Bismuth-Catalyzed Amide Reduction.

In this article we report that a cationic version of Akiba's BiIII complex catalyzes the reduction of amides to amines using silane as hydride donor. The catalytic system features low catalyst loadings and mild conditions, en route to secondary and tertiary aryl- and alkylamines. The system tolerates functional groups such as alkene, ester, nitrile, furan and thiophene. Kinetic studies on the reaction mechanism result in the identification of a reaction network with an important product inhibition that is in agreement with the experimental reaction profiles.

Hyperpolarized Metabolic and Parametric CMR Imaging of Longitudinal Metabolic-Structural Changes in Experimental Chronic Infarction.

BACKGROUND: Prolonged ischemia and myocardial infarction are followed by a series of dynamic processes that determine the fate of the affected myocardium toward recovery or necrosis. Metabolic adaptions are considered to play a vital role in the recovery of salvageable myocardium in the context of stunned and hibernating myocardium. OBJECTIVES: The potential of hyperpolarized pyruvate cardiac magnetic resonance (CMR) alongside functional and parametric CMR as a tool to study the complex metabolic-structural interplay in a longitudinal study of chronic myocardial infarction in an experimental pig model is investigated. METHODS: Metabolic imaging using hyperpolarized [1-13C] pyruvate and proton-based CMR including cine, T1/T2 relaxometry, dynamic contrast-enhanced, and late gadolinium enhanced imaging were performed on clinical 3.0-T and 1.5-T MR systems before infarction and at 6 days and 5 and 9 weeks postinfarction in a longitudinal study design. Chronic myocardial infarction in pigs was induced using catheter-based occlusion and compared with healthy controls. RESULTS: Metabolic image data revealed temporarily elevated lactate-to-bicarbonate ratios at day 6 in the infarcted relative to remote myocardium. The temporal changes of lactate-to-bicarbonate ratios were found to correlate with changes in T2 and impaired local contractility. Assessment of pyruvate dehydrogenase flux via the hyperpolarized [13C] bicarbonate signal revealed recovery of aerobic cellular respiration in the hibernating myocardium, which correlated with recovery of local radial strain. CONCLUSIONS: This study demonstrates the potential of hyperpolarized CMR to longitudinally detect metabolic changes after cardiac infarction over days to weeks. Viable myocardium in the area at risk was identified based on restored pyruvate dehydrogenase flux.

Radical Activation of N-H and O-H Bonds at Bismuth(II).

The development of unconventional strategies for the activation of ammonia (NH3) and water (H2O) is of capital importance for the advancement of sustainable chemical strategies. Herein we provide the synthesis and characterization of a radical equilibrium complex based on bismuth featuring an extremely weak Bi-O bond, which permits the in situ generation of reactive Bi(II) species. The ensuing organobismuth(II) engages with various amines and alcohols and exerts an unprecedented effect onto the X-H bond, leading to low BDFEX-H. As a result, radical activation of various N-H and O-H bonds─including ammonia and water─occurs in seconds at room temperature, delivering well-defined Bi(III)-amido and -alkoxy complexes. Moreover, we demonstrate that the resulting Bi(III)-N complexes engage in a unique reactivity pattern with the triad of H+, H-, and H• sources, thus providing alternative pathways for main group chemistry.

Catalytic synthesis of phenols with nitrous oxide.

The development of catalytic chemical processes that enable the revalorization of nitrous oxide (N2O) is an attractive strategy to alleviate the environmental threat posed by its emissions1-6. Traditionally, N2O has been considered an inert molecule, intractable for organic chemists as an oxidant or O-atom transfer reagent, owing to the harsh conditions required for its activation (>150 °C, 50‒200 bar)7-11. Here we report an insertion of N2O into a Ni‒C bond under mild conditions (room temperature, 1.5-2 bar N2O), thus delivering valuable phenols and releasing benign N2. This fundamentally distinct organometallic C‒O bond-forming step differs from the current strategies based on reductive elimination and enables an alternative catalytic approach for the conversion of aryl halides to phenols. The process was rendered catalytic by means of a bipyridine-based ligands for the Ni centre. The method is robust, mild and highly selective, able to accommodate base-sensitive functionalities as well as permitting phenol synthesis from densely functionalized aryl halides. Although this protocol does not provide a solution to the mitigation of N2O emissions, it represents a reactivity blueprint for the mild revalorization of abundant N2O as an O source.

