Channel transport: gating, geometry, and heterogeneous diffusion

TL;DR

This paper derives an explicit, accurate estimate for diffusive flux through biological channels considering gating, geometry, and heterogeneous diffusion, validated by simulations across diverse parameters.

Contribution

It provides a novel explicit formula for channel flux that incorporates gating, geometry, and diffusion heterogeneity, with validation and comparison to existing physics results.

Findings

The estimate is exact in certain regimes.

Simulations confirm broad accuracy of the estimate.

The formula differs from some prior physics-based results.

Abstract

Channel-mediated transport is ubiquitous in biology. A series of works by different theoreticians have sought to determine how the diffusive flux through a channel depends on (a) stochastic gating, (b) channel geometry, and (c) heterogeneous diffusion. In this paper, we derive an explicit estimate for the diffusive flux through a channel that accounts for these three factors. We show that our estimate is exact in certain parameter regimes. We further use stochastic simulations to confirm that our estimate remains accurate across a very broad range of parameters. Our estimate differs from some results in the physics literature.