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Our research program is primarily concerned with elucidating the mechanism
of the energy-storing reactions in photosynthetic organisms, as well as
understanding the origin and early evolution of photosynthesis.
The chemical reactions leading to long-term energy storage in
photosynthetic systems take place within the membrane-bound reaction
center complex and an associated group of proteins that make up an
electron transport chain. One of the central goals of our research is to
identify the molecular parameters responsible for the fact that
essentially every photon absorbed by the system leads to stable products.
To this end, we do a variety of kinetic, thermodynamic and structural
measurements on antenna complexes, reaction centers, electron transport
proteins and isolated pigments, using a number of techniques, including
ultrafast laser flash photolysis and UV-VIS, fluorescence and electron
spin resonance spectroscopies, as well as biochemical and molecular
biological analysis.
The appearance of photosynthesis and other metabolic processes such as
nitrogen fixation had profound effects on the evolution of advanced life
on Earth. Our analysis of whole bacterial genomes has revealed that these
metabolic processes have complex evolutionary histories, including
substantial horizontal gene transfer. We have also used a combination of
genomic, molecular evolution techniques and biochemical analysis to
identify and characterize previously unknown enzyme complexes with novel
activities.
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Electron microscopic tomogram of a dividing photosynthetic bacterium
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