EPR Facility



Electron Paramagnetic Resonance (EPR) Facility

A research facility for studying paramagnetic centers by continuous wave and pulsed EPR techniques to obtain information on the electronic, chemical, and geometric molecular structures.






Training, experimental design and/or sample service.

Carl S Marvel Map

Visit Us!


Carl S. Marvel Laboratories, Room 110A


Monday thru Friday

8:00 AM to 5:00 PM



The EPR facility serves the faculty of the UA Department of Chemistry and Biochemistry and outside customers, both academic and non-academic. We can perform various kinds of work, from a simple characterization by continuous wave EPR to in-depth studies by high resolution pulsed EPR techniques, including ESEEM, ENDOR, ELDOR (DEER), etc. We also help with interpreting the data in terms of chemical, geometrical, and electronic structures, and with describing the EPR results in publications. The instrumentation available includes the continuous wave EPR spectrometer (Bruker ElexSys E500) operating in X- and Q-bands and a broadband (2 – 40 GHz) pulsed EPR spectrometer capable of all kinds of pulsed experiments.



The facility performs, twice a year, lab demonstrations for students of Chem 412 class. Periodically, the facility manager makes seminar and conference presentations on the recent research projects the facility was engaged in. The students willing to learn the use of the EPR spectrometer are welcome to train on the techniques.

Facility Publications

Use the EPR Facility RRID!

University of Arizona - CBC Electron Paramagnetic Resonance (EPR) Facility, RRID:SCR_022883

  • Shuvaev, S.; Suturina, EA; Rotile, NJ: Astashkin, A; Ziegler, CJ; Ross, AW; Walker, TL; Caravan, P.; Taschner, IS. Revisiting dithiadiaza macrocyclic chelators for copper-64 PET imaging.  Dalton Trans. 49 (2020) 14088-14098.

  • KJ Colston, SA Dille, B Mogesa, AV Astashkin, JA Brant, M Zeller, P Basu.  Design, Synthesis, and Structure of Copper Dithione Complexes: RedoxDependent Charge Transfer.  Eur. J. Inorg. Chem. 46 (2019) 4939-4948.

  • Gautam, R.; Petritis, S. J.; Tomat, E. “Redox-switchable cyan fluorescence of a BODIPY analog inspired by propentdyopent pigments” Eur. J. Inorg. Chem. 2019, 68-72.

  • Tomat, E. “Propentdyopents: Brief history of a family of dipyrrolic pigments" J. Porphyrins Phthalocyanines 2019, 23, 1265-1272.

  • R Golovchak, MJ Davis, P Vullo, A Astashkin, L Nichols, A Ingram, H Jain.  The charge state of titanium ions in Pddoped Ti: CMAS glass and glassceramics.  J. Am. Ceram. Soc. 100 (2017), 2568-2581.

  • R Gautam, T M Chang, A V Astashkin, K M Lincoln, E Tomat (2016)  Propentdyopent: the scaffold of a hememetabolite as an electron reservoir in transitionmetal complexes. Chem. Commun. 52:  6585-6588.

  • J Ge, S D Bouriyaphone, T A Serebrennikova, A V Astashkin, Y E Nesmelov (2016)  Macromolecular Crowding Modulates Actomyosin Kinetics. Biophys. J. 111:  178-184. 2015

  • R Gautam, J J Loughrey, A V Astashkin, J Shearer, E Tomat (2015)  Tripyrrindione as a Redox-Active Ligand: Palladium(II) Coordination in Three Redox States. Angew. Chem. Int. Ed. 54:  14894–14897.

  • A V Astashkin, C Feng (2015)  Solving Kinetic Equations for the Laser Flash Photolysis Experiment on Nitric Oxide Synthases: Effect of Conformational Dynamics on the Interdomain Electron Transfer. J. Phys. Chem. A 119:  11066–11075.

  • A V Astashkin, L Chen, B O Elmore, D Kunwar, Y Miao, H Li, T L Poulos, L J Roman, C Feng (2015)  Probing the Hydrogen Bonding of the Ferrous–NO Heme Center of nNOS by Pulsed Electron Paramagnetic Resonance. J. Phys. Chem. A 119:  6641-6649.