Isolation and characterization of Streptomyces bacteriophages and Streptomyces strains encoding biosynthetic arsenals.

The threat to public health posed by drug-resistant bacteria is rapidly increasing, as some of healthcare's most potent antibiotics are becoming obsolete. Approximately two-thirds of the world's antibiotics are derived from natural products produced by Streptomyces encoded biosynthetic gene clusters. Thus, to identify novel gene clusters, we sequenced the genomes of four bioactive Streptomyces strains isolated from the soil in San Diego County and used Bacterial Cytological Profiling adapted for agar plate culturing in order to examine the mechanisms of bacterial inhibition exhibited by these strains. In the four strains, we identified 104 biosynthetic gene clusters. Some of these clusters were predicted to produce previously studied antibiotics; however, the known mechanisms of these molecules could not fully account for the antibacterial activity exhibited by the strains, suggesting that novel clusters might encode antibiotics. When assessed for their ability to inhibit the growth of clinically isolated pathogens, three Streptomyces strains demonstrated activity against methicillin-resistant Staphylococcus aureus. Additionally, due to the utility of bacteriophages for genetically manipulating bacterial strains via transduction, we also isolated four new phages (BartholomewSD, IceWarrior, Shawty, and TrvxScott) against S. platensis. A genomic analysis of our phages revealed nearly 200 uncharacterized proteins, including a new site-specific serine integrase that could prove to be a useful genetic tool. Sequence analysis of the Streptomyces strains identified CRISPR-Cas systems and specific spacer sequences that allowed us to predict phage host ranges. Ultimately, this study identified Streptomyces strains with the potential to produce novel chemical matter as well as integrase-encoding phages that could potentially be used to manipulate these strains.

TRAF6 Phosphorylation Prevents Its Autophagic Degradation and Re-Shapes LPS-Triggered Signaling Networks.

The ubiquitin E3 ligase TNF Receptor Associated Factor 6 (TRAF6) participates in a large number of different biological processes including innate immunity, differentiation and cell survival, raising the need to specify and shape the signaling output. Here, we identify a lipopolysaccharide (LPS)-dependent increase in TRAF6 association with the kinase IKKε (inhibitor of NF-κB kinase subunit ε) and IKKε-mediated TRAF6 phosphorylation at five residues. The reconstitution of TRAF6-deficient cells, with TRAF6 mutants representing phosphorylation-defective or phospho-mimetic TRAF6 variants, showed that the phospho-mimetic TRAF6 variant was largely protected from basal ubiquitin/proteasome-mediated degradation, and also from autophagy-mediated decay in autolysosomes induced by metabolic perturbation. In addition, phosphorylation of TRAF6 and its E3 ligase function differentially shape basal and LPS-triggered signaling networks, as revealed by phosphoproteome analysis. Changes in LPS-triggered phosphorylation networks of cells that had experienced autophagy are partially dependent on TRAF6 and its phosphorylation status, suggesting an involvement of this E3 ligase in the interplay between metabolic and inflammatory circuits.

Identification of compounds that bind the centriolar protein SAS-6 and inhibit its oligomerization.

