bpj.2021.07.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 06/19/2021] [Accepted: 07/20/2021] [Indexed: 11/16/2022] Open
Abstract
Axon bundles cross-linked by microtubule (MT) associate proteins and bounded by a shell skeleton are critical for normal function of neurons. Understanding effects of the complexly geometrical parameters on their mechanical properties can help gain a biomechanical perspective on the neurological functions of axons and thus brain disorders caused by the structural failure of axons. Here, the tensile mechanical properties of MT bundles cross-linked by tau proteins are investigated by systematically tuning MT length, axonal cross-section radius, and tau protein spacing in a bead-spring coarse-grained model. Our results indicate that the stress-strain curves of axons can be divided into two regimes, a nonlinear elastic regime dominated by rigid-body like inter-MT sliding, and a linear elastic regime dominated by affine deformation of both tau proteins and MTs. From the energetic analyses, first, the tau proteins dominate the mechanical performance of axons under tension. In the nonlinear regime, tau proteins undergo a rigid-body like rotating motion rather than elongating, whereas in the nonlinear elastic regime, tau proteins undergo a flexible elongating deformation along the MT axis. Second, as the average spacing between adjacent tau proteins along the MT axial direction increases from 25 to 125 nm, the Young's modulus of axon experiences a linear decrease whereas with the average space varying from 125 to 175 nm, and later reaches a plateau value with a stable fluctuation. Third, the increment of the cross-section radius of the MT bundle leads to a decrease in Young's modulus of axon, which is possibly attributed to the decrease in MT numbers per cross section. Overall, our research findings offer a new perspective into understanding the effects of geometrical parameters on the mechanics of MT bundles as well as serving as a theoretical basis for the development of artificial MT complexes potentially toward medical applications.
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Affiliation(s)
- Ning Liu
- College of Engineering, University of Georgia, Athens, Georgia
| | - Poorya Chavoshnejad
- Department of Mechanical Engineering, Binghamton University, Binghamton, New York
| | - Shaoheng Li
- College of Engineering, University of Georgia, Athens, Georgia
| | - Mir Jalil Razavi
- Department of Mechanical Engineering, Binghamton University, Binghamton, New York
| | - Tianming Liu
- Department of Computer Science, University of Georgia, Athens, Georgia
| | | | - Xianqiao Wang
- College of Engineering, University of Georgia, Athens, Georgia.
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17
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Bakshi S, M VV, Sarkar R, Majumdar S. Strain localization and yielding dynamics in disordered collagen networks. SOFT MATTER 2021; 17:6435-6444. [PMID: 34132288 DOI: 10.1039/d1sm00300c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Collagen is the most abundant extracellular-matrix protein found in mammals and the main structural and load-bearing element of connective tissues. Collagen networks show remarkable strain-stiffening, which tunes the mechanical functions of tissues and regulates cell behaviours. Linear and non-linear mechanics of in vitro disordered collagen networks have been widely studied using rheology for a range of self-assembly conditions in recent years. However, the correlation between the onset of macroscopic network failure and local deformations is not well understood in these systems. Here, using shear rheology and in situ high-resolution boundary imaging, we study the yielding dynamics of in vitro reconstituted networks of uncrosslinked type-I collagen. We find that in the non-linear regime, the differential shear modulus (K) of the network initially increases with applied strain and then begins to drop as the network starts to yield beyond a critical strain (yield strain). Measurement of the local velocity profile using colloidal tracer particles reveals that beyond the peak of K, strong strain-localization and slippage between the network and the rheometer plate sets in that eventually leads to a detachment. We generalize this observation for a range of collagen concentrations, applied strain ramp rates, as well as, different network architectures obtained by varying the polymerization temperature. Furthermore, using a continuum affine network model, we map out a state diagram showing the dependence of yield-stain and -stress on the microscopic network parameters. Our findings can have broad implications in tissue engineering and designing highly resilient biological scaffolds.
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Affiliation(s)
- Swarnadeep Bakshi
- Soft Condensed Matter Group, Raman Research Institute, Bengaluru 560080, India.
| | - Vaisakh V M
- Soft Condensed Matter Group, Raman Research Institute, Bengaluru 560080, India. and Department of Physics, HKUST, Clear Water Bay, Hong Kong
| | - Ritwick Sarkar
- Soft Condensed Matter Group, Raman Research Institute, Bengaluru 560080, India.
| | - Sayantan Majumdar
- Soft Condensed Matter Group, Raman Research Institute, Bengaluru 560080, India.
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18
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Slepukhin VM, Levine AJ. Braiding Dynamics in Semiflexible Filament Bundles under Oscillatory Forcing. Polymers (Basel) 2021; 13:2195. [PMID: 34279339 PMCID: PMC8271738 DOI: 10.3390/polym13132195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/25/2021] [Accepted: 06/25/2021] [Indexed: 11/16/2022] Open
Abstract
We examine the nonequilibrium production of topological defects-braids-in semiflexible filament bundles under cycles of compression and tension. During these cycles, the period of compression facilitates the thermally activated pair production of braid/anti-braid pairs, which then may separate when the bundle is under tension. As a result, appropriately tuned alternating periods of compression and extension should lead to the proliferation of braid defects in a bundle so that the linear density of these pairs far exceeds that expected in the thermal equilibrium. Secondly, we examine the slow extension of braided bundles under tension, showing that their end-to-end length creeps nonmonotonically under a fixed force due to braid deformation and the motion of the braid pair along the bundle. We conclude with a few speculations regarding experiments on semiflexible filament bundles and their networks.
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Affiliation(s)
- Valentin M Slepukhin
- Department of Physics & Astronomy, University of California, Los Angeles, CA 90095, USA
| | - Alex J Levine
- Department of Physics & Astronomy, University of California, Los Angeles, CA 90095, USA
- Department of Chemistry & Biochemistry, University of California, Los Angeles, CA 90095, USA
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19
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Ilami M, Bagheri H, Ahmed R, Skowronek EO, Marvi H. Materials, Actuators, and Sensors for Soft Bioinspired Robots. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2003139. [PMID: 33346386 DOI: 10.1002/adma.202003139] [Citation(s) in RCA: 95] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 08/15/2020] [Indexed: 05/23/2023]
Abstract
Biological systems can perform complex tasks with high compliance levels. This makes them a great source of inspiration for soft robotics. Indeed, the union of these fields has brought about bioinspired soft robotics, with hundreds of publications on novel research each year. This review aims to survey fundamental advances in bioinspired soft actuators and sensors with a focus on the progress between 2017 and 2020, providing a primer for the materials used in their design.
