Continuous-wave EPR at 275 GHz: application to high-spin Fe3+ systems

G. Mathies, H. Blok, J. A. J. M. Disselhorst, P. Gast, H. Van Der Meer, D. M. Miedema, R. M. Almeida, J. J. G. Moura, W. R. Hagen, E. J. J. Groenen

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24 Citations (Scopus)


The 275 GHz electron-paramagnetic-resonance spectrometer we reported on in 2004 has been equipped with a new probe head, which contains a cavity especially designed for operation in continuous-wave mode. The sensitivity and signal stability that is achieved with this new probe head is illustrated with 275 GHz continuous-wave spectra of a 1 mM frozen solution of the complex Fe(III)-ethylenediamine tetra-acetic acid and of 10 mM frozen solutions of the protein rubredoxin, which contains Fe3+ in its active site, from three different organisms. The high quality of the spectra of the rubredoxins allows the determination of the zero-field-splitting parameters with an accuracy of 0.5 GHz. The success of our approach results partially from the enhanced absolute sensitivity, which can be reached using a single-mode cavity. At least as important is the signal stability that we were able to achieve with the new probe head.

Original languageEnglish
Pages (from-to)126-132
Number of pages7
JournalJournal of magnetic resonance
Issue number1
Publication statusPublished - May 2011


  • Continuous-wave
  • EPR
  • Fe(III)-EDTA
  • High-field
  • High-frequency
  • Rubredoxin
  • Single-mode cavity


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