Foldamer-mediated transport across phospholipid bilayers.

Crucial physiological processes, like neural communication and muscle contraction, are mediated by protein channels in cell membranes. These natural channels typically have a central hydrophilic pore with tightly defined dimensions, which can be opened or closed ('gated') by external stimuli. Mimicking natural ion channels using synthetic molecules is a long-standing goal in artificial channel research. Although current synthetic channels have not yet achieved the same combination of high activity, high selectivity, and gating as natural channels, foldamers offer a new approach. Foldamers are unnatural oligomers that fold into defined three-dimensional shapes, similar to the way that natural polypeptides fold into secondary structures. With defined shapes and often multi-nanometre dimensions, foldamers have become valuable tools to mimic the behaviour of natural proteins in membranes. This review highlights selected recent examples of foldamer channels, examples that indicate how foldamer architectures may lead to controllable channels with high activity and selectivity.