LUVs with a diameter of approximately 180 nm (Figure ) were prepared from 1-palmitoyl-2-oleoylsn-glycero-3-phosphocholine (POPC) with the BUs preincorporated in the membranes at a concentration of 0.02 mol% with regard to the total lipid amount. The first series of experiments was performed without cholesterol in the membranes, after which the anion transport experiments were repeated with 30% cholesterol (vide infra). LUVs containing encapsulated lucigenin were dispersed in a NaHCO3 solution (225 mM interior and exterior) and the experiment was initiated by adding a NaCl solution (25 mM) to the LUV exterior to establish a chloride gradient. A quenching of the fluorescence of lucigenin over time can be observed, which is due to the transport of chloride anions into the LUVs (Figure ). For quantification of the obtained transport data, they were plotted as the inverse of the normalised curves (F0/F, see the ESI Figure ) which corresponds to the chloride concentrations inside the LUVs. The plotted curves were analysed using single and double exponential functions to obtain rate constants and initial transport rates, respectively (Table and Figure ). The results from the competition studies described above were used for the visual categorisation of the Cl -affinities of the BUs in the left panel of Figure , ranging from the weakest (light blue colour) in binding to the strongest ones (purple colour).