Salt-Excluding Artificial Water Channels Exhibiting Enhanced Dipolar Water and Proton Translocation

• Published in: Journal of the American Chemical Society Vol. 138; no. 16; pp. 5403 - 5409
• Main Authors: Licsandru, Erol, Kocsis, Istvan, Shen, Yue-xiao, Murail, Samuel, Legrand, Yves-Marie, van der Lee, Arie, Tsai, Daniel, Baaden, Marc, Kumar, Manish, Barboiu, Mihail
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.04.2016
• Subjects: Chemical Sciences; CHIRAL RECOGNITION; MOLECULES
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.6b01811

Aquaporins (AQPs) are biological water channels known for fast water transport (∼108–109 molecules/s/channel) with ion exclusion. Few synthetic channels have been designed to mimic this high water permeability, and none reject ions at a significant level. Selective water translocation has previously been shown to depend on water-wires spanning the AQP pore that reverse their orientation, combined with correlated channel motions. No quantitative correlation between the dipolar orientation of the water-wires and their effects on water and proton translocation has been reported. Here, we use complementary X-ray structural data, bilayer transport experiments, and molecular dynamics (MD) simulations to gain key insights and quantify transport. We report artificial imidazole-quartet water channels with 2.6 Å pores, similar to AQP channels, that encapsulate oriented dipolar water-wires in a confined chiral conduit. These channels are able to transport ∼106 water molecules/s, which is within 2 orders of magnitude of AQPs’ rates, and reject all ions except protons. The proton conductance is high (∼5 H+/s/channel) and approximately half that of the M2 proton channel at neutral pH. Chirality is a key feature influencing channel efficiency.