Columnar Self-Assemblies of Triarylamines as Scaffolds for Artificial Biomimetic Channels for Ion and for Water Transport

Abstract

Triarylamine molecules appended with crown-ethers or carboxylic moieties form self-assembled supramolecular channels within lipid bilayers. Fluorescence assays and voltage clamp studies reveal that the self-assemblies incorporating the crown ethers work as single channels for the selective transport of K⁺ or Rb⁺. The X-ray crystallographic structures confirm the mutual columnar self-assembly of triarylamines and crown-ethers. The dimensional fit of K⁺ cations within the 18-crown-6 leads to a partial dehydration and to the formation of alternating K⁺ cation-water wires within the channel. This original type of organization may be regarded as a biomimetic alternative of columnar K⁺-water wires observed for the natural KcsA channel. Supramolecular columnar arrangement was also shown for the triarylamine-carboxylic acid conjugate. In this latter case, stopped-flow light scattering analysis reveals the transport of water across lipid bilayer membranes with a relative water permeability as high as 17 μm s^-1.