1
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Nolte DD. Coherent light scattering from cellular dynamics in living tissues. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2024; 87:036601. [PMID: 38433567 DOI: 10.1088/1361-6633/ad2229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 01/24/2024] [Indexed: 03/05/2024]
Abstract
This review examines the biological physics of intracellular transport probed by the coherent optics of dynamic light scattering from optically thick living tissues. Cells and their constituents are in constant motion, composed of a broad range of speeds spanning many orders of magnitude that reflect the wide array of functions and mechanisms that maintain cellular health. From the organelle scale of tens of nanometers and upward in size, the motion inside living tissue is actively driven rather than thermal, propelled by the hydrolysis of bioenergetic molecules and the forces of molecular motors. Active transport can mimic the random walks of thermal Brownian motion, but mean-squared displacements are far from thermal equilibrium and can display anomalous diffusion through Lévy or fractional Brownian walks. Despite the average isotropic three-dimensional environment of cells and tissues, active cellular or intracellular transport of single light-scattering objects is often pseudo-one-dimensional, for instance as organelle displacement persists along cytoskeletal tracks or as membranes displace along the normal to cell surfaces, albeit isotropically oriented in three dimensions. Coherent light scattering is a natural tool to characterize such tissue dynamics because persistent directed transport induces Doppler shifts in the scattered light. The many frequency-shifted partial waves from the complex and dynamic media interfere to produce dynamic speckle that reveals tissue-scale processes through speckle contrast imaging and fluctuation spectroscopy. Low-coherence interferometry, dynamic optical coherence tomography, diffusing-wave spectroscopy, diffuse-correlation spectroscopy, differential dynamic microscopy and digital holography offer coherent detection methods that shed light on intracellular processes. In health-care applications, altered states of cellular health and disease display altered cellular motions that imprint on the statistical fluctuations of the scattered light. For instance, the efficacy of medical therapeutics can be monitored by measuring the changes they induce in the Doppler spectra of livingex vivocancer biopsies.
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Affiliation(s)
- David D Nolte
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, United States of America
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2
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Chen T, Karedla N, Enderlein J. Measuring sub-nanometer undulations at microsecond temporal resolution with metal- and graphene-induced energy transfer spectroscopy. Nat Commun 2024; 15:1789. [PMID: 38413608 PMCID: PMC10899616 DOI: 10.1038/s41467-024-45822-x] [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: 06/01/2023] [Accepted: 02/01/2024] [Indexed: 02/29/2024] Open
Abstract
Out-of-plane fluctuations, also known as stochastic displacements, of biological membranes play a crucial role in regulating many essential life processes within cells and organelles. Despite the availability of various methods for quantifying membrane dynamics, accurately quantifying complex membrane systems with rapid and tiny fluctuations, such as mitochondria, remains a challenge. In this work, we present a methodology that combines metal/graphene-induced energy transfer (MIET/GIET) with fluorescence correlation spectroscopy (FCS) to quantify out-of-plane fluctuations of membranes with simultaneous spatiotemporal resolution of approximately one nanometer and one microsecond. To validate the technique and spatiotemporal resolution, we measure bending undulations of model membranes. Furthermore, we demonstrate the versatility and applicability of MIET/GIET-FCS for studying diverse membrane systems, including the widely studied fluctuating membrane system of human red blood cells, as well as two unexplored membrane systems with tiny fluctuations, a pore-spanning membrane, and mitochondrial inner/outer membranes.
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Affiliation(s)
- Tao Chen
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, Göttingen, 37077, Germany
| | - Narain Karedla
- The Rosalind Franklin Institute, Harwell Campus, Didcot, OX11 OFA, UK
- Kennedy Institute of Rheumatology, University of Oxford, Roosevelt Drive, Oxford, OX3 7LF, UK
| | - Jörg Enderlein
- Third Institute of Physics - Biophysics, Georg August University, Friedrich-Hund-Platz 1, Göttingen, 37077, Germany.
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Universitätsmedizin Göttingen, Robert-Koch-Str. 40, Göttingen, 37075, Germany.
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3
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Agrawal V, Pandey V, Mitra D. Active buckling of pressurized spherical shells: Monte Carlo simulation. Phys Rev E 2023; 108:L032601. [PMID: 37849090 DOI: 10.1103/physreve.108.l032601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/06/2023] [Indexed: 10/19/2023]
Abstract
We study the buckling of pressurized spherical shells by Monte Carlo simulations in which the detailed balance is explicitly broken-thereby driving the shell to be active, out of thermal equilibrium. Such a shell typically has either higher (active) or lower (sedate) fluctuations compared to one in thermal equilibrium depending on how the detailed balance is broken. We show that, for the same set of elastic parameters, a shell that is not buckled in thermal equilibrium can be buckled if turned active. Similarly a shell that is buckled in thermal equilibrium can unbuckle if sedated. Based on this result, we suggest that it is possible to experimentally design microscopic elastic shells whose buckling can be optically controlled.
