title: Asymmetric droplet interface bilayers.
abstract: In cell membranes, the lipid compositions of the inner and outer leaflets differ. Therefore, a robust model system that enables single-channel electrical recording with asymmetric bilayers would be very useful. We and others recently developed the droplet interface bilayer (DIB), which is formed by connecting lipid monolayer-encased aqueous droplets submerged in an oil-lipid mixture. Here, we incorporate lipid vesicles of different compositions into aqueous droplets and immerse them in an oil bath to form asymmetric DIBs (a-DIBs). Both alpha-helical and beta-barrel membrane proteins insert readily into a-DIBs, and their activity can be measured by single-channel electrical recording. We show that the gating behavior of outer membrane protein G (OmpG) from Escherichia coli differs depending on the side of insertion in an asymmetric DIB with a positively charged leaflet opposing a negatively charged leaflet. The a-DIB system provides a general platform for studying the effects of bilayer leaflet composition on the behavior of ion channels and pores.
authors.affiliation: Chemistry Research Laboratory, Department of Chemistry, University of Oxford, OX1 3TA, England, UK. william.hwang@chem.ox.ac.uk
authors.forename: William L
authors.initials: WL
authors.lastname: Hwang
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Bríd
authors.initials: B
authors.lastname: Cronin
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Holden
authors.forename: Hagan
authors.initials: H
authors.lastname: Bayley
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry; D007473:Ion Channels / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D018272:Porins / Q000737:chemistry; D012996:Solutions; D014867:Water / Q000737:chemistry*
chemical_list: D000473:Alkanes; D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D008051:Lipid Bilayers; D008055:Lipids; D008565:Membrane Proteins; C114347:OmpG protein, E coli; D018272:Porins; D012996:Solutions; D014867:Water; C007932:n-hexadecane