Fig. 1.

ATP-induced changes in intrinsic fluorescence of the isomolar NBD1/NBD2 mixture in solution. a Fluorescence spectra of the NBD1/NBD2 mixture measured at different ATP concentrations. Extreme concentrations, 0 and 800 μM ATP, are indicated. Other intermediate concentrations are 25, 50, 100, 200 and 400 μM. b Spectra measured in control conditions (0 ATP an absence of potentiator) and at 0 and 800 μM ATP in the presence of 25 nM PBF. Notice that the fluorescence decay elicited by the CFTR potentiator does not impede to observe the ATP-induced quenching. c Fluorescence change, ΔF, as a function of the ATP concentration. ΔF was calculated as the normalised change of fluorescence between the 0 ATP and a saturating ATP concentration. Triangles correspond to the control experiments, and diamonds are data in the presence of 25 nM ATP. Data represent the average of 6 experiments in each condition, and error bars the standard error of the mean. The continuous line is the best fit with Eq. 1