Fig. 2.
Experimental (♦) and simulated (lines) IC50 values for the inhibition of mitochondrial respiration by NO. IC50 values obtained with model 1 (continuous line) were calculated by using Eq. 4 with kNOon = 4 × 107 M–1·s–1, kNOoff = 0.02 s–1, and kIV = 30 s–1.IC50 values obtained with model 2 (dashed line) were calculated from simulations in which O2 concentration was held constant and NO concentration was varied as a parameter; parameters used were as follows: kNOon = 4 × 107 M–1·s–1, kNOoff = 0.01 s–1, kIV = 1.5 × 106 M–1·s–1, kIII = 23.3 s–1, [cyt c]tot = 200 μM, and [COX]tot = 140 μM. kNOoff in model 2 was half of that in model 1. In both models, the functional dependency of kO2app on the concentration of O2 (see Supporting Text) was explicitly considered. Experimental data were taken from refs. 1, 4, 13, 19, 21, 47, and 48.