Centrioles are key eukaryotic organelles that are responsible for the formation of cilia and flagella, and for organizing the microtubule network and the mitotic spindle in animals. Centriole assembly requires oligomerization of the essential protein spindle assembly abnormal 6 (SAS-6), which forms a structural scaffold templating the organization of further organelle components. A dimerization interaction between SAS-6 N-terminal "head" domains was previously shown to be essential for protein oligomerization in vitro and for function in centriole assembly. Here, we developed a pharmacophore model allowing us to assemble a library of low-molecular-weight ligands predicted to bind the SAS-6 head domain and inhibit protein oligomerization. We demonstrate using NMR spectroscopy that a ligand from this family binds at the head domain dimerization site of algae, nematode, and human SAS-6 variants, but also that another ligand specifically recognizes human SAS-6. Atomistic molecular dynamics simulations starting from SAS-6 head domain crystallographic structures, including that of the human head domain which we now resolve, suggest that ligand specificity derives from favorable Van der Waals interactions with a hydrophobic cavity at the dimerization site.

Citclops: A next-generation sensor system for the monitoring of natural waters and a citizens' observatory for the assessment of ecosystems' status.

The European-Commission-funded project 'Citclops' (Citizens' observatory for coast and ocean optical monitoring) developed methods, tools and sensors, which can be used by citizens to monitor natural waters, with a strong focus on long-term data series related to environmental sciences. The new sensors, based on optical technologies, respond to a number of scientific, technical and societal objectives, ranging from more precise monitoring of key environmental descriptors of the aquatic environment (water colour, transparency and fluorescence) to an improved management of data collected with citizen participation. The sensors were tested, calibrated, integrated on several platforms, scientifically validated and demonstrated in the field. The new methods and tools were tested in a citizen-science context. The general conclusion is that citizens are valuable contributors in quality and quantity to the objective of collecting, integrating and analysing fragmented and diverse environmental data. An integration of these data into data-analysis tools has a large potential to support authoritative monitoring and decision-making. In this paper, the project's objectives, results, technical achievements and lessons learned are presented.

A dynamically interacting flexible loop assists oligomerisation of the Caenorhabditis elegans centriolar protein SAS-6.

Centrioles are conserved organelles fundamental for the organisation of microtubules in animal cells. Oligomerisation of the spindle assembly abnormal protein 6 (SAS-6) is an essential step in the centriole assembly process and may act as trigger for the formation of these organelles. SAS-6 oligomerisation is driven by two independent interfaces, comprising an extended coiled coil and a dimeric N-terminal globular domain. However, how SAS-6 oligomerisation is controlled remains unclear. Here, we show that in the Caenorhabditis elegans SAS-6, a segment of the N-terminal globular domain, unresolved in crystallographic structures, comprises a flexible loop that assists SAS-6 oligomerisation. Atomistic molecular dynamics simulations and nuclear magnetic resonance experiments suggest that transient interactions of this loop across the N-terminal dimerisation interface stabilise the SAS-6 oligomer. We discuss the possibilities presented by such flexible SAS-6 segments for the control of centriole formation.

Diversity and distribution of the bmp gene cluster and its Polybrominated products in the genus Pseudoalteromonas.

The production of pentabromopseudilin and related brominated compounds by Pseudoalteromonas spp. has recently been linked to the bmp biosynthetic gene cluster. This study explored the distribution and evolutionary history of this gene cluster in the genus Pseudoalteromonas. A phylogeny of the genus revealed numerous clades that do not contain type strains, suggesting considerable species level diversity has yet to be described. Comparative genomics revealed four distinct versions of the gene cluster distributed among 19 of the 101 Pseudoalteromonas genomes examined. These were largely localized to the least inclusive clades containing the Pseudoalteromonas luteoviolacea and Pseudoalteromonas phenolica type strains and show clear evidence of gene and gene cluster loss in certain lineages. Bmp gene phylogeny is largely congruent with the Pseudoalteromonas species phylogeny, suggesting vertical inheritance within the genus. However, the gene cluster is found in three different genomic environments suggesting either chromosomal rearrangement or multiple acquisition events. Bmp conservation within certain lineages suggests the encoded products are highly relevant to the ecology of these bacteria.

