Although quasi-amorphous iridium oxohydroxides have been identified repeatedly as superior electrocatalysts for the oxygen evolution reaction (OER), an exact description of the performance-relevant species has remained a challenge. In this context, we report the characterization of hydrothermally prepared iridium(III/IV) oxohydroxides that exhibit exceptional OER performances. Holes in the O 2p...

Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry Mn(IV)3GdO4 and Mn(IV)3CaO4 cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing si...

Seawater has been irradiated using a train of 70 ns flashes from a 440 nm laser source. This wavelength is on resonance with the blue absorption peak of Chlorophyll pigment associated with the photosystem of in vitro phytoplankton. The resulting fluorescence at 685 nm is instantaneously recorded during each laser pulse using a streak camera. Delayed fluorescence is observed, yielding clues abou...

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 ...

We first describe the history and methods of membrane protein crystallization, and show how the structure of the photosynthetic reaction centre from the purple bacterium Rhodopseudomonas viridis was solved. The structure of this membrane protein complex is correlated with its function as a light-driven electron pump across the photosynthetic membrane. Finally we draw conclusions on the structur...

Density functional theory (DFT) calculations are reported for a set of model compounds intended to represent the structure of the Photosystem II (PSII) water oxidising complex (WOC) as determined by the recent 1.9 Å resolution single crystal X-ray diffraction (XRD) study of Umena et al. In contrast with several other theoretical studies addressing this structure, we find that it is not necessar...

A recent femtosecond X-ray diffraction study produced the first high-resolution structural model of the oxygen-evolving complex of photosystem II that is free of radiation-induced manganese reduction (Protein Data Bank entries 4UB6 and 4UB8 ). We find, however, that the model does not match extended X-ray absorption fine structure and QM/MM data for the S1 state. This is attributed to uncertain...

In photosystem II (PSII), the Mn4CaO5 cluster catalyses the water splitting reaction. The crystal structure of PSII shows the presence of a hydrogen-bonded water molecule directly linked to O4. Here we show the detailed properties of the H-bonds associated with the Mn4CaO5 cluster using a quantum mechanical/molecular mechanical approach. When O4 is taken as a μ-hydroxo bridge acting as a hydrog...

G u d r u n Wälzlein, Ach im E . G a u , and El f r iede K. Pistorius Universität Bielefeld, Fakultät für Biologie, Lehrstuhl Zellphysiologie, D-4800 Bielefeld 1, Bundesrepublik Deutschland Z. Naturforsch. 43c, 545-553 (1988); received January 25, 1988 L-Amino Acid Oxidase, Flavoprotein, Photosystem II, Cyanobacteria, Anacystis nidulans The absorption spectrum of the previously purified L-amino...