Light-driven oxidation of water into dioxygen, catalysed by the oxygen-evolving complex (OEC) in photosystem II, is essential for life on Earth and provides the blueprint for devices for producing fuel from sunlight. Although the structure of the OEC is known at atomic level for its dark-stable state, the mechanism by which water is oxidized remains unsettled. Important mechanistic information ...

This paper reports computational studies of substrate water binding to the oxygen-evolving centre (OEC) of photosystem II (PSII), completely ligated by amino acid residues, water, hydroxide and chloride. The calculations are based on quantum mechanics/molecular mechanics hybrid models of the OEC of PSII, recently developed in conjunction with the X-ray crystal structure of PSII from the cyanoba...

Tanaka et al. (J. Am. Chem. Soc., 2017, 139, 1718) recently reported the three-dimensional (3D) structure of the oxygen evolving complex (OEC) of photosystem II (PSII) by X-ray diffraction (XRD) using extremely low X-ray doses of 0.03 and 0.12 MGy. They observed two different 3D structures of the CaMn4O5 cluster with different hydrogen-bonding interactions in the S1 state of OEC keeping the sur...

The second-shell ammonia binding sites near the OEC (oxygen-evolving complex) of PSII are characterized by combined Continuum Electrostatic/Monte Carlo (MCCE), QM/MM and DFT calculations and compared with new and earlier experimental measurements. MCCE shows ammonia has significant affinity at 6 positions but only two significantly influence the OEC. Although the pKa of ammonium ion is 9.25, it...

An online evolving clustering (OEC) method equivalent to ensemble modeling is proposed tackle prognostics problems of learning and the prediction remaining useful life (RUL). During phase, OEC extracts predominant operating modes as multiple clusters (EC). Each EC associated with its own Weibull distribution-inspired degradation (survivability) model that will receive incremental modifications ...

Exposure of isolated thylakoids or intact plants to elevated temperature is known to inhibit photosynthesis at multiple sites. We have investigated the effect of elevated temperature (40 degrees C) for 24 hr in dark on rice seedlings to characterize the extent of damage by in vivo heat stress on photofunctions of photosystem II (PSII). Chl a fluorescence transient analysis in the intact rice le...

We report the first (55)Mn pulsed ENDOR studies on the S2 state multiline spin ½ centre of the oxygen evolving complex (OEC) in Photosystem II (PS II), at temperatures below 4.2 K. These were performed on highly active samples of spinach PS II core complexes, developed previously in our laboratories for photosystem spectroscopic use, at temperatures down to 2.5 K. Under these conditions, relaxa...

The molecular oxygen produced in photosynthesis is generated via water oxidation at a manganese-calcium cluster called the oxygen-evolving complex (OEC). While studies in biophysics, biochemistry, and structural and molecular biology are well known to provide deeper insight into the structure and workings of this system, it is often less appreciated that biomimetic modelling provides the founda...

This paper discusses the suitability of manganese for its function in catalysing the formation of molecular oxygen from water. Manganese is an abundant element. In terms of its inherent properties, Mn has a particularly rich redox chemistry compared with other d-block elements, with several oxidizing states accessible. The most stable-state Mn2+ behaves like a Group 2 element--it is mobile, wea...

Efficient photoelectrochemical water oxidation may open a way to produce energy from renewable solar power. In biology, generation of fuel due to water oxidation happens efficiently on an immense scale during the light reactions of photosynthesis. To oxidize water, photosynthetic organisms have evolved a highly conserved protein complex, Photosystem II. Within that complex, water oxidation happ...