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

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.