Electron spin echo envelope modulation spectroscopic study of iron-nitrogen interactions in myoglobin hydroxide and Fe(III) tetraphenylporphyrin models

Journal Article · Tue Jan 14 04:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00116a028· OSTI ID:5616347

Magliozzo, R S; Peisach, J ^[1]

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1. Yeshiva Univ., Bronx, NY (United States)

The electron-nuclear coupling in low-spin iron complexes including myoglobin hydroxide (MbOH) and two related model compounds, Fe(III) tetraphenylporphyrin(pyridine)(OR{sup {minus}}) (R = H or CH{sub 3}) and Fe(III) tetraphenylporphyrin(butylamine)(OR{sup {minus}}) was investigated using electron spin echo envelope modulation (ESEEM) spectroscopy. The assignment of frequency components in ESEEM spectra was accomplished through the use of nitrogen isotopic substitution wherever necessary. For example, the proximal imidazole coupling in MbOH was investigated without interference from the contributions of porphyrin {sup 14}N nuclei after substitution of the heme in native Mb with {sup 15}N-labeled heme. Computer simulation of spectra using angle selected techniques enabled the assignment of parameters describing the hyperfine and quadrupole interactions for axially bound nitrogen of imidazole in MbOH, of axial pyridine and butylamine in the models, and for the porphyrin nitrogens of the heme in native MbOH. The isotropic component of axial nitrogen hyperfine interactions exhibits a trend from 5 to 4 MHz, with imidazole (MbOH) > pyridine > amine. A discussion is presented to the unusual results reported in a linear electric field effect in EPR (LEFE) study of MbOH published previously.

• OSTI ID: 5616347
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 31:1; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AZOLES
CARBOXYLIC ACIDS
ELECTRIC FIELDS
ELECTRON SPECTRA
ELECTRON SPIN RESONANCE
GLOBINS
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
ISOTOPES
LIGANDS
LIGHT NUCLEI
MAGNETIC RESONANCE
MYOGLOBIN
NITROGEN 15
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES