Electron-nuclear coupling in nitrosyl heme proteins and in nitrosyl ferrous and oxy cobaltous tetraphenylporphyrin complexes

Journal Article · Tue Dec 01 00:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00398a057· OSTI ID:5436029

Magliozzo, R S; McCracken, J; Peisach, J

Electron spin echo envelope modulation (ESEEM) spectroscopy has been used to study electron-nuclear interactions in the following isoelectronic S = 1/2 complexes: NO-Fe/sup II/(TPP) (TPP = tetraphenylporphyrin) with and without axial nitrogenous base, nitrosylhemoglobin in R and T states, and O/sub 2/-Co/sup II/(TPP) with and without axial base. Only the porphyrin pyrrole nitrogens contribute to the ESEEM of the 6-coordinate nitrosyl Fe/sup II/(TPP) complexes, nitrosylhemoglobin (R-state), and the nitrosyl complexes of ..cap alpha.. and ..beta.. chains. Pyrrole nitrogens in the 5-coordinate complex NO-Fe/sup II/(TPP) are coupled to weakly to unpaired spin and therefore do not contribute to the ESEEM. A partially saturated T-state nitrosyl-hemoglobin does not exhibit echo envelope modulations characteristic of 6-coordinate nitrosyl species, which confirms that the proximal imidazole bond to heme iron is disrupted. Study of 6-coordinate O/sub 2/-Co/sup II/(TPP)(L) complexes (L = nitrogenous base) using /sup 14/N- and /sup 15/N-labeled ligands and porphyrins enabled a detailed analysis of coupling parameters for both pyrrole and axial nitrogens. The pyrrole /sup 14/N coupling frequencies are similar to those in NO-Fe/sup II/(TPP)(L). The Fermi contact couplings for axially bound nitrogen, calculated from simulation of ESEEM spectra for a series of O/sub 2/-Co/sup II/(TPP)(L) complexes (L = pyridine, 4-picoline, 4-cyanopyridine, 4-carboxypyridine, and 1-, 2-, and 4-methylimidazole) illustrate a trend toward stronger hyperfine interactions with weaker bases.

• Research Organization: Albert Einstein College of Medicine, Bronx, NY
• OSTI ID: 5436029
• Journal Information: Biochemistry; (United States), Vol. 26:24
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
PORPHYRINS
ELECTRON SPIN RESONANCE
HEME
NITROGEN 14
NITROGEN 15
NITROSO COMPOUNDS
CARBOXYLIC ACIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
RESONANCE
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics