FIGURE 2.

Simulated heme redox titrations. The simulated data as well as the fitted Nernst curves are shown as two-step curves, which represent the sum of two single heme titration curves. The figure shows the simulated and experimental (Lancaster et al., 2000) redox titrations of hemes b_P and b_D of QFR at pH 7. ▪, Experimental data; ○, simulated data using model X; and ▵, simulated data for model W. The three fitted Nernst curves are also included: ——, experimental; · · · · , simulation, model X; and - - - -, simulation, model W. The vertical lines (same labeling as for the Nernst curves) indicate the positions of the individual oxidation-reduction (midpoint) potentials as they were obtained by the Nernst fit: low-potential heme, −149 mV (experiment), −149 mV (simulation, model X), and −125 mV (simulation, model W); and high-potential heme, −9 mV (experiment), −48 mV (simulation, model X), and −12 mV (simulation, model W). The low-potential heme corresponds to heme b_D and the high-potential to b_P.