  • D J Sommer, A Roy, A V Astashkin, G Ghirlanda (2015)  Modulation of Cluster Incorporation Specificity in a De Novo Iron-Sulfur Cluster Binding Peptide. Peptide Sci. 104:  412-418.

  • R Gautam, E A Akam, A V Astashkin, J J Loughrey, E Tomat (2015)  Sirtuin inhibitor sirtinol is an intracellular iron chelator. Chem. Commun. 51:  5104-5107. 2014

  • J J Griebel, N A Nguyen, A V Astashkin, R S Glass, M E Mackay, K Char, J Pyun (2014)  Preparation of Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur. ACS Macro Lett. 3:   1258-1261.

  • A V Astashkin, L Chen, X Zhou, H Li, T L Poulos, K J Liu, J G Guillemette, C Feng (2014)  Pulsed Electron Paramagnetic Resonance Study of Domain Docking in Neuronal Nitric Oxide Synthase: The Calmodulin and Output State Perspective. J. Phys. Chem. A 118:  6864-6872.

  • E A Akam, T M Chang, A V Astashkin, E Tomat (2014)  Intracellular reduction/activation of a disulfide switch in thiosemicarbazone iron chelators. Metallomics 6:  1905-1912.

  • T M Chang, S Sinharay, A V Astashkin, E Tomat (2014)  Prodigiosin analogue designed for metal coordination: stable zinc and copper pyrrolyldipyrrins. Inorg. Chem. 53:  7518-7526.

  • DOIE L Klein, A A Belaidi, A M Raitsimring, A C Davis, T Krämer, A V Astashkin, F Neese, G Schwarz, J H Enemark (2014)  Pulsed electron paramagnetic resonance spectroscopy of (33)S-labeled molybdenum cofactor in catalytically active bioengineered sulfite oxidase. Inorg. Chem. 53:  961-971.

  • A Roy, D J Sommer, R A Schmitz, C L Brown, D Gust, A Astashkin, G Ghirlanda (2014)  A de novo designed 2[4Fe-4S] ferredoxin mimic mediates electron transfer. J. Am. Chem. Soc. 136:  17343-17349.

  • M T Nelp, A V Astashkin, L A Breci, R M McCarty, V Bandarian (2014)  The Alpha Subunit of Nitrile Hydratase Is Sufficient for Catalytic Activity and Post-Translational Modification. Biochemistry 53:  3990-3994. 2013

  • A Raitsimring, A V Astashkin, J H Enemark, I Kaminker, D Goldfarb, E D Walter, Y Song, Thomas J Meade (2013)  Optimization of pulsed-DEER measurements for Gd-based labels: Choice of operational frequencies, pulse durations and positions, and temperature Appl. Magn. Reson. 44:  649-670.

  • S P Panda, W Li, P Venkatakrishnan, L Chen, A V Astashkin, B S S Masters, C Feng, L J Roman (2013)  Differential calmodulin-modulatory and electron transfer properties of neuronal nitric oxide synthase mu compared to the alpha variant FEBS Lett. 587:  3973-3978.

  • E L Klein, A V Astashkin, A M Raitsimring, J H Enemark (2013)  Applications of pulsed EPR spectroscopy to structural studies of sulfite oxidizing enzymes. Coord.Chem.Rev. 257:  110-118.

  • A V Astashkin, F A Walker (2013)  Determination of the principal g-values of Type I or highly-anisotropic low spin (HALS) ferriheme centers in frozen solutions. J. Magn. Reson. 231:  15-21.

  • A Roy, I Sarrou, M D Vaughn, A V Astashkin, G Ghirlanda (2013)  De novo design of an artificial bis [4Fe-4S] binding protein. Biochemistry 52:  7586-7594.

  • W Li, L Chen, C Lu, B O Elmore, A V Astashkin, D L Rousseau, S -R Yeh, C Feng (2013)  Regulatory Role of Glu546 in Flavin Mononucleotide−Heme Electron Transfer in Human Inducible Nitric Oxide Synthase. Inorg. Chem. 52:  4795-4801. 2012

  • A Raitsimring, A Astashkin, J H Enemark, A Blank, Y Twig, Y Song, T J Meade (2012)  Dielectric Resonator for Ka-Band Pulsed EPR Measurements at Cryogenic Temperatures: Probehead Construction and Applications Appl. Magn. Reson. 42:  441-452.

