Brian M. Hoffman
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 metalloenzymes 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.
Free H2 Rotation vs Jahn-Teller Constraints in the Nonclassical Trigonal (TPB)Co-H2 Complex. Gunderson WA, Suess DLM, Fong H, Wang X, Hoffmann CM, Cutsail GE, Peters JC, and Hoffman BM. Journal of the American Chemical Society. 2014 October 22;136(42):14998-15009.
Enzymatic and Cryoreduction EPR Studies of the Hydroxylation of Methylated Nω-Hydroxy-L-arginine Analogues by Nitric Oxide Synthase from Geobacillus stearothermophilus. Davydov R, Labby KJ, Chobot SE, Lukoyanov DA, Crane BR, Silverman RB, and Hoffman BM. Biochemistry. 2014 October 21;53(41):6511-6519.
Symmetrized Photoinitiated Electron Flow within the [Myoglobin:Cytochrome b5] Complex on Singlet and Triplet Time Scales: Energetics vs Dynamics. Co NP, Young RM, Smeigh AL, Wasielewski MR, and Hoffman BM. Journal of the American Chemical Society. 2014 September 10;136(36):12730-12736.
EPR, ENDOR, and Electronic Structure Studies of the Jahn-Teller Distortion in an FeV Nitride. Cutsail GE, Stein BW, Subedi D, Smith JM, Kirk ML, and Hoffman BM. Journal of the American Chemical Society. 2014 September 3;136(35):12323-12336.
Identification of the Valence and Coordination Environment of the Particulate Methane Monooxygenase Copper Centers by Advanced EPR Characterization. Culpepper MA, Cutsail GE, Gunderson WA, Hoffman BM, and Rosenzweig AC. Journal of the American Chemical Society. 2014 August 20;136(33):11767-11775.
Internal dynamics of a supramolecular nanofibre. Ortony JH, Newcomb CJ, Matson JB, Palmer LC, Doan PE, Hoffman BM, and Stupp SI. Nature Materials. 2014 August;13(8):812-816.
Synthesis and characterization of a porphyrazine–Gd(III) MRI contrast agent and in vivo imaging of a breast cancer xenograft model. Trivedi ER, Ma Z, Waters EA, MacRenaris KW, Subramanian R, Barrett AGM, Meade TJ, and Hoffman BM. Contrast Media & Molecular Imaging. 2014 July/August;9(4):313-322.
A Confirmation of the Quench-Cryoannealing Relaxation Protocol for Identifying Reduction States of Freeze-Trapped Nitrogenase Intermediates. Lukoyanov D, Yang Z-Y, Duval S, Danyal K, Dean DR, Seefeldt LC, and Hoffman BM. Inorganic Chemistry. 2014 April 7;53(7):3688-3693.
Electronic and Nuclear Structural Snapshots in Ligand Dissociation and Recombination Processes of Iron Porphyrin in Solution: A Combined Optical/X-ray Approach. Mara MW, Shelby M, Stickrath A, Harpham M, Huang J, Zhang X, Hoffman BM, and Chen LX. Journal of Physical Chemistry B. 2013 November 14;117(45):14089-14098.
On reversible H2 loss upon N2 binding to FeMo-cofactor of nitrogenase. Yang Z-Y, Khadka N, Lukoyanov D, Hoffman BM, Dean DR, and Seefeldt LC. PNAS. 2013 October 8;110(41):16327-16332.
View all publications by Brian M. Hoffman listed in the National Library of Medicine (PubMed). Current and former IBiS students in blue.