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Affiliation(s)
- Vipin Agrawal
- Nordita, KTH Royal Institute of Technology and Stockholm University, Hannes Alfvéns väg 12, 106 91 Stockholm, Sweden
- Department of Physics, Stockholm University, AlbaNova University Centre, Fysikum, 106 91 Stockholm, Sweden
| | - Vikash Pandey
- Nordita, KTH Royal Institute of Technology and Stockholm University, Hannes Alfvéns väg 12, 106 91 Stockholm, Sweden
| | - Dhrubaditya Mitra
- Nordita, KTH Royal Institute of Technology and Stockholm University, Hannes Alfvéns väg 12, 106 91 Stockholm, Sweden
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4
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Maitra A, Ramaswamy S. Erratum: Oriented Active Solids [Phys. Rev. Lett. 123, 238001 (2019)]. PHYSICAL REVIEW LETTERS 2023; 130:269901. [PMID: 37450834 DOI: 10.1103/physrevlett.130.269901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Indexed: 07/18/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevLett.123.238001.
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5
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Khoromskaia D, Salbreux G. Active morphogenesis of patterned epithelial shells. eLife 2023; 12:75878. [PMID: 36649186 PMCID: PMC9844985 DOI: 10.7554/elife.75878] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 11/18/2022] [Indexed: 01/11/2023] Open
Abstract
Shape transformations of epithelial tissues in three dimensions, which are crucial for embryonic development or in vitro organoid growth, can result from active forces generated within the cytoskeleton of the epithelial cells. How the interplay of local differential tensions with tissue geometry and with external forces results in tissue-scale morphogenesis remains an open question. Here, we describe epithelial sheets as active viscoelastic surfaces and study their deformation under patterned internal tensions and bending moments. In addition to isotropic effects, we take into account nematic alignment in the plane of the tissue, which gives rise to shape-dependent, anisotropic active tensions and bending moments. We present phase diagrams of the mechanical equilibrium shapes of pre-patterned closed shells and explore their dynamical deformations. Our results show that a combination of nematic alignment and gradients in internal tensions and bending moments is sufficient to reproduce basic building blocks of epithelial morphogenesis, including fold formation, budding, neck formation, flattening, and tubulation.
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Affiliation(s)
| | - Guillaume Salbreux
- The Francis Crick InstituteLondonUnited Kingdom
- University of GenevaGenevaSwitzerland
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6
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Cagnetta F, Škultéty V, Evans MR, Marenduzzo D. Universal properties of active membranes. Phys Rev E 2022; 105:L012604. [PMID: 35193286 DOI: 10.1103/physreve.105.l012604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 11/24/2021] [Indexed: 06/14/2023]
Abstract
We put forward a general field theory for nearly flat fluid membranes with embedded activators and analyze their critical properties using renormalization group techniques. Depending on the membrane-activator coupling, we find a crossover between acoustic and diffusive scaling regimes, with mean-field dynamical critical exponents z=1 and 2, respectively. We argue that the acoustic scaling, which is exact in all spatial dimensions, leads to an early-time behavior, which is representative of the spatiotemporal patterns observed at the leading edge of motile cells, such as oscillations superposed on the growth of the membrane width. In the case of mean-field diffusive scaling, one-loop corrections to the mean-field exponents reveal universal behavior distinct from the Kardar-Parisi-Zhang scaling of passive interfaces and signs of strong-coupling behavior.
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Affiliation(s)
- Francesco Cagnetta
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, Scotland, United Kingdom
| | - Viktor Škultéty
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, Scotland, United Kingdom
| | - Martin R Evans
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, Scotland, United Kingdom
| | - Davide Marenduzzo
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD, Scotland, United Kingdom
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7
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Cagnetta F, Škultéty V, Evans MR, Marenduzzo D. Renormalization group study of the dynamics of active membranes: Universality classes and scaling laws. Phys Rev E 2022; 105:014610. [PMID: 35193300 DOI: 10.1103/physreve.105.014610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 11/24/2021] [Indexed: 06/14/2023]
Abstract
Motivated by experimental observations of patterning at the leading edge of motile eukaryotic cells, we introduce a general model for the dynamics of nearly-flat fluid membranes driven from within by an ensemble of activators. We include, in particular, a kinematic coupling between activator density and membrane slope which generically arises whenever the membrane has a nonvanishing normal speed. We unveil the phase diagram of the model by means of a perturbative field-theoretical renormalization group analysis. Due to the aforementioned kinematic coupling the natural early-time dynamical scaling is acoustic, that is the dynamical critical exponent is 1. However, as soon as the the normal velocity of the membrane is tuned to zero, the system crosses over to diffusive dynamic scaling in mean field. Distinct critical points can be reached depending on how the limit of vanishing velocity is realized: in each of them corrections to scaling due to nonlinear coupling terms must be taken into account. The detailed analysis of these critical points reveals novel scaling regimes which can be accessed with perturbative methods, together with signs of strong coupling behavior, which establishes a promising ground for further nonperturbative calculations. Our results unify several previous studies on the dynamics of active membrane, while also identifying nontrivial scaling regimes which cannot be captured by passive theories of fluctuating interfaces and are relevant for the physics of living membranes.
