Research Stories

by Skip Derra

Plants have an ambivalent relationship with light. They need it to live. But too much light leads to the increased production of high-energy chemical intermediates. These substances can injure or kill the plant. The normal efficient mechanism for converting sunlight into chemical energy cannot keep up with sunlight streaming into the plant.

"The intermediates don't have anywhere to go because the system is jammed up down the line," says Devens Gust. Plants must use a sophisticated process to defend against damage.

To better understand the process, Gust and ASU colleagues Thomas and Ana Moore designed a molecule that mimics what happens in nature. All three are ASU professors of chemistry and biochemistry.

Plants naturally defend against sunlight overload by using a process called non-photochemical quenching (NPQ). The energy caused by the excess light is drained off as heat. As a result, it cannot generate the destructive high-energy substances.

The ASU-designed molecule works in a similar fashion. It converts absorbed light to electrochemical energy. But it reduces the efficiency of the conversion as light intensity increases. The molecule also adapts to its environment, regulating its behavior in response to the light intensity.

"One hallmark of living cells is their ability to sense and respond to surrounding conditions," explains Thomas Moore. "In the case of metabolic control, this process involves molecular-level recognition events that are translated into control of a chemical process."

The scientists say the new molecule functionally mimics one of the processes in photosynthesis, the amazing process that plants use to convert sunlight into chemical energy and food. By better understanding these events at the molecular level, researchers can move closer to designing better and more efficient methods for converting sunlight into abundant, useful energy.

Gust says the work is also important to better understanding regulation, one aspect of the exploding field of nanotechnology. Biological systems are known for their ability to engage in adaptive self-regulation. The nanoscale components respond to other nanoscale systems and to external stimuli. They have to in order to keep everything in balance and functioning properly.

"Achieving such behavior in human-made devices is vital if we are to realize the promise of nanotechnology," Gust adds. "Although the mechanism of control used in the ASU molecule is different from that employed in NPQ, the overall effect is the same as occurs in the natural photosynthetic process."

For more information about photosynthesis research at ASU, visit the Center for Bioenergy and Photosynthesis. Or contact Devens Gust, 480.965.4547. Send email to: gust@asu.edu