Enhanced reaction kinetics in biological cells

TL;DR

This paper presents an analytical model demonstrating how active transport in biological cells enhances reaction kinetics, especially for larger tracers like vesicles, by optimizing interaction times with motor proteins.

Contribution

It introduces the first analytical model of transport-limited reactions in active media, revealing universal features of optimal configurations for enhanced reactivity.

Findings

Active transport increases reaction rates for large tracers.

Optimal interaction times with motor proteins maximize reaction efficiency.

Universal features characterize the optimal transport configurations.

Abstract

The cell cytoskeleton is a striking example of "active" medium driven out-of-equilibrium by ATP hydrolysis. Such activity has been shown recently to have a spectacular impact on the mechanical and rheological properties of the cellular medium, as well as on its transport properties : a generic tracer particle freely diffuses as in a standard equilibrium medium, but also intermittently binds with random interaction times to motor proteins, which perform active ballistic excursions along cytoskeletal filaments. Here, we propose for the first time an analytical model of transport limited reactions in active media, and show quantitatively how active transport can enhance reactivity for large enough tracers like vesicles. We derive analytically the average interaction time with motor proteins which optimizes the reaction rate, and reveal remarkable universal features of the optimal configuration. We discuss why active transport may be beneficial in various biological examples: cell cytoskeleton, membranes and lamellipodia, and tubular structures like axons.