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Affiliation(s)
- Francesco Cagnetta
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD Scotland, United Kingdom
| | - Viktor Škultéty
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD Scotland, United Kingdom
| | - Martin R Evans
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD Scotland, United Kingdom
| | - Davide Marenduzzo
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3FD Scotland, United Kingdom
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8
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Ghosh S, Gutti S, Chaudhuri D. Pattern formation, localized and running pulsation on active spherical membranes. SOFT MATTER 2021; 17:10614-10627. [PMID: 34605510 DOI: 10.1039/d1sm00937k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Active force generation by an actin-myosin cortex coupled to a cell membrane allows the cell to deform, respond to the environment, and mediate cell motility and division. Several membrane-bound activator proteins move along it and couple to the membrane curvature. Besides, they can act as nucleating sites for the growth of filamentous actin. Actin polymerization can generate a local outward push on the membrane. Inward pull from the contractile actomyosin cortex can propagate along the membrane via actin filaments. We use coupled evolution of fields to perform linear stability analysis and numerical calculations. As activity overcomes the stabilizing factors such as surface tension and bending rigidity, the spherical membrane shows instability towards pattern formation, localized pulsation, and running pulsation between poles. We present our results in terms of phase diagrams and evolutions of the coupled fields. They have relevance for living cells and can be verified in experiments on artificial cell-like constructs.
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Affiliation(s)
- Subhadip Ghosh
- Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia.
| | - Sashideep Gutti
- BITS Pilani Hyderabad Campus, Hyderabad 500078, Telengana, India.
| | - Debasish Chaudhuri
- Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.
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9
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Al-Izzi SC, Morris RG. Active flows and deformable surfaces in development. Semin Cell Dev Biol 2021; 120:44-52. [PMID: 34266757 DOI: 10.1016/j.semcdb.2021.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 06/30/2021] [Accepted: 07/01/2021] [Indexed: 12/15/2022]
Abstract
We review progress in active hydrodynamic descriptions of flowing media on curved and deformable manifolds: the state-of-the-art in continuum descriptions of single-layers of epithelial and/or other tissues during development. First, after a brief overview of activity, flows and hydrodynamic descriptions, we highlight the generic challenge of identifying the dependence on dynamical variables of so-called active kinetic coefficients- active counterparts to dissipative Onsager coefficients. We go on to describe some of the subtleties concerning how curvature and active flows interact, and the issues that arise when surfaces are deformable. We finish with a broad discussion around the utility of such theories in developmental biology. This includes limitations to analytical techniques, challenges associated with numerical integration, fitting-to-data and inference, and potential tools for the future, such as discrete differential geometry.
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Affiliation(s)
- Sami C Al-Izzi
- School of Physics and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales - Sydney, 2052, Australia
| | - Richard G Morris
- School of Physics and EMBL Australia Node in Single Molecule Science, School of Medical Sciences, University of New South Wales - Sydney, 2052, Australia.
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10
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Frey F, Idema T. More than just a barrier: using physical models to couple membrane shape to cell function. SOFT MATTER 2021; 17:3533-3549. [PMID: 33503097 DOI: 10.1039/d0sm01758b] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The correct execution of many cellular processes, such as division and motility, requires the cell to adopt a specific shape. Physically, these shapes are determined by the interplay of the plasma membrane and internal cellular driving factors. While the plasma membrane defines the boundary of the cell, processes inside the cell can result in the generation of forces that deform the membrane. These processes include protein binding, the assembly of protein superstructures, and the growth and contraction of cytoskeletal networks. Due to the complexity of the cell, relating observed membrane deformations back to internal processes is a challenging problem. Here, we review cell shape changes in endocytosis, cell adhesion, cell migration and cell division and discuss how by modeling membrane deformations we can investigate the inner working principles of the cell.
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Affiliation(s)
- Felix Frey
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands.
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11
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The Actomyosin Cortex of Cells: A Thin Film of Active Matter. J Indian Inst Sci 2021. [DOI: 10.1007/s41745-020-00220-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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12
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Loewe B, Serafin F, Shankar S, Bowick MJ, Marchetti MC. Shape and size changes of adherent elastic epithelia. SOFT MATTER 2020; 16:5282-5293. [PMID: 32462170 DOI: 10.1039/d0sm00239a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Epithelial tissues play a fundamental role in various morphogenetic events during development and early embryogenesis. Although epithelial monolayers are often modeled as two-dimensional (2D) elastic surfaces, they distinguish themselves from conventional thin elastic plates in three important ways- the presence of an apical-basal polarity, spatial variability of cellular thickness, and their nonequilibrium active nature. Here, we develop a minimal continuum model of a planar epithelial tissue as an active elastic material that incorporates all these features. We start from a full three-dimensional (3D) description of the tissue and derive an effective 2D model that captures, through the curvature of the apical surface, both the apical-basal asymmetry and the spatial geometry of the tissue. Crucially, variations of active stresses across the apical-basal axis lead to active torques that can drive curvature transitions. By identifying four distinct sources of activity, we find that bulk active stresses arising from actomyosin contractility and growth compete with boundary active tensions due to localized actomyosin cables and lamellipodial activity to generate the various states spanning the morphospace of a planar epithelium. Our treatment hence unifies 3D shape deformations through the coupled mechanics of apical curvature change and in-plane expansion/contraction of substrate-adhered tissues. Finally, we discuss the implications of our results for some biologically relevant processes such as tissue folding at the onset of lumen formation.
