Catechols as membrane anion transporters.

We report that an amphiphilic bis-catechol (3) functions as a transmembrane anion transporter. Activity depends on the catechol's substitution and amphiphilicity. We also describe a liposomal assay that allows one to readily measure anion transport selectivity. This assay reveals that anion transport selectivity for this amphiphilic bis-catechol follows a Hofmeister sequence wherein anions that are easier to dehydrate are made more permeable to the membrane by 3.