Researchers capture image of first step of photosynthesis

"Part of my motivation for studying the natural photosynthetic system is there is also a need to develop more advanced technology for harvesting solar energy," researcher Jennifer Ogilvie said.
By Brooks Hays  |  March 20, 2018 at 2:54 PM
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March 20 (UPI) -- Scientists are finally beginning to understand how photosynthesis works.

For the first time, researchers were able to capture an image of a photon triggering the photosynthesis process' initial energy conversion step.

Photosynthesis involves the absorption of sunlight by pigment molecules inside proteins known as light-harvesting antenna complexes. The absorbed light is channeled into a photosynthetic reaction center protein where it is converted into usable energy.

"In photosynthesis, the basic architecture is that you've got lots of light-harvesting antennae complexes whose job is to gather the light energy," Jennifer Ogilvie, a professor of physics and biophysics at the University of Michigan, said in a news release. "They're packed with pigments whose relative positions are strategically placed to guide energy to where it needs to go for the first steps of energy conversion."

Photosynthetic organisms, like plants and bacteria, feature an arrangement of uniquely colored pigments to collect and channel light. Different organisms use different combinations of pigments.

"The antennae take solar energy and create a molecular excitation, and in the reaction center, the excitation is converted to a charge separation," Ogilvie said. "You can think of that kind of like a battery."

Until now, scientists have struggled to understand the mechanics of charge separation. But using a new imaging technology, 2D electronic spectroscopy, Ogilvie and her research partners were able to capture a snapshot at the moment of charge separation, the precise moment of initial energy conversion, inside bacteria.

The snapshots of this conversion, which lasts only a few trillionths of a second, revealed a hidden state or energy, an energy level never seen before.

"From x-ray crystallography, we know the structure of the system very well, but taking the structure and predicting exactly how it works is always very tricky," Ogilvie said. "Having a better understanding of where the energy levels are will be very helpful for establishing the structure-function relationships of these photosynthetic reaction centers."

Researchers believe their findings, published this week in the journal PNAS, will help scientists design more efficient solar panels.

"Part of my motivation for studying the natural photosynthetic system is there is also a need to develop more advanced technology for harvesting solar energy," Ogilvie said. "So by understanding how nature does it, the hope is that we can use the lessons from nature to help guide the development of improved materials for artificial light harvesting as well."

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