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Updated: Dec 23, 2025

Use of Electron Paramagnetic Resonance in Biological Samples at Ambient Temperature and 77 K
Published on: January 11, 2019
Temperature-cycle electron paramagnetic resonance
E Gabriele Panarelli1, Peter Gast, Edgar J J Groenen
1Department of Physics, Huygens-Kamerlingh Onnes Laboratory, Leiden University, PO Box 9504, 2300 RA Leiden, The Netherlands. groenen@physics.leidenuniv.nl.
Abstract:
We report on a novel approach to the study of rates and short-lived intermediates of (bio)chemical reactions that involve paramagnetic species. Temperature-cycle Electron Paramagnetic Resonance (EPR) concerns the repeated heating of a reaction mixture in the cavity of an EPR spectrometer by pulsed irradiation with a near-infrared diode laser combined with intermittent characterization of the sample by 275 GHz EPR at a lower temperature at which the reaction does not proceed. The new technique is demonstrated for the reduction of TEMPOL with sodium dithionite in aqueous solution down to the sub-second time scale. We show that a single sample suffices to obtain a complete kinetic trace. Variation of the length and power of the laser pulse offers great flexibility as regards the time scale of the experiment and the temperature at which the reaction can be studied. For water/glycerol mixtures we introduce a simple way to obtain and load an unreacted sample into the spectrometer at low temperature.
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