Harry Gray (chemist)

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Harry B. Gray is currently the Arnold O. Beckman Professor of Chemistry and Founding Director of the Beckman Institute at the California Institute of Technology. He received his B. S. from Western Kentucky University (1957) and his Ph.D. in 1960 with Fred Basolo at Northwestern University.

Professor Gray's interdisciplinary research program addresses a wide range of fundamental problems in inorganic chemistry, biochemistry, and biophysics. Electron transfer (ET) chemistry is a unifying theme for much of this research.

Great progress has been made in understanding how covalent bridges mediate long-range ET reactions. Questions remain, however, regarding the contributions of solvents to long-range interactions between electron donors and acceptors. Gray's research has shown that electron tunneling in aqueous glasses is much less efficient than tunneling across saturated covalent bridges. Investigations of ET reactions between excited metal complexes and electron acceptors in rigid protic and aprotic media are probing the factors that control distant couplings through solvents.

Over the past twenty years the Gray group has been measuring the kinetics of long-range ET reactions in metalloproteins labeled with inorganic redox reagents. Current research is aimed at understanding how intermediate protein radicals accelerate long-range ET. New techniques have been developed for measuring ET rates in crystals of Ru-, Os-, and Re-modified azurins, as well as crystals of Fe(III)-cytochrome c doped with Zn(II)-cytochrome c. This method of integrating photosensitizers into protein crystals has provided a powerful new tool for studying biochemical reaction dynamics.

Electron exchange with metal cofactors deeply buried in the interiors of redox enzymes is often quite slow. Researchers in the Gray group have succeeded in accelerating the delivery of electrons and holes to the buried active site of cytochrome P450 by tethering a photochemical redox sensitizer to P450 substrate analogs. This approach is now being exploited in studies of several other redox enzymes (e.g., nitric oxide synthase, catechol oxidase, amine oxidase).

The Gray group is also using ET chemistry to probe the dynamics of protein folding. A continuing challenge in this is field understanding how a heterogeneous ensemble of unfolded polypeptides evolves into a collection of neatly folded proteins. Laser-induced ET reactions are being used both to trigger and to probe the folding of redox active proteins. Research also is aimed at using fluorescence energy transfer to probe the heterogeneity of protein ensembles during folding.

[edit] Major Publications

Electron Tunneling Through Water: Oxidative Quenching of Electronically Excited Ru(tpy)22+ (tpy=2,2':6,2"-terpyridine) by Ferric Ions in Aqueous Glasses at 77 K, A. Ponce, H. B. Gray, and J. R. Winkler, J. Am. Chem. Soc. 2000, 122, 8187-8191.

Bond-Mediated Electron Tunneling in Ruthenium-Modified High-Potential Iron-Sulfur Protein, E. Babini, I. Bertini, M. Borsari, F. Capozzi, C. Luchinat, X. Y. Zhang, G. L. C. Moura, I. V. Kurnikov, D. N. Beratan, A. Ponce, A. J. Di Bilio, J. R. Winkler, and H. B. Gray, J. Am. Chem. Soc. 2000, 122, 4532-4533.

Electron Tunneling in Biological Molecules, J. R. Winkler, A. J. Di Bilio, N. A. Farrow, J. H. Richards, and H. B. Gray, Pure Appl. Chem. 1999, 71, 1753-1764.

Optical Detection of Cytochrome P450 by Sensitizer-Linked Substrates, I. J. Dmochowski, B. R. Crane, J. J. Wilker, J. R. Winkler, and H. B. Gray, Proc. Natl. Acad. Sci. USA 1999, 96, 12987-12990.

Substrates for Rapid Delivery of Electrons and Holes to Buried Active Sites in Proteins, J. J. Wilker, I. J. Dmochowski, J. H. Dawson, J. R. Winkler, and H. B. Gray, Angew. Chem. Int. Ed. 1999, 38, 90-92.

Protein Folding Triggered by Electron Transfer, J. R. Telford, P. Wittung-Stafshede, H. B. Gray, and J. R. Winkler, Acc. Chem. Res. 1998, 31, 755-763.

Electron Transfer in Proteins, H. B. Gray and J. R. Winkler, Annu. Rev. Biochem. 1996, 65, 537-561.

Protein Folding Triggered by Electron Transfer, T. Pascher, J. P. Chesick, J. R. Winkler, and H. B. Gray, Science 1996, 271, 1558-1560.

Electron-Tunneling in Proteins - Coupling Through a b-Strand, R. Langen, I-J. Chang, J. P. Germanas, J. H. Richards, J. R. Winkler, and H. B. Gray, Science 1995, 268, 1733-1735.

Mechanism of Catalytic Oxygenation of Alkanes by Halogenated Iron Porphyrins, M. W. Grinstaff, M. G. Hill, J. A. Labinger, and H. B. Gray, Science 1994, 264, 1311-1313