Zero-field splittings in metHb and metMb with aquo and fluoro ligands: A FD-FT THz-EPR study

Joscha Nehrkorn, Berta M. Martins, Karsten Holldack, Stefan Stoll, Holger Dobbek, Robert Bittl, Alexander Schnegg

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30 Citations (Scopus)


A combined X-band and frequency-domain Fourier-transform THz electron paramagnetic resonance (FD-FT THz-EPR) approach has been employed to determine heme Fe(III) S = 5/2 zero-field splitting (ZFS) parameters of frozen metHb and metMb solutions, both with fluoro and aquo ligands. Frequency-domain EPR measurements have been carried out by an improved synchrotron-based FD-FT THz-EPR spectrometer. ZFS has been determined by field dependence of spin transitions within the mS = ±1/2 manifold, for all four protein systems, and by zero-field spin transitions between mS = ±1/2 and mS = ±3/2 levels, for metHb and metMb flouro-states. FD-FT THz-EPR data were simulated with a novel numerical routine based on Easyspin, which allows now for direct comparison of EPR spectra in field and frequency domain. We found purely axial ZFSs of D = 5.0(1) cm -1 (flouro-metMb), D = 9.2(4) cm-1 (aquo-metMb), D = 5.1(1) cm-1 (flouro-metHB) and D = 10.4(2) cm-1 (aquo-metHb).

Original languageEnglish
Pages (from-to)2696-2707
Number of pages12
JournalMolecular Physics
Issue number18-19
Publication statusPublished - 1 Oct 2013
Externally publishedYes


  • EPR spectroscopy
  • haemoglobin
  • myoglobin
  • zero-field splitting

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