Cryo-EM structure of a photosystem I variant containing an unusual plastoquinone derivative in its electron transfer chain.

Photosystem I (PS I) is a light-driven oxidoreductase responsible for converting photons into chemical bond energy. Its application for renewable energy was revolutionized by the creation of the MenB deletion (Δ) variant in the cyanobacterium sp. PCC 6803, in which phylloquinone is replaced by plastoquinone-9 with a low binding affinity.

Revisiting the Preparation and Catalytic Performance of a Phosphine-Modified Co(II) Hydroformylation Precatalyst.

In light of recent conflicting reports regarding the hydroformylation catalytic activity derived from cationic Co(II) precatalysts of the form [Co(acac)(bis(phosphine))]BF, the synthetic procedures and characterization of [Co(acac)(dppBz)]BF, , are evaluated. Leveraging calibrated ESI-TOF MS methodologies, substantial quantities of Co(acac)(dppBz), , were observed within samples of . The source of the impurity, , is determined to derive from incomplete protonolysis of the Co(acac) precursor and ligand scrambling occurring during the synthesis of .

Assembly and Repair of Photosystem II in .

Oxygenic photosynthetic organisms use Photosystem II (PSII) to oxidize water and reduce plastoquinone. Here, we review the mechanisms by which PSII is assembled and turned over in the model green alga . This species has been used to make key discoveries in PSII research due to its metabolic flexibility and amenability to genetic approaches.

Conformational changes in a Photosystem II hydrogen bond network stabilize the oxygen-evolving complex.

The MnCaO oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ and catalyzes water oxidation. After OEC assembly, the PsbO extrinsic subunit docks to the lumenal face of PSII and both stabilizes the OEC and facilitates efficient proton transfer to the lumen. D1 residue R334 is part of a hydrogen bond network involved in proton release during catalysis and interacts directly with PsbO.

Chloride facilitates Mn(III) formation during photoassembly of the Photosystem II oxygen-evolving complex.

The MnCa oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ from free Mn, Ca, and water. In an early light-driven step, Mn in a protein high-affinity site is oxidized to Mn. Using dual-mode electron paramagnetic resonance spectroscopy, we observed that Mn accumulation increases as chloride concentration increases in spinach PSII membranes depleted of all extrinsic subunits.