Single-Molecular Artificial Transmembrane Water Channels

Abstract

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.

Highly permeable artificial water channels that can self-assemble into two-dimensional arrays

“…1) (30) as an excellent architecture for artificial water channels, and we present data for their single-channel permeability and selfassembly properties. Nonpeptide pillar [5]arene derivatives were among first-generation artificial water channels (1,23). Pillar [5]arene derivatives, including the one used in this study, have a pore of ∼5 Å in diameter and are excellent templates for functionalization into tubular structures (31)(32)(33)(34).…”

“…We addressed the challenges of accurately measuring single-channel water permeability and improving the water conduction rate over first-generation artificial water channels by using both experimental and simulation approaches. The presented PAP channel contains more hydrophobic regions (30) compared with its predecessor channel (23), which improves both its water permeability and its ability to insert into membranes. To determine single-channel permeability of PAPs, we combined stopped-flow light-scattering measurements of lipid vesicles containing PAPs with fluorescence correlation spectroscopy (FCS) (35,36).…”

“…However, two fundamental questions remain: (i) Can artificial channels approach the permeability and selectivity of AQP water channels? (ii) How can such artificial channels be packaged into materials with morphologies suitable for engineering applications?Because of the challenges in accurately replicating the functional elements of channel proteins, the water permeability and selectivity of first-generation artificial water channels were far below those of AQPs (SI Appendix, Table S1) (20)(21)(22)(23)(24)(25). In some cases, the conduction rate for water was much lower than that of AQPs as a result of excess hydrogen bonds being formed between the water molecules and oxygen atoms lining the channel (20).…”

“…Thus, there is a critical need for a method to accurately measure single-channel permeability of artificial water channels to allow for accurate comparison with those of biological water channels. Furthermore, first-generation artificial water channels were designed with a focus on demonstrating water conduction and one-dimensional assembly into tubular structures (20)(21)(22)(23)(24), but how the channels could be assembled…”

New Synthetic Host Pillararenes: Their Synthesis and Application to Supramolecular Materials

“…Hou et al developed a new class of artificial transmembrane proton channels from mono-and dimeric pillar [5]arenes and hydrazide-incorporated pillar [5]arenes. 64,99 These pillar [5]arene derivatives can function as single-molecular channels to transport water across the lipid membrane. We reported a thermoresponsive macromolecule consisting of 10 outer triethylene oxide groups and a pillar [5]arene core 52.…”