Resonance Raman and absorption spectra were examined for the species generated upon incubation of oxidized bovine cytochrome c oxidase at pH 8.0 with carbon monoxide in the presence or absence of O2. The anaerobic incubation yielded the CO isotope sensitive bands at 517 and 578 cm–1 for 12C16O, at 512 and 563 cm–1 for 13C16O, at 508 and 574 cm–1 for 12C18O, and at 503 and 557 cm–1 for 13C18O, i...