Artificial Ion Channel Formed by Cucurbit[n]uril Derivatives with a Carbonyl Group Fringed Portal Reminiscent of the Selectivity Filter of K+ Channels

摘要: Novel artificial ion channels (1 and 2) based on CB[n] (n = 6 5, respectively) synthetic receptors with carbonyl-fringed portals (diameter 3.9 2.4 A, can transport proton alkali metal ions across a lipid membrane selectivity. Fluorometric experiments using large unilamellar vesicles showed that 1 mediates the membranes, which be blocked by neurotransmitter, acetylcholine, reminiscent of blocking K+ polyamines. The activity follows order Li+ > Cs+ approximately Rb+ Na+, is opposite to binding affinity CB[6] toward ions. On other hand, 2 also these ions, but virtually no was observed for K+, Rb+, Cs+. It presumably because portal size A) smaller than diameters To determine mechanism, voltage-clamp planar bilayer membranes were carried out. single-channel current 5 pA, corresponds an flux 3 x 107 ions/s. These results are consistent channel mechanism. Not only structural resemblance selectivity filter remarkable makes this model system unique.