Continuous-wave EPR at 275GHz: application to high-spin Fe(3+) systems |
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| Authors: | Mathies G Blok H Disselhorst J A J M Gast P van der Meer H Miedema D M Almeida R M Moura J J G Hagen W R Groenen E J J |
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| Affiliation: | a Department of Molecular Physics, Huygens Laboratory, Leiden University, The Netherlands;b Department of Chemistry, Universidade Nova de Lisboa, Portugal;c Department of Biotechnology, Delft University of Technology, The Netherlands |
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| Abstract: | The 275GHz 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 275GHz continuous-wave spectra of a 1mM frozen solution of the complex Fe(III)-ethylenediamine tetra-acetic acid and of 10mM frozen solutions of the protein rubredoxin, which contains Fe(3+) 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 0.5GHz. 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. |
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| Keywords: | EPR High-field High-frequency Continuous-wave Single-mode cavity Fe(III)– EDTA Rubredoxin |
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