2z6t

==Overview==

Crystals of the ferric peroxo (Fe3+-O-O-) species of myoglobin (Mb) have, been successfully generated by radiolytic reduction of the oxy Mb crystals, at 100 K by irradiation with 1.0 A synchrotron radiation. X-ray, diffraction using 0.6 A synchrotron radiation has permitted, for the first, time, the determination of the crystal structure of the ferric peroxo heme, species, an important intermediate in mono-oxygenase heme enzyme, catalysis. The Fe-O-O geometry is similar to that found in the ferrous oxy, Mb, the crystal structure of which has been determined also by the 0.6 A, radiation. The optical absorption spectra of the crystals affirm that oxy, and peroxo species have been maintained during the diffraction, measurements, indicating that adverse photoreduction by the incident beam, could be mostly avoided by use of the 0.6 A wavelength synchrotron, radiation for the diffraction measurements. The Fe-O-O geometries of the, oxy and peroxo Mb found in the crystal structures are supported by the, QM/MM calculations, which also show that the existence of a strong, hydrogen bonding interaction between NepsilonH of His64 and distal oxygen, atom in both the oxy and peroxo Mb. The ground state of the peroxo Mb is, found as a doublet state, while that of the oxy Mb is an open-shell, singlet state with two unpaired alpha and beta electrons mainly, distributed on the Fe and O2 moiety.

==Reference==

Structural Characterization of the Fleeting Ferric Peroxo Species in Myoglobin: Experiment and Theory., Unno M, Chen H, Kusama S, Shaik S, Ikeda-Saito M, J Am Chem Soc. 2007 Nov 7;129(44):13394-13395. Epub 2007 Oct 12. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17929929 17929929]

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