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Affiliation(s)
- Mahdi Ilami
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Hosain Bagheri
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Reza Ahmed
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - E Olga Skowronek
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85287, USA
| | - Hamid Marvi
- School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85287, USA
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20
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Castaneda N, Park J, Kang EH. Regulation of Actin Bundle Mechanics and Structure by Intracellular Environmental Factors. FRONTIERS IN PHYSICS 2021; 9:675885. [PMID: 34422787 PMCID: PMC8376200 DOI: 10.3389/fphy.2021.675885] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The mechanical and structural properties of actin cytoskeleton drive various cellular processes, including structural support of the plasma membrane and cellular motility. Actin monomers assemble into double-stranded helical filaments as well as higher-ordered structures such as bundles and networks. Cells incorporate macromolecular crowding, cation interactions, and actin-crosslinking proteins to regulate the organization of actin bundles. Although the roles of each of these factors in actin bundling have been well-known individually, how combined factors contribute to actin bundle assembly, organization, and mechanics is not fully understood. Here, we describe recent studies that have investigated the mechanisms of how intracellular environmental factors influence actin bundling. This review highlights the effects of macromolecular crowding, cation interactions, and actin-crosslinking proteins on actin bundle organization, structure, and mechanics. Understanding these mechanisms is important in determining in vivo actin biophysics and providing insights into cell physiology.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, United States
| | - Jinho Park
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States
- Department of Physics, University of Central Florida, Orlando, FL, United States
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21
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Mulhall EM, Ward A, Yang D, Koussa MA, Corey DP, Wong WP. Single-molecule force spectroscopy reveals the dynamic strength of the hair-cell tip-link connection. Nat Commun 2021; 12:849. [PMID: 33558532 PMCID: PMC7870652 DOI: 10.1038/s41467-021-21033-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 01/08/2021] [Indexed: 01/11/2023] Open
Abstract
The conversion of auditory and vestibular stimuli into electrical signals is initiated by force transmitted to a mechanotransduction channel through the tip link, a double stranded protein filament held together by two adhesion bonds in the middle. Although thought to form a relatively static structure, the dynamics of the tip-link connection has not been measured. Here, we biophysically characterize the strength of the tip-link connection at single-molecule resolution. We show that a single tip-link bond is more mechanically stable relative to classic cadherins, and our data indicate that the double stranded tip-link connection is stabilized by single strand rebinding facilitated by strong cis-dimerization domains. The measured lifetime of seconds suggests the tip-link is far more dynamic than previously thought. We also show how Ca2+ alters tip-link lifetime through elastic modulation and reveal the mechanical phenotype of a hereditary deafness mutation. Together, these data show how the tip link is likely to function during mechanical stimuli.
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Affiliation(s)
- Eric M Mulhall
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience, Harvard University, Cambridge, MA, USA
| | - Andrew Ward
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
| | - Darren Yang
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
| | - Mounir A Koussa
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience, Harvard University, Cambridge, MA, USA
| | - David P Corey
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| | - Wesley P Wong
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
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22
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Boujemaa-Paterski R, Martins B, Eibauer M, Beales CT, Geiger B, Medalia O. Talin-activated vinculin interacts with branched actin networks to initiate bundles. eLife 2020; 9:e53990. [PMID: 33185186 PMCID: PMC7682986 DOI: 10.7554/elife.53990] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 11/12/2020] [Indexed: 12/18/2022] Open
Abstract
Vinculin plays a fundamental role in integrin-mediated cell adhesion. Activated by talin, it interacts with diverse adhesome components, enabling mechanical coupling between the actin cytoskeleton and the extracellular matrix. Here we studied the interactions of activated full-length vinculin with actin and the way it regulates the organization and dynamics of the Arp2/3 complex-mediated branched actin network. Through a combination of surface patterning and light microscopy experiments we show that vinculin can bundle dendritic actin networks through rapid binding and filament crosslinking. We show that vinculin promotes stable but flexible actin bundles having a mixed-polarity organization, as confirmed by cryo-electron tomography. Adhesion-like synthetic design of vinculin activation by surface-bound talin revealed that clustered vinculin can initiate and immobilize bundles from mobile Arp2/3-branched networks. Our results provide a molecular basis for coordinate actin bundle formation at nascent adhesions.
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Affiliation(s)
- Rajaa Boujemaa-Paterski
- Department of Biochemistry, University of ZurichZurichSwitzerland
- Université Grenoble AlpesGrenobleFrance
| | - Bruno Martins
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Matthias Eibauer
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Charlie T Beales
- Department of Biochemistry, University of ZurichZurichSwitzerland
| | - Benjamin Geiger
- Department of Immunology, Weizmann Institute of ScienceRehovotIsrael
| | - Ohad Medalia
- Department of Biochemistry, University of ZurichZurichSwitzerland
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23
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Park J, Lee M, Lee B, Castaneda N, Tetard L, Kang EH. Crowding tunes the organization and mechanics of actin bundles formed by crosslinking proteins. FEBS Lett 2020; 595:26-40. [PMID: 33020904 DOI: 10.1002/1873-3468.13949] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 09/14/2020] [Accepted: 09/21/2020] [Indexed: 01/05/2023]
Abstract
Fascin and α-actinin form higher-ordered actin bundles that mediate numerous cellular processes including cell morphogenesis and movement. While it is understood crosslinked bundle formation occurs in crowded cytoplasm, how crowding affects the bundling activities of the two crosslinking proteins is not known. Here, we demonstrate how solution crowding modulates the organization and mechanical properties of fascin- and α-actinin-induced bundles, utilizing total internal reflection fluorescence and atomic force microscopy imaging. Molecular dynamics simulations support the inference that crowding reduces binding interaction between actin filaments and fascin or the calponin homology 1 domain of α-actinin evidenced by interaction energy and hydrogen bonding analysis. Based on our findings, we suggest a mechanism of crosslinked actin bundle assembly and mechanics in crowded intracellular environments.
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Affiliation(s)
- Jinho Park
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA.,Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA
| | - Myeongsang Lee
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA
| | - Briana Lee
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA
| | - Nicholas Castaneda
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA.,Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL, USA
| | - Laurene Tetard
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA.,Department of Physics, University of Central Florida, Orlando, FL, USA
| | - Ellen Hyeran Kang
- NanoScience Technology Center, University of Central Florida, Orlando, FL, USA.,Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, USA.,Department of Physics, University of Central Florida, Orlando, FL, USA
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24
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Yasodharababu M, Nair AK. A Multiscale Model to Predict Neuronal Cell Deformation with Varying Extracellular Matrix Stiffness and Topography. Cell Mol Bioeng 2020; 13:229-245. [PMID: 32426060 PMCID: PMC7225237 DOI: 10.1007/s12195-020-00615-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 04/11/2020] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION Neuronal cells are sensitive to mechanical properties of extracellular matrix (ECM) such as stiffness and topography. Cells contract and exert a force on ECM to detect the microenvironment, which activates the signaling pathway to influence the cell functions such as differentiation, migration, and proliferation. There are numerous transmembrane proteins that transmit signals; however, integrin and neural cellular adhesion molecules (NCAM) play an important role in sensing the ECM mechanical properties. Mechanotransduction of cell-ECM is the key to understand the influence of ECM stiffness and topography; therefore, in this study, we develop a multiscale computational model to investigate these properties. METHODS This model couples the molecular behavior of integrin and NCAM to microscale interactions of neuronal cell and the ECM. We analyze the atomistic/molecular behavior of integrin and NCAM due to mechanical stimuli using steered molecular dynamics. The microscale properties of the neuronal cell and the ECM are simulated using non-linear finite element analysis by applying cell contractility. RESULTS We predict that by increasing the ECM stiffness, a neuronal cell exerts greater stress on the ECM. However, this stress reaches a saturation value for a threshold stiffness of ECM, and the saturation value is affected by the ECM thickness, topography, and clustering of integrin and NCAMs. Further, the ECM topography leads to asymmetric stress and deformation in the neuronal cell. Predicted stress distribution in neuronal cell and ECM are consistent with experimental results from the literature. CONCLUSION The multiscale computational model will guide in selecting the optimal ECM stiffness and topography range for in vitro studies.
