Substitution of H2 16O by H2 17O induces a substantial broadening of the high-field line in the electron-spin resonance spectrum of ferric myoglobin due to the presence of H2 17O at the axial ligand-site. Computer simulations of the experimental spectra yielded the values of the reciprocal relaxation time T2 -1 = 7.8 G and the 17O-hyperfine coupling constant A = 18 ± 1 G. Under identical experimental conditions no effect of H2 17O was observed in horseradish peroxidase. The latter finding excludes the possibility that a water molecule is liganded to the peroxidase haem-iron and supports either the idea that both axial ligands are amino acid residues or that the haem in ferric horseradish peroxidase is pentacoordinate.
|Original language||English (US)|
|Number of pages||5|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Dec 7 1977|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology