Figure 6.

Evidence for transmembrane transport of sulfate. Unilamellar POPC vesicles were loaded with 100 mM NaCl and 2 mM lucigenin buffered to pH 7.2 with 20 mM sodium phosphate salts and dispersed in a 100 mM NaCl solution (buffered to pH 7.2). At t = 30 s, a solution of the appropriate anion was added (final concentration of 40 mM NaNO₃ (red), 40 mM Na₂SO₄ (green) or 40 mM NaCl (blue)). At t = 60 s, a methanol solution of the putative transporter was added (2% molar carrier to lipid). At the end of the experiment (240 s), detergent was added to lyse the vesicles. Each point represents the average of three trials. A blank experiment was performed by addition of Na₂SO₄, followed by addition of methanol; (a) compound 8. (b) compound 3.