AsianScientist (Aug. 5, 2014) – Researchers have solved a long-standing question in photosynthesis, providing insight into the design of artificial photosynthetic systems that may serve as alternative energy devices by effectively utilizing the sunlight. The paper describing their findings has been published in the journal Nature Communications.
In photosynthesis, sunlight is used to extract electrons from water to produce oxygen. This chemical reaction occurs in the reaction center of the Photosystem II (PSII) protein, which many pigments such as chlorophyll. These pigments are distributed symmetrically into two branches; however, only one branch, namely the active chain, is responsible for transferring electrons to produce oxygen. In other words, only half of the pigments in the reaction center actively participate in the production of oxygen. The functional asymmetry of the two chains has remained a long-standing puzzle for scientists to understand the mechanisms of photosynthesis.
Using theoretical chemistry tools such as molecular dynamics and quantum mechanics calculations, a Hong Kong University of Science and Technology (HKUST) research team has revealed the secrets behind this phenomena. They discovered that the dynamic and asymmetric protein environment makes one specific cofactor called CLA606, in the active chain significantly easier to be activated by sunlight energy, thus leading to the electron transfer along the active chain. They further pinpointed several critical protein residues in this process, and found that the alteration of these residues may disable PSII’s ability to distinguish between the active and inactive chains.
Corresponding author Assistant Professor Xuhui Huang from HKUST’s Department of Chemistry explained that it is crucial to consider protein dynamics rather than the static X-ray structure in order to explain the preference of energy activation towards the active chain. The research team used high-performance computers including those from the HKUST School of Science’s computer cluster to successfully identify the site energy difference of the two chains and further pinpoint the critical active chain pigment CLA606.
The results will provide insight into the fundamental mechanisms of photosynthesis and potential applications for the rational design and engineering of the photosynthetic machinery. The insight gained from this study could also be applied in physical chemistry, molecular biology and material science.
The article can be found at: Zhang et al. (2014) Dynamic Protein Conformations Preferentially Drive Energy Transfer Along the Active Chain of the Photosystem II Reaction Centre.
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Source: Hong Kong University of Science and Technology.
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