Photosynthesis
Hierarchical Photosynthetic Systems for Photochemical Energy Conversion
The goal of this program is to identify the mechanisms responsible for
optimization of photochemical energy conversion in natural photosynthesis, and
to use this information for the development of artificial photochemical systems
with enhanced photochemical energy conversion. The project investigates the
correlations between sequential electron transfer with static and dynamic
structures in natural and artificial systems, and investigates strategies for
linking ultrafast, light-induced, one-electron transfer to slower,
energy-conserving redox and electrochemical processes in artificial
photosynthetic systems using biomimetic, hierarchical molecular architectures.
Novel approaches include the
use of isotopic and transition metal ion labeled photosynthetic proteins (Lisa
Utschig-Johnson) for
analysis of the structure and function of natural photosynthetic systems,
time-resolved and spin polarized electron paramagnetic resonance spectroscopies
(Oleg Poluektov)
for analysis of sequential electron transfer and electron donor/acceptor
geometries,
time-resolved x-ray absorption spectroscopy (Lin
Chen) for analysis of metal ion
structure and function in photosynthetic chemistry, and the
use of x-ray and
neutron scattering techniques (David
Tiede) for resolving molecular structure and
structural dynamics of photosynthetic assemblies in disordered media.
Specific project areas are described below.
Structure and Light-Induced Structural Dynamics in Natural Photosynthesis
This project investigates fundamental mechanisms for solar energy conversion
in natural photosynthesis. Photosynthetic reaction centers (RCs) are
investigated as models of molecular systems in which both the cofactors and the
surrounding media are tuned for optimized solar energy conversion. The program
approach features the resolution of structural dynamics linked to ET reactions
by the application of a suite of advanced, multi-frequency, pulsed magnetic
resonance, transient optical, and x-ray techniques together with capabilities to
prepare isotope and metal ion edited RC samples. The research develops a
fundamental understanding of structure-function relationships in biological
photosynthesis and establishes principles for the design of biomimetic systems
for solar energy conversion.
Structure and Light-Induced Structural Dynamics in Photosynthetic Model
Systems
This project investigates fundamental mechanisms for solar energy conversion
in biomimetic photosynthetic model systems and complements the project described
above by examining mechanisms for solar energy conversion across a broader range
of molecular charge carriers and reaction matrices than can be achieved in
biology. The subtask highlights the direct detection of atomic reorganization
accompanying photochemical charge separation by combining pioneering
time-resolved synchrotron x-ray spectroscopy and wide-angle x-ray scattering
techniques with transient optical techniques to follow light-activated
structural dynamics across multiple time (10-13 sec to 1 sec ) and length (1 Å
to 500 Å) scales. This program tests hypotheses and design concepts for solar
energy conversion that emerge from natural photosynthesis, and establishes the
groundwork for the development of advanced biomimetic artificial photosynthetic
systems.
Ultrafast Spatial Imaging of Solar Energy Flow In Photosynthesis
The goal of this project is to image solar energy flow through
quasi-crystalline arrays of light-harvesting proteins in natural photosynthetic
membranes and in laboratory-produced 2D and 3D crystalline arrays of isolated
photosynthetic proteins with ultrafast time resolution and nanometer to
molecular scale spatial resolution. This goal will be accomplished by combining
ultrafast transient laser spectroscopy with emergent technology in nanophotonics
for spatial control and imaging of light at the nanometer scale. This work will
resolve the design principles that underlie Nature’s remarkable hierarchical
architectures for solar energy conversion, and it will establish approaches for
follow-on research on the design and analysis of efficient, molecular-based
biomimetic systems for solar energy capture and conversion.
Contact
David M. Tiede, Group Leader
Photosynthesis
Chemical Sciences and Engineering Division
Argonne National Laboratory, Bldg. 200
phone: 630/252-3539
fax: 630/252-9289
e-mail: Tiede@anl.gov |