Transmembrane ion channels constructed of cholic acid derivatives.
A new class of supramolecular transmembrane ion channels was prepared by linking two amphiphilic cholic acid methyl ethers through biscarbamate bonds to afford bis(7,12-dimethyl-24-carboxy-3-cholanyl)-N,N'-xylylene dicarbamate 2 and bis[7,12-dimethyl-24-(N,N,N-trimethylethanaminium-2-carboxylate)-3-cholanyl]-N,N'-xylylene dicarbamate dichloride 3. When incorporated into a planar bilayer membrane, both compounds showed stable (lasting 10 ms to 10 s) single ion channel currents. Only limited numbers of relatively small conductances were characterized for these channels (5-20 pS for 2 and 5-10 pS for 3, 10 and 17 pS for 2, and 9 pS for 3 in particular). Both channels were cation selective, and permeability ratios of potassium cation to chloride anion were 17 and 7.9 for 2 and 3, respectively, reflecting the difference in ionic species of the headgroup. Both channels 2 and 3 showed significant potassium selectivity over sodium by a factor of 3.1 and 3.2, respectively. No Li(+) currents were observed for 2, showing sharp discrimination between Na(+) or K(+).
Kobuke
Y
Y
Graduate School of Materials Science, Nara Institute of Science and Technology, and CREST, Japan. kobuke@ms.aist-nara.ac.jp
Nagatani
T
T
D002264:Carboxylic Acids / Q000737:chemistry; D002793:Cholic Acids / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry*; D008567:Membranes, Artificial; D008670:Metals / Q000737:chemistry; D015221:Potassium Channels / Q000737:chemistry; D015222:Sodium Channels / Q000737:chemistry
D002264:Carboxylic Acids; D002793:Cholic Acids; D007473:Ion Channels; D008567:Membranes, Artificial; D008670:Metals; D015221:Potassium Channels; D015222:Sodium Channels