A synthetic carboxylic ionophore with eight ether oxygens and five aromatic rings mediated selective K+ ion transport through a liquid membrane; the coiled carboxylate-encapsulated potassium ion is highly lipophilic. ... Naturally occurring carboxylate ionophores are known to mediate active ion transport through lipophilic biological membranes by formation of hydrophobic complexes with metal cations. The ionophores adopt a cyclic conformation by head-to-tail hydrogen ...