High-frequency 180 GHz PELDOR |
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Authors: | V P Denysenkov T F Prisner J Stubbe M Bennati |
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Institution: | 1. Institute for Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance, J. W. Goethe University, Frankfurt am Main, Germany 2. Department of Chemistry and Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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Abstract: | For aromatic organic radicals, pulsed electron-electron double resonance (PELDOR) experiments at high magnetic fields offer
the possibility to achieve orientation-selective pumping and detection that could allow one not only to determine the distance
between paramagnetic species but also their relative orientation with respect to the interconnecting dipolar axis. We present
a PELDOR two-frequency setup that was introduced into our homebuilt 180 GHz pulsed electron paramagnetic resonance (EPR) spectrometer
and we discuss its technical and experimental features. The capability of 180 GHz PELDOR has been tested using the three-pulse
ELDOR sequence on the protein RNR-R2 (ribonucleotide reductase) fromEscherichia coli, which contains two tyrosyl radicals at a distance of 3.3 nm. At 180 GHz, orientation selectivity is observed and the modulation
frequency was found in good agreement with theoretical predictions, which take into account the relative orientation of the
radicals from X-ray data. |
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