Electron Paramagnetic Resonance of

The effects of high energy electron and gamma irradiation on hemoglobin have been studied at dry state by electron paramagnetic resonance spectroscopy at a temperature range from 77 K to room temperature. In the irradiated samples of oxyhemoglobin, methemoglohin, globin, hemin, and a mechanical mixture of globin with hemin, the radicals are found to be localized in the globin moieties. No indication of radiation damages being transfered from the protein to the heme part, and vice versa, is given. The spectra of hemoglobins at 77 K are attributed to a sum of the EPR spectra of various radicals of two types distributed randomly in the constituent amino acid residues:-CHR radicals produced by scission of polypeptide main chains and —NH—CH(R)—CO — radicals in side chains R. By warming, the former radicals are converted to the type —NH—CR—CO—, predominantly to —NH— CH—CO- of the glycine residue, while the latter are transferred or disappeared. The selective radical formation on the glycine residues at room temperature are attributed to the result of a series of radical transfer reactions initiated by radicals produced by main chain scission randomly in the protein molecule.