An initial attempt to study Cl -/HCO3 -antiport by 1 in these liposomes was unsuccessful as the runs in absence of 1 revealed significant leakage of lucigenin through the membrane, making these experiments unreliable. Therefore, we have switched to measuring Cl -/NO3 -antiport activity of 1 using N,N'-bis(3-sulfonatopropyl)-9,9'-biacridinium (SPBA), a more hydrophilic analogue of lucigenin, as fluorescence probe. The experiments were conducted in a homologous series of PCs (with 14:1, 16:1, 18:1, 20:1 and 22:1 acyl chains), in LUVs made of PC/cholesterol 7:3 (Figure ). It was observed that in the LUVs with the thinnest membrane (14:1 PC, light blue curve) the transport is the fastest, while it became slightly slower in the LUVs made of 16:1 and 18:1 PC (red and green curves, respectively). Interestingly, transport completely stopped in LUVs with thicker membranes (20:1 and 22:1 PC; orange and blue curves, respectively). This finding could suggest channel-like behaviour for 1, which is, however, unlikely based on the inactivity of 1 in LUVs made of DPPC at temperatures below the DPPC transition temperature. Our trend found for 1 is different from the results obtained for cholapod anion transporters, for which a steady decrease of the transport rates with increasing PC acyl chain lengths was observed. A decrease in the transport rate with increasing membrane thickness was also observed for anion transport relays. However, it should be noted that the mechanism of transport by these relays is different from the one by BUs.