Scientists capture snapshots of water splitting during photosynthesis


Arizona State University (ASU) scientists unlock means of capturing water splitting during photosynthesis, a step closer in making molecular movies a reality. Oxygen, electrons and protons now more easily observable.

Led by scientists from ASU, an international team published Wednesday an innovative study showing the first pictures of the photosynthetic process as it unfolds while splitting water into oxygen, electrons and protons. Team leader and senior author Petra Fromme said it is the first step towards the team's main aim of uncovering the nature of water splitting, consequentially gathering what is needed for a molecular movie.

Photosynthesis is a foundational process on Earth, responsible for converting the planet's atmosphere billions of years ago to make it possible to support life. Early Earth didn't have oxygen but water splitting changed all that. Today, photosynthesis is essentially what keeps the planet alive, supplying the oxygen needed for breathing.

Understanding the mechanism behind water splitting is an essential step towards developing artificial structures that have the potential to surpass natural systems in terms of efficiency. The ASU's Center for Bio-Inspired Solar Fuel Production is a major supporter of the study and one of its main goals is to develop an "artificial leaf."

"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," states center director Devens Gust. Organisms relying on photosynthesis already grasp how to tap into the process and people need to follow suit to determine how it all happens using calcium and manganese.

Oxygen is made at a specific metal site that contains a calcium atom and four manganese atoms. These atoms form a metal cluster and is bound to Photosystem II, a protein that catalyzes water splitting. For every four light flashes, one oxygen molecule is extracted from a couple of water molecules within the cluster.

For the very first time, Fromme's team has made it possible to directly look at how changes happen within the photosynthetic process, seeing structures change as photosynthesis is underway. Once the water-splitting mechanism is understood, scientists can start designing artificial catalysts that will allow for fuel production utilizing sunlight.

The ASU study is supported by BioXFEL Science and Technology Center, the National Laboratory the SLAC and Lawrence Livermore Directed Research and Development programs, the German Research Foundation, the National Science Foundation, the National Institutes of Health, and the Office of Science from the Department of Energy.

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