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Affiliation(s)
- Mohan Yasodharababu
- Multiscale Materials Modeling Lab, Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR USA
| | - Arun K. Nair
- Multiscale Materials Modeling Lab, Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR USA
- Institute for Nanoscience and Engineering, University of Arkansas, 731 W. Dickson Street, Fayetteville, AR USA
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25
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Wu H, Shen Y, Wang D, Herrmann H, Goldman RD, Weitz DA. Effect of Divalent Cations on the Structure and Mechanics of Vimentin Intermediate Filaments. Biophys J 2020; 119:55-64. [PMID: 32521238 DOI: 10.1016/j.bpj.2020.05.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 05/11/2020] [Accepted: 05/13/2020] [Indexed: 12/30/2022] Open
Abstract
Divalent cations behave as effective cross-linkers of intermediate filaments (IFs) such as vimentin IF (VIF). These interactions have been mostly attributed to their multivalency. However, ion-protein interactions often depend on the ion species, and these effects have not been widely studied in IFs. Here, we investigate the effects of two biologically important divalent cations, Zn2+ and Ca2+, on VIF network structure and mechanics in vitro. We find that the network structure is unperturbed at micromolar Zn2+ concentrations, but strong bundle formation is observed at a concentration of 100 μM. Microrheological measurements show that network stiffness increases with cation concentration. However, bundling of filaments softens the network. This trend also holds for VIF networks formed in the presence of Ca2+, but remarkably, a concentration of Ca2+ that is two orders higher is needed to achieve the same effect as with Zn2+, which suggests the importance of salt-protein interactions as described by the Hofmeister effect. Furthermore, we find evidence of competitive binding between the two divalent ion species. Hence, specific interactions between VIFs and divalent cations are likely to be an important mechanism by which cells can control their cytoplasmic mechanics.
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Affiliation(s)
- Huayin Wu
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts
| | - Yinan Shen
- Department of Physics, Harvard University, Cambridge, Massachusetts
| | - Dianzhuo Wang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois
| | - Harald Herrmann
- Division of Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Institute of Neuropathology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Robert D Goldman
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois
| | - David A Weitz
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts; Department of Physics, Harvard University, Cambridge, Massachusetts.
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26
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Mancl JM, Suarez C, Liang WG, Kovar DR, Tang WJ. Pseudomonas aeruginosa exoenzyme Y directly bundles actin filaments. J Biol Chem 2020; 295:3506-3517. [PMID: 32019868 DOI: 10.1074/jbc.ra119.012320] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 01/23/2020] [Indexed: 11/06/2022] Open
Abstract
Pseudomonas aeruginosa uses a type III secretion system (T3SS) to inject cytotoxic effector proteins into host cells. The promiscuous nucleotidyl cyclase, exoenzyme Y (ExoY), is one of the most common effectors found in clinical P. aeruginosa isolates. Recent studies have revealed that the nucleotidyl cyclase activity of ExoY is stimulated by actin filaments (F-actin) and that ExoY alters actin cytoskeleton dynamics in vitro, via an unknown mechanism. The actin cytoskeleton plays an important role in numerous key biological processes and is targeted by many pathogens to gain competitive advantages. We utilized total internal reflection fluorescence microscopy, bulk actin assays, and EM to investigate how ExoY impacts actin dynamics. We found that ExoY can directly bundle actin filaments with high affinity, comparable with eukaryotic F-actin-bundling proteins, such as fimbrin. Of note, ExoY enzymatic activity was not required for F-actin bundling. Bundling is known to require multiple actin-binding sites, yet small-angle X-ray scattering experiments revealed that ExoY is a monomer in solution, and previous data suggested that ExoY possesses only one actin-binding site. We therefore hypothesized that ExoY oligomerizes in response to F-actin binding and have used the ExoY structure to construct a dimer-based structural model for the ExoY-F-actin complex. Subsequent mutational analyses suggested that the ExoY oligomerization interface plays a crucial role in mediating F-actin bundling. Our results indicate that ExoY represents a new class of actin-binding proteins that modulate the actin cytoskeleton both directly, via F-actin bundling, and indirectly, via actin-activated nucleotidyl cyclase activity.
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Affiliation(s)
- Jordan M Mancl
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - Cristian Suarez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637
| | - Wenguang G Liang
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637
| | - David R Kovar
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637
| | - Wei-Jen Tang
- Ben May Department for Cancer Research, University of Chicago, Chicago, Illinois 60637.
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27
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Montanino A, Saeedimasine M, Villa A, Kleiven S. Localized Axolemma Deformations Suggest Mechanoporation as Axonal Injury Trigger. Front Neurol 2020; 11:25. [PMID: 32082244 PMCID: PMC7005088 DOI: 10.3389/fneur.2020.00025] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/09/2020] [Indexed: 12/19/2022] Open
Abstract
Traumatic brain injuries are a leading cause of morbidity and mortality worldwide. With almost 50% of traumatic brain injuries being related to axonal damage, understanding the nature of cellular level impairment is crucial. Experimental observations have so far led to the formulation of conflicting theories regarding the cellular primary injury mechanism. Disruption of the axolemma, or alternatively cytoskeletal damage has been suggested mainly as injury trigger. However, mechanoporation thresholds of generic membranes seem not to overlap with the axonal injury deformation range and microtubules appear too stiff and too weakly connected to undergo mechanical breaking. Here, we aim to shed a light on the mechanism of primary axonal injury, bridging finite element and molecular dynamics simulations. Despite the necessary level of approximation, our models can accurately describe the mechanical behavior of the unmyelinated axon and its membrane. More importantly, they give access to quantities that would be inaccessible with an experimental approach. We show that in a typical injury scenario, the axonal cortex sustains deformations large enough to entail pore formation in the adjoining lipid bilayer. The observed axonal deformation of 10–12% agree well with the thresholds proposed in the literature for axonal injury and, above all, allow us to provide quantitative evidences that do not exclude pore formation in the membrane as a result of trauma. Our findings bring to an increased knowledge of axonal injury mechanism that will have positive implications for the prevention and treatment of brain injuries.
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Affiliation(s)
- Annaclaudia Montanino
- Division of Neuronic Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden
| | - Marzieh Saeedimasine
- Department of Biosciences and Nutrition, Karolinska Institutet (KI), Stockholm, Sweden
| | - Alessandra Villa
- Department of Biosciences and Nutrition, Karolinska Institutet (KI), Stockholm, Sweden
| | - Svein Kleiven
- Division of Neuronic Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden
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28
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Martiel JL, Michelot A, Boujemaa-Paterski R, Blanchoin L, Berro J. Force Production by a Bundle of Growing Actin Filaments Is Limited by Its Mechanical Properties. Biophys J 2019; 118:182-192. [PMID: 31791547 DOI: 10.1016/j.bpj.2019.10.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 10/16/2019] [Accepted: 10/30/2019] [Indexed: 12/16/2022] Open
Abstract
Bundles of actin filaments are central to a large variety of cellular structures such as filopodia, stress fibers, cytokinetic rings, and focal adhesions. The mechanical properties of these bundles are critical for proper force transmission and force bearing. Previous mathematical modeling efforts have focused on bundles' rigidity and shape. However, it remains unknown how bundle length and buckling are controlled by external physical factors. In this work, we present a biophysical model for dynamic bundles of actin filaments submitted to an external load. In combination with in vitro motility assays of beads coated with formins, our model allowed us to characterize conditions for bead movement and bundle buckling. From the deformation profiles, we determined key biophysical properties of tethered actin bundles such as their rigidity and filament density.
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Affiliation(s)
- Jean-Louis Martiel
- CytomorphoLab, Biosciences & Biotechnology Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France; CNRS, CHU Grenoble-Alpes, Inserm, TIMC-IMAG, University Grenoble-Alpes, Grenoble, France.
| | - Alphée Michelot
- CytomorphoLab, Biosciences & Biotechnology Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France; CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille University, Marseille, France
| | - Rajaa Boujemaa-Paterski
- CytomorphoLab, Biosciences & Biotechnology Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France; Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Laurent Blanchoin
- CytomorphoLab, Biosciences & Biotechnology Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France
| | - Julien Berro
- CytomorphoLab, Biosciences & Biotechnology Institute of Grenoble, Laboratoire de Physiologie Cellulaire & Végétale, Université Grenoble-Alpes/CEA/CNRS/INRA, Grenoble, France; Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut; Nanobiology Institute, Yale University, West Haven, Connecticut; Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut.
