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Gigi B. Ray

Principal Senior Lecturer; Faculty Advisor for Chemistry Honors & STEM

A.B. (1985): Bryn Mawr College
M.A. (1987): Princeton University
Ph.D. (1992): Princeton University
Postdoctoral Research Associate:
(1993) University of Pennsylvania, Microbiology
(1994,1998) St. Jude Children’s Research Hospital, Tumor Cell & Structural Biology




Research Interest: Spectroscopic Characterization of Heme Protein Model Compounds

Research involves characterization of biomimetic manganese porphyrin complexes that model redox active heme proteins. In peroxidase and catalase enzymes the proximal ligand donates electron density into the central metal to facilitate electron transfer to distal H2O2, and helps stabilize high-valent metal oxidation states during catalysis. UV-Vis absorption and paramagnetic 1H-NMR spectroscopy are used to determine the basicity and binding affinity of ligands to Mn(III) porphryins, that can facilitate substrate oxidation. The paramagnetism of d4 Mn(III) porphyrins leads to reduced congestion in the 1H-NMR spectra, since resonances arising from the aromatic heme core and bound axial ligands fall outside the diamagnetic envelope. Oxidized Mn(IV) and reduced Mn(II) complexes with anionic ligands are also examined in order to model various spin, coordination and oxidation states of catalytic enzyme intermediates. Spectroscopic studies are used to probe intermolecular H-bonding effects as well as steric and electronic factors that influence the ligand’s ability to donate electrons to the metal. Students prepare and characterize model compounds of metalloproteins that catalyze oxidation reactions, with the goal of catalyst development. They explore structure-function relationships and gain mastery in spectroscopic and molecular modeling techniques commonly used in biochemistry.


Representative Publications

  1. Ray, G. B. and Cook, J. W. (2005). Molecular Modeling of Heme Proteins using MOE: Bio-Inorganic and Structure-Function Activity for Undergraduates, Biochem. Mol. Biol. Educ., 33, 194-201.
  2. Ray, G. B., Li, X.-Y., Ibers, J. A., Sessler, J. L., and Spiro, T. G. (1994). How Far Can Proteins Bend the FeCO Unit? Distal Polar and Steric Effects in Heme Proteins and Models, J. Am. Chem. Soc., 116, 162-176.
  3. Nick, R. J., Ray, G. B., Fish, K. M., Spiro, T. G., and Groves, J. T. (1991). Evidence for a Weak Mn=O Bond and a Non-porphyrin radical in Manganese-Substituted Horseradish Peroxidase Compound I, J. Am. Chem. Soc., 113, 1838-1840.
  4. Czernuszewicz, R. S., Wagner, W. D., Ray, G. B. and Nakamoto, K. (1991). Resonance Raman and Infrared Spectra of Azidoiron(III) and Azidomanganese(III) Porphyrins, J. Mol. Spec., 242, 99-117.
  5. Ray, G. B., Copeland, R. A., Lee, C. P., and Spiro, T. G. (1990). Resonance Raman Evidence for Low-spin Fe2+ Heme a3 in Energized Cytochrome c Oxidase: Implications for the Inhibition of O2 Reduction, Biochemistry, 29, 3208-3213.