  • A V Astashkin, Y E Nesmelov (2012)  Mn2+−Nucleotide coordination at the myosin active site as detected by pulsed electron paramagnetic resonance. J. Phys. Chem. B 116:  13655-13662.

  • A V Astashkin, B O Elmore, L Chen, W Fan, J G Guillemette, C Feng (2012)  Pulsed ENDOR Determination of the Arginine Location in Ferrous-NO Form of Neuronal NOS. J. Phys. Chem. A 116:  6731-6739.

  • E L Klein, A M Raitsimring, A V Astashkin, A Rajapakshe, K Johnson-Winters, A R Arnold, A Potapov, D Goldfarb, J H Enemark (2012)  Identity of the Exchangeable Sulfur-Containing Ligand at the Mo(V) Center of R160Q Human Sulfite Oxidase. Inorg. Chem. 51:  1408-1418.

  • A V Astashkin, A Rajapakshe, M J Cornelison, K Johnson-Winters, J H Enemark (2012)  Determination of the Distance between the Mo(V) and Fe(III) Heme Centers of Wild Type Human Sulfite Oxidase by Pulsed EPR Spectroscopy. J. Phys. Chem. B 116:  1942-1950.

  • A.V. Astashkin. "Integrated refocused virtual ESEEM: Detection of nuclear transition spectra without dead time and blind spots." J. Magn. Reson. 209 (2011) 69-74.
  • A.V. Astashkin, E.L. Klein, D. Ganyushin, K. Johnson-Winters, F. Neese, U. Kappler, and J.H. Enemark. "Exchangeable oxygens in the vicinity of the molybdenum center of the high-pH form of sulfite oxidase and sulfite dehydrogenase." Phys. Chem. Chem. Phys.. 11 (2009) 6733-6742.
  • A.V. Astashkin, K. Johnson-Winters, E.L. Klein, R.S.Byrne, A.M. Raitsimring, and J.H. Enemark. "Direct Demonstration of the Presence of Coordinated Sulfate in the Reaction Pathway of Arabidopsis thaliana Sulfite Oxidase Using 33S Labeling and ESEEM Spectroscopy." J. Amer. Chem. Soc. 129 (2007) 14800-14810.
  • A.V. Astashkin, J.H. Enemark and A.M. Raitsimring. 26.5-40 GHz Ka-band pulsed EPR spectrometer. Concepts in Magnetic Resonance. Part B. Magnetic Resonance Engineering. 29B (2006) 125-136.
  • A.V. Astashkin, F. Neese, A.M. Raitsimring, J.J.A. Cooney, E. Bultman, and J.H. Enemark. "Pulsed EPR Investigations of Systems Modeling Molybdenum Enzymes: Hyperfine and Quadrupole Parameters of Oxo-17O in [Mo17O(SPh)4]-." J. Am. Chem. Soc. 127 (2005) 16713-16722.
  • A.M. Raitsimring, A.V. Astashkin, O.G. Poluektov and P. Caravan. "High field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions." Appl. Magn. Reson. 28 (2005) 281-295.
  • A.V. Astashkin, A.M. Raitsimring, and P. Caravan. "Pulsed ENDOR Study of Water Coordination to Gd3+ Complexes in Orientationally Disordered Systems." J. Phys. Chem. A. (2004) 108(11); 1990-2001.
  • A.V. Astashkin and A.M. Raitsimring. "Electron spin echo envelope modulation theory for high electron spin systems in weak crystal field." J. Chem. Phys. 117 (2002) 6121-6132.
  • A.V. Astashkin and A.M. Raitsimring. "Properties of the HYSCORE spin echo signal." J. Magn. Reson. 148 (2001) 379-387.
  • A.V. Astashkin, V.V. Kozlyuk, and A.M. Raitsimring. "ESEEM measurements with time-resolved detection of the entire ESE signal shape. J. Magn. Reson. 145 (2000) 357-363.
  • A.V. Astashkin and A.M. Raitsimring. "Refocused primary echo: a zero dead time detection of the electron spin echo envelope modulation." J. Magn. Reson. 143 (2000) 280-291.
