A single-channel sensor based on gramicidin controlled by molecular recognition at bilayer lipid membranes containing receptor

A novel ion-channel sensor based on a membrane bound receptor and a single gramicidin channel is described, in which the binding of an analyte to the membrane bound receptor modulates the single-channel activity of gramicidin. The sensor is composed of a planar bilayer lipid membrane (BLM) containing biotin-labeled phosphatidylethanolamine as receptor for avidin and gramicidin as signal transducer. When the receptor catches an analyte (avidin or ferritin-labeled avidin (FA)) at the membrane surface, the bilayer structure is locally distorted and the gramicidin monomer/dimer kinetics is modulated in a manner that the fraction of channel opening with a short lifetime (≦100 ms) to the total opening events increases. The fraction was found to increase with the concentration of avidin from 1.0×10^-9 to 1.0×10^-6 M and of FA from 1.0×10^-9 to 1.0×10^-8 M. With dinitrophenyl-labeled PE embedded as receptor in the BLM for monoclonal anti-dinitrophenyl antibody (anti-DNP), the fraction of channel openings (≦100 ms) increased with the concentration of anti-DNP from 2.0×10^-9 to 2.0×10^-7 g/ml. Bovine serum albumin (BSA) and anti-BSA antibody caused no changes in the channel opening. The possible mechanism of analyte-induced modulation of single-channel activity of gramicidin is also discussed.