Training / Guides

EPR facility provides one-on-one or small group training on following topics: Basic EPR Spectrometer Operation, LN2 and LHe Cryostat Operation.

LN2 or LHe Cryostat training is mandatory for using related VT device.

If you are new to EPR facility, please contact Heike Hofstetter (hofstetter@chem.wisc.edu) for creating user account and basic EPR training.

If you need to use LN2 or LHe cryostat, please contact Heike Hofstetter (hofstetter@chem.wisc.edu) or Bob Shanks (robert.shanks@wisc.edu) for advanced EPR training.

EPR Useful Links:

There is an excellent set of EPR manuals(Theory and Practical parts) in Evert Duin's group website at Aubrun University. Click here to see his group website and then choose "EPR Manuals" on the left.

Acknowledgement: this manual was written by Evert Duin with contributions from and examples provided by Wilfred Hagen, Michael K. Johnson, Steven Mansoorabadi, Antonio Pierik and Simon. P. J. Albracht.

EPR Sample Preparation

The target concentration for our X-band EPR to obtain a decent signal to noise ratio is usually [400-2000 [(μmol spins)/L] (or ~200 μM sample). Minimum concentration could be 100 μM [(μmol spins)/L] of the desired signal. Higher concentrations can be beneficial, however, concentrations that are too high can potentially lead to artificial line broadening and enhanced relaxation from spin-spin interactions. This is not as important for typical protein samples as the surrounding protein usually acts as a buffer isolating the individual spins.

The last important aspect to consider is the solvent. Organic non polar solvents can typically be used with standard sized X-Band tubes at all temperatures. Unfortunately, samples in aqueous solvents present some difficulties at temperatures above 0° C. The large electric dipole of water interacts strongly with the E field of the standing microwave formed within the resonator. EPR microwave resonators are designed to limit the density of this field at the sample, but it is not possible to completely isolate the sample. The interaction between the two adversely affects the performance of the instrument and the ability to tune the resonator. Therefore, aqueous samples require the use of a thin sample holder called a flat cell or a Q-Band tube if the signal is strong enough. You can also consult with Heike Hofstetter (hofstetter@chem.wisc.edu) about using capillary for aqueous solvents.

EPR Sample Preparation Guide (updated 02/26/2020)