The Flip-Flop Diffusion Mechanism across Lipids in a Hybrid Bilayer Membrane

Christopher J. Barile, Edmund C.M. Tse, Ying Li, John P. Gewargis, Nicholas A. Kirchschlager, Steven C. Zimmerman, Andrew A. Gewirth

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


In this study, we examine the mechanism of flip-flop diffusion of proton carriers across the lipid layer of a hybrid bilayer membrane (HBM). The HBM consists of a lipid monolayer appended on top of a self-assembled monolayer containing a Cu-based O2 reduction catalyst on a Au electrode. The flip-flop diffusion rates of the proton carriers dictate the kinetics of O2 reduction by the electrocatalyst. By varying both the tail lengths of the proton carriers and the lipids, we find the combinations of lengths that maximize the flip-flop diffusion rate. These experimental results combined with biophysical modeling studies allow us to propose a detailed mechanism for transmembrane flip-flop diffusion in HBM systems, which involves the bending of the alkyl tail of the proton carrier as the rate-determining step. Additional studies with an unbendable proton carrier further validate these mechanistic findings.

Original languageEnglish
Pages (from-to)2451-2462
Number of pages12
JournalBiophysical Journal
Issue number11
StatePublished - 7 Jun 2016
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics


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