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29
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Adeli Koudehi M, Rutkowski DM, Vavylonis D. Organization of associating or crosslinked actin filaments in confinement. Cytoskeleton (Hoboken) 2019; 76:532-548. [PMID: 31525281 DOI: 10.1002/cm.21565] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/09/2019] [Accepted: 09/12/2019] [Indexed: 12/13/2022]
Abstract
A key factor of actin cytoskeleton organization in cells is the interplay between the dynamical properties of actin filaments and cell geometry, which restricts, confines and directs their orientation. Crosslinking interactions among actin filaments, together with geometrical cues and regulatory proteins can give rise to contractile rings in dividing cells and actin rings in neurons. Motivated by recent in vitro experiments, in this work we performed computer simulations to study basic aspects of the interplay between confinement and attractive interactions between actin filaments. We used a spring-bead model and Brownian dynamics to simulate semiflexible actin filaments that polymerize in a confining sphere with a rate proportional to the monomer concentration. We model crosslinking, or attraction through the depletion interaction, implicitly as an attractive short-range potential between filament beads. In confining geometries smaller than the persistence length of actin filaments, we show rings can form by curving of filaments of length comparable to, or longer than the confinement diameter. Rings form for optimal ranges of attractive interactions that exist in between open bundles, irregular loops, aggregated, and unbundled morphologies. The probability of ring formation is promoted by attraction to the confining sphere boundary and decreases for large radii and initial monomer concentrations, in agreement with prior experimental data. The model reproduces ring formation along the flat plane of oblate ellipsoids.
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30
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Yanakieva I, Erzberger A, Matejčić M, Modes CD, Norden C. Cell and tissue morphology determine actin-dependent nuclear migration mechanisms in neuroepithelia. J Cell Biol 2019; 218:3272-3289. [PMID: 31420451 PMCID: PMC6781452 DOI: 10.1083/jcb.201901077] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/29/2019] [Accepted: 07/18/2019] [Indexed: 11/22/2022] Open
Abstract
Using quantitative live imaging in the developing zebrafish embryo, Yanakieva et al. show that distinct actin-dependent mechanisms position nuclei in neuroepithelia of different morphology. In curved neuroepithelia, a novel formin-dependent mechanism is discovered for which the authors propose a proof-of-principle theoretical model. Correct nuclear position is crucial for cellular function and tissue development. Depending on cell context, however, the cytoskeletal elements responsible for nuclear positioning vary. While these cytoskeletal mechanisms have been intensely studied in single cells, how nuclear positioning is linked to tissue morphology is less clear. Here, we compare apical nuclear positioning in zebrafish neuroepithelia. We find that kinetics and actin-dependent mechanisms of nuclear positioning vary in tissues of different morphology. In straight neuroepithelia, nuclear positioning is controlled by Rho-ROCK–dependent myosin contractility. In contrast, in basally constricted neuroepithelia, a novel formin-dependent pushing mechanism is found for which we propose a proof-of-principle force generation theory. Overall, our data suggest that correct nuclear positioning is ensured by the adaptability of the cytoskeleton to cell and tissue shape. This in turn leads to robust epithelial maturation across geometries. The conclusion that different nuclear positioning mechanisms are favored in tissues of different morphology highlights the importance of developmental context for the execution of intracellular processes.
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Affiliation(s)
- Iskra Yanakieva
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Anna Erzberger
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany
| | - Marija Matejčić
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Carl D Modes
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Center for Systems Biology, Dresden, Germany
| | - Caren Norden
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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31
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Jun H, Shepherd TR, Zhang K, Bricker WP, Li S, Chiu W, Bathe M. Automated Sequence Design of 3D Polyhedral Wireframe DNA Origami with Honeycomb Edges. ACS NANO 2019; 13:2083-2093. [PMID: 30605605 PMCID: PMC6679942 DOI: 10.1021/acsnano.8b08671] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
3D polyhedral wireframe DNA nanoparticles (DNA-NPs) fabricated using scaffolded DNA origami offer complete and independent control over NP size, structure, and asymmetric functionalization on the 10-100 nm scale. However, the complex DNA sequence design needed for the synthesis of these versatile DNA-NPs has limited their widespread use to date. While the automated sequence design algorithms DAEDALUS and vHelix-BSCOR apply to DNA-NPs synthesized using either uniformly dual or hybrid single-dual duplex edges, respectively, these DNA-NPs are relatively compliant mechanically and are therefore of limited utility for some applications. Further, these algorithms are incapable of handling DNA-NP edge designs composed of more than two duplexes, which are needed to enhance DNA-NP mechanical stiffness. As an alternative, here we introduce the scaffolded DNA origami sequence design algorithm TALOS, which is a generalized procedure for the fully automated design of wireframe 3D polyhedra composed of edges of any cross section with an even number of duplexes, and apply it to DNA-NPs composed uniformly of single honeycomb edges. We also introduce a multiway vertex design that enables the fabrication of DNA-NPs with arbitrary edge lengths and vertex angles and apply it to synthesize a highly asymmetric origami object. Sequence designs are demonstrated to fold robustly into target DNA-NP shapes with high folding efficiency and structural fidelity that is verified using single particle cryo-electron microscopy and 3D reconstruction. In order to test its generality, we apply TALOS to design an in silico library of over 200 DNA-NPs of distinct symmetries and sizes, and for broad impact, we also provide the software as open source for the generation of custom NP designs.
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Affiliation(s)
- Hyungmin Jun
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Tyson R. Shepherd
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Kaiming Zhang
- Department of Bioengineering, Microbiology and Immunology, and James H. Clark Center, Stanford University, Stanford, California 94305, United States
| | - William P. Bricker
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Shanshan Li
- Department of Bioengineering, Microbiology and Immunology, and James H. Clark Center, Stanford University, Stanford, California 94305, United States
| | - Wah Chiu
- Department of Bioengineering, Microbiology and Immunology, and James H. Clark Center, Stanford University, Stanford, California 94305, United States
- SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, United States
| | - Mark Bathe
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Corresponding Author
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32
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Bianco V, Locatelli E, Malgaretti P. Globulelike Conformation and Enhanced Diffusion of Active Polymers. PHYSICAL REVIEW LETTERS 2018; 121:217802. [PMID: 30517801 DOI: 10.1103/physrevlett.121.217802] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Indexed: 06/09/2023]
Abstract
We study the dynamics and conformation of polymers composed by active monomers. By means of Brownian dynamics simulations we show that, when the direction of the self-propulsion of each monomer is aligned with the backbone, the polymer undergoes a coil-to-globulelike transition, highlighted by a marked change of the scaling exponent of the gyration radius. Concurrently, the diffusion coefficient of the center of mass of the polymer becomes essentially independent of the polymer size for sufficiently long polymers or large magnitudes of the self-propulsion. These effects are reduced when the self-propulsion of the monomers is not bound to be tangent to the backbone of the polymer. Our results, rationalized by a minimal stochastic model, open new routes for activity-controlled polymers and, possibly, for a new generation of polymer-based drug carriers.
