Photogating of ionic currents across the lipid bilayer

The ionic currents of positive and negative hydrophobic ions across a ~7-nm-thick lipid bilayer are gated by photoformation of metalloporphyrin cations in the ester region of the bilayer by electron transfer to aqueous acceptors. At low concentrations of the hydrophobic ions there is a 30% change in the conductivity upon photocharging the membrane. The conductivity decreases with increasing concentration of tetraphenylphosphonium cations (TPhP⁺) and increases greatly with increasing concentration of tetraphenylboride anions (TPhB^- ). The observed photogating of hydrophobic ion currents is attributed to space charge effects in the bilayer