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Our Challenge
A promising means of coupling terrestrial insolation to H2 production is to exploit the ability of certain photosynthetic organisms to catalyze H2 evolution under special conditions. Several species of green algae have been shown to possess this ability, including the free-living unicellular alga Chlamydomonas reinhardtii. This organism possesses hydrogenase enzymes capable of reducing protons with low-potential electrons from the photosynthetic light reactions that have been stored as starch. During anaerobiosis, starch is broken down, and the reducing equivalents funneled, in part, through the plastoquinone pool and into [2Fe-2S] ferredoxin, which serves as the immediate electron donor to hydrogenase. A variety of competing pathways exist, which limits the maximum electron flux that can be channeled into the proton reduction reactions. Thus, we seek to identify binding and electron transfer determinants between [2Fe-2S] ferredoxin and hydrogenases that could be engineered to produce greater electron flux—and thereby, greater H2 yield.
Our Approach
We combine homology modeling, empirical docking, visualization, quantitative free-energy calculations, and alchemical free-energy perturbation to identify likely docking complexes and effects of site-directed mutational engineering. Beginning with hydrogenase, we are exploring interactions with all known [2Fe-2S] ferredoxin partners in the chloroplast to gain a greater understanding of photosynthetic electron flow in C. reinhardtii.
Our Results
The research is ongoing. Information on results will become available later.
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