Hydrazide-appended pillar[5]arene derivatives have been synthesized. X-ray crystal structure analysis and (1)H NMR studies revealed that the molecules adopt unique tubular conformations. Inserting the molecules into the lipid membranes of vesicles leads to the transport of water through the channels produced by single molecules, as supported by dynamic light scattering and cryo-SEM experiments. The channels exhibit the transport activity at a very low channel to lipid ratio (0.027 mol %), and a water permeability of 8.6 × 10(-10) cm s(-1) is realized. In addition, like natural water channel proteins, the artificial systems also block the transport of protons.

Peptide-appended pillar[n]arene (n = 5, 6) derivatives have been synthesized. (1)H NMR and IR studies revealed that the molecules adopt a tubular conformation in solution and lipid bilayer membranes. Kinetic measurements using the fluorescent labeling method with lipid vesicles revealed that these molecules can efficiently mediate the transport of amino acids across lipid membranes at a very low channel-to-lipid ratio (EC(50) = 0.002 mol %). In several cases, chiral selectivity for amino acid enantiomers was achieved, which is one of the key functions of natural amino acid channels.

Lined up water molecules: Artificial transmembrane channels from pillar[5]arene monomeric and dimeric derivatives have been prepared. Single-channel conductance measurements and isotope effect experiments under acidic conditions showed selective proton transport through the channels, which were mediated by water wires formed in the pillar[5]arene backbones (see picture).

Aufgereihte Wassermoleküle: Künstliche transmembrane Kanäle aus monomeren und dimeren Pillar[5]aren‐Derivaten wurden hergestellt. Leitfähigkeitmessungen an einzelnen Kanälen und Experimente mit isotopenmarkierten Systemen im sauren Milieu offenbaren einen selektiven Protonentransfer durch die Kanäle, der durch „Wasserdrähte“ im Pillar[5]aren‐Rückgrat vermittelt wird (siehe Schema).

Sulfated titania solid superacids with dominant {001}, {001}/{101}, and {101} facets were prepared by the hydrothermal method and subsequent sulfation. Their facet-dependent acidic properties were investigated by the solid-state (31)P NMR technique and Pechmann condensation of 5,7-dihydroxy-4-methyl coumarin.