An artificial lipid bilayer formed on an agarose-coated glass for simultaneous electrical and optical measurement of single ion channels

The purpose of this study is to develop an apparatus for simultaneous measurement of electrical and spectroscopic parameters of single ion channels. We have combined the single channel recording apparatus with an artificial lipid bilayer and a fluorescence microscope designed to detect single fluorescent molecules. The artificial membranes were formed on an agarose-coated glass and observed with an objective-type total internal reflection fluorescence microscope (TIRFM). The lateral motion of a single lipid molecule (β-BODIPY 530/550 HPC) was recorded. The lateral diffusion constant of the lipid molecule was calculated from the trajectories of single molecules as D = 8.5 ± 4.9 x 10^-8 cm²/s. Ionic channels were incorporated into the membrane and current fluctuations were recorded at the single-channel level. After incorporation of Cy3-labeled alametithin molecules into the membrane, bright spots were observed moving rather slowly (D = 4.0 ± 1.6 x 10^-8 cm²/s) in the membrane, simultaneously with the alametithin-channel current. These data show the possibility of the present technique for simultaneous measurement of electrical and spectroscopic parameters of single-channel activities.