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Affiliation(s)
- Valentino Bianco
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, Wien 1090, Austria
- Faculty of Chemistry, Chemical Physics Deprtment, Universidad Complutense de Madrid, Plaza de las Ciencias, Ciudad Universitaria, Madrid 28040, Spain
| | - Emanuele Locatelli
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, Wien 1090, Austria
| | - Paolo Malgaretti
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
- Institute for Theoretical Physics IV, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
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33
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Adnan M, Pinnick RA, Tang Z, Taylor LW, Pamulapati SS, Carfagni GR, Pasquali M. Bending behavior of CNT fibers and their scaling laws. SOFT MATTER 2018; 14:8284-8292. [PMID: 30175834 DOI: 10.1039/c8sm01129j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Carbon nanotube (CNT) fibers are a promising material for wearable electronics and biomedical applications due to their combined flexibility and electrical conductivity. To engineer the bending properties for such applications requires understanding how the bending stiffness of CNT fibers scales with CNT length and fiber diameter. We measure bending stiffness with a cantilever setup interpreted within Euler Elastica theory. We find that the bending stiffness scales with a power law of 1.9 for the fiber diameter and 1.6 for the CNT length. The diameter scaling exponent for fiber diameter agrees with results from earlier experiments and theory for microscopic CNT bundles. We develop a simple model which predicts the experimentally observed scaling exponents within statistical significance.
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Affiliation(s)
- Mohammed Adnan
- Rice University, 6100 Main St. MS-369, Houston, TX, USA.
| | | | - Zhao Tang
- Rice University, 6100 Main St. MS-369, Houston, TX, USA.
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34
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Li S, Zhang J, Wang C, Nithiarasu P. Atomistic Modeling of F-Actin Mechanical Responses and Determination of Mechanical Properties. ACS Biomater Sci Eng 2018; 4:2794-2803. [DOI: 10.1021/acsbiomaterials.8b00640] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Si Li
- Zienkiewicz Centre for Computational Engineering, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, Wales SA1 8EN, U.K
| | - Jin Zhang
- Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China
| | - Chengyuan Wang
- Zienkiewicz Centre for Computational Engineering, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, Wales SA1 8EN, U.K
| | - Perumal Nithiarasu
- Zienkiewicz Centre for Computational Engineering, College of Engineering, Swansea University, Bay Campus, Fabian Way, Swansea, Wales SA1 8EN, U.K
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35
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Ghosh S, Park J, Thomas M, Cruz E, Cardona O, Kang H, Jewett T. Biophysical characterization of actin bundles generated by the Chlamydia trachomatis Tarp effector. Biochem Biophys Res Commun 2018; 500:423-428. [PMID: 29660331 DOI: 10.1016/j.bbrc.2018.04.093] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 04/12/2018] [Indexed: 11/24/2022]
Abstract
Chlamydia trachomatis entry into host cells is mediated by pathogen-directed remodeling of the actin cytoskeleton. The chlamydial type III secreted effector, translocated actin recruiting phosphoprotein (Tarp), has been implicated in the recruitment of actin to the site of internalization. Tarp harbors G-actin binding and proline rich domains required for Tarp-mediated actin nucleation as well as unique F-actin binding domains implicated in the formation of actin bundles. Little is known about the mechanical properties of actin bundles generated by Tarp or the mechanism by which Tarp mediates actin bundle formation. In order to characterize the actin bundles and elucidate the role of different Tarp domains in the bundling process, purified Tarp effectors and Tarp truncation mutants were analyzed using Total Internal Reflection Fluorescence (TIRF) microscopy. Our data indicate that Tarp mediated actin bundling is independent of actin nucleation and the F-actin binding domains are sufficient to bundle actin filaments. Additionally, Tarp-mediated actin bundles demonstrate distinct bending stiffness compared to those crosslinked by the well characterized actin bundling proteins fascin and alpha-actinin, suggesting Tarp may employ a novel actin bundling strategy. The capacity of the Tarp effector to generate novel actin bundles likely contributes to chlamydia's efficient mechanism of entry into human cells.
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Affiliation(s)
- Susmita Ghosh
- Division of Immunity and Pathogenesis, College of Medicine, University of Central Florida, United States
| | - Jinho Park
- NanoScience Technology Center, University of Central Florida, United States; Depatrment of Materials Science and Engineering, University of Central Florida, United States
| | - Mitchell Thomas
- Division of Immunity and Pathogenesis, College of Medicine, University of Central Florida, United States
| | - Edgar Cruz
- NanoScience Technology Center, University of Central Florida, United States
| | - Omar Cardona
- Division of Immunity and Pathogenesis, College of Medicine, University of Central Florida, United States
| | - Hyeran Kang
- NanoScience Technology Center, University of Central Florida, United States; Department of Physics, University of Central Florida, United States
| | - Travis Jewett
- Division of Immunity and Pathogenesis, College of Medicine, University of Central Florida, United States.
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36
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Castaneda N, Zheng T, Rivera-Jacquez HJ, Lee HJ, Hyun J, Balaeff A, Huo Q, Kang H. Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure. J Phys Chem B 2018; 122:3826-3835. [PMID: 29608304 DOI: 10.1021/acs.jpcb.8b00663] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.
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Affiliation(s)
- Nicholas Castaneda
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States.,Burnett School of Biomedical Sciences, College of Medicine , University of Central Florida , Orlando , Florida 32827 , United States
| | - Tianyu Zheng
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hector J Rivera-Jacquez
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hyun-Ju Lee
- Electron Microscopy Research Center , Korea Basic Science Institute (KBSI) , Cheongju-si , Chungcheongbuk-do 28119 , Republic of Korea
| | - Jaekyung Hyun
- Electron Microscopy Research Center , Korea Basic Science Institute (KBSI) , Cheongju-si , Chungcheongbuk-do 28119 , Republic of Korea
| | - Alexander Balaeff
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Qun Huo
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
| | - Hyeran Kang
- NanoScience Technology Center , University of Central Florida , Orlando , Florida 32826 , United States
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37
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Effects of the cross-linkers on the buckling of microtubules in cells. J Biomech 2018; 72:167-172. [PMID: 29551426 DOI: 10.1016/j.jbiomech.2018.03.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/13/2018] [Accepted: 03/03/2018] [Indexed: 11/23/2022]
Abstract
In cells, the protein cross-linkers lead to a distinct buckling behavior of microtubules (MTs) different from the buckling of individual MTs. This paper thus aims to examine this issue via the molecular structural mechanics (MSM) simulations. The transition of buckling responses was captured as the two-dimensional-linkers were replaced by the three-dimensional (3D) ones. Then, the effects of the radial orientation and the axial density of the 3D-linkers were examined, showing that more uniform distribution of the radial orientation leads to the higher critical load with 3D buckling modes, while the inhomogeneity of the axial density results in the localized buckling patterns. The results demonstrated the important role of the cross-linker in regulating MT stiffness, revealed the physics of the experimentally observed localized buckling and these results will pave the way to a new multi-component mechanics model for whole cells.
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38
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Rückerl F, Lenz M, Betz T, Manzi J, Martiel JL, Safouane M, Paterski-Boujemaa R, Blanchoin L, Sykes C. Adaptive Response of Actin Bundles under Mechanical Stress. Biophys J 2017; 113:1072-1079. [PMID: 28877490 PMCID: PMC5611681 DOI: 10.1016/j.bpj.2017.07.017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 07/24/2017] [Accepted: 07/31/2017] [Indexed: 11/17/2022] Open
Abstract
Actin is one of the main components of the architecture of cells. Actin filaments form different polymer networks with versatile mechanical properties that depend on their spatial organization and the presence of cross-linkers. Here, we investigate the mechanical properties of actin bundles in the absence of cross-linkers. Bundles are polymerized from the surface of mDia1-coated latex beads, and deformed by manipulating both ends through attached beads held by optical tweezers, allowing us to record the applied force. Bundle properties are strikingly different from the ones of a homogeneous isotropic beam. Successive compression and extension leads to a decrease in the buckling force that we attribute to the bundle remaining slightly curved after the first deformation. Furthermore, we find that the bundle is solid, and stiff to bending, along the long axis, whereas it has a liquid and viscous behavior in the transverse direction. Interpretation of the force curves using a Maxwell visco-elastic model allows us to extract the bundle mechanical parameters and confirms that the bundle is composed of weakly coupled filaments. At short times, the bundle behaves as an elastic material, whereas at long times, filaments flow in the longitudinal direction, leading to bundle restructuring. Deviations from the model reveal a complex adaptive rheological behavior of bundles. Indeed, when allowed to anneal between phases of compression and extension, the bundle reinforces. Moreover, we find that the characteristic visco-elastic time is inversely proportional to the compression speed. Actin bundles are therefore not simple force transmitters, but instead, complex mechano-transducers that adjust their mechanics to external stimulation. In cells, where actin bundles are mechanical sensors, this property could contribute to their adaptability.
