A gramicidin A derivative with a polyether linkage between both ethanolamine termini was synthesized and its ion channel properties were studied. The compound showed a duplication in the state of conductance for alkali cations in thick DOPC bilayer membranes, which is interpreted as the occurrence of twin-channels. In thinner DMPC membranes mono-channels were dominant. The influence of hydrophobic coupling on the mono channel/twin channel equilibrium is discussed. (C) 2005 Elsevier Inc. All rights reserved.