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Updated: Aug 19, 2026

Lipid-Protein Membrane Structure-Function Characterization using Droplet Interface Bilayers
Published on: June 12, 2026
Protons may leak through pure lipid bilayers via a concerted mechanism
Harald L Tepper1, Gregory A Voth
1Center for Biophysical Modeling and Simulation, and Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, USA.
Abstract:
Protons are known to permeate pure lipid bilayers at a rate that is anomalous compared to those of other small monovalent cations. The prevailing mechanism via which they cross the membrane is still unclear, and it is unknown how to probe the mechanism directly by experiment. One of the more popular theories assumes the formation of membrane-spanning single-file water wires providing a matrix along which the protons can "hop" over the barrier. However, free energy calculations on such structures (without the presence of an excess proton) suggest that this mechanism alone cannot account for the observed permeation rates. We use the multistate empirical valence bond method to directly study water structures surrounding a (delocalized) excess proton on its way through the membrane. We find that membrane-spanning networks, rather than single-file chains, are formed around the proton. We also find that such structures are considerably stabilized in the presence of the proton, with lifetimes of several hundreds of picoseconds. The observed structures are suggestive of a new, concerted, mechanism and provide some direction for further investigation.
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