Synthetic ion channels: functional analysis and structural studies.

Various synthetic ion channels were derived from the gramicidin A beta-helix-lead structure. The ion transport through these channels was studied by single-channel current measurements in planar lipid bilayers. For asymmetric THF-gramicidin hybrids a selective insertion into the phospholipid bilayer was observed. Ion-selectivity could be achieved by the use of synthetic cyclohexyl-ether amino acids as channel building blocks. The balance between the desolvation energy and the binding energy inside the channel is discussed. For minigramicidins, the hydrophobic coupling of the channel with membranes of different thickness was studied by dwelltime analysis. A conformational switch of a double stranded beta-helix into a single stranded beta-helix was observed upon addition of Cs(+)-ions.