(A) Inhibitory kinetics of bc1 complex by compound 5c. Each reaction mixture contains 100 mM PBS (pH 7.4), 0.3 mM EDTA, 20 mM succinate, 60 µM cytochrome c, 0.1 nM SCR, and certain amount of compound 5c (1, 0 nM; 2, 1 nM; 3, 1.5 nM; 4, 2 nM; and 5, 5 nM). Experimental data were shown as colored dots and theoretical values as black solid lines. Inset: plot of kobs against concentration of compound 5c. (B) Effect of cytochrome c concentration on the inhibition of bc1 complex by compound 5c. The assays were carried out in the presence of 5 nM compound 5c and various concentrations of cytochrome c (1, 4 µM; 2, 12 µM; and 3, 48 µM). Each reaction was initiated by adding 0.1 nM SCR. Inset: plot of kobs against concentration of cytochrome c.