Hannah Shafaat received her B.S. in Chemistry from the California Institute of Technology (Caltech) in 2006, where she performed research on spectroscopic endospore viability assays with Adrian Ponce (NASA Jet Propulsion Laboratory) and Harry Gray. She received her Ph.D. in Physical Chemistry from the University of California, San Diego (UCSD) in 2011, under the direction of Professor Judy Kim, as an NSF Graduate Research Fellow and a National Defense Science and Engineering Graduate Fellow. During her graduate research, she used many different types of spectroscopy to study the structure and dynamics of amino acid radical intermediates in biological electron transfer reactions. After earning her Ph.D., Hannah moved across the ocean to Germany to study hydrogenase proteins and learn advanced EPR techniques as a Humboldt Foundation Postdoctoral Fellow working under Director Wolfgang Lubitz at the Max Planck Institute for Chemical Energy Conversion (formerly Bioinorganic Chemistry). Hannah joined The Ohio State University Department of Chemistry and Biochemistry in August 2013.
Combining spectroscopy, theory, and bioinorganic chemistry to study biologically relevant energy conversion reactions
Our research centers on the study of metalloenzymes that carry out valuable reactions relevant to alternative energy sources and clean energy storage. Using nature as inspiration, we seek to harness the advantages of bioinorganic platforms while overcoming the limitations of fragile multimeric protein systems. Our projects utilize a diverse array of scientific tools, from wet chemistry— molecular biology, chemical synthesis, and metalloprotein design—to spectroscopy—steady state and time-resolved optical techniques along with visible and ultraviolet resonance Raman spectroscopy—to quantum chemical calculations. Obtaining molecular-level insight into the mechanisms of catalysis will guide our design of increasingly efficient and robust catalysts for application.
Computationally-guided resonance Raman spectroscopy
In nature, small molecule activation is generally performed by large enzymes containing many redox-active metallocofactors, resulting in complicated spectroscopic signatures. Spectral congestion can be avoided by using selective experimental techniques, such as resonance Raman (RR) spectroscopy. We are applying quantum chemical calculations to inform site- specific RR experiments throughout the UV, visible, and near-IR wavelengths. This approach can provide mechanistic information on a number of enzymatic reactions, including proton reduction, CO2 reduction, nitrogen fixation, water oxidation, and oxygen reduction.
The expanding field of semisynthetic metalloenzymes has demonstrated applications in the fields of enantioselective catalysis, DNA binding, and lignin oxidation, among others. We are extending this general approach to energy conversion reactions. The versatility of the amino acid “alphabet” and the accessibility of site-directed mutagenesis offer some distinct advantages over small-molecule synthetic chemistry, for it is possible to control secondary and tertiary coordination sphere interactions. The knowledge gained from biochemical, spectroscopic, and electrochemical characterization techniques will direct the rational design of progressively complex systems.
The Shafaat group is looking for enthusiastic and motivated graduate and undergraduate students interested in spectroscopy, bioinorganic chemistry, or theoretical spectroscopy. Inquiries about possible positions in the group are welcomed!
Riethausen, J., Rüdiger, O., Gärtner, W., Lubitz, W., and Shafaat, H. S. (2013) Spectroscopic and electrochemical characterization of the [NiFeSe] hydrogenase from Desulfovibrio vulgaris Miyazaki F: Reversible redox behavior and interactions between electron transfer centers, ChemBioChem in press, DOI.
Shafaat, H. S., Rüdiger, O., Ogata, H., and Lubitz, W. (2013) [NiFe] hydrogenases: A common active site for hydrogen metabolism under diverse conditions, Biochimica et Biophysica Acta (BBA) - Bioenergetics in press, DOI.
Weber, K., Krämer, T., Shafaat, H. S., Weyhermuller, T., Bill, E., van Gastel, M., Neese, F., and Lubitz, W. (2012) A functional [NiFe]-hydrogenase model compound that undergoes biologically relevant reversible thiolate protonation, J. Am. Chem. Soc. 134, 20745-20755.
Shafaat, H. S., Weber, K., Petrenko, T., Neese, F., and Lubitz, W. (2012) Key Hydride Vibrational Modes in [NiFe] Hydrogenase Model Compounds Studied by Resonance Raman Spectroscopy and Density Functional Calculations, Inorg. Chem. 51, 11787-11797.
Stoll, S., Shafaat, H. S., Krzystek, J., Ozarowski, A., Tauber, M. J., Kim, J. E., and Britt, R. D. (2011) Hydrogen Bonding of Tryptophan Radicals Revealed by EPR at 700 GHz, J. Am. Chem. Soc. 133, 18098-18101.
Shafaat, H. S., Leigh, B. S., Tauber, M. J., and Kim, J. E. (2010) Spectroscopic Comparison of Photogenerated Tryptophan Radicals in Azurin: Effects of Local Environment and Structure, J. Am. Chem. Soc. 132, 9030.
Shafaat, H. S., Sanchez, K. M., Neary, T. J., and Kim, J. E. (2009) Ultraviolet resonance Raman spectroscopy of a beta-sheet peptide: a model for membrane protein folding, J. Raman Spectrosc. 40, 1060-1064.
Shafaat, H. S., Leigh, B. S., Tauber, M. J., and Kim, J. E. (2009) Resonance Raman Characterization of a Stable Tryptophan Radical in an Azurin Mutant, J. Phys. Chem. B 113, 382-388.