Instabilities and oscillations in isotropic active gels

Banerjee, Shiladitya

doi:10.1039/c0sm00494d

Cited by 46 publications

(49 citation statements)

References 48 publications

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“…Motor cooperativity then leads to a dynamical phase transition to spontaneous directed motion despite the system's spatial symmetry. Thinking of the cytoskeleton, an assembly of filamentous polar polymers actively connected by cross-linkers, as an active polar gel has allowed the construction of continuum theories, based on conservation laws and symmetry considerations, which also generate active flows (13)(14)(15)(16). Pattern formation in active fluids has also been discussed based on a reaction-diffusion-advection mechanism (17).…”

mentioning

confidence: 99%

On the spontaneous collective motion of active matter

Wang

Wolynes

2011

Proc. Natl. Acad. Sci. U.S.A.

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Spontaneous directed motion, a hallmark of cell biology, is unusual in classical statistical physics. Here we study, using both numerical and analytical methods, organized motion in models of the cytoskeleton in which constituents are driven by energy-consuming motors. Although systems driven by small-step motors are described by an effective temperature and are thus quiescent, at higher order in step size, both homogeneous and inhomogeneous, flowing and oscillating behavior emerges. Motors that respond with a negative susceptibility to imposed forces lead to an apparent negativetemperature system in which beautiful structures form resembling the asters seen in cell division.nonequilibrium structures | symmetry breaking | emergent phenomenon | soft condensed matter S pontaneous directed motion driven by active processes is crucial to biology. Such motion is only possible because the cell is a far-from-equilibrium many-body system. The cytoskeleton of eukaryotic cells is built, maintained, and adaptively reorganized through active transport and force generation powered by ATP hydrolysis. Oscillations of the mitotic spindle during cell division (1) and cytoplasmic streaming (2) dramatically illustrate that the cell is not at equilibrium. Driven motions of cells are also important at higher levels of organization in living things ranging from mechanosensation (3) to the developmental processes in which the genetic code unfolds to create a multicellar organism (4). Sustained spontaneous collective motion is quite remarkable in many-body physics. Superfluidity and superconductivity are examples of metastable states of motion made possible by quantum statistics. The biological example provided by the cytoskeleton is seemingly quite different, leading not to infinitely long-lived states but to ones that go away when the cell is depleted of fuel and dies. Nevertheless, like the quantum examples, the motion of the cytoskeleton is an emergent many-body phenomenon reflecting broken symmetries.Here we explore the origin of spontaneous collective motion for systems of many interacting biomacromolecules with motordriven active processes using a systematic perturbative expansion of the many-body master equation treating nonequilibrium motorized processes. We model the motors as generating a time series of isotropic kicks on the constituents of a many-body assembly. Earlier (5) we showed that quite generally the corresponding master equation, when expanded to the lowest order in the kick step size, yields an effective temperature, T eff , which explicitly depends on the total motor activity and on the way in which motors respond to imposed forces. A system described by an effective temperature alone (6-8) cannot undergo spontaneous directed motion unless it is quantum mechanical so that spatial and momentum degrees of freedom are coupled by the uncertainty principle. Pursuing the expansion to higher order, however, reveals the possible emergence of spontaneous directed collective motion quite generally from a quiescent homogene...

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mentioning

confidence: 99%

On the spontaneous collective motion of active matter

Wang

Wolynes

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…It is the spontaneous emergence of order, regularity, coherence, and coordination within the system from numerous short-range interactions among the constituents [27] [30] [31]. The simple microscopic local interaction rules are the key factors that give rise to a global self-organized collective state leading to various fascinating natural patterns.…”

Section: Self-organization Of Protein Filamentsmentioning

confidence: 99%

Molecular Motors—Self-Organization of Cytoskeletal Network

Dutta¹

2017

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Molecular motors play an important role in the organization of cytoskeletal filament networks. These nanometer-sized natural molecular machines opened up a new frontier of nano-technology. This article describes biomolecular nano-machines, their internal structures, and dynamical interactions between molecular motors and their molecular tracks which reorganize a network of long protein filaments, particularly during cell division to form cytoskeleton of daughter cells. Towards the end, the article also takes up some still-to-be resolved matters and prospects for future developments in this exciting multidisciplinary area of science.

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“…The fluid and elastic components are coupled through incompressibility and a drag term Γ, an effect of matrix permeability to fluid. Similar approaches were used to model collagenous tissue (27) and active gels (28). Using this model, we calculate the response function G ijkl ðx, tÞ to describe propagation of mechanical stress within the ECM (Supporting Information).…”

Section: Physical Model Of Cardiac Mechanical Signalingmentioning

confidence: 99%

Mechanical signaling coordinates the embryonic heartbeat

Chiou

Rocks

Chen

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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In the beating heart, cardiac myocytes (CMs) contract in a coordinated fashion, generating contractile wave fronts that propagate through the heart with each beat. Coordinating this wave front requires fast and robust signaling mechanisms between CMs. The primary signaling mechanism has long been identified as electrical: gap junctions conduct ions between CMs, triggering membrane depolarization, intracellular calcium release, and actomyosin contraction. In contrast, we propose here that, in the early embryonic heart tube, the signaling mechanism coordinating beats is mechanical rather than electrical. We present a simple biophysical model in which CMs are mechanically excitable inclusions embedded within the extracellular matrix (ECM), modeled as an elastic-fluid biphasic material. Our model predicts strong stiffness dependence in both the heartbeat velocity and strain in isolated hearts, as well as the strain for a hydrogel-cultured CM, in quantitative agreement with recent experiments. We challenge our model with experiments disrupting electrical conduction by perfusing intact adult and embryonic hearts with a gap junction blocker, β-glycyrrhetinic acid (BGA). We find this treatment causes rapid failure in adult hearts but not embryonic hearts-consistent with our hypothesis. Last, our model predicts a minimum matrix stiffness necessary to propagate a mechanically coordinated wave front. The predicted value is in accord with our stiffness measurements at the onset of beating, suggesting that mechanical signaling may initiate the very first heartbeats. mechanotransduction | excitable media | cardiac development | heartbeat | reaction-diffusion

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Instabilities and oscillations in isotropic active gels

Cited by 46 publications

References 48 publications

On the spontaneous collective motion of active matter

On the spontaneous collective motion of active matter

Molecular Motors—Self-Organization of Cytoskeletal Network

Mechanical signaling coordinates the embryonic heartbeat

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