Biology subjects

Velegol, D.

Publications and source records attributed to Velegol, D..

2 recordsLinked to original sources

bioRxiv2019

Motility of Enzyme-Powered Vesicles

Autonomous nanovehicles powered by energy derived from chemical catalysis have potential applications as active delivery agents. For in vivo applications, it is necessary that the engine and its fuel, as well as the chassis itself, be biocompatible. Enzyme molecules have been shown to generate mechanical force through substrate turnover and are attractive candidates as engines; phospholipid vesicles are biocompatible and can serve as cargo containers. Herein, we describe the autonomous movement of vesicles with membrane-bound enzymes in the presence of the substrate. We find that the motility of the vesicles increases with increasing enzymatic turnover rate. The enhanced diffusion of these enzyme-powered systems was further substantiated in real time by tracking the motion of the vesicles using optical microscopy. The membrane-bound protocells that move by transducing chemical energy into mechanical motion serve as models for motile living cells and are key to the elucidation of the fundamental mechanisms governing active membrane dynamics and cellular movement.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC=\"FIGDIR/small/645986v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (30K):\norg.highwire.dtl.DTLVardef@49a48org.highwire.dtl.DTLVardef@2d0bc0org.highwire.dtl.DTLVardef@15e9466org.highwire.dtl.DTLVardef@60ba5e_HPS_FORMAT_FIGEXP M_FIG \"For Table of Contents Only\"\n\nC_FIG

biochemistry↗

bioRxiv2019

Non-uniform Crowding Enhances Transport: Relevance to Biological Environments

The cellular cytoplasm is crowded with macromolecules and other species that occupy up to 40% of the available volume. Previous studies have reported that for high crowder molecule concentrations, colloidal tracer particles have a dampened diffusion due to the higher solution viscosity. However, these studies employed uniform distributions of crowder molecules. We report a scenario, previously unexplored experimentally, of increased tracer transport driven by a non-uniform concentration of crowder macromolecules. In gradients of polymeric crowder, tracer particles undergo transport several times higher than that of their bulk diffusion rate. The direction of the transport is toward regions of lower crowder concentration. Mechanistically, hard-sphere interactions and the resulting volume exclusion between the tracer and crowder increases the effective diffusion by inducing a convective motion of tracers. Strikingly, soft deformable particles show even greater enhancement in transport in crowder gradients compared to similarly sized hard particles. We propose a model that supports the data and quantifies a \"diffusiophoretic buoyancy force\" when a tracer is in a gradient of crowder concentration. Overall, this demonstration of enhanced transport in non-uniform distributions of crowder is anticipated to clarify aspects of multi-component intracellular transport.

biophysics↗