Chemical modification of a glass and fused silica
nanopore surfaces results in surface properties that are ideal for localized
bilayer formation over a
nanopore and subsequent
ion channel recording. With no
surface modification, one may form a
bilayer supported on the glass capillary extending across the
nanopore orifice. Changing the surface properties from that of bare glass to a moderately hydrophobic surface produces a lipid
monolayer above the glass and spontaneously yields a
bilayer across the nanopore orifice, effectively corralling a single
protein ion channel in the
lipid bilayer region spanning nanopore orifice. The bilayer structure over the modified nanopore is such that current can only flow through the
protein ion channel. The
protein ion channel is able to diffuse in the bilayer above the pore opening, but cannot leave this area to enter the lipid
monolayer. The bilayer formed across the nanopore orifice exhibits high
electrical breakdown voltage, is stable to mechanical vibrations, and is long lived. Resistance through the protein channel can be measured electrically and is exploited for stochastic single-molecule detection.
Protein ion channels can be inserted and removed from the bilayer by adjusting
transmembrane pressure, and adapter molecules can be electrostatically trapped in the
ion channel by applying high transmembrane voltages.