OXYGEN EQUILIBRIUM AND ELECTRON-PARAMAGNETIC-RESONANCE STUDIES ON COPPER(II)-IRON(II) HYBRID HEMOGLOBINS AT ROOM-TEMPERATURE

Copper(II)-iron(II) hybrid hemoglobins, in which hemes in either the a lpha or beta subunits are substituted with copper(II protoporphyrin IX , have been prepared, The affinities of the ferrous-subunits in both h ybrids for the first binding oxygen are as low as the affinity of deox yhemoglobin under various solution conditions, indicating the equality of behavior in copper(II) protoporphyrin IX and deoxyheme, Electron p aramagnetic resonance (EPR) examinations on these hybrids at room temp erature show that the interaction between copper(II) and the proximal histidine (F8) is specifically weakened in the alpha subunits within a low affinity conformation of hemoglobin, These results suggest that c opper(II) protoporphyrin IX is a useful EPR probe at room temperature for investigating the deoxyheme environment in hemoglobin.