The Adjusted HPTS Transport Assay The adjusted HPTS assay uses synthetic EYPC vesicles that are made in the same way as those used for the HPTS transport selectivity assay, apart from being made from EYPC rather than POPC, 100 nm in size instead of 200 nm, and the intra-and extra-vesicular solutions were buffered to pH 7.2 instead of pH 7.0. The modified assay also used a single excitation wavelength at 450 nm to excite the pH-sensitive fluorescent HPTS probe and recorded fluorescence emission data at a wavelength of 510 nm, instead of a dual excitation wavelength. Also, compared to the 30 s leakage check performed for the HPTS transport selectivity assay, the modified assay performs a 100 s leakage check after the NaOH base pulse was added. At t = 100 s, the transporters were then added as DMSO solutions, with each transport experiment continuing for a further 200 s, after which vesicle lysis occurred to record the 100% Cl -efflux value for data normalisation. The data collection of each transport experiment was stopped at t = 270 s, and the fluorescence data was normalised to the 100% fluorescence emission value before being fitted to the Hill equation (Equation ) to derive Hill coefficients and EC50 values.