Analysis of powder and single-crystal electron paramagnetic resonance spectra for manganese(II) protoporphyrin IX myoglobin at various microwave frequencies

Hiroshi Hori, Masao Ikeda-Saito, George H. Reed, Takashi Yonetani

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

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.

Original languageEnglish
Pages (from-to)177-185
Number of pages9
JournalJournal of Magnetic Resonance (1969)
Volume58
Issue number2
DOIs
Publication statusPublished - 1984 Jun 15

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