NITROSYL HEMOGLOBINS - EPR ABOVE 80 K

The EPR spectra of nitrosyl hemoglobin and myoglobin in different cond itions (native, denatured and lyophilized), as well as of hematin-NO w ere obtained in the temperature range of 80-280 K. There is a substant ial and reversible decrease of the areas of the EPR spectra of all the hemoglobin samples above 150 K. The interpretation of the results imp lies the existence of two conformational states in thermal equilibrium , only one of which is EPR detectable. Thermodynamical parameters are determined for the hexa- and penta-coordinated cases.