Deep within spinach leaves, vibrations enhance efficiency of photosynthesis


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The findings could potentially help engineers make more efficient solar cells and energy storage systems. They also inject new evidence into an ongoing “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 fully understand how it works.

The U-M findings identify specific molecular vibrations that help enable charge separation – 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.



The researchers worked with Charles Yocum, U-M professor emeritus in the Department of Molecular, Cellular 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 of plant cells, photosystem II is the group of proteins and pigments that does the photosynthetic heavy lifting. It’s also the only known natural enzyme that uses solar energy to split water into hydrogen and oxygen.

To get a sample, the researchers bought a bag of spinach leaves from a grocery store. “We removed the stems and veins, put it in the blender and then performed several extraction steps to gently remove the protein complexes from the membrane while keeping them intact.

“This particular system is of great interest to people because the charge separation process happens extremely efficiently,” she said. “In artificial materials, we have lots of great light absorbers and systems that can create charge separation, but it’s hard to maintain that separation long enough to extract it to do useful work. In the photosystem II reaction center, that problem is nicely solved.”


“We can carefully track what’s happening,” Ogilvie said. “We can look at where the energy is transferring and when the charge separation has occurred.”


“What we’ve found is that when the gaps in energy level are close to vibrational frequencies, you can have enhanced charge separation,” Ogilvie said. “It’s a bit like a bucket-brigade: how much water you transport down the line of people depends on each person getting the right timing and the right motion to maximize the throughput. Our experiments have told us about the important timing and motions that are used to separate charge in the photosystem II reaction center.”

She envisions using this information to reverse engineer the process – to design materials that have appropriate vibrational and electronic structure to mimic this highly efficient charge separation process.


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