Combining one kind of these proteins, called photosystem I (PSI), with platinum nanoparticles, microscopic particles that can perform a chemical reaction that produces hydrogen - a valuable clean energy source - creates a biohybrid catalyst. That is, the light absorbed by PSI drives hydrogen production by the platinum nanoparticle.
In a recent breakthrough, researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory and Yale University have determined the structure of the PSI biohybrid solar fuel catalyst. Building on more than 13 years of research pioneered at Argonne, the team reports the first high-resolution view of a biohybrid structure, using an electron microscopy method called cryo-EM. With structural information in hand, this advancement opens the door for researchers to develop biohybrid solar fuel systems with improved performance, which would provide a sustainable alternative to traditional energy sources.
PSI is a large protein complex that is found in plants, algae and photosynthetic bacteria. This protein plays a critical role in capturing and converting sunlight into energy. Uniquely, PSI is able to very efficiently convert sunlight into energy - for every one photon that is absorbed by the protein, one electron is almost always generated. These electrons can then be transferred to the bound platinum nanoparticles of the biohybrid, which facilitates the production of hydrogen gas.
In earlier work, Argonne chemist Lisa Utschig was able to use PSI to manipulate photosynthesis and produce hydrogen fuel. Now, she and her team have been able to see the structure of the PSI biohybrid in detail. ?"It's been really exciting to now directly look at the system we've worked at for 13 years," Utschig said.
Although a few studies have explored the properties of PSI biohybrid catalysts, researchers have not known where the platinum nanoparticles attach to the protein. Using high-resolution cryo-EM, the researchers were able to more thoroughly study the structure of the biohybrid and found exactly where the nanoparticles bind to PSI.
"We assumed the nanoparticles were binding where PSI's electron transfer partners connect," Utschig said. ?"But the structure shows there's actually two sites. And that was very much a surprise."
With this structural information, researchers can now begin to optimize how the nanoparticles attach and interact to further enhance catalytic efficiency. They can engineer the biohybrid by altering the protein properties and by adjusting the nanoparticles.
"It's amazing to see bioenergy at the molecular level and to see how a man-made particle and a natural protein come together to create energy," said Utschig.
Other contributors to this work include Christopher J. Gisriel, Tirupathi Malavath, Tianyin Qiu, Jan Paul Menzel, Victor S. Batista and Gary W. Brudvig.
The results of this research were published in Nature Communications. In this study, synthesis, design and cryo-EM of the biohybrid system was funded by the DOE Office of Basic Energy Sciences, and cryo-EM was additionally funded by the National Institute of General Medical Sciences of the National Institutes of Health.
Research Report:Structure of a biohybrid photosystem I-platinum nanoparticle solar fuel catalyst
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