title: Low-temperature studies on mixed-valence cytochrome oxidase by using magnetic circular dichroism.
abstract: The spin states of the haem components of mixed-valence cytochrome oxidase were studied at room temperature and at temperature down to 20K by using magnetic circular dichroism. The room-temperature studies show the presence of a low-spin ferrous haem together with a low-spin ferric haem, which we attribute to heams a3 and a respectively. At temperatures below 100K it appears that the CO of the mixed-valence CO complex may be irreversibly photolysed, and that in this case haems a and a3 assume their high-spin states. Thus in this enzyme haem-haem interactions appear possible at temperatures below 100K.
mesh_terms: D002248:Carbon Monoxide; D002942:Circular Dichroism; D003576:Electron Transport Complex IV; D006418:Heme; D013696:Temperature
chemical_list: D006418:Heme; D002248:Carbon Monoxide; D003576:Electron Transport Complex IV