X-ray spectroscopy of the photosynthetic oxygen-evolving complex

Sauer, Kenneth; Yano, Junko; Yachandra, Vittal K.

doi:10.1016/j.ccr.2007.08.009

Cited by 133 publications

(96 citation statements)

References 76 publications

(126 reference statements)

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“…Because of the importance of understanding the chemistry of the water-splitting reaction of PSII, there has been a wide range of techniques applied to probe the molecular mechanisms involved and to investigate the structure of the catalytic centre (see various articles in references [23,24]), being particularly spurred by the recent structural analyses of PSII by X-ray absorption spectroscopy [25][26][27] and X-ray crystallography [28 -32]. These studies, coupled with quantum mechanical analyses, have provided a refinement of the structure of the WOC [33][34][35] and given detailed schemes for the water-splitting chemistry leading to O -O bond formation [36][37][38][39][40][41][42][43].…”

Section: Photosystem IImentioning

confidence: 99%

From natural to artificial photosynthesis

Barber

Tran

2013

J. R. Soc. Interface.

324

253

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Demand for energy is projected to increase at least twofold by mid-century relative to the present global consumption because of predicted population and economic growth. This demand could be met, in principle, from fossil energy resources, particularly coal. However, the cumulative nature of carbon dioxide (CO 2 ) emissions demands that stabilizing the atmospheric CO 2 levels to just twice their pre-anthropogenic values by mid-century will be extremely challenging, requiring invention, development and deployment of schemes for carbon-neutral energy production on a scale commensurate with, or larger than, the entire present-day energy supply from all sources combined. Among renewable and exploitable energy resources, nuclear fusion energy or solar energy are by far the largest. However, in both cases, technological breakthroughs are required with nuclear fusion being very difficult, if not impossible on the scale required. On the other hand, 1 h of sunlight falling on our planet is equivalent to all the energy consumed by humans in an entire year. If solar energy is to be a major primary energy source, then it must be stored and despatched on demand to the end user. An especially attractive approach is to store solar energy in the form of chemical bonds as occurs in natural photosynthesis. However, a technology is needed which has a year-round average conversion efficiency significantly higher than currently available by natural photosynthesis so as to reduce land-area requirements and to be independent of food production. Therefore, the scientific challenge is to construct an 'artificial leaf' able to efficiently capture and convert solar energy and then store it in the form of chemical bonds of a high-energy density fuel such as hydrogen while at the same time producing oxygen from water. Realistically, the efficiency target for such a technology must be 10 per cent or better. Here, we review the molecular details of the energy capturing reactions of natural photosynthesis, particularly the water-splitting reaction of photosystem II and the hydrogen-generating reaction of hydrogenases. We then follow on to describe how these two reactions are being mimicked in physico-chemical-based catalytic or electrocatalytic systems with the challenge of creating a large-scale robust and efficient artificial leaf technology.

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Section: Photosystem IImentioning

confidence: 99%

From natural to artificial photosynthesis

Barber

Tran

2013

J. R. Soc. Interface.

324

253

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“…The geometric and electronic structural changes that occur during the catalytic cycle have been studied over the last few decades using spectroscopic methods such as electron paramagnetic resonance (EPR) spectroscopy (4), FTIR spectroscopy (5,6), and x-ray absorption spectroscopy (XAS) (7,8). Among them, the information regarding the geometric structural changes comes largely from extended x-ray absorption fine structure (EXAFS) studies (9,10).…”

mentioning

confidence: 99%

Structural Changes of the Oxygen-evolving Complex in Photosystem II during the Catalytic Cycle

Glöckner

Kern

Broser

et al. 2013

Journal of Biological Chemistry

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151

197

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Background: Mn 4 CaO 5 cluster catalyzes water oxidation in photosystem II. Results: Mn-Mn/Ca/ligand distances and changes in the structure of the Mn 4 CaO 5 cluster are determined for the intermediate states in the reaction using x-ray spectroscopy. Conclusion: Position of one bridging oxygen and related geometric changes may be critical during catalysis. Significance: Knowledge about structural changes during catalysis is crucial for understanding the O-O bond formation mechanism in PSII.