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Affiliation(s)
- Florian Rückerl
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Martin Lenz
- CNRS, LPTMS, University Paris-Sud, Orsay, France
| | - Timo Betz
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - John Manzi
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Jean-Louis Martiel
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France
| | - Mahassine Safouane
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France
| | - Rajaa Paterski-Boujemaa
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France
| | - Laurent Blanchoin
- CNRS/CEA/INRA/UJF, Laboratoire de Physiologie Cellulaire Végétale, Institut de Recherches en Technologies et Sciences pour le Vivant, Grenoble, France.
| | - Cécile Sykes
- CNRS, Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, Paris, France; Sorbonne Universités, UPMC University Paris 06, Paris, France.
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39
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Strehle D, Mollenkopf P, Glaser M, Golde T, Schuldt C, Käs JA, Schnauß J. Single Actin Bundle Rheology. Molecules 2017; 22:E1804. [PMID: 29064446 PMCID: PMC5860748 DOI: 10.3390/molecules22101804] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 10/17/2017] [Accepted: 10/19/2017] [Indexed: 11/17/2022] Open
Abstract
Bundled actin structures play an essential role in the mechanical response of the actin cytoskeleton in eukaryotic cells. Although responsible for crucial cellular processes, they are rarely investigated in comparison to single filaments and isotropic networks. Presenting a highly anisotropic structure, the determination of the mechanical properties of individual bundles was previously achieved through passive approaches observing bending deformations induced by thermal fluctuations. We present a new method to determine the bending stiffness of individual bundles, by measuring the decay of an actively induced oscillation. This approach allows us to systematically test anisotropic, bundled structures. Our experiments revealed that thin, depletion force-induced bundles behave as semiflexible polymers and obey the theoretical predictions determined by the wormlike chain model. Thickening an individual bundle by merging it with other bundles enabled us to study effects that are solely based on the number of involved filaments. These thicker bundles showed a frequency-dependent bending stiffness, a behavior that is inconsistent with the predictions of the wormlike chain model. We attribute this effect to internal processes and give a possible explanation with regard to the wormlike bundle theory.
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Affiliation(s)
- Dan Strehle
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
| | - Paul Mollenkopf
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), DNA Nanodevices Group, Perlickstraße 1, 04103 Leipzig, Germany.
| | - Martin Glaser
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), DNA Nanodevices Group, Perlickstraße 1, 04103 Leipzig, Germany.
| | - Tom Golde
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
| | - Carsten Schuldt
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), DNA Nanodevices Group, Perlickstraße 1, 04103 Leipzig, Germany.
| | - Josef A Käs
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
| | - Jörg Schnauß
- Faculty of Physics and Earth Sciences, Peter Debye Institute, Leipzig University, Linnéstr. 5, 04103 Leipzig, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology (IZI), DNA Nanodevices Group, Perlickstraße 1, 04103 Leipzig, Germany.
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40
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Ruiz-Martinez A, Bartol TM, Sejnowski TJ, Tartakovsky DM. Efficient Multiscale Models of Polymer Assembly. Biophys J 2017; 111:185-96. [PMID: 27410746 DOI: 10.1016/j.bpj.2016.05.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 04/24/2016] [Accepted: 05/09/2016] [Indexed: 12/25/2022] Open
Abstract
Protein polymerization and bundling play a central role in cell physiology. Predictive modeling of these processes remains an open challenge, especially when the proteins involved become large and their concentrations high. We present an effective kinetics model of filament formation, bundling, and depolymerization after GTP hydrolysis, which involves a relatively small number of species and reactions, and remains robust over a wide range of concentrations and timescales. We apply this general model to study assembly of FtsZ protein, a basic element in the division process of prokaryotic cells such as Escherichia coli, Bacillus subtilis, or Caulobacter crescentus. This analysis demonstrates that our model outperforms its counterparts in terms of both accuracy and computational efficiency. Because our model comprises only 17 ordinary differential equations, its computational cost is orders-of-magnitude smaller than the current alternatives consisting of up to 1000 ordinary differential equations. It also provides, to our knowledge, a new insight into the characteristics and functioning of FtsZ proteins at high concentrations. The simplicity and versatility of our model render it a powerful computational tool, which can be used either as a standalone descriptor of other biopolymers' assembly or as a component in more complete kinetic models.
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Affiliation(s)
- Alvaro Ruiz-Martinez
- Department of Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California
| | - Thomas M Bartol
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California
| | - Terrence J Sejnowski
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, California; Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, California; The Division of Biological Studies Sciences, University of California-San Diego, La Jolla, California.
| | - Daniel M Tartakovsky
- Department of Mechanical and Aerospace Engineering, University of California-San Diego, La Jolla, California.
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41
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Dmitrieff S, Alsina A, Mathur A, Nédélec FJ. Balance of microtubule stiffness and cortical tension determines the size of blood cells with marginal band across species. Proc Natl Acad Sci U S A 2017; 114:4418-4423. [PMID: 28400519 PMCID: PMC5410777 DOI: 10.1073/pnas.1618041114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The fast bloodstream of animals is associated with large shear stresses. To withstand these conditions, blood cells have evolved a special morphology and a specific internal architecture to maintain their integrity over several weeks. For instance, nonmammalian red blood cells, mammalian erythroblasts, and platelets have a peripheral ring of microtubules, called the marginal band, that flattens the overall cell morphology by pushing on the cell cortex. In this work, we model how the shape of these cells stems from the balance between marginal band rigidity and cortical tension. We predict that the diameter of the cell scales with the total microtubule polymer and verify the predicted law across a wide range of species. Our analysis also shows that the combination of the marginal band rigidity and cortical tension increases the ability of the cell to withstand forces without deformation. Finally, we model the marginal band coiling that occurs during the disk-to-sphere transition observed, for instance, at the onset of blood platelet activation. We show that when cortical tension increases faster than cross-linkers can unbind, the marginal band will coil, whereas if the tension increases more slowly, the marginal band may shorten as microtubules slide relative to each other.
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Affiliation(s)
- Serge Dmitrieff
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Adolfo Alsina
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Aastha Mathur
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - François J Nédélec
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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42
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Gerbal F, Wang Y. Optical detection of nanometric thermal fluctuations to measure the stiffness of rigid superparamagnetic microrods. Proc Natl Acad Sci U S A 2017; 114:2456-2461. [PMID: 28228530 PMCID: PMC5347538 DOI: 10.1073/pnas.1608697114] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The rigidity of numerous biological filaments and crafted microrods has been conveniently deduced from the analysis of their thermal fluctuations. However, the difficulty of measuring nanometric displacements with an optical microscope has so far limited such studies to sufficiently flexible rods, of which the persistence length ([Formula: see text]) rarely exceeds 1 m at room temperature. Here, we demonstrate the possibility to probe 10-fold stiffer rods by a combination of superresolutive optical methods and a statistical analysis of the data based on a recent theoretical model that predicts the amplitude of the fluctuations at any location of the rod [Benetatos P, Frey E (2003) Phys Rev E Stat Nonlin Soft Matter Phys 67(5):051108]. Using this approach, we report measures of [Formula: see text] up to 0.5 km. We obtained these measurements on recently designed superparamagnetic [Formula: see text]40-[Formula: see text]m-long microrods containing iron-oxide nanoparticles connected by a polymer mesh. Using their magnetic properties, we provide an alternative proof of validity of these thermal measurements: For each individual studied rod, we performed a second measure of its rigidity by deflecting it with a uniform magnetic field. The agreement between the thermal and the magnetoelastic measures was realized with more than a decade of values of [Formula: see text] from 5.1 m to 129 m, corresponding to a bending modulus ranging from 2.2 to 54 (×[Formula: see text] Jm). Despite the apparent homogeneity of the analyzed microrods, their Young modulus follows a broad distribution from 1.9 MPa to 59 MPa and up to 200 MPa, depending on the size of the nanoparticles.
