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Foldamer-based ultrapermeable and highly selective artificial water channels that exclude protons

Abstract

The outstanding capacity of aquaporins (AQPs) for mediating highly selective superfast water transport1,2,3,4,5,6,7 has inspired recent development of supramolecular monovalent ion-excluding artificial water channels (AWCs). AWC-based bioinspired membranes are proposed for desalination, water purification and other separation applications8,9,10,11,12,13,14,15,16,17,18. While some recent progress has been made in synthesizing AWCs that approach the water permeability and ion selectivity of AQPs, a hallmark feature of AQPs—high water transport while excluding protons—has not been reproduced. We report a class of biomimetic, helically folded pore-forming polymeric foldamers that can serve as long-sought-after highly selective ultrafast water-conducting channels with performance exceeding those of AQPs (1.1 × 1010 water molecules per second for AQP1), with high water-over-monovalent-ion transport selectivity (~108 water molecules over Cl ion) conferred by the modularly tunable hydrophobicity of the interior pore surface. The best-performing AWC reported here delivers water transport at an exceptionally high rate, namely, 2.5 times that of AQP1, while concurrently rejecting salts (NaCl and KCl) and even protons.

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Fig. 1: Molecular design and synthesis of foldamer-derived polymer-based synthetic water channels.
Fig. 2: Selective water permeation through foldamer-based polymeric AWCs.
Fig. 3: MD simulations of water transport and mechanism of proton rejection by proton wire breakers created due to presence of fluctuating alkyl groups.

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Data availability

The datasets that support the finding of this study are available in figshare repository with the identifier(s) https://figshare.com/s/0354959049b2c0ed4c61. Source data are provided with this paper.

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Acknowledgements

This study was supported by the Institute of Advanced Synthesis, Northwestern Polytechnical University, China; NanoBio Lab (Biomedical Research Council, Agency for Science, Technology and Research, Singapore); the Singapore National Research Foundation under its Environment and Water Research Programme and administered by PUB; the National Science Foundation (USA) under grant no. DMR-1827346; and the National Institutes of Health under grant no. P41-GM104601. The work in M.K.’s lab was supported by the US National Science Foundation under grant nos. CBET 1946392 and CBET 1952295. Supercomputer time was provided through the Early Allocation grant on Frontera (FTA-Chemla), XSEDE Allocation grant no. MCA05S028 and the Blue Waters petascale supercomputer system at the University of Illinois at Urbana–Champaign.

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Authors and Affiliations

Authors

Contributions

A.R. synthesized polymers 3 and 5 and conducted the water/ion transport study. J.S. synthesized polymer 4 and conducted the water/ion transport study. H.J. and A.A. performed the MD study. W.S., Y.-M.T. and M.K. determined water-over-chloride selectivity and proton transport rates. R.C. and M.K. conducted analysis of proton exclusion simulations. R.Y., N.L. and C.R. performed some ion transport studies. H.Z. conceived the project and wrote the manuscript with inputs from A.R. and M.K. All the authors edited the manuscript.

Corresponding author

Correspondence to Huaqiang Zeng.

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The authors declare no competing interests.

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Peer review information Nature Nanotechnology thanks the anonymous reviewers for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Experimental procedure, Supplementary Schemes 1–3, Tables 1–3, Figs. 1–19 and 1H/13C NMR spectra.

Supplementary Video 1

MD-generated video illustrating how water gets transported across the hollow cavity of channel 3.

Supplementary Video 2

MD-generated video illustrating how water gets transported across the hollow cavity of channel 4.

Supplementary Video 3

MD-generated video illustrating how water gets transported across the hollow cavity of channel 5.

Source data

Source Data Fig. 2

Original data in Excel format.

Source Data Fig. 3

Original data in Excel format.

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Roy, A., Shen, J., Joshi, H. et al. Foldamer-based ultrapermeable and highly selective artificial water channels that exclude protons. Nat. Nanotechnol. 16, 911–917 (2021). https://doi.org/10.1038/s41565-021-00915-2

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