ABSTRACT The accumulation of bioenergy carriers was assessed in two starchless mutants Chlamydomonas reinhardtii (the sta6 [ADP-glucose pyrophosphorylase] and sta7 - 10 [isoamylase] mutants), a control strain (CC124), complemented strains the mutant. results indicate that genetic blockage starch synthesis increases lipids on cellular basis during nitrogen deprivation relative to CC124 as determined by conversion fatty acid methyl esters. However, this increased level lipid is energetically...

Charging up cobalt for hydroformylation Hydroformylation reactions are applied at massive scale in the chemical industry to transform olefins into aldehydes. The original catalysts were neutral complexes. Hood et al. now report that positively charged complexes, stabilized by chelating phosphine ligands, show higher activities lower pressures than their counterparts, approaching of precious rhodium catalysts. These particularly adept accelerating internal while avoiding decomposition....

Nickel precatalysts are potentially a more sustainable alternative to traditional palladium for the Suzuki–Miyaura coupling reaction. Currently, there is significant interest in reactions involving readily accessible phenolic derivatives such as aryl sulfamates, sulfamate moiety can act directing group prefunctionalization of aromatic backbone electrophile prior cross-coupling. By evaluating complexes Ni(0), (I), and (II) oxidation states we report precatalyst, (dppf)Ni(o-tolyl)(Cl) (dppf =...

Significance Models of the CO 2 concentrating mechanism (CCM) green algae and diatoms postulate that chloroplast is generated from HCO 3 − brought into acidic thylakoid lumen converted to by specific carbonic anhydrases. However, identity transporter required for uptake has remained elusive. In this work, bestrophin-like proteins, BST1–3, located on membrane have been found be essential CCM Chlamydomonas . Reduction in expression BST1–3 markedly reduced inorganic carbon affinity alga. These...

Abstract Ni‐based precatalysts for the Suzuki–Miyaura reaction have potential chemical and economic advantages compared to commonly used Pd systems. Here, we compare Ni supported by dppf ligand in 3 oxidation states, 0, I II. Surprisingly, at 80 °C they give similar catalytic activity, with all systems generating significant amounts of during reaction. At room temperature a readily accessible bench‐stable II precatalyst is highly active can couple synthetically important heterocyclic...

Firefly luciferase produces light by converting substrate beetle luciferin into the corresponding adenylate that it subsequently oxidizes to oxyluciferin, emitter of bioluminescence. We have confirmed generally held notions oxidation step is initiated formation a carbanion intermediate and hydroperoxide (anion) involved. Additionally, structural evidence presented accounts for delivery oxygen reaction site. Herein, we report key convincing spectroscopic participation superoxide anion in...

Far-red light (FRL) photoacclimation in cyanobacteria provides a selective growth advantage for some terrestrial by expanding the range of photosynthetically active radiation to include far-red/near-infrared (700–800 nm). During this process, photosystem II (PSII), water:plastoquinone photooxidoreductase involved oxygenic photosynthesis, is modified. The resulting FRL-PSII comprised FRL-specific core subunits and binds chlorophyll (Chl) d Chl f molecules place several found when cells are...

Synchronization of the circadian clock in cyanobacteria with day/night cycle proceeds without an obvious photoreceptor, leaving open question its specific mechanism. The oscillator can be reconstituted vitro, where activities two proteins, KaiA and KaiC, are affected by metabolites that reflect photosynthetic activity: KaiC phosphorylation is directly influenced ATP/ADP ratio, stimulation blocked oxidized, but not reduced, quinones. Manipulation ratio reset timing peaks vitro oscillator....

The six-electron oxidation of two nitrides to N2 is a key step ammonia synthesis and decomposition reactions on surfaces. In molecular complexes, nitride coupling has been observed with terminal nitrides, but not bridging complexes that more closely resemble catalytically important surface species. Further, reported in systems where the are derived from N2. Here, we show diiron(II) diiron(III) bis(nitride) complex reacts Lewis bases, leading rapid form Surprisingly, these mild reagents...

A recent femtosecond X-ray diffraction study produced the first high-resolution structural model of oxygen-evolving complex photosystem II that is free radiation-induced manganese reduction (Protein Data Bank entries 4UB6 and 4UB8 ). We find, however, does not match extended absorption fine structure QM/MM data for S1 state. This attributed to uncertainty about positions oxygen atoms remain partially unresolved, even at 1.95 Å resolution, next heavy centers. In addition, crystals may contain...

