1.D.246. The Crown Ether Macrocycle K+ Channel (CEM_K+C) Family
Yuan et al. 2024 reported and reviewed the characterization of crown ether macrocycles having multiple –OCH2CH2–ether repeating units. Crown ethers exhibit hydrophilic cavities due to the inward-facing O-atoms, with the outward-facing ethyl portions provide a lipophilic shell. The optimal polyether ring size for binding different alkali cations was systematically evaluated revealing a close correlation between ring size (hole) and ionic radius that 15-crown-5, 18-crown-6 and 21-crown-7 selectively favors Na+, K+, and Cs+, respectively. Both the unique amphiphilicity and binding selectivity make crown ethers a good ion-binding and -transporting motif for constructing APCs, and in some cases, selective recognition and transport of specific ions have been achieved.