Molecular Swings as Highly Active Ion Transporters

Ions are transported across membrane mostly via carrier or channel mechanisms. Herein, a unique class of molecular-machine-inspired membrane transporters, termed molecular swings is reported that utilize a previously unexplored swing mechanism for promoting ion transport in a highly efficient manner. In particular, the molecular swing, which carries a 15-crown-5 unit as the ion-binding and transporting unit, exhibits extremely high ion-transport activities with EC₅₀ values of 46 nm (a channel:lipid molar ratio of 1:4800 or 0.021 mol % relative to lipid) and 110 nm for K⁺ and Na⁺ ions, respectively. Remarkably, such ion transport activities remain high in a cholesterol-rich environment, with EC₅₀ values of 130 (0.045 mol % relative to lipid/cholesterol) and 326 nm for K⁺ and Na⁺ ions, respectively.