Scientists have shown that certain algae which use quantum effects to optimize photosynthesis are also capable of switching it off. It's a discovery that could lead to highly efficient organic solar cells and quantum-based electronics.
Like quantum computers, some organisms are capable of scanning all possible options in order to choose the most efficient path or solution. For plants and some photosynthetic algae, this means the ability to make the most of the energy they receive and then deliver that energy from leaves with near perfect efficiency. This effect, called quantum decoherence, is what allows some algae to survive in very low levels of light.
Recently, scientists from the UNSW School of Physics studied one of these algae, a tiny single-celled organism called cryptophytes. They typically live at the bottom of pools of water, or under thick ice, where light is scarce. The researchers found that there's a class of cryptophytes in which quantum decoherence is switched off, and it's on account of a single genetic mutation that alters the shape of a light-harvesting protein.
In quantum mechanics, a system is coherent when all quantum waves are in step with each other. When it's coherent, it can exist in many different states simultaneously, an effect known as superposition.
The researchers used X-ray crystallography to determine the crystal structure of the light-harvesting complexes from three different species. Two cryptophyte species had a mutation that led to the insertion of an extra amino acid that changes the structure of the protein complex, which disrupts decoherence.
The next step for the scientists will be to determine whether the switching effect is assisting the algae's survival. What's more, further understanding of this phenomenon could eventually lead to technological advances, such as better organic solar cells and quantum-based electronic devices.
Read the entire study at PNAS: "Single-residue insertion switches the quaternary structure and exciton states of cryptophyte light-harvesting proteins." Supplementary information via UNSW.
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