 |
| Born Anderson, South Carolina, 1941. |
| University of North Carolina, B.S., 1963. |
| Washington University, Ph.D., 1968. |
| Argonne National Laboratory, 1969-95. |
| The University of Chicago, Professor, 1986-. |
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| Accolades |
| Fellow, American Academy of Arts and Sciences. |
| 1994 Zavoisky Award, Russian Academy of Science. |
| 1992 Alexander von Humboldt Research Award for Senior US Scientists. |
| 1992 Rumford Premium, American Academy of Arts and Sciences. |
| 1990-1991 Fellowship, The Institute for Advanced Studies, The Hebrew University of Jerusalem. |
| 1990 Ernest Orlando Lawrence Memorial Award. |
| 1988 R&D 100 Award. |
| 1986 Argonne National Laboratory Director's Annual Award. |
| 1986 Argonne Pacesetter Award. |
| 1977 University of Chicago Award for Distinguished Performance. |
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|
| James R. Norris, Jr. |
| Robert A. Millikan Distinguished Service Professor of Chemistry |
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| Research Interests: |
| The research of the group involves studies of natural
and artificial photosynthesis. The goal of the research is
a more complete understanding of the beginning of the
process of natural photosynthesis such that artificial
photosynthesis can be a reality. The mechanism and
structural requirements of photosynthesis are explored
via a series of photosynthetic proteins altered by sitedirected
mutagenesis and by model compounds. The
work involves the following areas: |
| |
| (1) Time domain x-ray diffraction. |
| Single crystals of the reaction-center protein from
Blastochloris viridis were analyzed by monochromatic
and Laue diffraction, in the dark and 3 ms after
illuminating the crystal with a pulsed laser. Refinement
shows that ubiquinone binds only in the "proximal" QB
binding site and that no significant quinone motion
occurs during initial electron flow. |
| |
| (2) Charge migration in photosynthetic arrays. |
| Upon chemical oxidation, light harvesting complex 1
(LH1) of photosynthetic bacteria behave like molecular
wires. Experimentally, charge migration within an
oxidized LH1 array is monitored by following the
temperature dependent changes of the electron
paramagnetic resonance (EPR) line shape of oxidized
bacteriochlorophyll free radicals contained in the LH1
complex. At temperatures below 10 K charge transport is
very slow while at higher temperatures, rapid charge
migration occurs, resulting in large changes in the EPR
line shape. The temperature dependence of the EPR
spectra could be described only by taking into account
the glass like behavior of the protein medium, consistent
with the view that the protein behaves as a frozen glass
"solvent" for charge migration, even at room temperature.
The glassÐlike nature of proteins shows that considerable
heterogeneity exists for electron transfer in LH1, a novel
molecular wire. Future experiments in our lab are
intended to provide a better understanding of
heterogeneity and thus aid the development of solvated
Ómolecular wiresÒ that function in the solid state. |
| |
| (3) Photoinduced charge separation explored by
chemically induced dynamic electron polarization
(CIDEP). |
| A novel combination of nanosecond pulsed EPR
spectroscopy and CIDEP has been developed to quantify
the distance dependence of electron transfer in liquid
solventÐseparated radical ion pairs composed of quinone
anions and several cation radicals. Using a superexchange
mechanism mediated by the intervening solvent
molecules, a simple three-dimensional model of the
Marcus matrix element that characterizes the rate electron
transfer as a function of distance has been developed. This
model explains the distance dependence of electron
transfer including data previously reported on the charge
transfer reactions both in liquid and frozen (77 K)
solutions. Currently we are extending the electron transfer
parameters of covalently linked triads that perform
efficient photoinduced charge separation. |
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| Additional Interests |
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growth of photosynthetic organisms |
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biochemical investigation of photosynthesis |
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the physical chemistry of natural photosynthesis |
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the spectroscopy of photoinduced electron-transfer reactions, both optical and electron paramagnetic resonance |
|
the growth of integral membrane protein single crystals |
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x-ray crystallography including protein crystallography |
|
EXAFS spectroscopy of model systems and proteins |
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linear prediction methods of spectral analysis |
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 |
| Clockwise from top left: |
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X-ray diffraction pattern of the Photosynthetic Reaction Center (Laue Method) |
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Structure of the Photosynthetic Reaction Center of Rhodopseudomonas viridis |
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Time-resolved EPR spectrum of benzoquinone in silica nanobubbles |
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TEM image of silica nanobubbles |
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Structure of the Photosynthetic Reaction Center of Rhodopseudomonas viridis |
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TEM image of intact membrane from Rhodopseudomonas viridis |
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| Selected References |
| Superexchange Electron Tunneling
Mediated by Solvent Molecules:
Pulsed Electron Paramagnetic
Resonance Study on Electronic
Coupling in Solvent-Separated
Radical Ion Pairs. J. Phys. Chem. B, 108, 10226 (2004). |
| Time-resolved
crystallographic studies of lightinduced
structural changes in the
photosynthetic reaction center. P.N.A.S., 101(16), 5982 (2004). |
| Exploring charge migration in
light-harvesting complexes using
electron paramagnetic resonance
line narrowing. J. Phys. Chem. B, 107(9), 2127 (2003). |
| Characterization
of expressed pigmented core light
harvesting complex (LH 1) in a
reaction center deficient mutant of
Blastochloris viridis. Photosynthesis Research, 77(1), 53 (2003). |
| Contribution of colliding parallel electron spins to electron paramagnetic resonance spectral narrowing. J. Chem. Phys., 118, 5582 (2003). |
| Exploring complex CIDEP of pbenzosemiquinones
with time
resolved CW-EPR. Molecular Physics, 100(9), 1323 (2002). |
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Physical Chemistry 