Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international team is working to change that. They focused on a key protein complex called Photosystem II. They captured the most complete and highest-resolution images to date of Photosystem II at work. The team's pictures and movies show all four stable intermediate states of Photosystem II that produce the oxygen we breathe. Also, they caught fleeting steps in between. Their work opens doors to creating artificial photosynthesis to produce energy from sunlight and water.
Photosynthesis is how plants, algae, and certain bacteria use sunlight to make sugars and other energy-rich compounds that they need to survive and grow. During photosynthesis, the sunlight is used to extract electrons from water, splitting the water into oxygen and hydrogen in the process. Creating similar systems could lead to clean, renewable energy from sunlight and water. Knowing how a key protein complex in photosynthesis, Photosystem II, works is key to designing such system. This research offers an unprecedented view of how the protein complex shifts and stretches during water splitting. Such detailed snapshots unlock the doors to cleaner energy.
More than 2 billion years ago, tiny organisms on Earth started photosynthesizing. Nearly all life on Earth now depends on photosynthesis but it's not understood in detail. Scientists want to understand the nuances of the process and use those insights to design systems that use sunlight and water to produce fuel. The challenge is that the process is incredibly complex and certain steps happen quickly at the scale of individual atoms. Now, a team from the United States, Germany, Sweden, and the United Kingdom has obtained detailed pictures and movies of a key aspect of photosynthesis. In particular, they focused on the workhorse protein complex, called Photosystem II. They saw how it stretched and shifted, breaking and making metal oxygen bonds, during four of the five reaction states involved in breaking water apart. They obtained the images using SLAC's Linac Coherent Light Source X-ray laser with serial femtosecond X-ray crystallography and simultaneous X-ray emission spectroscopy. The resolution of the images is 2 angstroms at room temperature. Previous techniques offered a slightly less detailed view and required cooler conditions. With this more detailed view, the researchers saw lighter atoms, such as oxygen, in addition to the metal atoms in the catalytic center, and better described the area inside Photosystem II where water splitting occurs. They also observed two transient moments between reaction states. The results will help clarify how water binds to the complex and how oxygen forms. The results are a key part of efforts to offer new insights for renewable energy.
Lawrence Berkeley National Laboratory
Vittal K. Yachandra
Lawrence Berkeley National Laboratory
This work was supported by the Department of Energy, Office of Science, Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences, and Biosciences (J.Y., V.K.Y.); National Institutes of Health (NIH) (V.K.Y., J.Y., J.K., N.K.S., J.M.H.); the Ruth L. Kirschstein National Research Service Award (F.D.F.); and Human Frontiers Science Project (J.Y., U.B., A.Z.). The authors acknowledge the German Research Foundation Cluster of Excellence "UniCat" (A.Z., H.D.); the Artificial Leaf Project (K&A Wallenberg Foundation) and Vetenskapsrådet (J.M.); and the Diamond Light Source, Biotechnology and Biological Sciences Research Council and a Strategic Award from the Wellcome Trust (A.M.O.). This research used the National Energy Research Scientific Computing Center supported by DOE. Synchrotron facilities at the Advanced Light Source and Stanford Synchrotron Radiation Lightsource (SSRL) were funded by DOE BES. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Science, Office of Biological and Environmental Research and the NIH. Linac Coherent Light Source and SSRL, SLAC National Accelerator Laboratory, are supported by DOE BES.
J. Kern, R. Chatterjee, I.D. Young, et al., "Structures of the intermediates of Kok's photosynthetic water oxidation clock." Nature 563, 421 (2018).[DOI: 10.1038/s41586-018-0681-2]
Lawrence Berkeley National Laboratory news center: Scientists capture photosynthesis in unprecedented detail
SLAC National Accelerator Laboratory press release: Researchers create most complete high-res atomic movie of photosynthesis to date