The photosystem II cycle has four steps. There is a large conformation change between status S1 and status S3, as shown by the new inverstigations. Credit: Shibom Basu/Arizona State University
An international team, led by Arizona State University scientists, has published today in Nature a groundbreaking study that shows the first snapshots of photosynthesis in action as it splits water into protons, electrons and oxygen, the process that maintains Earth's oxygen atmosphere.
Photosynthesis is one of the fundamental processes of life on Earth. The early Earth contained no oxygen and was converted to the oxygen-rich atmosphere we have today 2.5 billion years ago by the "invention" of the water splitting process in Photosystem II (PSII). All higher life on Earth depends on this process for its energy needs and PSII produces the oxygen we breathe, which ultimately keeps us alive.
The revealing of the mechanism of this water splitting process is essential for the development of artificial systems that mimic and surpass the efficiency of natural systems. The development of an "artificial leaf" is one of the major goals of the ASU Center for Bio-Inspired Solar Fuel Production, which was the main supporter of this study.
"A crucial problem facing our Center for Bio-Inspired Fuel Production (Bisfuel) at ASU and similar research groups around the world is discovering an efficient, inexpensive catalyst for oxidizing water to oxygen gas, hydrogen ions and electrons," said ASU Regents' Professor and Center Director Devens Gust. "Photosynthetic organisms already know how to do this, and we need to know the details of how photosynthesis carries out the process using abundant manganese and calcium.
"The research by Fromme and coworkers gives us, for the very first time, a look at how the catalyst changes its structure while it is working," Gust added. "Once the mechanism of photosynthetic water oxidation is understood, chemists can begin to design artificial photosynthetic catalysts that will allow them to produce useful fuels using sunlight."
"This is a major step toward the goal of making a movie of the molecular machine responsible for photosynthesis, the process by which plants make the oxygen we breathe, from sunlight and water," explained John Spence, ASU Regents' Professor of physics, team member and scientific leader of the National Science Foundation funded BioXFEL Science and Technology Center, which develops methods for biology with free electron lasers.