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Affiliation(s)
- Fabien Gerbal
- Laboratoire Matière et Systèmes Complexes UMR 7057 (CNRS) and Université Denis Diderot-Sorbonne Paris Cité, 75013 Paris, France;
- Université Pierre et Marie Curie-Paris 6, Sorbonne Universités, 75252 Paris Cedex 05, France
| | - Yuan Wang
- Laboratoire Matière et Systèmes Complexes UMR 7057 (CNRS) and Université Denis Diderot-Sorbonne Paris Cité, 75013 Paris, France
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43
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Meng F, Terentjev EM. Theory of Semiflexible Filaments and Networks. Polymers (Basel) 2017; 9:E52. [PMID: 30970730 PMCID: PMC6432424 DOI: 10.3390/polym9020052] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 01/25/2017] [Accepted: 01/26/2017] [Indexed: 01/07/2023] Open
Abstract
We briefly review the recent developments in the theory of individual semiflexible filaments, and of a crosslinked network of such filaments, both permanent and transient. Starting from the free energy of an individual semiflexible chain, models on its force-extension relation and other mechanical properties such as Euler buckling are discussed. For a permanently crosslinked network of filaments, theories on how the network responds to deformation are provided, with a focus on continuum approaches. Characteristic features of filament networks, such as nonlinear stress-strain relation, negative normal stress, tensegrity, and marginal stability are discussed. In the new area of transient filament network, where the crosslinks can be dynamically broken and re-formed, we show some recent attempts for understanding the dynamics of the crosslinks, and the related rheological properties, such as stress relaxation, yield stress and plasticity.
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Affiliation(s)
- Fanlong Meng
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, UK.
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44
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Krieg M, Stühmer J, Cueva JG, Fetter R, Spilker K, Cremers D, Shen K, Dunn AR, Goodman MB. Genetic defects in β-spectrin and tau sensitize C. elegans axons to movement-induced damage via torque-tension coupling. eLife 2017; 6. [PMID: 28098556 PMCID: PMC5298879 DOI: 10.7554/elife.20172] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 01/17/2017] [Indexed: 12/24/2022] Open
Abstract
Our bodies are in constant motion and so are the neurons that invade each tissue. Motion-induced neuron deformation and damage are associated with several neurodegenerative conditions. Here, we investigated the question of how the neuronal cytoskeleton protects axons and dendrites from mechanical stress, exploiting mutations in UNC-70 β-spectrin, PTL-1 tau/MAP2-like and MEC-7 β-tubulin proteins in Caenorhabditis elegans. We found that mechanical stress induces supercoils and plectonemes in the sensory axons of spectrin and tau double mutants. Biophysical measurements, super-resolution, and electron microscopy, as well as numerical simulations of neurons as discrete, elastic rods provide evidence that a balance of torque, tension, and elasticity stabilizes neurons against mechanical deformation. We conclude that the spectrin and microtubule cytoskeletons work in combination to protect axons and dendrites from mechanical stress and propose that defects in β-spectrin and tau may sensitize neurons to damage. DOI:http://dx.doi.org/10.7554/eLife.20172.001
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Affiliation(s)
- Michael Krieg
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States.,Department of Chemical Engineering, Stanford University, Stanford, United States
| | - Jan Stühmer
- Department of Informatics, Technical University of Munich, , Germany
| | - Juan G Cueva
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Richard Fetter
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Kerri Spilker
- Department of Biology, Stanford University, Stanford, United States
| | - Daniel Cremers
- Department of Informatics, Technical University of Munich, , Germany
| | - Kang Shen
- Department of Biology, Stanford University, Stanford, United States
| | - Alexander R Dunn
- Department of Chemical Engineering, Stanford University, Stanford, United States
| | - Miriam B Goodman
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
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45
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Schnauß J, Händler T, Käs JA. Semiflexible Biopolymers in Bundled Arrangements. Polymers (Basel) 2016; 8:polym8080274. [PMID: 30974551 PMCID: PMC6432226 DOI: 10.3390/polym8080274] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/18/2016] [Accepted: 07/19/2016] [Indexed: 12/15/2022] Open
Abstract
Bundles and networks of semiflexible biopolymers are key elements in cells, lending them mechanical integrity while also enabling dynamic functions. Networks have been the subject of many studies, revealing a variety of fundamental characteristics often determined via bulk measurements. Although bundles are equally important in biological systems, they have garnered much less scientific attention since they have to be probed on the mesoscopic scale. Here, we review theoretical as well as experimental approaches, which mainly employ the naturally occurring biopolymer actin, to highlight the principles behind these structures on the single bundle level.
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Affiliation(s)
- Jörg Schnauß
- Institute for Experimental Physics I, Universität Leipzig, Linnéstraße 5, Leipzig 04103, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, Leipzig 04103, Germany.
| | - Tina Händler
- Institute for Experimental Physics I, Universität Leipzig, Linnéstraße 5, Leipzig 04103, Germany.
- Fraunhofer Institute for Cell Therapy and Immunology, Perlickstraße 1, Leipzig 04103, Germany.
| | - Josef A Käs
- Institute for Experimental Physics I, Universität Leipzig, Linnéstraße 5, Leipzig 04103, Germany.
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46
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Letort G, Nedelec F, Blanchoin L, Théry M. Centrosome centering and decentering by microtubule network rearrangement. Mol Biol Cell 2016; 27:2833-43. [PMID: 27440925 PMCID: PMC5025270 DOI: 10.1091/mbc.e16-06-0395] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 07/11/2016] [Indexed: 11/11/2022] Open
Abstract
Numerical simulations are used to investigate the role of microtubule network architecture in centrosome positioning. Microtubule gliding along cell edges and pivoting around the centrosome are key regulators of the orientation of pushing forces, the magnitude of which depends on the number, dynamics, and stiffness of microtubules. The centrosome is positioned at the cell center by pushing and pulling forces transmitted by microtubules (MTs). Centrosome decentering is often considered to result from asymmetric, cortical pulling forces exerted in particular by molecular motors on MTs and controlled by external cues affecting the cell cortex locally. Here we used numerical simulations to investigate the possibility that it could equally result from the redistribution of pushing forces due to a reorientation of MTs. We first showed that MT gliding along cell edges and pivoting around the centrosome regulate MT rearrangement and thereby direct the spatial distribution of pushing forces, whereas the number, dynamics, and stiffness of MTs determine the magnitude of these forces. By modulating these parameters, we identified different regimes, involving both pushing and pulling forces, characterized by robust centrosome centering, robust off-centering, or “reactive” positioning. In the last-named conditions, weak asymmetric cues can induce a misbalance of pushing and pulling forces, resulting in an abrupt transition from a centered to an off-centered position. Taken together, these results point to the central role played by the configuration of the MTs on the distribution of pushing forces that position the centrosome. We suggest that asymmetric external cues should not be seen as direct driver of centrosome decentering and cell polarization but instead as inducers of an effective reorganization of the MT network, fostering centrosome motion to the cell periphery.
