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.

Underwater spectral reflectance measurements: the reflectance standard submersion factor and its impact on derived target reflectance.

For Earth observation remote sensing, high quality reflectance spectra are necessary for model input, algorithm development, and validation of derived products. In the aquatic environment, a common approach for making spectral reflectance measurements involves using a calibrated reflectance standard such as a Spectralon plaque underwater. The manufacturer provides a National Institute of Standards and Technology traceable reflectance curve with each standard, measured in air.

An automated liquid jet for fluorescence dosimetry and microsecond radiolytic labeling of proteins.

X-ray radiolytic labeling uses broadband X-rays for in situ hydroxyl radical labeling to map protein interactions and conformation. High flux density beams are essential to overcome radical scavengers. However, conventional sample delivery environments, such as capillary flow, limit the use of a fully unattenuated focused broadband beam.

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.

Molting strategies of Arctic seals drive annual patterns in metabolism.

Arctic seals, including spotted (), ringed () and bearded () seals, are directly affected by sea ice loss. These species use sea ice as a haul-out substrate for various critical functions, including their annual molt. Continued environmental warming will inevitably alter the routine behavior and overall energy budgets of Arctic seals, but it is difficult to quantify these impacts as their metabolic requirements are not well known-due in part to the difficulty of studying wild individuals.

Reciprocal regulation of TORC signaling and tRNA modifications by Elongator enforces nutrient-dependent cell fate.

Nutrient availability has a profound impact on cell fate. Upon nitrogen starvation, wild-type fission yeast cells uncouple cell growth from cell division to generate small, round-shaped cells that are competent for sexual differentiation. The TORC1 (TOR complex 1) and TORC2 complexes exert opposite controls on cell growth and cell differentiation, but little is known about how their activity is coordinated.

Transfer RNA Induces IL-12p70 via Synergistic Activation of Pattern Recognition Receptors within a Cell Network.

Upon recognition of a microbial pathogen, the innate and adaptive immune systems are linked to generate a cell-mediated immune response against the foreign invader. The culture filtrate of contains ligands, such as tRNA, that activate the innate immune response and secreted Ags recognized by T cells to drive adaptive immune responses. In this study, bioinformatics analysis of gene-expression profiles derived from human PBMCs treated with distinct microbial ligands identified a mycobacterial tRNA-induced innate immune network resulting in the robust production of IL-12p70, a cytokine required to instruct an adaptive Th1 response for host defense against intracellular bacteria.

Self-referenced single-shot THz detection.

We demonstrate a self-referencing method to reduce noise in a single-shot terahertz detection scheme. By splitting a single terahertz pulse and using a reflective echelon, both the signal and reference terahertz time-domain waveforms were measured using one laser pulse. Simultaneous acquisition of these waveforms significantly reduces noise originating from shot-to-shot fluctuations.

Oxidation of phosphorothioate DNA modifications leads to lethal genomic instability.

Genomic modification by sulfur in the form of phosphorothioate (PT) is widespread among prokaryotes, including human pathogens. Apart from its physiological functions, PT sulfur has redox and nucleophilic properties that suggest effects on bacterial fitness in stressful environments. Here we show that PTs are dynamic and labile DNA modifications that cause genomic instability during oxidative stress.

Photocatalytic effects of titanium dioxide nanoparticles on aquatic organisms-Current knowledge and suggestions for future research.

Nanoparticles are entering natural systems through product usage, industrial waste and post-consumer material degradation. As the production of nanoparticles is expected to increase in the next decade, so too are predicted environmental loads. Engineered metal-oxide nanomaterials, such as titanium dioxide, are known for their photocatalytic capabilities.

Open-ocean fish reveal an omnidirectional solution to camouflage in polarized environments.

Despite appearing featureless to our eyes, the open ocean is a highly variable environment for polarization-sensitive viewers. Dynamic visual backgrounds coupled with predator encounters from all possible directions make this habitat one of the most challenging for camouflage. We tested open-ocean crypsis in nature by collecting more than 1500 videopolarimetry measurements from live fish from distinct habitats under a variety of viewing conditions.

Use of Hyperspectral Imagery to Assess Cryptic Color Matching in Sargassum Associated Crabs.

Mats of the pelagic macroalgae Sargassum represent a complex environment for the study of marine camouflage at the air-sea interface. Endemic organisms have convergently evolved similar colors and patterns, but quantitative assessments of camouflage strategies are lacking. Here, spectral camouflage of two crab species (Portunus sayi and Planes minutus) was assessed using hyperspectral imagery (HSI).

Quantitative analysis of ribonucleoside modifications in tRNA by HPLC-coupled mass spectrometry.

Post-transcriptional modification of RNA is an important determinant of RNA quality control, translational efficiency, RNA-protein interactions and stress response. This is illustrated by the observation of toxicant-specific changes in the spectrum of tRNA modifications in a stress-response mechanism involving selective translation of codon-biased mRNA for crucial proteins. To facilitate systems-level studies of RNA modifications, we developed a liquid chromatography-mass spectrometry (LC-MS) technique for the quantitative analysis of modified ribonucleosides in tRNA.

Benthic effects on the polarization of light in shallow waters.

Measurements of the upwelling polarized radiance in relatively shallow waters of varying depths and benthic conditions are compared to simulations, revealing the depolarizing nature of the seafloor. The simulations, executed with the software package RayXP, are solutions to the vector radiative transfer equation, which depends on the incident light field and three types of parameters: inherent optical properties, the scattering matrix, and the benthic reflectance. These were measured directly or calculated from measurements with additional assumptions.

A system for exposing molecules and cells to biologically relevant and accurately controlled steady-state concentrations of nitric oxide and oxygen.

Nitric oxide (NO) plays key roles in cell signaling and physiology, with diverse functions mediated by NO concentrations varying over three orders-of-magnitude. In spite of this critical concentration dependence, current approaches to NO delivery in vitro result in biologically irrelevant and poorly controlled levels, with hyperoxic conditions imposed by ambient air. To solve these problems, we developed a system for controlled delivery of NO and O(2) over large concentration ranges to mimic biological conditions.

Safety, immunogenicity, and efficacy of an alphavirus replicon-based swine influenza virus hemagglutinin vaccine.

A single-cycle, propagation-defective replicon particle (RP) vaccine expressing a swine influenza virus hemagglutinin (HA) gene was constructed and evaluated in several different animal studies. Studies done in both the intended host (pigs) and non-host (mice) species demonstrated that the RP vaccine is not shed or spread by vaccinated animals to comingled cohorts, nor does it revert to virulence following vaccination. In addition, vaccinated pigs develop both specific humoral and IFN-γ immune responses, and young pigs are protected against homologous influenza virus challenge.

microRNA modulation of circadian-clock period and entrainment.

microRNAs (miRNAs) are a class of small, noncoding RNAs that regulate the stability or translation of mRNA transcripts. Although recent work has implicated miRNAs in development and in disease, the expression and function of miRNAs in the adult mammalian nervous system have not been extensively characterized. Here, we examine the role of two brain-specific miRNAs, miR-219 and miR-132, in modulating the circadian clock located in the suprachiasmatic nucleus.