2004/12/22 by Norman Packard, Norman H. Packard, Packard, Norman +3 · 1 citation
Biochemistry, Genetics and Molecular Biology · Chemistry · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #FOS: Physical sciences #Lipid Membrane Structure and Behavior #Statistical Mechanics (cond-mat.stat-mech) #cond-mat.stat-mech #thermodynamics and calorimetric analyses
paper · pdf · doi:10.48550/arxiv.cond-mat/0412626
17 pages, 8 figures v3: one additional figure, several additional references, conceptually unchanged
openalex publication_date 2004/12/22 · arxiv created 2005/09/14 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Diffusion rates through a membrane can be asymmetric, if the diffusing particles are spatially extended and the pores in the membrane have asymmetric structure. This phenomenon is demonstrated here via a deterministic simulation of a two-species hard-disk gas, and via simulations of two species in Brownian motion, diffusing through a membrane that is permeable to one species but not the other. In its extreme form, this effect will rapidly seal off flow in one direction through a membrane, while allowing free flow in the other direction. The system thus relaxes to disequilibrium, with very different densities of the permeable species on each side of the membrane. A single species of appropriately shaped particles will exhibit the same effect when diffusing through appropriately shaped pores. We hypothesize that purely geometric effects discussed here may play a role in common biological contexts such as membrane ion channels.