Quantum Biology: Algae Study Could Help Scientists Make Solar Cells Efficient

Algae can switch on and off a quantum effect - coherence - researchers have found. This biological "kill switch" helps the organism harvest solar energy during photosynthesis with more efficiency.

In the future, scientists could draw inspiration from pond scum to design better organic solar cells and superfast electronic devices.

Previous research has shown that quantum mechanics are at work in living organisms and not just laboratory setting. Now, researchers at the University of New South Wales have found that certain species of algae can turn on and off quantum coherence during photosynthesis. These algae live at the bottom of water bodies, meaning that they get low amounts of sunlight. Using a "kill switch" helps them use the limited amount of sunlight efficiently.

In 2010, the team at UNSW and colleagues had observed quantum coherence in the molecules of light harvesting systems that were transferring energy. The phenomenon was seen in two different cryptophyte species.

In quantum coherence during photosynthesis, energy waves temporarily exist in multiple locations at once, The Australian reported.

Green sulphur bacteria lives in dark places and also uses quantum mechanics to increase efficiency of photosynthesis.

"We studied tiny single-celled algae called cryptophytes that thrive in the bottom of pools of water, or under thick ice, where very little light reaches them," said senior author, Professor Paul Curmi, of the UNSW School of Physics.

"Most cryptophytes have a light-harvesting system where quantum coherence is present. But we have found a class of cryptophytes where it is switched off because of a genetic mutation that alters the shape of a light-harvesting protein," Curmi said in a news release.

According to the researchers, using quantum coherence helps bacteria and algae survive in low light areas. Once light harvesting molecules trap light, they need to send the light to a reaction center as fast as possible. At the reaction center, light is converted into chemical energy. Previous assumption was that light is sent randomly to the center. Now, researchers believe that quantum coherence could allow light harvesting molecules to test every possible way to make energy transfer more efficient.

For the study, researchers used x-ray crystallography to understand the crystal structure that harvests and sends light.

They found that two out of three cryptophytes species studied had a genetic mutation in the crystals. The altered genes add an extra amino acid to the protein group and disrupt the quantum coherence. "This shows cryptophytes have evolved an elegant but powerful genetic switch to control coherence and change the mechanisms used for light harvesting," said Professor Curmi.

Understanding quantum mechanics at work in nature could help scientists make energy efficient solar cells and electronic devices. In the next part of the research, UNSW scientists will be comparing the biology of different cryptophytes.

The study is published in the journal Proceedings of the National Academy of Sciences.