Aminocyclodextrin Ion Channels: Development of a Model for Ligand Gating and Investigations of the Effects of Channel Structure on *Transport Properties and Ion Selectivity

Abstract

While it was previously shown that a heptaaminopentabutylene glycol beta-cyclodextrin ion channel was highly active and selectively transported anions, the requirements for the number of aminopentabutylene glycol substitutions were not known. beta-Cyclodextrin channels with four and two aminopentabutylene glycol chains and beta-cyclodextrins substituted with a glycine-pentabutylene glycol conjugate were synthesized. Their ion transport properties were assessed with a fluorescence assay using the pH sensitive dye HPTS. The amino acid containing channel showed little activity, while the di- and tetraamino channels showed increasing activity with increasing substitution. The tetraamino channel showed selectivity for anion transport that followed the trend ClO4- > I- > NO3- > Br- > Cl-. The preferences for ClO4-, I-, NO3-, and Br- transport were roughly 32, 16, 7, and 2 times that of Na+, respectively. The rate of transport of Cl- was roughly equivalent to the rate of Na + transport.