Interaction of CYP3A4(C58,C64)-CPM with ANF monitored by the changes in the fluorescence of the probe. (a) A series of emission spectra of 1.5 µM CYP3A4(C58,C64)-CPM recorded at 0, 0.4, 1.2, 2, 3, 4, 5, 8, 10, 12, 16 and 24 µM of ANF. (b) Relative fluorescence intensity versus substrate concentration. The lines show the fitting of the data sets to the Hill equation with S50 = 13 µM and n = 1.1. Experimental conditions as indicated in Figure 3.