  • A. Potapov, Y. Song, T.J. Meade, D. Goldfarb, A.V. Astashkin, and A. Raitsimring. "Distance measurements in model bis-Gd(III) complexes with flexible 'bridge'. Emulation of biological molecules having flexible structure with Gd(III) labels attached." J. Magn. Reson. 205 (2010) 38-49.
  • A.V. Astashkin, B.O. Elmore, W. Fan, J.G. Guillemette, and C. Feng. "Pulsed EPR determination of the distance between heme iron and FMN centers in a human inducible nitric oxide synthase." J. Am. Chem. Soc. 132 (2010) 12059-12067.
  • A.V. Astashkin and A. Kawamori. Distance measurements in photosynthetic reaction centers by pulsed EPR. in Biophysical techniques in Photosynthesis v. II (Advances in Photosynthesis and Respiration v. 26), eds. T.J. Aartsma and J. Matysik, 2008, Springer, Dordrecht, 325-343.
  • A.V. Astashkin, J. Seravalli, S.O. Mansoorabadi, G.H. Reed, and S.W. Ragsdale. "Pulsed electron paramagnetic resonance experiments identify the paramagnetic intermediates in the pyruvate ferredoxin oxidoreductase Catalytic Cycle." J. Am. Chem. Soc. 128 (2006) 3888-3889.
  • J.H. Enemark, A.M. Raitsimring, A.V. Astashkin, and E.L. Klein. "Implications for the mechanism of sulfite oxidizing enzymes from pulsed EPR spectroscopy and DFT calculations for 'difficult' nuclei." Faraday Discuss. 148 (2011) 249-267.
  • J.H. Enemark, A.V. Astashkin, and A.M. Raitsimring. "Investigation of the coordination structures of the molybdenum(V) sites of sulfite oxidizing enzymes by pulsed EPR spectroscopy." Dalton Trans. (2006) 3501-3514.
  • A.V. Astashkin, A.M. Raitsimring, F.A. Walker, C. Rensing, and M. McEvoy. "Characterization of the copper(II) binding site in the pink copper binding protein CusF by electron paramagnetic resonance spectroscopy." J. Biol. Inorg. Chem. 10 (2005) 221-230.
  • L.M. Utschig, A.V. Astashkin, A.M. Raitsimring, M.C. Thurnauer, and O.G. Poluektov. "Pulsed EPR/ENDOR Characterization of the Cu2+ Surface Site in Photosynthetic Bacterial Reaction Centers." J. Phys. Chem. B. 108 (2004) 11150-11156.
  • S.G. Zech, W.C. Sun, V. Jacques, P. Caravan, A.V. Astashkin, and A.M. Raitsimring. "Probing the Water Coordination of Protein-Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy." ChemPhysChem 6 (2005) 2570-2577.
  • A.V. Astashkin, A.M. Raitsimring, and P. Caravan. "Pulsed ENDOR study of water coordination to Gd3+ complexes in orientationally disordered systems." J. Phys. Chem. A. 108 (2004) 1990-2001.
  • A.V. Astashkin, A.M. Raitsimring, A.R. Kennedy, T.Kh. Shokhireva, and F.A. Walker. "Pulsed EPR characterization of the low-spin iron(III) porphyrinate complexes with phenyl isocyanide ligands having the dxy orbital ground state." J. Phys. Chem. A 106 (2002) 74-82.
  • A.V. Astashkin, A.M. Raitsimring, and F.A. Walker. "1H pulsed ENDOR and ESEEM evidence that the bis-imidazole complexes of iron(III) tetraphenylchlorin and tetraphenylporphyrin have the same order of g-values, and the same electronic ground state." J. Am. Chem. Soc. 123 (2001) 1905-1913.

Contact Us:

Andrei Astachkine, Ph.D.

Assistant Staff Scientist