Photosynthesis photographed for the first time
Researchers at ASU capture a 'molecular
movie' of water splitting into oxygen, protons and electrons.
Thu, Jul 10, 2014 at 12:25 PM
Photosynthesis is one of the most fundamental processes of life on Earth. (Photo: Philip Male/Flickr. Inset by Mary Zhu/ASU)
Every school kid learns about photosynthesis, but a new study shows the life-giving process in action for the first time.
As published this week in the journal Nature,
an international team of researchers has photographed photosynthesis in
action using the world's fastest X-ray laser, which captures events
that take place in one-quadrillionth of a second. Using this ultrafast
laser, the researchers were able to document the previously unseen
moments when photosynthesis converts water into oxygen, protons and
electrons. "This study is the first step towards our ultimate goal of
unraveling the secrets of water splitting and obtaining molecular movies
of biomolecules," said the paper's senior author, Arizona State
University professor Petra Fromme.
The
photosynthetic process visualized in the new study involves the moment
when water molecules and light combine in a cluster of metal including
four manganese atoms and one calcium atom. The cluster is bound to a
protein in the plant called PSII (Photosystem II), which catalyzes the
process. Four flashes of light allow two water molecules to become one
oxygen molecule, four hydrogen ions and four hydrogen electrons.
The researchers have been studying photosynthesis to mimic it in
artificial systems. ASU's Center for Bio-Inspired Solar Fuel, which
supported the study, is trying to develop what it calls an "artificial leaf"
that could generate electricity. ASU Regents' professor Devens Gust
said in a news release that one of the major challenges in creating the
artificial leaf is "discovering an efficient, inexpensive catalyst for
oxidizing water to oxygen gas, hydrogen ions and electrons.
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 current research will allow chemists to move forward in
creating artificial photosynthetic catalysts, which can convert create
fuels using sunlight. "The research ... gives us, for the very first
time, a look at how the catalyst changes its structure while it is
working," Gust said in a news release.
The next stage of the research, as Fromme hinted, is to go beyond
the snapshot to create "molecular movies" of the entire process by which
plants make the oxygen the rest of the world depends upon. This, in
turn, will further the research into fuels that can be generated by
photosynthetic-like processes. ASU graduate student Shibom Basu, one of
the lead authors of the new paper, called this "the most exciting aspect
of the work."
The research was funded by a broad coalition of organizations,
including the Department of Energy and the National Institutes of
Health.
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