Our lab has been funded by the National Science Foundation, most recently between 2021-2025, by the Molecular & Cellular Biosciences Division. In the past, our lab received funding, between 2010-13 and 2013-2017, from the Chemistry of Life Processes (CLP) Program. 
All the projects in the Popescu Lab involve solely undergraduate students and are in various stages of planning or accomplishment. For the latter, see our publications list.

Current Projects

• Studies of iron-sulfur proteins, cellular iron trafficking and regulation.(see Image attached)
• Studies of the dual-function enzyme dehaloperoxidase (DHP) from Amphitrite ornata and from other marine worms.
• Characterization of novel Fe(I) and other unusual bio-inspired complexes.
• Studies of iron complexes exhibiting spin transitions.
• The study of novel complexes that aim to model the active site of hydrogenase enzymes.

These projects combine spectroscopic characterization of iron bio-inspired complexes with the analysis of enzyme active sites, calculations and biochemical characterization of enzymes, such as DHP. These collaborative projects involve world-class scientists, both synthetic chemists and biochemists, from Montana State University, Louisiana State University, Marquette University, and North Carolina State University (Raleigh).

Recent Developments in the Mössbauer Spectroscopy of Iron-Sulfur Proteins

In collaboration with Dr. Huangen Ding and his group from Louisiana State, Dr. Popescu's lab studied the structure and redox state of the Fur protein in E. coli by whole-cell Mössbauer spectroscopy. Some of these studies, involving the analysis of Mössbauer spectra of the purified Fur protein, were done by undergraduate student Thomas Hoepner, under Dr. Popescu’s mentoring.

The findings were published in a collaborative paper in the Journal of Inorganic Biochemistry in 2025.
Link to our paper in the Journal of Inorganic Biochemistry on whole-cell Mössbauer studies of the Fur protein

Currently, we are continuing to study new model complexes and iron-sulfur proteins with Mössbauer spectroscopy. In addition, we are pursuing protein purification and spectroscopic studies of globins from marine worms, in collaboration with Drs. Stefan Franzen and Reza Ghiladi from North Carolina State University (Raleigh).

Fontenot, C. R.; *Hoepner, T.; Xiong, J.; Ding, H.; Popescu, C. V. “Mössbauer Studies of the Redox State of the Ferric Uptake Regulator [2Fe–2S]2+ Cluster in Escherichia Coli”. J. Inorg. Biochem. 2025, 270, 112928. https://doi.org/10.1016/j.jinorgbio.2025.112928.

Devkota, L.; Xiong, J.; Fischer, A. A.; *Murphy, K.; Kumar, P.; Balensiefen, E. L.; Lindeman, S. L.; Popescu, C. V.; Fiedler, A. T. “Observation of Oxygenated Intermediates in Functional Mimics of Aminophenol Dioxygenase”. J. Inorg. Biochem. 2024, 259. (Undergraduate co-authors: Kate Murphy)

Popescu, C. V.; Dinh, T.; Chen, H.; Miller, D.; Washburn, A.; McGuire, A.; Dumarieh, R.; D'Antonio, J.; Ghiladi, R. A., Mössbauer studies of the ferryl, ferrous, and ferric states of the dehaloperoxidase from A. ornata. J. Inorg. Biochem. 2022, 234, 111867.

Ekanayake, D.M., *Pham, D., *Probst, A.L., Miller, J.R., Popescu, C.V., Fiedler, A.T. “Electronic structures and spectroscopic signatures of diiron intermediates generated by O2 activation of nonheme iron(II)–thiolate complexes” Dalton Trans. (2021) 50, 14432-14443. (*Undergraduate co-authors: Dao Pham and Drew Probst)

Wang,P., Saber, M., VanNatta, P., Yap, G., Popescu, C.V., Scarborough, C., Kieber-Emmons, M., Dunbar, K., Riordan, C. G. "Molecular and electronic structures, and single-molecule magnet behavior of tris(thioether)-iron complexes containing redox-active α-diimine ligands" Inorg. Chem. (2021) 60 (9) 6480-6491. DOI: 10.1021/acs.inorgchem.1c00214

Ekanayake, D.E, Fischer, A.A, *Elwood, M.E, Guzek, A.M, Lindeman, S.V, Popescu, C.V., Fiedler, A.T. "Nonheme Iron-Thiolate Complexes as Structural Models of Sulfoxide Synthase Active Sites" Dalton Trans. (2020) 49, 17745-17757. DOI: 1039/D0DT03403G (*Maya Elwood is an undergraduate student)

Fontenot, C.R., Tasnim, H. *Valdes, K.A., Popescu, C.V., Ding, H. "Ferric uptake regulator (Fur) reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis in Escherichia coli" Biol. Chem. (2020) 295, 15454-15463. DOI: doi.org/10.1074/jbc.RA120.014814 (*Kate Valdes is an undergraduate student) EDITOR'S PICK!

