scholarly journals Interplay between Brownian motion and cross-linking kinetics controls bundling dynamics in actin networks

2021 ◽  
Author(s):  
Ondrej Maxian ◽  
Aleksandar Donev ◽  
Alex Mogilner
Keyword(s):  
Brownian Motion ◽  
Brownian Dynamics ◽  
Mesh Size ◽  
Cross Linking ◽  
Strong Function ◽  
Actin Networks ◽  
Cross Links ◽  
Two Phases ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractMorphology changes in cross-linked actin networks are important in cell motility, division, and cargo transport. Here we study the transition from a weakly cross-linked network of actin filaments to a heavily cross-linked network of actin bundles through microscopic Brownian dynamics simulations. We show that this transition occurs in two phases: first, a composite bundle network of small and highly aligned bundles evolves from cross linking of individual filaments; second, small bundles coalesce into the clustered bundle state. We demonstrate that Brownian motion speeds up the first phase of this process at a faster rate than the second. We quantify the time to reach the composite bundle phase and show that it is a strong function of mesh size only when the concentration of cross links is small, and that it remains roughly constant if we decrease the relative ratio of cross linkers as we increase the actin concentration. Finally, we examine the dependence of the bundling timescale on filament length, finding that shorter filaments bundle faster because they diffuse faster.

scholarly journals Crosslinking actin networks produces compressive force

2019 ◽  
Author(s):  
Rui Ma ◽  
Julien Berro
Keyword(s):  
Actin Filaments ◽  
Brownian Dynamics ◽  
Actin Polymerization ◽  
Turgor Pressure ◽  
Compressive Force ◽  
Yeast Cells ◽  
Actin Networks ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations ◽  
Over Time

AbstractActin has been shown to be essential for clathrin-mediated endocytosis in yeast. However, actin polymerization alone is likely insufficient to produce enough force to deform the membrane against the huge turgor pressure of yeast cells. In this paper, we used Brownian dynamics simulations to demonstrate that crosslinking of a meshwork of non-polymerizing actin filaments is able to produce compressive forces. We show that the force can be up to thousands of piconewtons if the crosslinker has a high stiffness. The force decays over time as a result of crosslinker turnover, and is a result of converting chemical binding energy into elastic energy.

The effect of Brownian motion on the stability of sedimenting suspensions of polarizable rods in an electric field

2009 ◽  
Vol 624 ◽  
pp. 361-388 ◽  
Author(s):  
BRENDAN D. HOFFMAN ◽  
ERIC S. G. SHAQFEH
Keyword(s):  
Brownian Motion ◽  
Electric Fields ◽  
Brownian Dynamics ◽  
Mean Field ◽  
Thermal Motion ◽  
Particle Orientation ◽  
Induced Charge ◽  
The Stability ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We examine the collective dynamics of polarizable, Brownian, sedimenting rods of high aspect ratio. Previous work of Koch and Shaqfeh (J. Fluids Mech., vol. 209, 1989 pp. 521–542) has shown that in the absence of Brownian motion, sedimenting suspensions of rods are unstable to concentration fluctuations and form dense streamers via interparticle hydrodynamic interactions. Recently, Saintillan, Shaqfeh & Darve (Phys. Fluids, vol. 18 (121701), 2006b p. 1) demonstrated that electric fields can act to stabilize these non-Brownian suspensions of polarizable rods through induced-charge electrokinetic rotation, which forces particle alignment. In this paper, we employ a mean-field linear stability analysis as well as Brownian dynamics simulations to study the effect of thermal motion on the onset of instability. We find that in the absence of electric fields, Brownian motion consistently suppresses instability formation through randomization of particle orientation. However, when electric fields are applied, thermal motion can act to induce instability by counteracting the stabilizing effect of induced-charge orientation.

Brownian Dynamics Simulations of a Dispersion Composed of Two-Types of Spherical Particles (for Development of a New Technology of Improving the Visibility of Rivers and Lakes)

