The biological ion channel gramicidin A (gA) was modified by synthetic means to obtain the tail-to-tail linked asymmetric gA-derived dimer com-pound3. Single-channel current measurements for 3in planar lipid bilayers exhibit an Eisenman I ion selectivity for alkali cations. The structural asymmetry does not lead to an observable functional asymmetry. The structure of 3in solution without and with Cs cations was investigated by 1 H-NMR spectroscopy. In CDCl3 ⁄CD3OH (1 : 1, v⁄v),3forms a mixture of double-strandedb-helices
