Ligand‐Gated Synthetic Ion Channels

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Abstract
Supramolecular π-stack architecture is fundamental in DNA chemistry but absent in biological and synthetic ion channels and pores. Here, a novel rigid-rod π-stack architecture is introduced to create synthetic ion channels with characteristics that are at the forefront of rational design, that is, ligand gating by a conformational change of the functional supramolecule. Namely, the intercalation of electron-rich aromatics is designed to untwist inactive electron-poor helical π-stacks without internal space into open barrel-stave ion channels. Conductance experiments in planar lipid bilayers corroborate results from spherical bilayers and molecular modeling: Highly cooperative and highly selective ligand gating produces small, long-lived, weakly anion selective, ohmic ion channels. Structural studies conducted under conditions relevant for function provide experimental support for helix–barrel transition as origin of ligand gating. Control experiments demonstrate that minor structural changes leading to internal decrowding suffice to cleanly annihilate chiral self-organization and function.