EPR - Electron Paramagnetic Resonance Spectroscopy

EPR - Electron Paramagnetic Resoncance Spectroscopy

Please acknowledge the SIP core facility ( RRID: SCR_018986) in publications, on posters, or in talks if you use any instruments in the SIP core facility. Please include SIP's RRID (RRID: SCR_018986) and the grant numbers for instruments funded through instrumentation grants in your acknowledgements. This is a requirement from the funding agencies and is crucial for future funding. Find example text on the Acknowledgement Page or the individual instrument pages.

EPR in Biochemistry, Biophysics and Structural Biology

EPR spectroscopy, sometimes referred to as ESR spectroscopy, is a powerful tool for studying paramagnetic centres. It is similar to NMR spectroscopy, but instead of exciting the spins of atomic nuclei, EPR excites the electron spins of unpaired electrons. This technique has a wide range of applications, particularly in biology and biophysics. This short introduction only scratches the surface of what is possible. EPR can be used to investigate organic radicals in proteins, such as tyrosyl, tryptophanyl, glycyl, semiquinones, and flavins. It is also effective for studying metal centres in protein complexes, including Cu, Ni, Co, Mn, Mo, Fe, Cr, heme, FeS clusters, and Mn/Cr ATP complexes.

Site-directed spin labelling with nitroxide-based spin labels enables EPR studies to be extended to proteins, nucleic acids, lipids, and nucleotides that do not have indigenous paramagnetic centres. This technique provides researchers with valuable information about structures, conformational changes, membrane insertion, and more.

Another valuable application of EPR spectroscopy is spin trapping of short-lived radicals, such as hydroxyls, superoxides, and carbon-based radicals. These small radical species play crucial roles in processes like oxidative stress, wound healing, immune responses, and ageing. By capturing and stabilising these fleeting radicals, spin trapping allows for their detailed study, contributing to a deeper understanding of their roles in various physiological and pathological conditions.

Methods and Instruments

Interacting spin labels and resulting lineshapes of EPR spectra

Key highlights of EPR in Biology, Biochemistry, and Biophysics

  • Investigation of proteins, peptides, RNA, DNA, lipids, membrane-bound complexes, and surface-attached biomolecules and more.
  • Samples under near-physiological conditions, requiring as little as 4 μl of a 25 to 100 μM sample.
  • No size or solubility limitations.
  • Analysis of secondary structure elements and tertiary/quaternary interaction sites.
  • Study of protein and DNA/RNA folding processes.
  • Observation of conformational changes.
  • Examination of protein membrane insertion, including depth, geometry, and changes during ligand binding.
  • Determination of binding curves and stoichiometries by directly measuring the amount of bound (EPR-active) ligand.
  • Spin trapping of small radicals (such as hydroxyls, superoxides, and carbon-based radicals), relevant to wound healing, immune defence, or ageing-related processes.
  • And much more...
EPR spectrometer

Instrument and Accesories

EPR spectrometer 

  • Bruker Elexsys E 500, X-band, continuous wave (cw) EPR spectrometer

Resonators

  • Bruker Super-High Sensitivity Resonator (SHQE cavity)
  • Standard Rectangular TE102 Resonator (Bruker 4102ST)
  • Loop Gap Resonator (Molecular Specialties)

Temperature Control

  • N2 temperature control system (Bruker) with an accessible temperature range from 100 K to 500 K

Essential Information for Using SIP's EPR

Acknowledgements Protocols Training Scheduling Cost Location
Acknowledgements

Why?

Acknowledgements are essential for ensuring the continued success of the Shared Instruments Pool (SIP). They enable us to secure the necessary funding to sustain and expand the SIP, ensuring that our instruments are in optimal working condition and that the methods we offer are at the forefront of biochemical and biophysical research.

Please include SIP's RRID number (RRID: SCR_018986) in your acknowledgements. This allows funding organisations and potential grant reviewers to easily locate publications supported by SIP, helping to evaluate the impact of SIP on our research community.

If facility staff have provided substantial assistance, please consider acknowledging them. If they contributed significantly to the intellectual aspects or conducted important experiments, co-authorship may also be appropriate.

Example text:

We thank the Shared Instruments Pool (RRID: SCR_018986), Department of Biochemistry, University of Colorado Boulder for the use of the Bruker Elexsys E 500 EPR spectrometer. We also thank [Name and title of the facility member providing significant help] for their invaluable assistance with data collection and evaluation.

Please contact Dr Erbse to obtain detailed protocols and arrange an initial project consultation and personalised training sessions. Protocols are available as PDF files on the instrument computer, with printed copies stored alongside the instruments.

Interested users can contact Dr Erbse to discuss planned experiments and to arrange for training. The training comprises a minimum of three sessions: the first session utilises a standard sample, while sessions two and three involve the user's own samples. Users are welcome to request additional training or support sessions at any time. We are always happy to provide a refresher if it has been a while.

After your training is completed, you will be invited to join the EPR Google calendar. You must sign up for instrument time using the calendar and send Dr. Erbse an email at the same time you sign up.

Sign Up Rules: 
Up to Friday the week before the planned experiment users can sign up for a maximum of 2 days. Users from groups that are part of the S10 Grant that provided the funding to purchase the EPR can sign up for up to 3 days. In the week of the experiment users can sign up for additional time if available.

  • Initial consultation is free. SIP staff are happy to assist with a short pilot experiment if it can be accommodated within SIP's resources.
  • Regular user groups are expected to buy into SIP with a monthly flat fee according to their SIP usage level. For detailed information, please contact Dr Annette Erbse.
  • Users are required to provide all consumables specific to their experiments. This includes EPR tubes and capillaries.
  • Costs for necessary repairs, services, or replacement parts due to normal wear and tear will be shared among all user groups, based on the time used over the past two years. Please note that assuming the instrument is handled properly, such repairs or replacements are infrequent, and costs may arise after a user’s period of use has ended.
  • Users are responsible for covering the costs of repairs or replacement parts needed due to damage caused by carelessness or neglect.

The EPR is located in the basement of JSCBB in the C-Wing, room C1B60, on East Campus. Proxcard access is required at all times.