TY - JOUR
T1 - Analysis of powder and single-crystal electron paramagnetic resonance spectra for manganese(II) protoporphyrin IX myoglobin at various microwave frequencies
AU - Hori, Hiroshi
AU - Ikeda-Saito, Masao
AU - Reed, George H.
AU - Yonetani, Takashi
N1 - Funding Information:
We thank Dr. T. Inubushi and Dr. H. Morimoto for useful discussions. supported by National Institutes of Health Grants HL 14508 (T.Y.), AM-17517 (MI.-S.)., and by National Science Foundation Grant PCM 79-22841 (T.Y.).
PY - 1984/6/15
Y1 - 1984/6/15
N2 - Powder and single-crystal electron paramagnetic resonance spectra for manganese(II protoporphyrin IX myoglobin (Mn2+Mb) were measured at S-, X-, K-, and Q-band microwave frequencies to determine principal g values, hyperfine coupling constants, and zero-field splitting parameters. The effective EPR parameters for the lowest Kramers doublet were found to be g{norm of matrix} = 1.99, g{norm of matrix} = 5.90, A{norm of matrix} = 8.64 mT, and A⊥ = 8.24 mT. Zerofield splitting between the lowest Kramers doublet (Ms = ± 1 2) and the second Kramers doublet (Ms = ± 3 2) was estimated to be 1.39 cm-1. The effective g tensor is approximately axially symmetric. Hyperfine coupling with the 55Mn nucleus was nearly isotropic, but also reflects axial symmetry. The orientation of manganese(II) protoporphyrin plane in single crystals of Mn 2+Mb is nearly identical to that for high-spin iron(III) myoglobin single crystals. The spin-Hamiltonian parameters for Mn 2+Mb are fully consistent with single-crystal or powder spectra obtained at all four microwave frequencies.
AB - Powder and single-crystal electron paramagnetic resonance spectra for manganese(II protoporphyrin IX myoglobin (Mn2+Mb) were measured at S-, X-, K-, and Q-band microwave frequencies to determine principal g values, hyperfine coupling constants, and zero-field splitting parameters. The effective EPR parameters for the lowest Kramers doublet were found to be g{norm of matrix} = 1.99, g{norm of matrix} = 5.90, A{norm of matrix} = 8.64 mT, and A⊥ = 8.24 mT. Zerofield splitting between the lowest Kramers doublet (Ms = ± 1 2) and the second Kramers doublet (Ms = ± 3 2) was estimated to be 1.39 cm-1. The effective g tensor is approximately axially symmetric. Hyperfine coupling with the 55Mn nucleus was nearly isotropic, but also reflects axial symmetry. The orientation of manganese(II) protoporphyrin plane in single crystals of Mn 2+Mb is nearly identical to that for high-spin iron(III) myoglobin single crystals. The spin-Hamiltonian parameters for Mn 2+Mb are fully consistent with single-crystal or powder spectra obtained at all four microwave frequencies.
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U2 - 10.1016/0022-2364(84)90208-7
DO - 10.1016/0022-2364(84)90208-7
M3 - Article
AN - SCOPUS:0000527399
VL - 58
SP - 177
EP - 185
JO - Journal of Magnetic Resonance (1969)
JF - Journal of Magnetic Resonance (1969)
SN - 0022-2364
IS - 2
ER -