Kephart, J.A., Hecht, Z.H., Livesay, B.N., Shores, M.P., Popescu, C.V., Arulsamy, N., Hulley, E.B."Self-assembly of an Organometallic Fe₉O₆ Cluster from Aerobic Oxidation of (tmeda)Fe(CH₂tBu)₂" Chem. Comm. (2020) 56 (37) 4994-4997. DOI: 10.1039/D0CC00011F

Gordon, Z., Miller, .T.J., Leahy, C.A., Matson, E.M., Burgess, M., Drummond, M.J., Popescu, C.V., *Smith, C.M., Lord, R.L., Rodríguez-López, J., Fout, A.R. Chem. (2019) Inorg. Chem. (2019) 58 (23) 15801–15811. DOI: 10.1021/acs.inorgchem.9b02079. (*Connor Smith is an undergraduate student)

Popescu, C.V., Ding, S., Ghosh, P., Hall, *Cohara, M. Mössbauer Spectroscopic and Theoretical Studies of bimetallic complexes showing electrocatalytic hydrogen evolution Chem. (2019) 58 (10) 7069-7077. DOI: 10.1021/acs.inorgchem.9b00746. (*Morgan Cohara was an undergraduate student)

Drummond, M. J., Ford, C. J., Gray, D. G., Popescu, C. V., Fout, A. R. Radical Rebound Hydroxylation Versus H-Atom Transfer in Non-Heme Iron(III)-Hydroxo Complexes: Reactivity and Structural Differentiation Am. Chem. Soc. (2019) 141 (16), 6639–6650. DOI: 10.1021/jacs.9b01516.

The ACS National Meeting, Washington, D.C. – August 17-21, 2025, “Whole-cell Mössbauer spectroscopy of the ferric uptake regulator (Fur): features, successes, and limitations” Popescu, C.V.(presenter), *Hoepner, Thomas, Fontenot, C., Ding, H.

The National Conference of Undergraduate Research, Pittsburgh, April 2025 – “Multi-disciplinary Study of the Material Composition of Ceramics Fragments from the Soline Bay Roman Villa in Croatia” C. V. Popescu (presenter), *R. A. Johnson, V. Rousseau, I. Schrunk.

The 17th European Biological Inorganic Chemistry Conference (EUROBIC 17) – August, 2024, Münster, Germany “Mössbauer spectroscopic studies of Fur proteins isolated and in whole cells” C. V. Popescu, (presenter) *T. Hoepner, C. Fontenot, H. Ding.

The 16th International Symposium on Applications of Bioinorganic Chemistry (ISABC 16) – June, 2023, Ioannina, Greece “Mössbauer spectroscopic studies of the Fur and Isc proteins in whole cells” Popescu, C.V. (presenter), *Elmi, S.A., Fontenot, C., Ding, H.

2021-2025: National Science Foundation Award - NSF-MCB Standard Grant
Collaborative Research: The ferric uptake regulator (Fur) regulates intracellular iron homeostasis via reversible binding of a [2Fe-2S] cluster in Escherichia coli (Collaborative research with Dr. Huangen Ding, at Louisiana State University, Baton, Rouge, LA)

Past Awards

2014-2017: National Science Foundation – RUI: Mössbauer Studies of Iron Containing Model complexes and enzymatic active sites ($ 189,000) – CHE-1445959;

2013-2014: National Science Foundation – RUI: Mössbauer Studies of Iron Containing Model complexes and enzymatic active sites - CHE-1307650

2010-2014: National Science Foundation – RUI: Mössbauer Studies of Iron Containing Model complexes and enzymatic active sites ($ 165,000) – CHE-0956779

2004-2007: National Science Foundation – Major Research Instrumentation Award for Acquisition of a Mössbauer Spectrometer at Ursinus College ($124,000) – MRI-0421116

2002-2003: NIH Ruth Kirschstein National Research Service Award for post-doctoral research – Structural Dynamics of Methane Monooxygenase by Nitroxide-EPR and Fluorescence Energy Transfer (FET).