2008 ◽  
Author(s):  
Akira Satoh ◽  
Eiji Taneko
Keyword(s):  
Brownian Motion ◽  
Gravity Field ◽  
Brownian Dynamics ◽  
New Technology ◽  
Spherical Particles ◽  
Important Conclusion ◽  
Large Particles ◽  
Rivers And Lakes ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We have carried out Brownian dynamics simulations of sedimentation phenomena of a dispersion composed of two-kinds of spherical particles in water under the gravity field. This study may be the first step to develop a new technology which enables us to improve the visibility of rivers and lakes. In the present study, we have modeled sub-micrometer-dimension particles, or dirty particles in lakes, as small spherical particles, and capturing particles as large spherical particles; these two kinds of particles conduct Brownian motion in water, and large particles adsorb small particles to sediment gradually toward the bottom in the gravity field. From the results of Brownian dynamics simulations, the influences of Brownian motion, particle-particle interaction forces, the size of each particle, and the gravity force on the performance of the adsorption of large particles have been discussed. In addition, we have discussed what the most appropriate situation of large particles is to accomplish the most effective adsorption rate or improve the visibility of water most effectively in terms of capturing particles. The most important conclusion derived from the present results is that, in order to improve the capturing performance, the Brownian motion of large particles have to be activated in an appropriate number density without losing the influence of the gravity.

scholarly journals Structure evolution of suspensions under time-dependent electric or magnetic field

2021 ◽  
Author(s):  
Konstantinos Manikas ◽  
Markus Hütter ◽  
Patrick D. Anderson
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Brownian Dynamics ◽  
Thermal Fluctuations ◽  
Time Dependent ◽  
Structure Evolution ◽  
Strength Increase ◽  
Large Rotation ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractThe effect of time-dependent external fields on the structures formed by particles with induced dipoles dispersed in a viscous fluid is investigated by means of Brownian Dynamics simulations. The physical effects accounted for are thermal fluctuations, dipole-dipole and excluded volume interactions. The emerging structures are characterised in terms of particle clusters (orientation, size, anisotropy and percolation) and network structure. The strength of the external field is increased in one direction and then kept constant for a certain amount of time, with the structure formation being influenced by the slope of the field-strength increase. This effect can be partially rationalized by inhomogeneous time re-scaling with respect to the field strength, however, the presence of thermal fluctuations makes the scaling at low field strength inappropriate. After the re-scaling, one can observe that the lower the slope of the field increase, the more network-like and the thicker the structure is. In the second part of the study the field is also rotated instantaneously by a certain angle, and the effect of this transition on the structure is studied. For small rotation angles ($$\theta \le 20^{{\circ }}$$ θ ≤ 20 ∘ ) the clusters rotate but stay largely intact, while for large rotation angles ($$\theta \ge 80^{{\circ }}$$ θ ≥ 80 ∘ ) the structure disintegrates and then reforms, due to the nature of the interactions (parallel dipoles with perpendicular inter-particle vector repel each other). For intermediate angles ($$20<\theta <80^{{\circ }}$$ 20 < θ < 80 ∘ ), it seems that, during rotation, the structure is altered towards a more network-like state, as a result of cluster fusion (larger clusters). The details provided in this paper concern an electric field, however, all results can be projected into the case of a magnetic field and paramagnetic particles.

scholarly journals Influence of size polydispersity on magnetic field tunable structures in magnetic nanofluids containing superparamagnetic nanoparticles.

2021 ◽  
Author(s):  
Dillip Kumar Mohapatra ◽  
Philip James Camp ◽  
John Philip
Keyword(s):  
Magnetic Field ◽  
Particle Size ◽  
Light Scattering ◽  
Optical Microscopy ◽  
Brownian Dynamics ◽  
Phase Contrast ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Nanofluids ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

We probe the influence of particle size polydispersity on field-induced structures and structural transitions in magnetic fluids (ferrofluids) using phase contrast optical microscopy, light scattering and Brownian dynamics simulations. Three...

scholarly journals Hard discs under steady shear: comparison of Brownian dynamics simulations and mode coupling theory

2009 ◽  
Vol 367 (1909) ◽  
pp. 5033-5050 ◽  
Author(s):  
Oliver Henrich ◽  
Fabian Weysser ◽  
Michael E. Cates ◽  
Matthias Fuchs
Keyword(s):  
Brownian Dynamics ◽  
Mode Coupling ◽  
Transition Density ◽  
Two Dimensions ◽  
Coupling Theory ◽  
Mode Coupling Theory ◽  
Stationary Structure ◽  
Homogeneous Shear Flow ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

Brownian dynamics simulations of bidisperse hard discs moving in two dimensions in a given steady and homogeneous shear flow are presented close to and above the glass transition density. The stationary structure functions and stresses of shear-melted glass are compared quantitatively to parameter-free numerical calculations of monodisperse hard discs using mode coupling theory within the integration through transients framework. Theory qualitatively explains the properties of the yielding glass but quantitatively overestimates the shear-driven stresses and structural anisotropies.

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