Entropy-driven pumping across zeolites and biological channels

TL;DR

This paper demonstrates through simulations that single-file channels like zeolites and biomembranes can use entropy to pump molecules against their gradients, revealing new insights into transport phenomena.

Contribution

It introduces a model showing entropy-driven diffusional pumping in single-file channels, explaining negative osmosis and guiding future experiments.

Findings

Entropy can drive molecules against their chemical potential gradients.

Transport rates depend on transmembrane potential, pore length, and interactions.

Results align qualitatively with recent experimental observations.

Abstract

When two binary solutions are separated by a permeable barrier, the individual species typically diffuse and mix, dissipating their chemical potential gradients. However, we use model lattice simulations to show that single-file molecular-sized channels (such biomembrane channels and zeolites) can exhibit diffusional pumping, where one type of particle uses its entropy of mixing to drive another up its chemical potential gradient. Quantitative analyses of rates and efficiencies of transport are plotted as functions of transmembrane potential, pore length, and particle-pore interactions. Our results qualitatively explain recent measurements of ``negative'' osmosis and suggest new, more systematic experiments, particularly in zeolite transport systems.