Left ventricular blood flow patterns at rest and under dobutamine stress in healthy pigs.

Intracardiac blood flow patterns are affected by the morphology of cardiac structures and are set up to support the heart's pump function. Exercise affects contractility and chamber size as well as pre- and afterload. The aim of this study was to test the feasibility of four-dimensional phase contrast cardiovascular MRI under pharmacological stress and to study left ventricular blood flow under stress. 4D flow data were successfully acquired and analysed in 12 animals. During dobutamine infusion, heart rate and ejection fraction increased (82 ± 5 bpm versus 124 ± 3 bpm/46 ± 9% versus 65 ± 7%; both p < 0.05). A decrease in left ventricular end-diastolic volume (72 ± 14 mL versus 55 ± 8 mL; p < 0.05) and end-systolic volume (40 ± 15 mL versus 19 ± 6 mL; p < 0.05) but no change in stroke volume were observed. Trans-mitral diastolic inflow velocity increased under dobutamine and the trajectory of inflowing blood was directed towards the anterior septum with increased inflow angle (26 ± 5°) when compared with controls (15 ± 2°). In 5/6 animals undergoing stress diastolic vortices developed later, and in 3/6 animals vortices collapsed earlier with significantly smaller cross-sectional area during diastole. The vorticity index was not affected. Under the stress condition direct flow (% ejection within the next heart beat) increased from 43 ± 6% to 53 ± 8%. 4D MRI blood flow acquisition and analysis are feasible in pig hearts under dobutamine-induced stress. Flow patterns characterized by high blood velocity and antero-septally oriented diastolic inflow as well as decreased ventricular volumes are unfavourable conditions for diastolic vortex development under pharmacological stress, and cardiac output is increased by a rise in heart rate and directly ejected left ventricular blood volume.

Quantitative myocardial first-pass cardiovascular magnetic resonance perfusion imaging using hyperpolarized [1-13C] pyruvate.

BACKGROUND: The feasibility of absolute myocardial blood flow quantification and suitability of hyperpolarized [1-13C] pyruvate as contrast agent for first-pass cardiovascular magnetic resonance (CMR) perfusion measurements are investigated with simulations and demonstrated in vivo in a swine model. METHODS: A versatile simulation framework for hyperpolarized CMR subject to physical, physiological and technical constraints was developed and applied to investigate experimental conditions for accurate perfusion CMR with hyperpolarized [1-13C] pyruvate. Absolute and semi-quantitative perfusion indices were analyzed with respect to experimental parameter variations and different signal-to-noise ratio (SNR) levels. Absolute myocardial blood flow quantification was implemented with an iterative deconvolution approach based on Fermi functions. To demonstrate in vivo feasibility, velocity-selective excitation with an echo-planar imaging readout was used to acquire dynamic myocardial stress perfusion images in four healthy swine. Arterial input functions were extracted from an additional image slice with conventional excitation that was acquired within the same heartbeat. RESULTS: Simulations suggest that obtainable SNR and B0 inhomogeneity in vivo are sufficient for the determination of absolute and semi-quantitative perfusion with ≤25% error. It is shown that for expected metabolic conversion rates, metabolic conversion of pyruvate can be neglected over the short duration of acquisition in first-pass perfusion CMR. In vivo measurements suggest that absolute myocardial blood flow quantification using hyperpolarized [1-13C] pyruvate is feasible with an intra-myocardial variability comparable to semi-quantitative perfusion indices. CONCLUSION: The feasibility of quantitative hyperpolarized first-pass perfusion CMR using [1-13C] pyruvate has been investigated in simulations and demonstrated in swine. Using an approved and metabolically active compound is envisioned to increase the value of hyperpolarized perfusion CMR in patients.

The Direct and Indirect Roles of NF-κB in Cancer: Lessons from Oncogenic Fusion Proteins and Knock-in Mice.

