Q-band electron paramagnetic resonance study of nitrosylprotoheme dimethyl ester complexes with N-,O-, and S-donor ligand as model systems for nitrosylhemoproteins |
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Authors: | Tetsuhiko Yoshimura |
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Institution: | The Environmental Science Institute of Hyogo Prefecture, Kobe, Japan |
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Abstract: | Electron paramagnetic resonance (epr) spectra (at X- and Q band frequency) of nitrosyl(proto-porphyrin IX dimethyl ester) iron( II) complexes with a trans axial ligand of nitrogen-, oxygen-, and sulfur-donor ligand, in the trozen glass state at 77°K, have been investigated in order to understand the epr spectra of nitrosylhemoproteins. The Q-band spectra resolved the spectral features more clearly than the X-band spectra and distinctly exhibited two groups of absorptions, which were attributable to two molecular species. Significant relations were found between two g values (e.g., gx-gz, gx-gy) and between the g value and the degree of the hyperfine splitting in central absorption. The epr parameters were not very sensitive to the π-bonding ability of the axial ligand, but registered the steric interaction of the axial ligand with porphynnato core. These findings can be utilized in the characterization of an axial ligand trans to the nitrosyl group in nitrosylhemoproteins. |
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Keywords: | epr electron paramagnetic resonance NOHb nitrosylhemoglobin NOMb nitrosylmyoglobin PPDME protoporphyrin IX dimethyl ester NAclm 1-acetylimidazole NMeIm 1-methylimidazole 4MeIm 4-methylimidazole 1 2DMeIm 1 2-dimethylimidazole Py pyridine 2MePy 2-methlylpyridine Pip piperdine Anil aniline EtMeS ethl methyl sulfide THF tetrahydrofaurn TPP tetraphenylphyrinato |
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