Scientists from the U.S. Department of Energy's (DOE) Argonne National
Laboratory and collaborators from Washington University in St. Louis have
solved a critical part of the age-old mystery of photosynthesis, homing in
on the initial, ultrafast events through which photosynthetic proteins
capture light and use it to initiate a series of electron transfer
reactions.

In photosynthesis, the movement of electrons is crucial as it's how work is
accomplished inside a cell, according to Argonne biophysicist Philip Laible.
These processes begin when a photon absorbs light pigments localized in
proteins. Each photon propels an electron across a membrane inside
specialized compartments within the cell. The Argonne and Washington
University research team has gained valuable insight into the initial steps
in this process: the electron's journey.

When the structure of these complexes was discovered nearly 35 years ago,
scientists were surprised to know that there are two pathways for the
electron to travel. Plants, algae, and photosynthetic bacteria use just one
of them. The research team managed to interfere with each one of them to
change the electron's trajectory. "We have managed to switch the direction
of initial electron transfer," said Christine Kirmaier, Washington
University chemist and project leader. She added that in nature, the
electron chose one path 100 percent of the time. Through their efforts, they
were able to make the electron switch to an alternate path 90 percent of the
time.

[www.anl.gov]
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