Brian Hoffman

PhD, Caltech

Interdisciplinary Biological Sciences Program

Office Phone: 847.491.3104
Fax: 847.491.7713
Hoffman Group


Long-range interprotein electron transfer; ENDOR of metalloenzymes
We have discovered that long-range electron transfer between proteins can be studied by substituting zinc protoporphyrin for heme in one of the partners of a protein-electron transfer complex. Electron transfer is initiated by flash photoproduction of the zinc protoporphyrin triplet state, which reduces its ferriheme partner by a long-range tunneling process.Mixed-metal (Zn, Fe) hybrid hemoglobins exhibit electron transfer between redox centers that are in a crystallographically known protein environment and are separated by protein residues at a metal- metal distance of 25.

We are applying this approach to physiological electron transfer reactions, such as between yeast cytochrome c peroxidase (CCP) and cytochrome c (cyt c). However, this complex is not conformationally rigid. The use of different cyt c species and of site-directed mutagenesis to vary individual residues of cyt c gives a precise means of investigating both the role of the protein matrix in electron transfer and the influence of conformational dynamics at the protein-protein interface.

Electron-nuclear double resonance (ENDOR) is a technique that combines NMR and EPR. Studies of native and isotopically enriched metaloenzymes hold the promise of individually characterizing every atom of the catalytically active metal center. The systems we are studying include peroxidases, copper proteins containing the blue-copper center, and proteins that contain multimetal centers such as aconitase, cytochrome oxidase, and hydrogenase. Our work includes the development of multifrequency CW and pulsed (nsec) ENDOR spectrometers.


"Dynamic Docking and Electron Transfer Between Zn-myoglobin and Cytochrome b5," Liang, Z.-X.; Nocek, J.; Huang, K.; Hayes, R. T.; Kurnikov, I. V.; Beratan, D. N.; Hoffman, B. M. J. Am. Chem. Soc. 2002, 124, 6849-6859.

"Interprotein Electron Transfer in a Confined Space: Uncoupling Protein Dynamics from Electron Transfer by Sol-gel Encapsulation," Nocek, J.; Hatch, S. L.; Seifert, J. L.; Hunter, G.; Thomas, D. D.; Hoffman, B. M. J. Am. Chem. Soc. 2002, 124, 9404-9411.

"Myoglobin and Cytochrome b5: A Nuclear Magnetic Resonance Study of a Highly Dynamic Protein Complex," Worrall, J. A. R.; Liu, Y.; Crowley, P. B.; Nocek, J.; Hoffman, B. M.; Ubbink, M. Biochemistry 2002, 41, 11721-11730.

"Dynamic Docking and Electron-Transfer between Cytochrome b5 and a Suite of Myoglobin Surface-Charge Mutants. Introduction of a Functional-Docking Algorithm for Protein-Protein Complexes," Liang, Z.-X.; Kurnikov, I. V.; Nocek, J. M.; Mauk, A. G.; Beratan, D. N.; Hoffman, B. M. J. Am. Chem. Soc. 2004, 126, 2785-2798.

"Electrostatic Influence on Rotational Mobilities of Sol-Gel Encapsulated Solutes by NMR and EPR Spectroscopies," Wheeler, K. E.; Lees, N. S.; Gurbiel, R. J.; Hatch, S. L.; Nocek, J. M.; Hoffman, B. M. J. Am. Chem. Soc. 2004, 126, 13459-13463.

"Hopping in the Electron-Transfer Photocycle of the 1:1 Complex of Zn-Cytochrome c Peroxidase with Cytochrome c," Seifert, J. L.; Pfister, T. D.; Nocek, J. M.; Lu, Y.; Hoffman, B. M. J. Am. Chem. Soc. 2005, 127, 5750-5751.

"Differential Influence of Dynamic Processes on Forward and Reverse Electron Transfer Across a Protein-Protein Interface," Hoffman, B. M.; Celis, L. M.; Cull, D. A.; Patel, A. D.; Seifert, J. L.; Wheeler, K. E.; Wang, J.; Yao, J.; Kurnikov, I. V.; Nocek, J. Proc. Natl. Acad. Sci. 2005, 102, 3564-3569.

"Equilibrium/Non-Equilibrium Initial Configurations in Forward/Reverse Electron Transfer Within Mixed-Metal Hemoglobin Hybrids," Patel, A. D.; Nocek, J. M.; Hoffman, B. M. J. Am. Chem. Soc. 2005, 127, 16766-16767.

"Rapid Freeze-Quench ENDOR Study of Chloroperoxidase Compound I: The Site of the Radical," Kim, S. H.; Perera, R.; Hager, L. P.; Dawson, J. H.; Hoffman, B. M. J. Am. Chem. Soc. 2006, 128, 5598-5599.

"NMR Spectroscopy Can Characterize Proteins Encapsulated in a Sol-Gel Matrix," Wheeler, K. E.; Nocek, J. M.; Hoffman, B. M. J. Am. Chem. Soc. 2006, 128, 14782-14783.

"How an Enzyme Tames Reactive Intermediates:Positioning of the Active-Site Components of Lysine 2,3- aminomutase During Enzymatic Turnover as Determined by ENDOR Spectroscopy," Lees, N. S.; Chen, D.; Walsby, C. J.; Behshad, E.; Frey, P. A.; Hoffman, B. M. J. Am. Chem. Soc. 2006, 128, 10145-10154.

"Breaking the N2 triple bond: insights into the nitrogenase mechanism," Barney, B. M.; Lee, H.-I.; Dos Santos, P. C.; Hoffman, B. M.; Dean, D. R.; Seefeldt, L. C. Dalton Transactions 2006, 2277-2284.

"Dynamic Docking of Cytochrome b5 with Myoglobin and α-Hemoglobin: Heme-Neutralization 'Squares' and the Binding of Electron-Transfer-Reactive Configurations," Wheeler, K. E.; Nocek, J.; Cull, D. A.; Yatsunyk, L. A.; Rosenzweig, A. C.; Hoffman, B. M. J. Am. Chem. Soc. 2007, 129, 3906-3917.

"Connecting nitrogenase intermediates with the kinetic scheme for N2 reduction by a relaxation protocol and identification of the N2 binding state,” Lukoyanov, D.; Barney, B. M.; Dean, D. R.; Seefeldt, L. C.; Hoffman, B. M. Proc. Natl. Acad. Sci. 2007, 104, 1451-1455.


Publications by Brian M. Hoffman

Recent Photos

April 16, 2015