Critical appraisal of electronic structure of metmyoglobin. 14N and 57Fe hyperfine interactions.

The electronic structure of metmyoglobin is subjected to a critical examination by comparison of results of recent ENDOR measurements of nitrogen hyperfine interaction constants on the porphyrin ring and on the proximal histidine linking the heme to the protein with theoretical values for these properties from calculated electronic wavefunctions for this molecule. The observed interesting trends of the 14N hyperfine data as well as available 57Fe data are both successfully explained showing that theory has provided a satisfactory description of the electronic distribution in this important molecule.