Structure-activity relationships in linear oligoester ion-channels

The ion transport activity of eighteen linear oligoesters was assessed using a quantitative fluorescence assay to monitor the collapse of a pH gradient across a vesicle bilayer membrane. Significant activity was associated with compounds that have extended lengths comparable to the thickness of the bilayer membrane, and with the most hydrophilic members of the compounds surveyed. Substantial differences in activity between constitutional isomers were also observed. The aggregation of active compounds in aqueous solution was detected by a pyrene fluorescence probe, and subsequently detected as a rate-limiting step in a sequential vesicle experiment.