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“… and one imidazole, respectively. According to the previous electron paramagnanetic resonance (EPR) [13,14] and extended X-ray absorption fine structure (EXAFS) [15,16] studies, the valences of four Mn ions are S 1 (+4, +4, +3, +3), S 0 (+4, +3, +3, +3) or (+4, +4, +3, +2). Considering the Mn 4 Ca-cluster is located inside of proteins, DFT calculations were only performed on the model containing 0, or +1 or 1 net charge.…”

Section: Dft Calculationsmentioning

confidence: 98%

Assignment of the μ4-O5 atom in catalytic center for water oxidation in photosystem II

et al. 2013

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The detailed structure of catalytic center of water oxidation, Mn 4 Ca-cluster, in photosystem II (PSII) has been reported recently. However, due to the radiation damage induced by X-ray and the complexity of the Mn 4 Ca-cluster, the assignment of the  4 -O5 atom coordinated by three Mn and one Ca 2+ ions is still lack of essential evidences. In this article, we synthesized one Mn complex containing two  4 -O atoms. It is found that the lengths of all  4 -O-Mn bonds in this Mn complex are in the range of 1.89-2.10 Å, which are significantly shorter than 2.40-2.61 Å distance of  4 -O5-Mn bonds in Mn 4 Ca-cluster observed in the crystal structure of PSII. In addition, DFT calculations have been carried out on the Mn 4 Ca-cluster. It is found that the O atom of  4 -O or  4 -OH always trends to deviate from the center position of four metal ions, resulting in unequal bond lengths of four  4 -O-M (M=Mn or Ca), which is obviously different with larger and nearly equal distances between  4 -O and four metal ions observed in the crystal structure. Based on these results, we suggest that the  4 -atom in Mn 4 Ca-cluster of PSII is unlikely to be a Recently, Umena et al. [7] have reported the crystal structure of PSII at a resolution of 1.9 Å, which revealed the detailed structure of the Mn 4 Ca-cluster. The core of the Mn 4 Ca-cluster is shown in Figure 1, wherein four Mn and one Ca ions are connected by five -O atoms. The distances between  3 -O/ 2 -O and Mn ions are all in the range of 1.8-2.1 Å; while the lengths of three  4 -O5-Mn bonds are in the range of 2.4-2.61 Å. The latter is significant longer than those of  2 -O-Mn or  3 -O-Mn bonds. The apparently larger and nearly equal lengths of three  4 -O-Mn bonds indicate that the  4 -O5 atom is very special. In fact, this  4 -O5 atom has attracted extensive attentions by theoretical studies recently, and several groups [8][9][10] suggested that the  4 -O5 atom may play crucial roles to provide one oxygen source for the O-O bond formation. However, due to radiation damage induced by X-ray [11,12] and the complexity of the Mn 4 Ca-cluster, especially the assignment of this  4 -O5 atom was suffered by its weak electron density compared with all other O atoms in Mn 4 Ca-cluster in X-ray diffraction data [7]. Therefore, the assignment of  4 -O5 is still an open question. Here, we have carried out DFT calculations on Mn 4 Ca-cluster to check the rationality of the assignment of  4 -O5 atom. In addition, we have also synthesized a manganese complex containing  4 -O atom. The structural analysis on this compound further provides a clue to demonstrate the possible structure characters of the  4 -O in

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X-ray spectroscopy of the photosynthetic oxygen-evolving complex

Cited by 133 publications

References 76 publications

From natural to artificial photosynthesis

From natural to artificial photosynthesis

Structural Changes of the Oxygen-evolving Complex in Photosystem II during the Catalytic Cycle

Assignment of the μ4-O5 atom in catalytic center for water oxidation in photosystem II

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