Figure 1.

(a) Depiction of pore geometries: lipids in an intact bilayer may be parted by thermal fluctuations to form a hydrophobic pore (1). At larger radii, these defects rearrange to a toroidal (hydrophilic) pore (2) in order to minimize exposure of the hydrophobic membrane interior to water. (b) Cartoon of the droplet-interface bilayer setup. A bilayer is formed through contact between a droplet and a planar agarose hydrogel, both incubated in lipid in hexadecane (C₁₆). The bilayer is interrogated electrically by a patch-clamp amplifier connected via electrodes in the droplet and the agarose, and optically by a totally internally reflected laser beam. See §2b–d for details. (c) Illustrative energy curves for the two pore geometries. A hydrophobic pore that surmounts the energy barrier (closed to open) will convert to a toroidal pore. The applied transmembrane potential lowers the pore free energy (increasing voltage from black to grey solid lines).