Highly Selective Artificial K⁺ Channels: An Example of Selectivity-Induced Transmembrane Potential

Natural KcsA K⁺ channels conduct at high rates with an extraordinary selectivity for K⁺ cations, excluding the Na⁺ or other cations. Biomimetic artificial channels have been designed in order to mimick the ionic activity of KcSA channels, but simple artificial systems presenting high K⁺/Na⁺ selectivity are rare. Here we report an artificial ion channel of H-bonded hexyl-benzoureido-15-crown-5-ether, where K⁺ cations are highly preferred to Na⁺ cations. The K⁺-channel conductance is interpreted as arising in the formation of oligomeric highly cooperative channels, resulting in the cation-induced membrane polarization and enhanced transport rates without or under pH-active gradient. These channels are selectively responsive to the presence of K⁺ cations, even in the presence of a large excess of Na⁺. From the conceptual point of view, these channels express a synergistic adaptive behavior: the addition of the K⁺ cation drives the selection and the construction of constitutional polarized ion channels toward the selective conduction of the K⁺ cation that promotes their generation in the first place

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

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

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