Dual-mode EPR spectrometry of O2-pulsed cytochrome c oxidase

O2-activated bovine heart cytochrome c oxidase has been examined by dual-mode EPR spectrometry. Resonances have been observed at g = 10 and 4.5 in the parallel mode and at g = 10, 5, 1.8 and 1.7 in the normal mode. The bulk of these signals are interpreted to come from a stoichiometric S = 2 system with magnitude of a = 0.17 cm-1, D = +2.1 cm-1, magnitude of E = 0.026 cm-1, g = 2. Exchange coupling between cytochrome a3 and CuB is not indicated.