Electromagnetic Properties of Hemoproteins

Low temperature electron paramagnetic resonance absorption spectra of randomly oriented preparations of cytochrome c peroxidase, ferrimyoglobin, ferrimyoglobin-azide, and ferrimyoglobin-fluoride are measured in various physical states.In general, the line width of resonance absorptions increases in relation to the physical state of preparation in the following order: concentrated solutions < wet polycrystalline suspensions < lyophilized preparations < dried polycrystalline preparations.The broadening of resonance absorptions caused by dehydration can be reversed by rehydration and dissolution of the dried preparation.When cytochrome c peroxidase and ferrimyoglobin-azide are dehydrated, their spin types are reversibly fixed in the state at dehydration and become temperature-independent until these compounds are rehydrated.The intensity of the high spin resonance absorption of ferrimyoglobin decreases by a factor of 10 to 20 on dehydration.The initial intensity can be restored by rehydration and dissolution of the dehydrated ferrimyoglobin.Resonance spectra of dehydrated ferrimyoglobin exhibit hitherto unreported absorptions in the high field region.These absorptions may represent a compound or compounds which may be responsible for the low spin characteristics of lyophilized ferrimyoglobin detected by Mossbauer absorption spectroscopy.The dehydration of a hemoprotein sometimes induces certain changes in electromagnetic properties of the heme prosthetic group. Zeynek (2) and Haurowitz(3) reported that the dehydration of ferrohemoglobin was accompanied by a reversible change in light absorption spectra.Subsequently, Keilin and Hartree (4) made a similar observation in ferrihemoglobin.