Reversible Ion Transportation Switch by a Ligand-Gated Synthetic Supramolecular Ion Channel

Abstract

Inspired by the regulation of cellular activities found in the ion channel proteins, here we developed membrane-embedded synthetic chiral receptors <b>1</b> and <b>2</b> with different terminal structures, where receptor <b>1</b> has hydrophobic triisopropylsilyl (TIPS) groups and receptor <b>2</b> has hydrophilic hydroxy groups. The receptors have ligand-binding units that interact with cationic amphiphiles such as 2-phenethylamine (PA). Conductance study revealed that the receptors hardly show ion transportation at the ligand-free state. After ligand binding involving a conformational change, receptor <b>1</b> bearing TIPS termini displays a significant current enhancement due to ion transportation. The current substantially diminishes upon addition of β-cyclodextrin (βCD) that scavenges the ligand from the receptor. Importantly, the receptor again turns into the conductive state by the second addition of PA, and the activation/deactivation of the ion transportation can be repeated. In contrast, receptor <b>2</b> bearing the hydroxy terminal groups hardly exhibits ion transportation, suggesting the importance of terminal TIPS groups of <b>1</b> that likely anchor the receptor in the membrane