NF-κB signaling pathways play an important role in the regulation of cellular immune and stress responses. Aberrant NF-κB activity has been implicated in almost all the steps of cancer development and many of the direct and indirect contributions of this transcription factor system for oncogenesis were revealed in the recent years. The indirect contributions affect almost all hallmarks and enabling characteristics of cancer, but NF-κB can either promote or antagonize these tumor-supportive functions, thus prohibiting global NF-κB inhibition. The direct effects are due to mutations of members of the NF-κB system itself. These mutations typically occur in upstream components that lead to the activation of NF-κB together with further oncogenesis-promoting signaling pathways. In contrast, mutations of the downstream components, such as the DNA-binding subunits, contribute to oncogenic transformation by affecting NF-κB-driven transcriptional output programs. Here, we discuss the features of recently identified oncogenic RelA fusion proteins and the characterization of pathways that are regulating the transcriptional activity of NF-κB by regulatory phosphorylations. As NF-κB's central role in human physiology prohibits its global inhibition, these auxiliary or cell type-specific NF-κB regulating pathways are potential therapeutic targets.

LC-MS/MS Detection of Karlotoxins Reveals New Variants in Strains of the Marine Dinoflagellate Karlodinium veneficum from the Ebro Delta (NW Mediterranean).

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the detection and quantitation of karlotoxins in the selected reaction monitoring (SRM) mode. This novel method was based upon the analysis of purified karlotoxins (KcTx-1, KmTx-2, 44-oxo-KmTx-2, KmTx-5), one amphidinol (AM-18), and unpurified extracts of bulk cultures of the marine dinoflagellate Karlodinium veneficum strain CCMP2936 from Delaware (Eastern USA), which produces KmTx-1 and KmTx-3. The limit of detection of the SRM method for KmTx-2 was determined as 2.5 ng on-column. Collision induced dissociation (CID) spectra of all putative karlotoxins were recorded to present fragmentation patterns of each compound for their unambiguous identification. Bulk cultures of K. veneficum strain K10 isolated from an embayment of the Ebro Delta, NW Mediterranean, yielded five previously unreported putative karlotoxins with molecular masses 1280, 1298, 1332, 1356, and 1400 Da, and similar fragments to KmTx-5. Analysis of several isolates of K. veneficum from the Ebro Delta revealed small-scale diversity in the karlotoxin spectrum in that one isolate from Fangar Bay produced KmTx-5, whereas the five putative novel karlotoxins were found among several isolates from nearby, but hydrographically distinct Alfacs Bay. Application of this LC-MS/MS method represents an incremental advance in the determination of putative karlotoxins, particularly in the absence of a complete spectrum of purified analytical standards of known specific potency.

A highly conserved sequence of the viral TAP inhibitor ICP47 is required for freezing of the peptide transport cycle.

The transporter associated with antigen processing (TAP) translocates antigenic peptides into the endoplasmic reticulum (ER) lumen for loading onto MHC class I molecules. This is a key step in the control of viral infections through CD8+ T-cells. The herpes simplex virus type-1 encodes an 88 amino acid long species-specific TAP inhibitor, ICP47, that functions as a high affinity competitor for the peptide binding site on TAP. It has previously been suggested that the inhibitory function of ICP47 resides within the N-terminal region (residues 1-35). Here we show that mutation of the highly conserved 50PLL52 motif within the central region of ICP47 attenuates its inhibitory capacity. Taking advantage of the human cytomegalovirus-encoded TAP inhibitor US6 as a luminal sensor for conformational changes of TAP, we demonstrated that the 50PLL52 motif is essential for freezing of the TAP conformation. Moreover, hierarchical functional interaction sites on TAP dependent on 50PLL52 could be defined using a comprehensive set of human-rat TAP chimeras. This data broadens our understanding of the molecular mechanism underpinning TAP inhibition by ICP47, to include the 50PLL52 sequence as a stabilizer that tethers the TAP-ICP47 complex in an inward-facing conformation.

