Michigan State University / Department of Chemistry
Warren F. Beck
Office: 3 Chemistry, basement level
Telephone: 517/355-9715 x213
Fax: 517/353-1793
Email: beckw at msu.edu
Laboratories: 4, 6, 16, 40, and 52 Chemistry
Vitae: B.S. 1982, Davidson College; Ph.D., Yale University, 1988 (with Gary Brudvig); Miller Institute Postdoctoral Fellowship, University of California, Berkeley, 1989-91 (with Kenneth Sauer).
Honors: Phi Beta Kappa (1982); National Science Foundation Graduate Fellowship (1982–1985); Kent Fellowship, Department of Chemistry, Yale University (1982–1986); Richard Wolfgang Dissertation Prize, Department of Chemistry, Yale University (1988); Miller Institute Postdoctoral Fellowship, University of California, Berkeley (1989–1991); Searle Scholarship, Chicago Community Trust/Searle Scholars Program (1992–1995); Lilly Endowment Teaching Fellowship (1993–1994); Cottrell Scholars Award, Research Corporation (1994).
Teaching
CEM 384: Introduction to Physical Chemistry II, Spring 2012
CEM 419/987: Chemical Applications of Ultrafast Laser Spectroscopy, Fall 2011
Research: Ultrafast Spectroscopy, Photosynthesis, and Protein Dynamics
The Beck group uses ultrafast spectroscopy to study how photosynthetic light-harvesting proteins and reaction centers work. Our focus has been on how motions of the protein medium around the light-harvesting and redox chromophores occur in response to the formation and decay of excited-state chromophores and on how these motions are optimized by the protein structure to enhance the quantum efficiency for the overall process. These questions have led to our interest in nonequilibrium protein dynamics: how a protein moves when it has been displaced from the equilibrium structure.
In our current NSF-funded project (MCB-092010, from the Biomolecular Dynamics, Structure, and Function program), we are studying how partially unfolded states of ZnII-substituted cytochrome c are generated when we excite the ZnII porphyrin well above the 0–0 vibronic transition of the lowest energy π→π* transition. The results show that the excess vibrational energy flows from the ZnII porphyrin into the surrounding protein structure and enables it to cross the local activation enthalpy barriers that stabilize the native folded structure. The ZnII porphyrin can then be used as an intrinsic fluorescent probe that senses the protein motions that occur as the energy landscape is searched for the native structure through its dynamic Stokes shift and anisotropy response.
We have also been interested in the structural origin and functional role of low-frequency vibrational coherence in the purple-bacterial photosynthetic reaction center. This project employs femtosecond pump–probe spectroscopy with impulsive (sub-vibrational period) laser pulses to detect coherent wavepacket motions on the ground electronic state or on the resonant excited state of a bacteriochlorophyll or ZnII porphyrin. Our results show that the low-frequency modes that contribute to the vibrational coherence predominantly arise from van der Waals modes with clustered molecules in the first solvation shell. Not only do the intermolecular modes have a dominant impact on the electron-transfer dynamics by controlling the Marcus reorganization energy and hence the overall activation energy for the reaction, they mediate the structural reorganization that traps the net charges in the product states. Thus, these interactions play an important role in making the electron-transfer reactions in photosynthesis highly quantum efficient by rendering them effectively irreversible.
In a new project that we are very excited about, we are setting up to apply femtosecond 2D-electronic and photon-echo spectroscopies to study chlorophyll–carotenoid interactions in photosynthetic light harvesting proteins. We plan to address questions concerning the role played by electronic coherence and electron-transfer reactions in enhancing or regulating, respectively, the quantum efficiency of energy transport.
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Peridinin–chlorophyll protein (1PPR.pdb). From: Hofmann et al., Structural basis of light harvesting by carotenoids: peridinin-chlorophyll-protein from Amphidinium carterae. Science 1996, 272, 1788. |
Recent Publications
Dillman, K. L.; Beck, W. F. Vibrational coherence from van der Waals modes in the native and molten-globule states of ZnII-substituted cytochrome c. J. Phys. Chem. B 2011, 115, 8657–8666.
