A biosensor that depends upon the alignment of ion half-channels embedded in the immobile inner and the fluid outer leaflets of a lipid bilayer to permit the flux of ions (e.g. monovalent cations through gramicidin channels) across a bilayer which coats and electronically insulates an ion-sensitive electrode. This ion flux is interrupted when alignment of half-channels is prevented because the outer leaflet half-channel is tethered to a bilayer-spanning lipid molecule anchored in the inner leaflet and projects through the outer leaflet where it is linked to an Fab fragment which binds the antigenic anylate, and via a second Fab fragment is fixed to the outer leaflet half-channel. Thus, the anylate prevents sliding of the outer leaflet over the inner leaflet, which is observed as an attenuation of ion flux sensed by the electrode. Alternatively, smaller, less immunogenic anylate molecules may be detected by their competition with an antigen which links the two Fab fragments, and the presence of such molecules would be observed by an increase in ion flux.