Faculty

My laboratory focuses on two areas of biological chemistry. In one area, we seek to understand the remarkable catalytic prowess of enzymes, in particular those that use free radicals in catalysis. Recently, we have also begun to explore the potential for developing novel biological catalysts and therapeutic agents offered by the de-novo design and synthesis of novel proteins incorporating highly fluorinated amino acids. Our research is inherently inter-disciplinary in nature and draws on a synergistic combination of bio-organic, bio-inorganic and bio-physical chemistry.

Our major interest is in enzymes that use free radicals (a carbon with an unpaired electron) to catalyze a variety of unusual reactions, many of which have no ready counterpart in organic chemistry. Normally, organic radicals are thought of as highly reactive species that are dangerous to biological systems. However, enzymes can profoundly alter the reactivity of free radicals so that a radical with a lifetime of microseconds in free solution may be stable for days when generated within a protein! Enzymes are therefore able to exploit free radicals as "sparks" with which to ignite reactions on otherwise un-reactive substrate molecules.

We are studying a class of enzymes that use the cobalt-containing organo-metallic coenzyme B12 to generate free radicals. These enzymes provide excellent model systems with which to study free radical catalysis. We are using a variety of kinetic and spectroscopic techniques, together with site-specific mutagenesis to understand how the enzymes generate and control reactive organic radical species.

In a new area of research, we are exploring the interface between biological macromolecules and materials chemistry though the de-novo design of extensively fluorinated 'Teflon' proteins. Perfluorocarbons exhibit unique and useful physical properties that are not found in nature. For example, Teflon derives its highly inert and non-stick properties from the perfluorinated polymer polytetrafluoroethylene. We are examining the effects of replacing 'greasy' hydrophobic amino acids that are found in the interior of proteins with extensively fluorinated analogs to create a 'Teflon' interior. We expect that such proteins may exhibit useful new properties such as increased thermal stability, resistance to unfolding in organic solvents, and resistance to degradation by proteases. Teflon proteins may also exhibit novel protein:protein interactions and provide model systems to test theories of protein folding.

Awards

Research Fellow of the Royal Society
Fellow of the Royal Society of Chemistry
Sc.D., University of Cambridge

Representative Publications

1. Gottler, L.M., Lee, H.-Y, Shelburne, C.E., Ramamoorthy, A., and Marsh, E.N.G. "Enhancing the biological activity of an antimicrobial peptide using fluorous amino acids", ChemBioChem, 2008, 9, 370-373. [Full Article]

2. Yoon, M., Kalli, A., Lee, H.-Y, Hakansson, K., and Marsh, E.N.G. "Intrinsic deuterium kinetic isotope effects in glutamate mutase measured by an intramolecular competition experiment", Angew. Chem., 2007, 44, 8455-8459. [Full Article]

3. Lee, H.-Y, Yoon, M., and Marsh, E.N.G. "Synthesis of mono- and di-deuterated (2S,3S)-3-methylaspartic acids to facilitate measurement of intrinsic kinetic isotope effects in enzymes", Tetrahedron, 2007, 63, 4663-4668. [Full Article]

4. Cheng, M.C. and Marsh, E.N.G. "Evidence for coupled motion and hydrogen tunneling the reaction catalyzed by glutamase mutase", Biochem., 2007, 46, 883-888. [Full Article]

5. Li, L. and Marsh, E.N.G. "Mechanism of benzylsuccinate synthase probed by substrate exchange", J. Am. Chem. Soc., 2006, 128, 16056-16058. [Full Article]

6. Li, L. and Marsh, E.N.G. "Deuterium isotope effects in the unusual addition of toluene to fumarate catalyzed by benzylsuccinate synthase", Biochem., 2006, 45, 13932-13938. [Full Article]

7. Yoon, M., Patwardhan, A., Qiao, C., Mansoorabadi, S., Menefee, A.L., Reed, G.R., and Marsh, E.N.G. "The reaction of adenosylcobalamin-dependent glutamase mutase with 2-thioglutarate", Biochem., 2006, 45, 11650-11657. [Full Article]

8. Lee, H.-Y, Lee, K.-H, Al-Hashimi, H.M., and Marsh, E.N.G. "Modulating protein structure with fluorous amino acids: increased stability and native-like structure conferred on a 4-helix bundle protein by hexafluoroleucine", J. Am. Chem. Soc., 2006, 128, 337-343. [Full Article]