Selective transport of potassium ions across a planar phospholipid bilayer by a calix[4]arene-crown-5 as a synthetic carrier

摘要

The ion transport ability in a planar phospholipid bilayer, of two p-tert-butylcalix[4]arene-crown-5 derivatives (1, 2),na p-tert-butylcalix[5]arene ester 3, dibenzo-18-crown-6, and valinomycin have been investigated using a voltage clampnmethod. Membrane current measurements showed that the synthetic calixarene ionophores except for dibenzo-18-ncrown-6, show ion transport activities for Ku0001 in the bilayer membranes. The order of Ku0001 transport activities of thencompounds was valinomycin >1 > 3 > 2. From the measurements of reversal potentials, the relative ion permeabilitynacross the bilayer was determined for 1, 3 and valinomycin. Both 1 and 3 showed ion transport selectivity for Ku0001,nwhile valinomycin showed ion transport selectivity for Rbu0001. Among the calixarene ionophores, compound 1 showednthe highest Ku0001 conductivity and Ku0001/Nau0001 selectivity. Although the Ku0001/Nau0001 selectivity of 1 is less than that ofnvalinomycin by a factor of ca. 2, calix[4]arene-based ionophore 1 has the potential for use as a synthetic Ku0001 carriernin phospholipid bilayer membranes.