Localization and diffusion of tracer particles in viscoelastic media with active force dipoles

Abstract

Optical tracking in vivo experiments reveal that diffusion of particles in biological cells is strongly enhanced in the presence of ATP and the experimental data for animal cells could previously be reproduced within a phenomenological model of a gel with myosin motors acting within it [EPL 110, 48005 (2015)]. Here, the two-fluid model of a gel is considered where active macromolecules, described as force dipoles, cyclically operate both in the elastic and the fluid components. Through coarse-graining, effective equations of motions for tracer particles displaying local deformations and local fluid flows are derived. The equation for deformation tracers coincides with the earlier phenomenological model and thus confirms it. For flow tracers, diffusion enhancement caused by active force dipoles in the fluid component, and thus due to metabolic activity, is found. The latter effect may explain why ATP-dependent diffusion enhancement could also be observed in bacteria that lack molecular motors in their skeleton or when the activity of myosin motors was chemically inhibited.

References in corpus (9)

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• The response function of a sphere in a viscoelastic two-fluid medium
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Cited by in corpus (9)

• Active mechanics reveal molecular-scale force kinetics in living oocytes
• Non-reciprocal response of a two-dimensional fluid with odd viscosity
• Hydrodynamic lift of a two-dimensional liquid domain with odd viscosity
• Mechanochemical enzymes and protein machines as hydrodynamic force dipoles: The active dimer model
• Diffusion in crowded colloids of particles cyclically changing their shapes
• Lateral diffusion induced by active proteins in a biomembrane
• Anomalous diffusion in viscoelastic media with active force dipoles
• Generalized Three-Sphere Microswimmers
• A three-sphere microswimmer in a structured fluid