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Affiliation(s)
- Benjamin Loewe
- Department of Physics, University of California Santa Barbara, Santa Barbara, California 93106, USA.
| | - Francesco Serafin
- Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
| | - Suraj Shankar
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
| | - Mark J Bowick
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA
| | - M Cristina Marchetti
- Department of Physics, University of California Santa Barbara, Santa Barbara, California 93106, USA.
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13
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Liang CC, Yasuda K, Komura S, Wu KA, Chen HY. Dynamics of a membrane coupled to an active fluid. Phys Rev E 2020; 101:042601. [PMID: 32422731 DOI: 10.1103/physreve.101.042601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 03/11/2020] [Indexed: 11/07/2022]
Abstract
The dynamics of a membrane coupled to an active fluid on top of a substrate is considered theoretically. It is assumed that the director field of the active fluid has rotational symmetry in the membrane plane. This situation is likely to be relevant for in vitro reconstructed actomyosin-membrane system. Different from a membrane coupled to a polar active fluid, this model predicts that only when the viscosity of the fluid above the membrane is sufficiently large, a contractile active fluid is able to slow down the relaxation of the membrane for perturbations with wavelength comparable to the thickness of the active fluid. Hence, our model predicts a finite-wavelength instability in the limit of strong contractility, which is different from a membrane coupled to a polar active fluid. However, a membrane coupled to an extensile active fluid is always unstable against long-wavelength perturbations due to active extensile stress enhanced membrane undulation.
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Affiliation(s)
- Chia-Chun Liang
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Kento Yasuda
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 192-0397 Tokyo, Japan
| | - Shigeyuki Komura
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 192-0397 Tokyo, Japan
| | - Kuo-An Wu
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Hsuan-Yi Chen
- Department of Physics, National Central University, Jhongli 32001, Taiwan.,Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
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14
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Sahu A, Glisman A, Tchoufag J, Mandadapu KK. Geometry and dynamics of lipid membranes: The Scriven-Love number. Phys Rev E 2020; 101:052401. [PMID: 32575240 DOI: 10.1103/physreve.101.052401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/07/2020] [Indexed: 06/11/2023]
Abstract
The equations governing lipid membrane dynamics in planar, spherical, and cylindrical geometries are presented here. Unperturbed and first-order perturbed equations are determined and nondimensionalized. In membrane systems with a nonzero base flow, perturbed in-plane and out-of-plane quantities are found to vary over different length scales. A new dimensionless number, named the Scriven-Love number, and the well-known Föppl-von Kármán number result from a scaling analysis. The Scriven-Love number compares out-of-plane forces arising from the in-plane, intramembrane viscous stresses to the familiar elastic bending forces, while the Föppl-von Kármán number compares tension to bending forces. Both numbers are calculated in past experimental works, and span a wide range of values in various biological processes across different geometries. In situations with large Scriven-Love and Föppl-von Kármán numbers, the dynamical response of a perturbed membrane is dominated by out-of-plane viscous and surface tension forces-with bending forces playing a negligible role. Calculations of non-negligible Scriven-Love numbers in various biological processes and in vitro experiments show in-plane intramembrane viscous flows cannot generally be ignored when analyzing lipid membrane behavior.
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Affiliation(s)
- Amaresh Sahu
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Alec Glisman
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Joël Tchoufag
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
| | - Kranthi K Mandadapu
- Department of Chemical & Biomolecular Engineering, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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15
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Abstract
The essential features of many interfaces driven out of equilibrium are described by the same equation—the Kardar-Parisi-Zhang (KPZ) equation. How do living interfaces, such as the cell membrane, fit into this picture? In an endeavour to answer such a question, we proposed in [F. Cagnetta, M. R. Evans, D. Marenduzzo, PRL 120, 258001 (2018)] an idealised model for the membrane of a moving cell. Here we discuss how the addition of simple ingredients inspired by the dynamics of the membrane of moving cells affects common kinetic roughening theories such as the KPZ and Edwards-Wilkinson equations.
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16
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Maitra A, Srivastava P, Marchetti MC, Ramaswamy S, Lenz M. Swimmer Suspensions on Substrates: Anomalous Stability and Long-Range Order. PHYSICAL REVIEW LETTERS 2020; 124:028002. [PMID: 32004049 DOI: 10.1103/physrevlett.124.028002] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 09/08/2019] [Indexed: 06/10/2023]
Abstract
We present a comprehensive theory of the dynamics and fluctuations of a two-dimensional suspension of polar active particles in an incompressible fluid confined to a substrate. We show that, depending on the sign of a single parameter, a state with polar orientational order is anomalously stable (or anomalously unstable), with a nonzero relaxation (or growth) rate for angular fluctuations, not parallel to the ordering direction, at zero wave number. This screening of the broken-symmetry mode in the stable state does lead to conventional rather than giant number fluctuations as argued by Bricard et al., Nature 503, 95 (2013), but their bend instability in a splay-stable flock does not exist and the polar phase has long-range order in two dimensions. Our theory also describes confined three-dimensional thin-film suspensions of active polar particles as well as dense compressible active polar rods, and predicts a flocking transition without a banding instability.