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Affiliation(s)
- Gaëlle Letort
- CytoMorpho Lab, Biosciences and Biotechnology Institute of Grenoble, UMR5168, CEA/INRA/CNRS/Université Grenoble-Alpes, 38054 Grenoble, France
| | - Francois Nedelec
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Laurent Blanchoin
- CytoMorpho Lab, Biosciences and Biotechnology Institute of Grenoble, UMR5168, CEA/INRA/CNRS/Université Grenoble-Alpes, 38054 Grenoble, France CytoMorpho Lab, Hopital Saint Louis, Institut Universitaire d'Hematologie, UMRS1160, INSERM/Université Paris Diderot, 75010 Paris, France
| | - Manuel Théry
- CytoMorpho Lab, Biosciences and Biotechnology Institute of Grenoble, UMR5168, CEA/INRA/CNRS/Université Grenoble-Alpes, 38054 Grenoble, France CytoMorpho Lab, Hopital Saint Louis, Institut Universitaire d'Hematologie, UMRS1160, INSERM/Université Paris Diderot, 75010 Paris, France
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47
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Abstract
Axonal microtubule (MT) bundles crosslinked by microtubule-associated protein (MAP) tau are responsible for vital biological functions such as maintaining mechanical integrity and shape of the axon as well as facilitating axonal transport. Breaking and twisting of MTs have been previously observed in damaged undulated axons. Such breaking and twisting of MTs is suggested to cause axonal swellings that lead to axonal degeneration, which is known as "diffuse axonal injury". In particular, overstretching and torsion of axons can potentially damage the axonal cytoskeleton. Following our previous studies on mechanical response of axonal MT bundles under uniaxial tension and compression, this work seeks to characterize the mechanical behavior of MT bundles under pure torsion as well as a combination of torsional and tensile loads using a coarse-grained computational model. In the case of pure torsion, a competition between MAP tau tensile and MT bending energies is observed. After three turns, a transition occurs in the mechanical behavior of the bundle that is characterized by its diameter shrinkage. Furthermore, crosslink spacing is shown to considerably influence the mechanical response, with larger MAP tau spacing resulting in a higher rate of turns. Therefore, MAP tau crosslinking of MT filaments protects the bundle from excessive deformation. Simultaneous application of torsion and tension on MT bundles is shown to accelerate bundle failure, compared to pure tension experiments. MAP tau proteins fail in clusters of 10-100 elements located at the discontinuities or the ends of MT filaments. This failure occurs in a stepwise fashion, implying gradual accumulation of elastic tensile energy in crosslinks followed by rupture. Failure of large groups of interconnecting MAP tau proteins leads to detachment of MT filaments from the bundle near discontinuities. This study highlights the importance of torsional loading in axonal damage after traumatic brain injury.
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Affiliation(s)
- Carole Lazarus
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California
| | - Mohammad Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California.
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48
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Bruekers SMC, Jaspers M, Hendriks JMA, Kurniawan NA, Koenderink GH, Kouwer PHJ, Rowan AE, T S Huck W. Fibrin-fiber architecture influences cell spreading and differentiation. Cell Adh Migr 2016; 10:495-504. [PMID: 26910190 DOI: 10.1080/19336918.2016.1151607] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The mechanical and structural properties of the extracellular matrix (ECM) play an important role in regulating cell fate. The natural ECM has a complex fibrillar structure and shows nonlinear mechanical properties, which are both difficult to mimic synthetically. Therefore, systematically testing the influence of ECM properties on cellular behavior is very challenging. In this work we show two different approaches to tune the fibrillar structure and mechanical properties of fibrin hydrogels. Addition of extra thrombin before gelation increases the protein density within the fibrin fibers without significantly altering the mechanical properties of the resulting hydrogel. On the other hand, by forming a composite hydrogel with a synthetic biomimetic polyisocyanide network the protein density within the fibrin fibers decreases, and the mechanics of the composite material can be tuned by the PIC/fibrin mass ratio. The effect of the changes in gel structure and mechanics on cellular behavior are investigated, by studying human mesenchymal stem cell (hMSC) spreading and differentiation on these gels. We find that the trends observed in cell spreading and differentiation cannot be explained by the bulk mechanics of the gels, but correlate to the density of the fibrin fibers the gels are composed of. These findings strongly suggest that the microscopic properties of individual fibers in fibrous networks play an essential role in determining cell behavior.
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Affiliation(s)
- Stéphanie M C Bruekers
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands
| | - Maarten Jaspers
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands
| | - José M A Hendriks
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands
| | - Nicholas A Kurniawan
- b Systems Biophysics Department, FOM Institute AMOLF , Amsterdam , The Netherlands.,c Department of Biomedical Engineering , Eindhoven University of Technology , Eindhoven , The Netherlands
| | - Gijsje H Koenderink
- b Systems Biophysics Department, FOM Institute AMOLF , Amsterdam , The Netherlands
| | - Paul H J Kouwer
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands
| | - Alan E Rowan
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands.,d Australian Institute for Bioengineering and Nanotechnology, The University of Queensland , Brisbane , Australia
| | - Wilhelm T S Huck
- a Institute for Molecules and Materials, Radboud University , Nijmegen , The Netherlands
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49
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Piechocka IK, Jansen KA, Broedersz CP, Kurniawan NA, MacKintosh FC, Koenderink GH. Multi-scale strain-stiffening of semiflexible bundle networks. SOFT MATTER 2016; 12:2145-56. [PMID: 26761718 DOI: 10.1039/c5sm01992c] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Bundles of polymer filaments are responsible for the rich and unique mechanical behaviors of many biomaterials, including cells and extracellular matrices. In fibrin biopolymers, whose nonlinear elastic properties are crucial for normal blood clotting, protofibrils self-assemble and bundle to form networks of semiflexible fibers. Here we show that the extraordinary strain-stiffening response of fibrin networks is a direct reflection of the hierarchical architecture of the fibrin fibers. We measure the rheology of networks of unbundled protofibrils and find excellent agreement with an affine model of extensible wormlike polymers. By direct comparison with these data, we show that physiological fibrin networks composed of thick fibers can be modeled as networks of tight protofibril bundles. We demonstrate that the tightness of coupling between protofibrils in the fibers can be tuned by the degree of enzymatic intermolecular crosslinking by the coagulation factor XIII. Furthermore, at high stress, the protofibrils contribute independently to the network elasticity, which may reflect a decoupling of the tight bundle structure. The hierarchical architecture of fibrin fibers can thus account for the nonlinearity and enormous elastic resilience characteristic of blood clots.
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50
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Maier AM, Weig C, Oswald P, Frey E, Fischer P, Liedl T. Magnetic Propulsion of Microswimmers with DNA-Based Flagellar Bundles. NANO LETTERS 2016; 16:906-10. [PMID: 26821214 PMCID: PMC4819949 DOI: 10.1021/acs.nanolett.5b03716] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/25/2016] [Indexed: 05/21/2023]
Abstract
We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials.
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Affiliation(s)
- Alexander M. Maier
- Faculty of Physics
and Center for NanoScience, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München, Germany
| | - Cornelius Weig
- Arnold Sommerfeld Center for Theoretical Physics and
Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333 Munich, Germany
| | - Peter Oswald
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and
Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333 Munich, Germany
- E-mail:
| | - Peer Fischer
- Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
- Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
- E-mail:
| | - Tim Liedl
- Faculty of Physics
and Center for NanoScience, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München, Germany
- E-mail:
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