Ammonia binds directly to the oxygen-evolving complex of photosystem II (PSII) upon formation S2 intermediate, as evidenced by electron paramagnetic resonance spectroscopy. We explore binding mode using quantum mechanics/molecular mechanics methods and simulations extended X-ray absorption fine structure spectra. find that NH3 an additional terminal ligand dangling Mn4, instead exchanging with water. Because water ammonia are electronic structural analogues, these findings suggest...

Photosynthetic water oxidation occurs at the oxygen-evolving complex (OEC) of Photosystem II (PSII). The OEC, which contains a Mn₄CaO₅inorganic cluster ligated by oxides, waters and amino-acid residues, cycles through five redox intermediates known as S_istates (<italic>i</italic>= 0–4). electronic structural properties transient S₄intermediate that forms O–O bond are not well understood. In order to gain insight into how is activated for formation...

The oxygen-evolving complex (OEC) of photosystem II has been studied in the S3 state by electron paramagnetic resonance, extended X-ray absorption fine structure (EXAFS), and femtosecond diffraction (XRD). However, actual OEC yet to be established. Here, we apply hybrid quantum mechanics/molecular mechanics methods propose a structural model that is consistent with EXAFS XRD. supports binding water ligands cluster S2 → transition through carousel rearrangement around Mn4, inspired studies...

The sulfur-containing nucleosides in transfer RNA (tRNAs) are present all three domains of life; they have critical functions for accurate and efficient translation, such as tRNA structure stabilization proper codon recognition. modification enzymes ThiI (in bacteria archaea) Ncs6 archaea eukaryotic cytosols) catalyze the formation 4-thiouridine (s4U) 2-thiouridine (s2U), respectively. homologs were proposed to sulfur via cysteine persulfide enzyme adducts, whereas reaction mechanism remains...

Upon nutrient deprivation, microalgae partition photosynthate into starch and lipids at the expense of protein synthesis growth. We investigated role biosynthesis with respect to photosynthetic growth carbon partitioning in Chlamydomonas reinhardtii starchless mutant, sta6, which lacks ADP-glucose pyrophosphorylase. This mutant is unable convert glucose-1-phosphate ADP-glucose, precursor biosynthesis. During nutrient-replete culturing, sta6 does not re-direct metabolism make more proteins or...

Significance Metal clusters play important roles in a wide variety of proteins. In cyanobacteria, algae, and plants, photosystem II uses light energy to oxidize water release O 2 at an active site that contains 1 calcium 4 manganese atoms. This cluster must be built within the protein environment through process known as photoassembly. Through experiments simulations, we found efficiency photoassembly was highly dependent on protons chloride. Surprisingly, when solvent switched from H...

The S2 redox intermediate of the oxygen-evolving complex in photosystem II is present as two spin isomers. S = 1/2 isomer gives rise to a multiline electron paramagnetic resonance (EPR) signal at g 2.0, whereas 5/2 exhibits broad EPR 4.1. electronic structures these isomers are known, but their role catalytic cycle water oxidation remains unclear. We show that formation state from exergonic temperatures above 160 K. However, decays S1 more slowly than isomer. These differences support...

Objective— The importance of PI3K/Akt signaling in the vasculature has been demonstrated several models, as global loss Akt1 results impaired postnatal ischemia- and VEGF-induced angiogenesis. ubiquitous expression Akt1, however, raises possibility cell-type–dependent Akt1-driven actions, thereby necessitating tissue-specific characterization. Approach Results— Herein, we used an inducible, endothelial-specific Akt1-deleted adult mouse model (Akt1iECKO) to characterize endothelial cell...

[HCo(CO)x(bisphosphine)](BF4), x = 1–3, is a highly active hydroformylation catalyst system, especially for internal branched alkenes. In situ infrared spectroscopy (IR), electron paramagnetic resonance (EPR), and nuclear magnetic studies support the proposed formulation. IR reveal formation of dicationic Co(I) CO-bridged dimer, [Co2(μ-CO)2(CO)(bisphosphine)2]2+, at lower temperatures formed from reaction two complexes via elimination H2. DFT indicate dimer structure with square-pyramidal...

The D1 protein of Photosystem II (PSII) provides most the ligating amino acid residues for Mn4CaO5 water-oxidizing complex (WOC) and half reaction center cofactors, it is present as two isoforms in cyanobacterium Synechococcus elongatus PCC 7942. These isoforms, D1:1 D1:2, confer functional advantages photosynthetic growth at low high light intensities, respectively. D1:1, seven point mutations D1:2 background that are native to were expressed green alga Chlamydomonas reinhardtii. We used...