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Affiliation(s)
- Ananyo Maitra
- Sorbonne Université and CNRS, Laboratoire Jean Perrin, F-75005, Paris, France
- LPTMS, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
| | - Pragya Srivastava
- The Francis Crick Institute, Lincoln's Inn Fields Laboratory, 44 Lincoln's Inn Fields WC2A 3LY, London
- School of Engineering & Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - M Cristina Marchetti
- Department of Physics, University of California Santa Barbara, Santa Barbara, California 93106, USA
| | - Sriram Ramaswamy
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012, India
- Tata Institute of Fundamental Research, Centre for Interdisciplinary Sciences, Hyderabad 500 107, India
| | - Martin Lenz
- LPTMS, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay, France
- PMMH, CNRS, ESPCI Paris, PSL University, Sorbonne Université, Université de Paris, F-75005, Paris, France
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17
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Maitra A, Ramaswamy S. Oriented Active Solids. PHYSICAL REVIEW LETTERS 2019; 123:238001. [PMID: 31868448 DOI: 10.1103/physrevlett.123.238001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 09/08/2019] [Indexed: 06/10/2023]
Abstract
We present a complete analysis of the linearized dynamics of active solids with uniaxial orientational order, taking into account a hitherto overlooked consequence of rotation invariance. Our predictions include a purely active response of two-dimensional orientationally ordered solids to shear, the possibility of stable active solids with quasi-long-range order in two dimensions and long-range order in three dimensions, generic instability of the solid for one sign of active forcing, and the instability of the uniaxially ordered phase in momentum-conserved systems for large active forcing irrespective of its sign.
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Affiliation(s)
- Ananyo Maitra
- Sorbonne Université and CNRS, Laboratoire Jean Perrin, F-75005 Paris, France
| | - Sriram Ramaswamy
- Centre for Condensed Matter Theory, Department of Physics, Indian Institute of Science, 560 012 Bangalore, India
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18
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Senoussi A, Kashida S, Voituriez R, Galas JC, Maitra A, Estevez-Torres A. Tunable corrugated patterns in an active nematic sheet. Proc Natl Acad Sci U S A 2019; 116:22464-22470. [PMID: 31611385 PMCID: PMC6842637 DOI: 10.1073/pnas.1912223116] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Active matter locally converts chemical energy into mechanical work and, for this reason, it provides new mechanisms of pattern formation. In particular, active nematic fluids made of protein motors and filaments are far-from-equilibrium systems that may exhibit spontaneous motion, leading to actively driven spatiotemporally chaotic states in 2 and 3 dimensions and coherent flows in 3 dimensions (3D). Although these dynamic flows reveal a characteristic length scale resulting from the interplay between active forcing and passive restoring forces, the observation of static and large-scale spatial patterns in active nematic fluids has remained elusive. In this work, we demonstrate that a 3D solution of kinesin motors and microtubule filaments spontaneously forms a 2D free-standing nematic active sheet that actively buckles out of plane into a centimeter-sized periodic corrugated sheet that is stable for several days at low activity. Importantly, the nematic orientational field does not display topological defects in the corrugated state and the wavelength and stability of the corrugations are controlled by the motor concentration, in agreement with a hydrodynamic theory. At higher activities these patterns are transient and chaotic flows are observed at longer times. Our results underline the importance of both passive and active forces in shaping active matter and demonstrate that a spontaneously flowing active fluid can be sculpted into a static material through an active mechanism.
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Affiliation(s)
- Anis Senoussi
- Laboratoire Jean Perrin, Sorbonne Université and CNRS, F-75005 Paris, France
| | - Shunnichi Kashida
- Laboratoire Jean Perrin, Sorbonne Université and CNRS, F-75005 Paris, France
| | - Raphael Voituriez
- Laboratoire Jean Perrin, Sorbonne Université and CNRS, F-75005 Paris, France
- Laboratoire de Physique Théorique de la Matière Condensée, Sorbonne Université and CNRS, F-75005 Paris, France
| | | | - Ananyo Maitra
- Laboratoire Jean Perrin, Sorbonne Université and CNRS, F-75005 Paris, France;
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19
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Soni H, Luo W, Pelcovits RA, Powers TR. Stability of the interface of an isotropic active fluid. SOFT MATTER 2019; 15:6318-6330. [PMID: 31322161 DOI: 10.1039/c9sm01216h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We study the linear stability of an isotropic active fluid in three different geometries: a film of active fluid on a rigid substrate, a cylindrical thread of fluid, and a spherical fluid droplet. The active fluid is modeled by the hydrodynamic theory of an active nematic liquid crystal in the isotropic phase. In each geometry, we calculate the growth rate of sinusoidal modes of deformation of the interface. There are two distinct branches of growth rates; at long wavelength, one corresponds to the deformation of the interface, and one corresponds to the evolution of the liquid crystalline degrees of freedom. The passive cases of the film and the spherical droplet are always stable. For these geometries, a sufficiently large activity leads to instability. Activity also leads to propagating damped or growing modes. The passive cylindrical thread is unstable for perturbations with wavelength longer than the circumference. A sufficiently large activity can make any wavelength unstable, and again leads to propagating damped or growing modes. Our calculations are carried out for the case of zero Frank elasticity. While Frank elasticity is a stabilizing mechanism as it penalizes distortions of the order parameter tensor, we show that it has a small effect on the instabilities considered here.
