Cyanide-induced CT complex formation in SQOR. A, SQOR (10 μM, red line) in 100 mM potassium phosphate, pH 7.4 containing 0.03% DHPC, was mixed 1:1 (v/v) with KCN (4 mM) and monitored over 1.5 s at 4 °C for the formation of the cyanide-induced CT complex at 695 mn (blue line). B, Representative stopped flow kinetic trace for the reaction in (A) monitored at 695 mn. C, Dependence of the kobs at 4 °C for cyanide-induced CT complex formation on cyanide concentration. The data are representative of two independent experiments, with each data point obtained in triplicate. D, SQOR (5 μM, red line) was treated with KCN (5 mM) to form the CT complex (blue line), immediately followed by the addition of Na2S (200 μM) and incubated for 5 min at 20 °C, which led to CT complex decay and FAD reduction (black line). The data are representative of three independent experiments.