Photosynthetic algae develop unique pigments to protect against sunlight and increase energy efficiency
Green marine algae have developed a remarkable defense against the harmful effects of excess sunlight, according to a study by Osaka Metropolitan University and its international research partners. The research found that a pigment called siphonin acts as a protective shield, allowing algae to maintain efficient photosynthesis without risking damage from excessive light exposure.
The research focused on the marine algae Codium fragile, which, like land plants, contains light-harvesting complexes equipped with chlorophyll to absorb sunlight. However, Codium fragile is distinguished by the addition of unique carotenoids, especially siphonine and siphonaxanthin, which enable effective use of green light underwater.
“Organisms use carotenoids to quickly dissipate excess energy, or quench these triplet states, through a process called triplet-triplet energy transfer (TTET),” says Ritsuko Fujii, associate professor at Osaka Metropolitan University. Using a specialized electron paramagnetic resonance spectroscopy method, the team immediately found that Codium’s carotenoids eliminate fragile potentially harmful chlorophyll triplet states much more effectively than in spinach plants.
The scientists found that the placement of siphonine in the light-harvesting antenna structure is crucial for this energy-dissipating process, and further quantum chemical simulation confirmed the electronic structure’s key role in preventing oxidative damage while improving photosynthetic performance.
The evolutionary adaptation of algae shown in this study not only helps them withstand harsh marine sunlight, but could also pave the way for bio-inspired improvements in solar energy technology. The team now hopes to identify structural features in carotenoids that maximize energy quenching, potentially revolutionizing the design of artificial photosynthetic and renewable energy systems.
“Our research has shown that the antennal structure of photosynthetic green algae has an excellent photoprotective function,” says Alessandro Agostini, University of Padua, co-lead author of the study. “We hope to further elucidate the structural features of carotenoids that increase quenching efficiency, ultimately enabling the molecular design of pigments that optimize photosynthetic antennae,” Fujii said.
Research report:Siphonein enables an effective photoprotective triplet quenching mechanism in green algae light-harvesting complexes
