Scientists successfully 'hack' photosynthesis

Researchers have ‘hacked’ the early stages of photosynthesis and discovered ways to extract energy from the process — a finding that could lead to new ways of generating clean fuel and renewable energy.

Led by the University of Cambridge, a team of physicists, chemists and biologists studied photosynthesis in live cells at an ultrafast timescale: a millionth of a millionth of a second.

Though photosynthesis is already a very well-known and well-studied process, the researchers found that it has more secrets to tell. By using spectroscopic techniques to study the movement of energy, the researchers found the chemicals that can extract electrons from the molecular structures responsible for photosynthesis do so at the initial stages, rather than much later, as was previously thought. This ‘rewiring’ may improve ways to deal with excess energy and create new and more efficient ways of using its power. The results are reported in the journal Nature.

Jenny Zhang, who coordinated the research, said, “We didn’t know as much about photosynthesis as we thought we did, and the new electron transfer pathway we found here is completely surprising.”

Scientists have also been studying how photosynthesis could be used to help address the climate crisis by mimicking photosynthetic processes to generate clean fuels from sunlight and water, for example.

Zhang and her colleagues were originally trying to understand why a ring-shaped molecule called a quinone is able to ‘steal’ electrons from photosynthesis. Quinones are common in nature, and they can accept and give away electrons easily. The researchers used a technique called ultrafast transient absorption spectroscopy to study how the quinones behave in photosynthetic cyanobacteria.

Zhang said this had not been properly studied in the past, but the team initially thought they had just been using a new technique to confirm what they already knew.

“Instead, we found a whole new pathway, and opened the black box of photosynthesis a bit further,” she said.

Using ultrafast spectroscopy to watch the electrons, the researchers found that the protein scaffold where the initial chemical reactions of photosynthesis take place is ‘leaky’, allowing electrons to escape. This leakiness could help plants protect themselves from damage from bright or rapidly changing light.

“The physics of photosynthesis is seriously impressive,” said co-first author Tomi Baikie. “Normally, we work on highly ordered materials, but observing charge transport through cells opens up remarkable opportunities for new discoveries on how nature operates.”

“Since the electrons from photosynthesis are dispersed through the whole system, that means we can access them,” said co-first author Laura Wey. “The fact that we didn’t know this pathway existed is exciting, because we could be able to harness it to extract more energy for renewables.”

According to the researchers, being able to extract charges at an earlier point in the process of photosynthesis could make the process more efficient when manipulating photosynthetic pathways to generate fuels from the sun. The process could also help make plants more tolerant to intense sunlight.

Zhang said many scientists have been unsuccessful in trying to extract electrons from an earlier point in photosynthesis because the energy is buried in the protein scaffold. The team of researchers thought they had made a mistake when they initially did so.

The use of ultrafast spectroscopy was key to the discovery. It allowed the researchers to follow the flow of energy in the living photosynthetic cells on a femtosecond scale — a thousandth of a trillionth of a second.

“The use of these ultrafast methods has allowed us to understand more about the early events in photosynthesis, on which life on Earth depends,” said co-author Christopher Howe.

The research was supported in part by the Engineering and Physical Sciences Research Council (EPSRC), Biotechnology and Biological Sciences Research Council (BBSRC) part of UK Research and Innovation (UKRI), as well as the Winton Programme for the Physics of Sustainability at University of Cambridge, the Cambridge Commonwealth, European & International Trust, and the European Union’s Horizon 2020 research and innovation program.

Image credit: Tomi Baikie