Nature-inspired synthetic oligourea foldamer channels allow water transport with high salt rejection

Biomimetic membranes incorporating artificial water channels (AWCs) are being developed for industrial water purification. Designing AWCs to achieve high water permeation with salt rejection is a challenge. We designed and synthesized oligourea foldamers, which form predictable helical structures that can be used to create biomimetic porin-like architectures. Two of these foldamers (H2OC1 and H2OC2) allow superior water permeability and almost total salt rejection across lipid membranes. Solid-state NMR, cryo-EM, and molecular dynamics analyses suggest proper insertion of foldamers into lipid vesicles. The H2OC1 crystal structure shows hydrophilic pores of diameters 4.8 and 6.4 A. The oligourea helices pack together by hydrophobic and salt bridge interactions to build two channel-like assemblies. Besides their proteolytic stability and microbial resistance, the sequence of foldamers can be tailored to regulate selectivity. The ease of designing, synthesizing, and purifying oligourea foldamers is an added advantage. Our findings can help to develop novel AWCs for water purification applications.