CO photolysis of cytochrome oxidase investigated by PS resonance Raman spectroscopy

Low-power picosecond resonance Raman spectroscopy was used to investigate the identity of the axial ligand of heme a(3) and relaxation processes in the heme a(3) pocket of cytochroms oxidase after CO photolysis. Our results show that the proximal histidine remains ligated to heme a(3) after CO photolysis excluding the transient ligation of a photolabile, endogenous ligand. Furthermore, the relaxation of the heme a(3) macrocycle modes occurs on the sub ps time scale, while relaxation of the heme pocket to its equilibrium conformation takes place on the mu s time scale.