Fig. . Determination of anion transport selectivity of 1 using an anion gradient (pH gradient induction) assay (a, c) and a pH gradient dissipation assay (b, d). In (c) purple line, efficient Cl -/I -exchange led to rapid dissipation of the initially induced pH gradient. Note that in (d) 1 was tested at a higher concentration because of the lowered transporter activity under the assay conditions (pH 8.0 outside). Error bars represent standard deviations from two runs.