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Affiliation(s)
- Harsh Soni
- School of Engineering, Brown University, Providence, RI 02912, USA.
| | - Wan Luo
- School of Engineering, Brown University, Providence, RI 02912, USA.
| | | | - Thomas R Powers
- School of Engineering, Brown University, Providence, RI 02912, USA. and Department of Physics, Brown University, Providence, RI 02912, USA
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20
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Abstract
During typical early-stage embryo development, single-cell-thick tissues of tightly bound epithelial cells autonomously generate profound changes in their shape, forming the basis of organism anatomy. We report on a (covariant) active-hydrodynamic theory of such monolayer morphogenesis that is closed under its shape-changing dynamics-i.e., the degrees of freedom that encode monolayer geometry appear properly as broken-symmetry variables. In our theory, the salient physics of tissue-scale deformations emerges from a balance between the displacement and/or shear of a low-Reynolds-number embedding fluid (the "yolk") and cell-autonomous stresses, themselves a result of combining apical contractile stresses with an elastic-like mechanical response under the constraint of constant cell volume. The leading-order hydrodynamic instabilities include both passive constrained-buckling and active deformation, which can be further categorized by cell shape changes that are either "squamous to columnar" or "regular-prism to truncated-pyramid." The deformations resulting from the latter qualitatively reproduce in vivo observations of the onset of both mesoderm and posterior midgut invaginations, which take place during gastrulation in the model organism Drosophila melanogaster.
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Affiliation(s)
- Richard G Morris
- EMBL-Australia node in Single Molecule Science, University of New South Wales, Sydney, Australia
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India
| | - Madan Rao
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute for Fundamental Research, Bangalore, India
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21
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Bächer C, Gekle S. Computational modeling of active deformable membranes embedded in three-dimensional flows. Phys Rev E 2019; 99:062418. [PMID: 31330647 DOI: 10.1103/physreve.99.062418] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Indexed: 06/10/2023]
Abstract
Active gel theory has recently been very successful in describing biologically active materials such as actin filaments or moving bacteria in temporally fixed and simple geometries such as cubes or spheres. Here we develop a computational algorithm to compute the dynamic evolution of an arbitrarily shaped, deformable thin membrane of active material embedded in a three-dimensional flowing liquid. For this, our algorithm combines active gel theory with the classical theory of thin elastic shells. To compute the actual forces resulting from active stresses, we apply a parabolic fitting procedure to the triangulated membrane surface. Active forces are then dynamically coupled via an immersed-boundary method to the surrounding fluid whose dynamics can be solved by any standard, e.g., Lattice-Boltzmann, flow solver. We validate our algorithm using the Green's functions of Berthoumieux et al. [New J. Phys. 16, 065005 (2014)10.1088/1367-2630/16/6/065005] for an active cylindrical membrane subjected (i) to a locally increased active stress and (ii) to a homogeneous active stress. For the latter scenario, we predict in addition a nonaxisymmetric instability. We highlight the versatility of our method by analyzing the flow field inside an actively deforming cell embedded in external shear flow. Further applications may be cytoplasmic streaming or active membranes in blood flows.
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Affiliation(s)
- Christian Bächer
- Biofluid Simulation and Modeling, Theoretische Physik VI, Universität Bayreuth, Universitätsstrasse 30, Bayreuth, Germany
| | - Stephan Gekle
- Biofluid Simulation and Modeling, Theoretische Physik VI, Universität Bayreuth, Universitätsstrasse 30, Bayreuth, Germany
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22
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Cagnetta F, Evans MR, Marenduzzo D. Statistical mechanics of a single active slider on a fluctuating interface. Phys Rev E 2019; 99:042124. [PMID: 31108715 DOI: 10.1103/physreve.99.042124] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Indexed: 01/01/2023]
Abstract
We study the statistical mechanics of a single active slider on a fluctuating interface, by means of numerical simulations and theoretical arguments. The slider, which moves by definition towards the interface minima, is active as it also stimulates growth of the interface. Even though such a particle has no counterpart in thermodynamic systems, active sliders may provide a simple model for ATP-dependent membrane proteins that activate cytoskeletal growth. We find a wide range of dynamical regimes according to the ratio between the timescales associated with the slider motion and the interface relaxation. If the interface dynamics is slow, the slider behaves like a random walker in a random environment, which, furthermore, is able to escape environmental troughs by making them grow. This results in different dynamic exponents to the interface and the particle: the former behaves as an Edward-Wilkinson surface with dynamic exponent 2, whereas the latter has dynamic exponent 3/2. When the interface is fast, we get sustained ballistic motion with the particle surfing a membrane wave created by itself. However, if the interface relaxes immediately (i.e., it is infinitely fast), particle motion becomes symmetric and goes back to diffusive. Due to such a rich phenomenology, we propose the active slider as a toy model of fundamental interest in the field of active membranes and, generally, whenever the system constituent can alter the environment by spending energy.
