An international team of scientists has caught an important step of
photosynthesis for the first time. Led by Prof. Petra Fromme from Arizona
State University, the team used the world's most powerful X-ray flashlight
at the SLAC National Accelerator Laboratory in the U.S. to record still
frames of a molecular complex called photosystem II as it splits water into
hydrogen and oxygen, a process that maintains the oxygen in the earth's
atmosphere.

Professor Fromme said "This is the very first scene of a molecular movie
showing light-driven water splitting in photosystem II, the mechanism which
makes all oxygen in the atmosphere." The observations show with molecular
resolution that photosystem II significantly changes shape during this
process. To observe photosystem II in action, the team grew tiny
nano-crystals of the photosystem II complex of Thermosynechococcus elongatus
cyanobacteria . These crystals were illuminated with a visible laser to
start the water splitting process, which is otherwise driven by sunlight.
The researchers used double light flashes to trigger the transition from
stage S1 to stage S3, as this transition was expected to show the largest
dynamics.


<[www.desy.de]
=8441> [www.desy.de]