Scientists at Lawrence Berkeley National Laboratory, or LBNL, and SLAC National Accelerator Laboratory captured the previously missed oxygen-producing step of photosynthesis in a recent study published in Nature.
LBNL Project Scientist Asmit Bhowmick explained that this new discovery was made possible with the use of several different types of X-rays and light sources. He added that LBNL researchers studied enzymes by shining ultrashort and ultrabright X-ray pulses on enzyme crystals using a piece of technology called the X-ray free-electron laser, or XFEL, allowing them to capture enzyme structures.
Bhowmick noted in an email that researchers analyzed the structures of enzymes throughout different points of the reaction process, detailing the “missing” step of photosynthesis in which molecular oxygen is formed.
LBNL postdoctoral researcher Philipp Simon noted that to use the X-ray lasers, which span just short of a mile at the SLAC National Accelerator Laboratory, one must deliver the protein sample to the beam in a controlled manner. This is because the intense XFEL pulses can destroy the protein sample in a single shot, Simon added.
According to Simon, researchers at the lab created a conveyor belt system to bypass this obstacle by placing smaller protein samples and generating reactions using shorter light pulses. He noted in an email that researchers could then “probe the atomic structure” with a stronger X-ray pulse and compile all the X-ray images together in one final image.
“You can imagine that this requires a lot of different research groups with different expertise in order to get successful results,” Simon said in an email.
Campus graduate student and LBNL researcher Isabel Bogacz explained that, because of the conveyor belt delivery system the researchers developed, they were able to measure unimpaired data of Photosystem II’s atomic structure during the oxygen catalyzing process.
According to Simon, the technology used in their findings could continue to help other scientists understand the structure of enzymes and support energy research. Technologies and further research could also help discover enzymes valuable for producing new vaccines or antibiotics, he added.
“The sample delivery and XFEL technologies were essential for this discovery because by nature, Photosystem II is difficult to purify and sensitive to longer X-ray exposures,” Bogacz said in an email. “The single-use droplet method minimized wasted samples and the short XFEL pulses collected data before X-ray damage was initiated.”
Bhowmick said their findings have substantial implications for comprehending an enzyme that has supported various organisms that need oxygen to survive for over two billion years. He added that this discovery can support LBNL researchers in developing artificial photosynthetic devices like solar fuel cells to offer clean energy for a more sustainable future.
While the research field is still young, Bogacz added, technology used in their findings can be useful in other scientific fields.
“It seems like anything is possible when you have a powerful probe that looks at nature’s building blocks,” Bogacz said in the email. “Understanding how an enzyme’s structure adapts to perform a function opens the door for scientists to emulate nature.”