Tripathy, J.; Beck, W. F. Nanosecond-regime correlation timescales for equilibrium protein structural fluctuations of metal-free cytochrome c from picosecond time-resolved fluorescence spectroscopy and the dynamic Stokes shift. J. Phys. Chem. B 2010, 114, 15958–15968.
Dillman, K. L.; Beck, W. F. Excited-state vibrational coherence in methanol solution of ZnII tetrakis (N‑methylpyridyl) porphyrin: charge-dependent intermolecular mode frequencies and implications for electron-transfer dynamics in photosynthetic reaction centers. J. Phys. Chem. B. 2010, 114, 15269–15277.
Dillman, K. L.; Shelly, K. R.; Beck, W. F. Vibrational coherence in polar solutions of ZnII tetrakis (N‑methylpyridyl) porphyrin with Soret-band excitation: rapidly damped intermolecular modes with clustered solvent molecules and slowly damped intramolecular modes from the porphyrin macrocycle. J. Phys. Chem. B 2009, 113, 6127–6139.
Barns, K. J.; Lampa-Pastirk, S.; Dillman, K. L.; Wegener, A. J.; Beck, W. F. Intramolecular vibrational excitation of unfolding reactions in ZnII-substituted and metal-free cytochromes c: activation enthalpies from integrated fluorescence Stokes shift and lineshape excitation profiles. J. Phys. Chem. B 2008, 112, 15108–15115.
Shelly, K. R.; Golovich, E. C., Dillman, K. L., and Beck, W. F. Intermolecular vibrational coherence in the bacteriochlorophyll proteins B777 and B820 from Rhodospirillum rubrum. J. Phys. Chem. B 2008, 112, 1299–1307.
Lampa-Pastirk, S.; Beck, W. F. Intramolecular vibrational preparation of the unfolding transition state of Zn(II)-substituted cytochrome c. J. Phys. Chem. B 2006, 110, 22971–22974. Featured as the cover article for the 23 November 2006 issue.
Shelly, K. R.; Golovich, E. C.; Beck, W. F. Intermolecular vibrational coherence in bacteriochlorophyll a with clustered polar solvent molecules. J. Phys. Chem. B 2006, 110, 20586–20595.
Lampa-Pastirk, S.; Beck, W. F. Polar solvation dynamics in Zn(II)-substituted cytochrome c: diffusive sampling of the energy landscape in the hydrophobic core and solvent-contact layer. J. Phys. Chem. B 2004, 108, 16288–16294.
Lampa-Pastirk, S.; Lafuente, R. C.; Beck, W. F. Excited-state axial-ligand photodissociation and nonpolar protein-matrix reorganization in Zn(II)-substituted cytochrome c. J. Phys. Chem. B 2004, 108, 12602–12607.
Carson, E. A.; Diffey, W. M.; Shelly, K. R.; Lampa-Pastirk, S.; Dillman, K. L.; Schleicher, J. M.; Beck, W. F. Dynamic-absorption spectral contours: vibrational phase-dependent resolution of low-frequency coherent wave-packet motion of IR144 on the ground-state and excited-state π→π* surfaces. J. Phys. Chem. A 2004, 108, 1489–1500.
Shelly, K. R.; Carson, E. A.; Beck, W. F. Vibrational coherence from the dipyridine complex of bacteriochlorophyll a: intramolecular modes in the 10–220-cm-1 regime, intermolecular solvent modes, and relevance to photosynthesis. J. Am. Chem. Soc. 2003, 125, 11810–11811.
Beck, W. F. Ultrafast Spectroscopy. In Encyclopedia of Chemical Physics and Physical Chemistry; Moore, J. H., Spencer, N. D., Eds.; Institute of Physics Publishing, Ltd.: Bristol, England, 2001; Volume II, pp 1743–1772.
7 January 2012