Biophysics researchers at the University of Michigan have used short pulses of light to peer into the mechanics of photosynthesis¹ and illuminate² the role that molecule³ vibrations⁴ play in the energy conversion⁵ process that powers life on our planet. The findings could potentially help engineers make more efficient solar cells and energy storage systems. They also inject new evidence into an ongoing⁶ "quantum biology" debate over exactly how photosynthesis manages to be so efficient.

 

Through photosynthesis, plants and some bacteria turn sunlight, water and carbon dioxide into food for themselves and oxygen for animals to breathe. It's perhaps the most important biochemical process on Earth and scientists don't yet fully⁷ understand how it works.

 

The U-M findings identify specific molecular⁸ vibrations that help enable charge separation（电荷分离） -- the process of kicking electrons free from atoms in the initial steps of photosynthesis that ultimately converts solar energy into chemical energy for plants to grow and thrive.

 

"Both biological and artificial photosynthetic⁹ systems take absorbed light and convert it to charge separation. In the case of natural photosynthesis, that charge separation leads to biochemical energy. In artificial systems, we want to take that charge separation and use it to generate electricity or some other useable energy source such as biofuels," said Jennifer Ogilvie, an associate professor of physics and biophysics at the University of Michigan and lead author of a paper on the findings that will be published July 13 in Nature Chemistry.

 

It takes about one-third of a second to blink your eye. Charge separation happens in roughly one-hundredth of a billionth of that amount of time. Ogilvie and her research group developed an ultrafast laser pulse experiment that can match the speed of these reactions. By using carefully timed sequences of ultrashort laser pulses, Ogilvie and coworkers were able to initiate¹⁰ photosynthesis and then take snapshots of the process in real time.

 

The researchers worked with Charles Yocum, U-M professor emeritus¹¹ in the Department of Molecular, Cellular¹² and Developmental Biology and the Department of Chemistry, both in the College of Literature, Science, and the Arts to extract what's called the photosystem II reaction centers from the leaves. Located in the chloroplasts（叶绿体） of plant cells, photosystem II is the group of proteins and pigments¹³ that does the photosynthetic heavy lifting. It's also the only known natural enzyme¹⁴ that uses solar energy to split water into hydrogen and oxygen.

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