Entropy-Driven Pumping in Zeolites and Biological Channels

We simulate constrained dynamics of two species transport across single-file molecular-sized pores such as biomembrane channels and zeolites. We focus on diffusional pumping where one type of particle uses its entropy of mixing to drive another along 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 with zeolites.