Chi-Kwong Chang
Professor Office: 424 Chemistry
Phone: 517-355-9715 101 /
Websites: Area
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Genealogy/Graduates
Structure, Synthesis, and Spectroscopy of Porphyrins and Metalloporphyrins
(Research Description PDF - 816 kb)Research in this laboratory emphasizes the application of synthetic organic methods to construct enzyme analogs and models suitable for detailed mechanistic studies. Our efforts focus on the porphyrin and metalloporphyrin chemistry.
The significance and diversity of the biological functions of porphyrin molecules in nature have always been appreciated in photosynthesis and respiration:
Among hemoproteins the role of the heme group spans a broad spectrum of functions ranging from oxygen transport (hemoglobin) to electron transport (cytochrome c) to drug detoxification (cytochrome P-450). To understand the underlying principles that govern the reactivities and functions of the heme prosthetic group has always been the goal of our research. Most heme catalysts involve either a valence change at the metal center or an altering of the redox state of the porphyrin ring or both. It is the unusual flexibility of the porphyrin system to accommodate extreme redox changes, coupled with the convenient coordination and electron-transfer ability of the metal center that makes the metalloporphyrins such versatile catalysts.
Variations in heme functions can be brought about by axial ligand, steric and environmental effects. These effects can often be tested and amplified individually by using suitable synthetic model compounds. Since porphyrin syntheses can be lengthy and difficult, we are developing better ways to synthesize these heterocyclic molecules. The investigation of the properties of model systems also necessitates the use of a wide variety of modern instrumentation and experimental techniques including UV-VIS, NMR, EPR and resonance Raman spectroscopy, CV and other electrochemical analyses, stopped-flow and flash photolysis.
Some examples of bacterial heme prosthetic groups characterized and synthesized in our laboratory include those diagrammed here
Selected Publications
Facile Synthesis of b-Derivatized Porphyrins ? Structural Characterization of a b?b-Bis-Porphyrin, Y. Deng, C. K. Chang, and D. Nocera, Angew. Chem. Int. Ed. Engle. 2000, 39, 1066.The Role of Sub-cellular Localization in Initiation of Apoptosis by Photodynamic Therapy, D. Kessel, Y. Luo, Y. Deng, and C. K. Chang, Photochem. Photobiol. 1997, 65, 422.
Molecular Recognition with C-Clamp Porphyrins: Synthesis, Structural, and Complexation Studies, Y. Liang, C. K. Chang, and S.-M. Peng, J. Mol. Recogn. 1996, 9, 149.
Conformational Control of Intramolecular H-Bonding in Heme Models: Maximal Co(II)-O2 Binding in a C-Clamp Porphyrin, C. K. Chang, Y. Liang, G. Avilés, and S.-M. Peng, J. Am. Chem. Soc. 1995, 117, 4191.
Verdoheme-like Oxaporphyrin Formation by Oxygenation of a Co(II) Porphyrinyl Naphthoic Acid. A New Model of Heme Degradation, C. K. Chang, G. Avilés, and N. Bag, J. Am. Chem. Soc. 1994, 116, 12127
