Abstract
The oxygen-evolving center (OEC) in photosystem II (PSII) of plants, algae and cyanobacteria is a unique natural catalyst that splits water into electrons, protons and dioxygen. The crystallographic studies of PSII have revealed that the OEC is an asymmetric Mn4CaO5-cluster. The understanding of the structure-function relationship of this natural Mn4CaO5-cluster is impeded mainly due to the complexity of the protein environment and lack of a rational chemical model as a reference. Although it has been a great challenge for chemists to synthesize the OEC in the laboratory, significant advances have been achieved recently. Different artificial complexes have been reported, especially a series of artificial Mn4CaO4-clusters that closely mimic both the geometric and electronic structures of the OEC in PSII, which provides a structurally well-defined chemical model to investigate the structure-function relationship of the natural Mn4CaO5-cluster. The deep investigations on this artificial Mn4CaO4-cluster could provide new insights into the mechanism of the water-splitting reaction in natural photosynthesis and may help the development of efficient catalysts for the water-splitting reaction in artificial photosynthesis.
Highlights
The oxygen-evolving center (OEC) in photosystem II (PSII) of plants, algae and cyanobacteria is a unique natural catalyst that provides electrons and protons to produce the biomass or biofuel, and a dioxygen molecule to maintain the oxygenic atmosphere on our planet [1,2,3,4,5,6,7,8]
In 1980s, it was revealed that the OEC is composed by one calcium and four manganese ions, embedded into the large protein environment of PSII through some carboxylate and imidazole groups [13,14,15]
It has been found that the structural modifications of the OEC would take place due to the radiation damage induced by X-ray free electron laser (XFEL) such as the position of the μ4 -oxide bridge (O5, Figure 2), which can be significantly disturbed by XFEL [57,64,65]
Summary
The oxygen-evolving center (OEC) in photosystem II (PSII) of plants, algae and cyanobacteria is a unique natural catalyst that provides electrons and protons to produce the biomass or biofuel, and a dioxygen molecule to maintain the oxygenic atmosphere on our planet [1,2,3,4,5,6,7,8]. A long-standing goal in science seeks to reveal the structure-function relationship and the catalytic mechanism of the OEC, which would provide a blueprint to develop efficient artificial catalysts for the water-splitting reaction in artificial photosynthesis [2,7,9,10]. Some groups proposed a low-oxidation widely in the field of photosynthetic research. The structure and catalytic mechanism of the capability of PSII and it can only be functionally replaced by strontium [28,29,30]. Catalytic mechanism of the OEC have attracted studies during the last three decades [2,6,7]. The valences of the manganese ions in different are according to the high-oxidation paradigm (see main fortext details). States are according to the high-oxidation paradigm (seetext main for details)
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