138 research outputs found
Hydrodynamic collective effects of active proteins in biological membranes
Lipid bilayers forming biological membranes are known to behave as viscous 2D
fluids on submicrometer scales; usually they contain a large number of active
protein inclusions. Recently, it has been shown [Proc. Nat. Acad. Sci. USA 112,
E3639 (2015)] that such active proteins should in- duce non-thermal fluctuating
lipid flows leading to diffusion enhancement and chemotaxis-like drift for
passive inclusions in biomembranes. Here, a detailed analytical and numerical
investigation of such effects is performed. The attention is focused on the
situations when proteins are concentrated within lipid rafts. We demonstrate
that passive particles tend to become attracted by active rafts and are
accumulated inside them.Comment: 12 pages, 7 figure
Slowing and stopping of chemical waves in a narrowing canal
The propagation of a chemical wave in a narrow, cone-shaped glass capillary
was investigated. When a chemical wave propagates from the wider end to the
narrower end, it slows, stops, and then disappears. A phenomenological model
that considers the surface effect of the glass is proposed, and this model
reproduces the experimental trends.Comment: 8 pages, 5 figure
Anomalous diffusion and transport by a reciprocal convective flow
Under low-Reynolds-number conditions, dynamics of convection and diffusion
are usually considered separately because their dominant spatial and temporal
scales are different, but cooperative effects of convection and diffusion can
cause diffusion enhancement [Koyano et al., Phys. Rev. E, 102, 033109 (2020)].
In this study, such cooperative effects are investigated in detail. Numerical
simulations based on the convection-diffusion equation revealed that
anisotropic diffusion and net shift as well as diffusion enhancement occur
under a reciprocal flow. Such anomalous diffusion and transport are
theoretically derived by the analyses of the Langevin dynamics.Comment: 10 pages, 9 figure
Reaction-induced molecular dancing and boosted diffusion of enzymes
A novel mechanism of reaction-induced active molecular motion, not involving
any kind of self-propulsion, is proposed and analyzed. Because of the momentum
exchange with the surrounding solvent, conformational transitions in
mechano-chemical enzymes are accompanied by motions of their centers of mass.
As we show, in combination with rotational diffusion, such repeated reciprocal
motions generate an additional random walk - or molecular dancing - and hence
boost translational diffusion of an enzyme. A systematic theory of this
phenomenon is developed, using as an example a simple enzyme model of a rigid
two-state dumbbell. To support the analysis, numerical simulations are
performed. Our conclusion is that the phenomenon of molecular dancing could
underlie the observations of reaction-induced diffusion enhancement in enzymes.
Major experimental findings, such as the occurrence of leaps, the
anti-chemotaxis, the linear dependence on the reaction turnover rate and on the
rate of energy supply, become thus explained. Moreover, the dancing behavior is
possible in other systems, natural and synthetic, too. In the future,
interesting biotechnology applications may be developed using such effects.Comment: 19 pages, 6 figure
Mode Selection in the Spontaneous Motion of an Alcohol Droplet
An alcohol (pentanol) droplet exhibits spontaneous agitation on an aqueous
solution, driven by a solutal Marangoni effect. We found that the droplet's
mode of motion is controlled by its volume. A droplet with a volume of less
than shows irregular translational motion, whereas
intermediate-sized droplets of show vectorial motion. When
the volume is above , the droplet splits into smaller drops.
These experimental results regarding mode selection are interpreted in terms of
the wave number selection depending on the droplet volume.Comment: 4 pages, 5 figure
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