Assignment of proximal histidine proton nmr peaks in myoglobin and hemoglobin

The proton nmr spectra of model compounds of deoxy myoglobin and hemoglobin have yielded the assignment of the axial imidazole resonances. The information leads directly to an assignment of all three proximal histidyl imidazole proton resonances in sperm whale deoxy myoglobin, and the two non-equivalent proximal histidyl imidazole NH signals of the α and β chains in deoxy hemoglobin A. The NH peaks are expected to serve as valuable probes for the T ⇌ R transition in hemoglobins.