Planar lipid bilayers containing gramicidin A as a molecular sensing system based on an integrated current.

The channel activity of gramicidin A in free-standing planar lipid bilayers with different charges of polar head groups and various lengths of hydrocarbon tails were analyzed in terms of the channel conductance, the lifetime of channel events and the magnitude of integrated currents. The channel activity of gramicidin A in lipid bilayers is tunable by adjusting the membrane composition. The in situ coupling of the anti-BSA antibody as a model protein to the amine moiety of phosphatidylethanolamine (PE) in a lipid bilayer by the amine coupling method allowed us to design an antigen (BSA)-sensitive interface, in which the integrated current, rather than the frequency of channel event, can be used as an analytical signal. The potential of the present system for highly sensitive and selective detection of BSA at 10(-9) g/mL level is demonstrated.