Effect of ANF on fluorescence of CYP3A4(C58,C64)BADAN in the presence of 3 mM GSH. (a) A series of emission spectra of 1.5 µM protein recorded at 0, 2, 5, 10, 15, 20, 25, 30, 35, and 50 µM ANF. (b) Relative fluorescence intensity versus substrate concentration. The line shows the fitting of the data sets to the Hill equation with S50 = 16.6 µM, n=1.7, and the maximal amplitude of the fluorescence decrease of 56%.