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          1.D.291.  The Artificial Water Channel (AWC) Family  

Aquaporins (AQPs) selectively transport water across cell membranes. Heterogeneous H-bonding of water with the inner wall of AQP pores is imporant for optimal stabilization of water clusters within channels, leading to selective water transport against ions. Simpler artificial water channels (AWCs) have been developed. Several H-bonding motifs (i.e., imidazole, polyhydroxy, etc.) have been reported as distinct and efficient for water-cluster stabilization within AWCs. Huang et al. 2024 combined two pyridine-2,6 dicarboxamide and imidazole to conceive multivalent U-shaped AWCs able to stabilize, like in AQP water clusters via different H-bonding groups. The crystal structures reveal that stable water superstructures are formed in the solid state, one with hydrophilic pores of ∼9 Å diameter, accommodating water clusters, and one with sterically hindered hydrophobic channels of ∼3 Å diameter, stabilizing water wires. As a result, a single-channel permeability of 1.2 × 107 H2O/s/channel has been achieved by the U-channels, which is only 1 order of magnitude lower than that of AQPs. U-channels perform proton transport and completely reject anions and potentially can be applied in desalination membranes. Molecular simulation confirmed that U-channels can generate stable supramolecular porous sponges when they are decorated with hydrophobic alkyl chains featuring multivalent water H-bonding units that serve as water-cluster relays within the channel. This is a rare biomimetic example of the importance of water-cluster stabilization via multivalent H-bonding and toward selective transport through water channels.

References associated with 1.D.291 family:

Huang, L.B., D.D. Su, A. Hardiagon, I. Kocsis, A. van der Lee, F. Sterpone, M. Baaden, and M. Barboiu. (2024). Water-Pore Flow Permeation through Multivalent H-Bonding Pyridine-2,6-dicarboxamide-histamine/Histidine Water Channels. J. Am. Chem. Soc. [Epub: Ahead of Print] 39680597