Sima Baghbanzadeh et al. Geometry, Supertransfer, and Optimality in the Light Harvesting of Purple Bacteria, The Journal of Physical Chemistry Letters (2016). DOI: 10.1021/acs.jpclett.6b01779
In its billions of years on earth, plant life has become super-efficient at using light – and now it’s showing how it does it. A quantum – minuscule – examination of chlorophyll within certain purple bacteria shows an exceptionally efficient geometric arrangement for light harvesting, say scientists from The University of Queensland and Iran’s Institute for Research in Fundamental Sciences. UQ’s Dr Ivan Kassal, said the bacteria used “quantum coherence” – particles’ wave-like properties – to harvest light during photosynthesis.
“Inside, the bacteria’s chlorophyll molecules – which collect energy from light – are arranged in symmetrical rings,” Dr Kassal said.
“This geometric organisation is exceptionally good for light harvesting. “By Understanding how the purple bacteria harvest light, we may be able to use these lessons to improve how we do artificial light harvesting.” Dr Kassal said previous research had proposed the theory that quantum coherence played a role in how the purple bacteria harvested light.
“There has been debate in the field about whether coherent effects are possible in photosynthetic systems at all.”
The remarkable rotational symmetry of the photosynthetic antenna complexes of purple bacteria has long been thought to enhance their light harvesting and excitation energy transport. We study the role of symmetry by modeling hypothetical antennas whose symmetry is broken by altering the orientations of the bacteriochlorophyll pigments. We find that in both LH2 and LH1 complexes, symmetry increases energy transfer rates by enabling the cooperative, coherent process of supertransfer. The enhancement is particularly pronounced in the LH1 complex, whose natural geometry outperforms the average randomized geometry by 5.5 standard deviations, the most significant coherence-related enhancement found in a photosynthetic complex.
“We know now that quantum effects cannot be neglected in studies on biological light harvesting,” he said.
“This is a fertile ground for developing new technologies for simulating quantum systems in noisy environments.”
“The study also opens avenues for research into whether quantum coherence already occurs in organic solar cells, and whether humans can deliberately engineer that coherence to make them more efficient.” https://www.uq.edu.au/news/article/2016/10/purple-bacteria-shine-path-super-efficient-light-harvesting
http://pubs.acs.org/doi/abs/10.1021/acs.jpclett.6b01779
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