ARTIFICIAL ION CHANNELS OF AMPHIPHILIC ION-PAIRS COMPOSED OF OLIGOETHER-AMMONIUM AND HYDROPHOBIC CARBOXYLATE OR PHOSPHATES

,10,15,20-Tetraoxa-tetracosane-1-trimethylammonium cation was paired w ith anions from stearic acid, dioctadecyl phosphate, L-alpha-phosphati dic acid and cardiolipin to afford membrane-insertable amphiphilic ion pairs. These ion pairs were incorporated into planar lipid bilayer me mbranes to observe single ion channel currents. The ion pair with L-al pha-phosphatidic acid gave the most stable single ion channel currents with cation selectivity. An ion pair with dioctadecyl phosphate also gave a cation selective supramolecular ion channel. Even the stearate pair afforded single ion channel currents, although the cardiolipin di d not give any sign of ion channel formation. These examples provide a dditional support for supramolecular ion channel formation from simple amphiphilic ion pairs. Among these supramolecular ion channels, only the pair with phosphatidic acid afforded a voltage dependent supramole cular ion channel. The combined evidence strongly suggests that the vo ltage dependence results simply from the incorporation of charges into the membrane phase. (C) 1998 Elsevier Science S.A. All rights reserve d.