Hyperpolarized 13C urea myocardial first-pass perfusion imaging using velocity-selective excitation.

BACKGROUND: A velocity-selective binomial excitation scheme for myocardial first-pass perfusion measurements with hyperpolarized 13C substrates, which preserves bolus magnetization inside the blood pool, is presented. The proposed method is evaluated against gadolinium-enhanced 1H measurements in-vivo. METHODS: The proposed excitation with an echo-planar imaging readout was implemented on a clinical CMR system. Dynamic myocardial stress perfusion images were acquired in six healthy pigs after bolus injection of hyperpolarized 13C urea with the velocity-selective vs. conventional excitation, as well as standard 1H gadolinium-enhanced images. Signal-to-noise, contrast-to-noise (CNR) and homogeneity of semi-quantitative perfusion measures were compared between methods based on first-pass signal-intensity time curves extracted from a mid-ventricular slice. Diagnostic feasibility is demonstrated in a case of septal infarction. RESULTS: Velocity-selective excitation provides over three-fold reduction in blood pool signal with a two-fold increase in myocardial CNR. Extracted first-pass perfusion curves reveal a significantly reduced variability of semi-quantitative first-pass perfusion measures (12-20%) for velocity-selective excitation compared to conventional excitation (28-93%), comparable to that of reference 1H gadolinium data (9-15%). Overall image quality appears comparable between the velocity-selective hyperpolarized and gadolinium-enhanced imaging. CONCLUSION: The feasibility of hyperpolarized 13C first-pass perfusion CMR has been demonstrated in swine. Comparison with reference 1H gadolinium data revealed sufficient data quality and indicates the potential of hyperpolarized perfusion imaging for human applications.

SmartFluo: A Method and Affordable Adapter to Measure Chlorophyll a Fluorescence with Smartphones.

In order to increase the monitoring capabilities of inland and coastal waters, there is a need for new, affordable, sensitive and mobile instruments that could be operated semi-automatically in the field. This paper presents a prototype device to measure chlorophyll a fluorescence: the SmartFluo. The device is a combination of a smartphone offering an intuitive operation interface and an adapter implying a cuvette holder, as well as a suitable illumination source. SmartFluo is based on stimulated fluorescence of water constituents such as chlorophyll a. The red band of the digital smartphone camera is sensitive enough to detect quantitatively the characteristic red fluorescence emission. The adapter contains a light source, a strong light emitting diode and additional filters to enhance the signal-to-noise ratio and to suppress the impact of scattering. A novel algorithm utilizing the red band of the camera is provided. Laboratory experiments of the SmartFluo show a linear correlation (R 2 = 0.98) to the chlorophyll a concentrations measured by reference instruments, such as a high-performance benchtop laboratory fluorometer (LS 55, PerkinElmer).

Metagenomic discovery of polybrominated diphenyl ether biosynthesis by marine sponges.

Naturally produced polybrominated diphenyl ethers (PBDEs) pervade the marine environment and structurally resemble toxic man-made brominated flame retardants. PBDEs bioaccumulate in marine animals and are likely transferred to the human food chain. However, the biogenic basis for PBDE production in one of their most prolific sources, marine sponges of the order Dysideidae, remains unidentified. Here, we report the discovery of PBDE biosynthetic gene clusters within sponge-microbiome-associated cyanobacterial endosymbionts through the use of an unbiased metagenome-mining approach. Using expression of PBDE biosynthetic genes in heterologous cyanobacterial hosts, we correlate the structural diversity of naturally produced PBDEs to modifications within PBDE biosynthetic gene clusters in multiple sponge holobionts. Our results establish the genetic and molecular foundation for the production of PBDEs in one of the most abundant natural sources of these molecules, further setting the stage for a metagenomic-based inventory of other PBDE sources in the marine environment.