Sulfur-Containing Foldamer-Based Artificial Lithium Channels.

Unlike many other biologically relevant ions (Na+, K+, Ca2+, Cl-, etc) and protons, whose cellular concentrations are closely regulated by highly selective channel proteins, Li+ ion is unusual in that its concentration is well tolerated over many orders of magnitude and that no lithium-specific channel proteins have so far been identified. While one naturally evolved primary pathway for lithium ions to traverse across the cell membrane is through sodium channels by competing with sodium ions, highly sought-after artificial lithium-transporting channels remain a major challenge to develop. Here we show that sulfur-containing organic nanotubes derived from intramolecularly H-bonded helically folded aromatic foldamers of 3.6 Å in hollow cavity diameter could facilitate highly selective and efficient transmembrane transport of Li+ ions, with high transport selectivity factors of 14.9 and 18.4 over Na+ and K+ ions, respectively.