ARTIFICIAL NONPEPTIDE SINGLE ION CHANNELS

We report the synthesis of amphiphilic molecules composed of glycolate ethers of monoalkyloligo(1,4-butylene glycol) complexed with dioctadecyldimethylammonium cation. When inserted into a bilayer lipid membrane, these molecules exhibited several properties characteristic of single ion channels. Stable and constant conductance levels were observed, with transitions between open and closed states at a millisecond to second range. The conductance levels were on the order of 10(1)-10(3) pS, and the channels were classified into three types on the basis of their conductances and gating properties. The channels were cation selective over anion by a factor of approximately 5. In channels having the largest conductance, reversible and repeatable inactivation occurred with transmembrane voltages greater than 70 mV, while the other types of channels did not show voltage-dependent gating. We tentatively interpret these single ion channel properties to result from the formation of a molecular aggregate wherein the polar oligoether-carboxylates are covered with the hydrophobic alkyl groups of the ammonium in the bilayer membrane.