HEAT DENATURATION OF METHB AND HBNO - EPR EVIDENCE FOR THE EXISTENCE OF A NEW HEMICHROME

Electron paramagnetic resonance was used to follow the time dependence of heat denaturation of met- and nitrosyl-haemoglobin (metHb and HbNO) at 60-degrees-C, 70-degrees-C and 80-degrees-C. The spectral changes of both complexes indicate that conformational changes in the protein manifest themselves in changes of the equilibrium of hemichromes in metHb and of six- and five-coordinated iron in HbNO. The formation of a hemichrome which has not been described before, with g = 2.45, 2.27 and 1.85, is observed A His-Fe-Cys complex is proposed for its structure.