An international group of researchers says it has obtained the first direct look at photosynthesis in action, observing the process that creates and maintains oxygen crucial to life on our planet.
The research team representing 18 institutions and led by Arizona State University says the accomplishment could help in the search for a renewable and green energy source.
Using a powerful laser allowed the capturing of "snapshots" of a critical step in photosynthesis, the researchers report in the journal Nature Communications.
The step being studied is a catalytic reaction that yields molecular oxygen when energized by solar photons.
In this photosynthetic reaction a protein complex known as photosystem II is able to split water into its oxygen and hydrogen components using energy that comes from light.
That's the process scientists say they hope one day to mimic to create energy through artificial photosynthesis.
"An effective method of solar-based water-splitting is essential for artificial photosynthesis to succeed but developing such a method has proven elusive," says study author and chemist Vittal Yachandra of the Lawrence Berkeley National Laboratory.
Although the chemistry of the process is understood, it has never been directly observed before, the researchers said.
"The water splitting process is known to be divided into four steps," says study co-author Henry Chapman of the University of Hamburg. "But no-one has actually seen these four steps."
Using bacteria that engage in photosynthesis, the researchers grew nano-crystals involved in the photosystem II process, then lit them up with a potent laser at the SLAC National Accelerator Laboratory at Stanford University to initiate the water-splitting progression.
Monitoring it with X-ray flashes allowed them to observe the changes in the complex's molecular structure during the photosynthesis process.
"We were surprised by the large conformational changes we could witness," team member Petra Fromme, a bio-physical chemist from Arizona State University. Says. "Actually, the changes are so large that there is an overall structure change, which even changes the dimensions of the unit cell, the smallest building block in a crystal."
The laser-X-ray technique could be useful for studying all kinds of catalytic reactions, as observing all the steps in such reactions would let scientists optimize them, the researchers said.
Each X-ray flash created a still image, and multiple images can be stitched together to create a movie of ultrafast dynamics taking place in catalytic reactions such as photosynthesis.
The study is one more step toward being "tantalizingly close" to engineering artificial photosynthesis, the researchers say.
