Biophysics researchers at the University of Michigan have used short pulses of light to peer into the mechanics of photosynthesis and illuminate the role that molecule vibrations play in the energy conversion 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 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.
"Both biological and artificial photosynthetic 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 initiate photosynthesis and then take snapshots of the process in real time.
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."
The researchers used their unique spectroscopic approach to excite the photosystem II complexes and examine the signals that were produced. In this way, they gained insights about the pathways that energy and charge take in the leaves.
"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."
The spectroscopic signals they recorded contained long-lasting echoes, of sorts, that revealed specific vibrational motions that occurred during charge separation.
"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.
The paper is titled "Vibronic Coherence in Oxygenic Photosynthesis," scheduled for publication online on July 13 in Nature Chemistry. Other co-authors are from Vilnius University and the Center for Physical Sciences and Technology, both in Vilnius, Lithuania. The work is funded by the U.S. Department of Energy, the National Science Foundation and the U-M Center for Solar and Thermal Energy Conversion, as well as the Research Council of Lithuania.
Nicole Casal Moore | Eurek Alert!
Discovery of a fundamental limit to the evolution of the genetic code
03.05.2016 | Institute for Research in Biomedicine (IRB Barcelona)
03.05.2016 | Christian-Albrechts-Universität zu Kiel
Using an ultra fast-scanning atomic force microscope, a team of researchers from the University of Basel has filmed “living” nuclear pore complexes at work for the first time. Nuclear pores are molecular machines that control the traffic entering or exiting the cell nucleus. In their article published in Nature Nanotechnology, the researchers explain how the passage of unwanted molecules is prevented by rapidly moving molecular “tentacles” inside the pore.
Using high-speed AFM, Roderick Lim, Argovia Professor at the Biozentrum and the Swiss Nanoscience Institute of the University of Basel, has not only directly...
If a person pushes a broken-down car alone, there is a certain effect. If another person helps, the result is the sum of their efforts. If two micro-particles are pushing another microparticle, however, the resulting effect may not necessarily be the sum their efforts. A recent study published in Nature Communications, measured this odd effect that scientists call “many body.”
In the microscopic world, where the modern miniaturized machines at the new frontiers of technology operate, as long as we are in the presence of two...
Researchers from the Max Planck Institute Stuttgart have developed self-propelled tiny ‘microbots’ that can remove lead or organic pollution from contaminated water.
Working with colleagues in Barcelona and Singapore, Samuel Sánchez’s group used graphene oxide to make their microscale motors, which are able to adsorb lead...
Neutron scattering and computational modeling have revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid or solid states.
In a paper published in Physical Review Letters, researchers at the Department of Energy's Oak Ridge National Laboratory describe a new tunneling state of...
Honeycomb structures as the basic building block for industrial applications presented using holo pyramid
Researchers of the Alfred Wegener Institute (AWI) will introduce their latest developments in the field of bionic lightweight design at Hannover Messe from 25...
27.04.2016 | Event News
15.04.2016 | Event News
12.04.2016 | Event News
03.05.2016 | Physics and Astronomy
03.05.2016 | Life Sciences
03.05.2016 | Physics and Astronomy