Before the transport experiment, a solution of anion transporter (anionophore) is added to the liposome suspension to post-insert the anionophore into the membrane. After that, a pulse of chloride solution is added to the exterior of liposomes resulting in a 25 mM exterior Cl -concentration, to create a gradient across the membrane. The dissipation of this gradient by the anionophore is monitored by measuring the decrease of fluorescence intensity over time, due to the quenching of the fluorescence of lucigenin by chloride (see Section 2). The advantages of the lucigenin assay are a great time resolution, versatility, and easy utilisation. Alternative experiments started with lucigenin encapsulated together with a high concentration of a quencher such as NaCl, and the increase of fluorescence intensity caused by the efflux of the quencher was monitored. Compared to the assay in Figure , such experiments would in principle give a poorer signal-to-noise ratio, are more difficult to quantify, and do not allow to test transport of nondeliverable transporters.