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Affiliation(s)
- F Cagnetta
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - M R Evans
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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23
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Cagnetta F, Evans MR, Marenduzzo D. Active Growth and Pattern Formation in Membrane-Protein Systems. PHYSICAL REVIEW LETTERS 2018; 120:258001. [PMID: 29979071 DOI: 10.1103/physrevlett.120.258001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 02/14/2018] [Indexed: 06/08/2023]
Abstract
Inspired by recent experimental observations of patterning at the membrane of a living cell, we propose a generic model for the dynamics of a fluctuating interface driven by particlelike inclusions which stimulate its growth. We find that the coupling between interfacial and inclusions dynamics yields microphase separation and the self-organization of traveling waves. These patterns are strikingly similar to those detected in experiments on biological membranes. Our results further show that the active growth kinetics do not fall into the Kardar-Parisi-Zhang universality class for growing interfaces, displaying instead a novel superposition of scaling and sustained oscillations.
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Affiliation(s)
- F Cagnetta
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - M R Evans
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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24
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Sahu A, Sauer RA, Mandadapu KK. Irreversible thermodynamics of curved lipid membranes. Phys Rev E 2017; 96:042409. [PMID: 29347561 DOI: 10.1103/physreve.96.042409] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Indexed: 01/15/2023]
Abstract
The theory of irreversible thermodynamics for arbitrarily curved lipid membranes is presented here. The coupling between elastic bending and irreversible processes such as intramembrane lipid flow, intramembrane phase transitions, and protein binding and diffusion is studied. The forms of the entropy production for the irreversible processes are obtained, and the corresponding thermodynamic forces and fluxes are identified. Employing the linear irreversible thermodynamic framework, the governing equations of motion along with appropriate boundary conditions are provided.
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Affiliation(s)
- Amaresh Sahu
- Department of Chemical & Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA
| | - Roger A Sauer
- Aachen Institute for Advanced Study in Computational Engineering Science (AICES), RWTH Aachen University, Templergraben 55, 52056 Aachen, Germany
| | - Kranthi K Mandadapu
- Department of Chemical & Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA
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25
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Li T, Brandani G, Marenduzzo D, Clegg PS. Colloidal Spherocylinders at an Interface: Flipper Dynamics and Bilayer Formation. PHYSICAL REVIEW LETTERS 2017; 119:018001. [PMID: 28731771 DOI: 10.1103/physrevlett.119.018001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Indexed: 06/07/2023]
Abstract
We study the response of a film of colloidal spherocylinders to compression by combining pressure-area isotherm measurements, microscopy, and computer simulations. We find that the behavior of the film depends strongly on the geometry of the particles. For a small aspect ratio, a uniform monolayer forms and then buckles. For a higher aspect ratio, particles flip to orient perpendicular to the interface; we show that flipping occurs in locations where the nematic ordering is low. Our experiments and simulations further demonstrate that the longest particles rearrange to self-assemble a colloidal bilayer, which is stable due to the unique geometry of spherocylinders at an interface.
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Affiliation(s)
- T Li
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - G Brandani
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
| | - P S Clegg
- SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom
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26
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Nikola N, Solon AP, Kafri Y, Kardar M, Tailleur J, Voituriez R. Active Particles with Soft and Curved Walls: Equation of State, Ratchets, and Instabilities. PHYSICAL REVIEW LETTERS 2016; 117:098001. [PMID: 27610886 DOI: 10.1103/physrevlett.117.098001] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Indexed: 06/06/2023]
Abstract
We study, from first principles, the pressure exerted by an active fluid of spherical particles on general boundaries in two dimensions. We show that, despite the nonuniform pressure along curved walls, an equation of state is recovered upon a proper spatial averaging. This holds even in the presence of pairwise interactions between particles or when asymmetric walls induce ratchet currents, which are accompanied by spontaneous shear stresses on the walls. For flexible obstacles, the pressure inhomogeneities lead to a modulational instability as well as to the spontaneous motion of short semiflexible filaments. Finally, we relate the force exerted on objects immersed in active baths to the particle flux they generate around them.
