CLAS: Electron paramagnetic resonance laboratory

Equipment/facility: Facility

  • Location

    United States


The Electron Paramagnetic Resonance (EPR) Facilitys primary mission is to determine structural details of proteins that contain paramagnetic centers. It is used to characterize a wide variety of biochemical systems, providing information on an atomic scale in free radicals and in the vicinity of certain paramagnetic metal ions. Changes in structure often occur during the functional cycle of a protein, and tracking these changes by EPR has become a much-used technique for determining mechanism and function from structure. The facility also provides instruction in instrument operation.

Bruker Elexys E580 EPR spectrometer
The EPR facility is equipped with a Bruker ELEXSYS spectrometer operating at three different microwave (mw) frequencies. There are several mw bridges available working with different resonance cavities. The setups available are the following:

1) S-band (2.6 GHz and 3.8 GHz): A continuous wave (CW) broad band mw bridge (ER 061) working with two different split ring resonators.

2) X-band (9.8 GHz): A hybrid mw bridge (E580) used to run either CW or pulsed experiments.

a) CW mode. EPR experiments can be performed on solid-state or liquid-solution samples using a standard resonator (ER 4102ST) or a cylindrical mode resonator (ER 4103TM), respectively. Furthermore, electron-nuclear double resonance (ENDOR) experiments can be performed using the EN 801 resonance cavity.

b) Pulsed mode. The complete repertoire of modern EPR techniques (echo-detected EPR, ESEEM, HYSCORE, ELDOR, Davies and Mims ENDOR) can be performed using the dielectric ring resonators ER 4118X-MD5 and EN 4118X-MD4.

3) Q-band (34 GHz): A pulsed mw bridge (Super Q-FTu) with capabilities to perform the full set of pulsed EPR techniques.

Contact: Marco Flores


electron paramagnetic resonance
continuous radiation
S band
information systems
microwave frequencies
superhigh frequencies
free radicals
metal ions
solid state