In the presence of CCCP, transport experiments can identify whether there is a Cl -> H + selectivity in the transport process. An increase in the rate of transport in the presence of CCCP indicates that the transport of protons is the rate-limiting step. An acceleration in pH dissipation was not observed for compounds 1-10 in the presence of CCCP and, in some cases, a decrease in the rate of transport was observed (Figure ). To couple to CCCP, a transporter must be able to facilitate electrogenic chloride uniport. These results are further evidence that the acridinone-based compounds do not facilitate transport by this mechanism. Subsequently, the vesicles were treated with bovine serum albumin (BSA) and stirred vigorously for three hours to remove trace fatty acids from the lipid bilayer. Transport experiments were repeated, and a decrease in the rate of pH dissipation compared to the non-treated vesicles was observed in all cases (Figure ). The decrease in the rate of pH dissipation in the absence of membrane fatty acids suggest that the transporters facilitate a fatty acid-dependent pH dissipation pathway. Fatty acids deprotonate to release protons into the extravesicular solution and then a transporter molecule can bind to the carboxylate headgroup to mediate its transport through the bilayer to the vesicle interior. The carboxylate is then reprotonated by the intravesicular solution and can flip back to the vesicle exterior as a neutral species, thereby completing the H + transport cycle.