Immobilizing channel molecules in artificial lipid bilayers for simultaneous electrical and optical single channel recordings

There has been much interest in imaging single drug bindings to ion channel proteins while simultaneously recording single channel current. We developed an experimental apparatus for simultaneous optical and electrical measurement of single channel proteins by combining the single molecule imaging technique and the artificial bilayer technique. However, one major problem is that single molecule imaging of drug bindings is limited by the innate thermal diffusion of channel proteins in the artificial bilayer. Therefore, immobilizing channel proteins in the bilayers is imperative for stable measurements of channel-drug interactions. For future studies on channel-drug interactions, we describe here three different methods for simultaneous optical and electrical observation of single channels in which channel proteins are immobilized. (i) Membrane binding protein annexin V reduces the lateral diffusion of single channel proteins in a concentration-dependent manner. (ii) Channel proteins are immobilized by anchorage through a polyethylene glycol (PEG) molecule to the glass substrate. (iii) Channels immobilized on a gel bead can be directly incorporated into artificial bilayers.