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Affiliation(s)
| | - Alexandre P Solon
- Université Paris Diderot, Sorbonne Paris Cité, MSC, UMR 7057 CNRS, 75205 Paris, France
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Yariv Kafri
- Department of Physics, Technion, Haifa 32000, Israel
| | - Mehran Kardar
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Julien Tailleur
- Université Paris Diderot, Sorbonne Paris Cité, MSC, UMR 7057 CNRS, 75205 Paris, France
| | - Raphaël Voituriez
- Laboratoire de Physique Théorique de la Matière Condensée, UMR 7600 CNRS /UPMC, 4 Place Jussieu, 75255 Paris Cedex, France
- Laboratoire Jean Perrin, UMR 8237 CNRS /UPMC, 4 Place Jussieu, 75255 Paris Cedex, France
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27
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Yasuda K, Komura S, Okamoto R. Dynamics of a membrane interacting with an active wall. Phys Rev E 2016; 93:052407. [PMID: 27300924 DOI: 10.1103/physreve.93.052407] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Indexed: 11/07/2022]
Abstract
Active motions of a biological membrane can be induced by nonthermal fluctuations that occur in the outer environment of the membrane. We discuss the dynamics of a membrane interacting hydrodynamically with an active wall that exerts random velocities on the ambient fluid. Solving the hydrodynamic equations of a bound membrane, we first derive a dynamic equation for the membrane fluctuation amplitude in the presence of different types of walls. Membrane two-point correlation functions are calculated for three different cases: (i) a static wall, (ii) an active wall, and (iii) an active wall with an intrinsic time scale. We focus on the mean squared displacement (MSD) of a tagged membrane describing the Brownian motion of a membrane segment. For the static wall case, there are two asymptotic regimes of MSD (∼t^{2/3} and ∼t^{1/3}) when the hydrodynamic decay rate changes monotonically. In the case of an active wall, the MSD grows linearly in time (∼t) in the early stage, which is unusual for a membrane segment. This linear-growth region of the MSD is further extended when the active wall has a finite intrinsic time scale.
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Affiliation(s)
- Kento Yasuda
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Shigeyuki Komura
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Ryuichi Okamoto
- Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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28
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Risler T, Peilloux A, Prost J. Homeostatic Fluctuations of a Tissue Surface. PHYSICAL REVIEW LETTERS 2015; 115:258104. [PMID: 26722948 DOI: 10.1103/physrevlett.115.258104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Indexed: 06/05/2023]
Abstract
We study the surface fluctuations of a tissue with a dynamics dictated by cell-rearrangement, cell-division, and cell-death processes. Surface fluctuations are calculated in the homeostatic state, where cell division and cell death equilibrate on average. The obtained fluctuation spectrum can be mapped onto several other spectra such as those characterizing incompressible fluids, compressible Maxwell elastomers, or permeable membranes in appropriate asymptotic regimes. Since cell division and cell death are out-of-equilibrium processes, detailed balance is broken, but a generalized fluctuation-response relation is satisfied in terms of appropriate observables. Our work is a first step toward the description of the out-of-equilibrium fluctuations of the surface of a thick epithelium and its dynamical response to external perturbations.
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Affiliation(s)
- Thomas Risler
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d'Ulm, 75005 Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire Physico Chimie Curie, 75005 Paris, France
| | - Aurélien Peilloux
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d'Ulm, 75005 Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire Physico Chimie Curie, 75005 Paris, France
| | - Jacques Prost
- Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS, 26 rue d'Ulm, 75005 Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire Physico Chimie Curie, 75005 Paris, France
- Mechanobiology Institute, National University of Singapore, 5A Engineering Drive 1, 117411 Singapore
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29
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Sarkar N, Basu A. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052306. [PMID: 26651694 DOI: 10.1103/physreve.92.052306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 06/05/2023]
Abstract
We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ. Being controlled by Γ, our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ. Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems.
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Affiliation(s)
- Niladri Sarkar
- Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Calcutta 700064, India
- Max-Planck Institut für Physik Komplexer Systeme, Nöthnitzer Str. 38, Dresden, D-01187 Germany
| | - Abhik Basu
- Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Calcutta 700064, India
- Max-Planck Institut für Physik Komplexer Systeme, Nöthnitzer Str. 38, Dresden, D-01187 Germany
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30
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Johannes L, Parton RG, Bassereau P, Mayor S. Building endocytic pits without clathrin. Nat Rev Mol Cell Biol 2015; 16:311-21. [PMID: 25857812 DOI: 10.1038/nrm3968] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
How endocytic pits are built in clathrin- and caveolin-independent endocytosis still remains poorly understood. Recent insight suggests that different forms of clathrin-independent endocytosis might involve the actin-driven focusing of membrane constituents, the lectin-glycosphingolipid-dependent construction of endocytic nanoenvironments, and Bin-Amphiphysin-Rvs (BAR) domain proteins serving as scaffolding modules. We discuss the need for different types of internalization processes in the context of diverse cellular functions, the existence of clathrin-independent mechanisms of cargo recruitment and membrane bending from a biological and physical perspective, and finally propose a generic scheme for the formation of clathrin-independent endocytic pits.
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Affiliation(s)
- Ludger Johannes
- Institut Curie, PSL Research University, Endocytic Trafficking and Therapeutic Delivery Group, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Centre National de la Recherche Scientifique UMR3666, 75005 Paris, France; and INSERM U1143, 75005 Paris, France
| | - Robert G Parton
- University of Queensland, Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, St Lucia QLD 4072, Australia
| | - Patricia Bassereau
- Institut Curie, PSL Research University, Membrane and Cell Functions Group, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Centre National de la Recherche Scientifique UMR168, 75005 Paris, France; and Université Pierre et Marie Curie, 75252 Paris, France
| | - Satyajit Mayor
- National Centre for Biological Sciences, Cellular Organization and Signaling Group, and at Institute for Stem Cell Biology and Regenerative Medicine, UAS-GKVK Campus, 560 065 Bangalore, India
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