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Daniel S Müller, Olivier Baslé, Marc Mauduit
Stereoretentive olefin metathesis based on ruthenium dithiolate complexes has become a very active field of research within the past years. This unique catalyst class is able to kinetically produce both Z - and E -alkenes in high stereochemical purity (typically >95:5) starting from stereochemically pure Z - or E -alkenes. The aim of this tutorial review is to organize the reported information concerning ruthenium dithiolate catalysts in a logic manner, thus providing an "operators handbook" for chemists who wish to apply this methodology in synthesis...
2018: Beilstein Journal of Organic Chemistry
Mathieu Dubois, Anna-Maria Empl, Greg Jaudzems, Quentin Basle, Erik Konings
Background: Monochloropropanediol (MCPD) and its fatty acid esters as well as glycidyl fatty acid esters are substances generated during oil refining or food processing. The free form released during digestion, 3-MCPD and glycidol, have shown adverse effects in animal studies. Objective: So far, the available analytical methods have not been validated in a collaborative study for infant and adult nutritional formulas. This manuscript describes a single-laboratory validation method in view of a future multilaboratory validation trial...
November 26, 2018: Journal of AOAC International
Anaxi Houbaert, Cheng Zhang, Manish Tiwari, Kun Wang, Alberto de Marcos Serrano, Daniel V Savatin, Mounashree J Urs, Miroslava K Zhiponova, Gustavo E Gudesblat, Isabelle Vanhoutte, Dominique Eeckhout, Sjef Boeren, Mansour Karimi, Camilla Betti, Thomas Jacobs, Carmen Fenoll, Montaña Mena, Sacco de Vries, Geert De Jaeger, Eugenia Russinova
Stomatal cell lineage is an archetypal example of asymmetric cell division (ACD), which is necessary for plant survival1-4 . In Arabidopsis thaliana, the GLYCOGEN SYNTHASE KINASE3 (GSK3)/SHAGGY-like kinase BRASSINOSTEROID INSENSITIVE 2 (BIN2) phosphorylates both the mitogen-activated protein kinase (MAPK) signalling module5,6 and its downstream target, the transcription factor SPEECHLESS (SPCH)7 , to promote and restrict ACDs, respectively, in the same stomatal lineage cell. However, the mechanisms that balance these mutually exclusive activities remain unclear...
November 2018: Nature
Jennifer R Fleming, Michael Schupfner, Florian Busch, Arnaud Baslé, Alexander Ehrmann, Reinhard Sterner, Olga Mayans
Tryptophan synthase (TrpS) is a heterotetrameric αββα enzyme that exhibits complex substrate channeling and allosteric mechanisms and is a model system in enzymology. In this work, we characterize proposed early and late evolutionary states of TrpS and show that they have distinct quaternary structures, caused by insertions-deletions of sequence segments (indels) in the β-subunit. Remarkably, indole hydrophobic channels that connect α and β active sites have re-emerged in both TrpS types, yet they follow different paths through the β-subunit fold...
October 24, 2018: Journal of Molecular Biology
Alan Cartmell, Jose Muñoz-Muñoz, Jonathon A Briggs, Didier A Ndeh, Elisabeth C Lowe, Arnaud Baslé, Nicolas Terrapon, Katherine Stott, Tiaan Heunis, Joe Gray, Li Yu, Paul Dupree, Pearl Z Fernandes, Sayali Shah, Spencer J Williams, Aurore Labourel, Matthias Trost, Bernard Henrissat, Harry J Gilbert
Glycans are major nutrients for the human gut microbiota (HGM). Arabinogalactan proteins (AGPs) comprise a heterogenous group of plant glycans in which a β1,3-galactan backbone and β1,6-galactan side chains are conserved. Diversity is provided by the variable nature of the sugars that decorate the galactans. The mechanisms by which nutritionally relevant AGPs are degraded in the HGM are poorly understood. Here we explore how the HGM organism Bacteroides thetaiotaomicron metabolizes AGPs. We propose a sequential degradative model in which exo-acting glycoside hydrolase (GH) family 43 β1,3-galactanases release the side chains...
November 2018: Nature Microbiology
Daniel S Müller, Idriss Curbet, Yann Raoul, Jérôme Le Nôtre, Olivier Baslé, Marc Mauduit
The in situ preparation of highly stereoretentive ruthenium-based metathesis catalysts is reported. This approach completely avoids the isolation of intermediates and air-sensitive catalysts, thus allowing for the rapid access and evaluation of numerous dithiolate Ru catalysts. A procedure was established to perform cross-metathesis reactions without the use of a glovebox, and on a small scale even Schlenk techniques are not required. Consequently, the chemistry displayed in this report is available to every practicing organic chemist and presents a powerful approach for the identification of new stereoretentive catalysts...
November 2, 2018: Organic Letters
Christina Bligaard Pedersen, Finn Cilius Nielsen, Maria Rossing, Lars Rønn Olsen
Breast cancer is a highly heterogeneous disease that can be classified into multiple subtypes based on the tumor transcriptome. Most of the subtyping schemes used in clinics today are derived from analyses of microarray data from thousands of different tumors together with clinical data for the patients from which the tumors were isolated. However, RNA sequencing (RNA-Seq) is gradually replacing microarrays as the preferred transcriptomics platform, and although transcript abundances measured by the two different technologies are largely compatible, subtyping methods developed for probe-based microarray data are incompatible with RNA-Seq as input data...
October 5, 2018: Molecular Oncology
Javier Abellón-Ruiz, Michael Zahn, Arnaud Baslé, Bert van den Berg
Acinetobacter baumannii is becoming a major threat to human health due to its multidrug resistance. This is owing in a large part to the low permeability of its outer membrane (OM), which prevents high internal antibiotic concentrations and makes antibiotic-resistance mechanisms more effective. To exploit OM channels as potential delivery vehicles for future antibiotics, structural information is required. One abundant OM protein in A. baumannii is Omp33. This protein has been reported to be important for the in vivo fitness and virulence of A...
September 1, 2018: Acta Crystallographica. Section D, Structural Biology
Catherine Mansfield, Jacob L Newman, Tjelvar S G Olsson, Matthew Hartley, Jordi Chan, Enrico Coen
Tissue-wide polarity fields, in which cell polarity is coordinated across the tissue, have been described for planar organs such as the Drosophila wing and are considered important for coordinating growth and differentiation [1]. In planar plant organs, such as leaves, polarity fields have been identified for subgroups of cells, such as stomatal lineages [2], trichomes [3, 4], serrations [5], or early developmental stages [6]. Here, we show that ectopic induction of the stomatal protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) reveals a tissue-wide epidermal polarity field in leaves throughout development...
August 20, 2018: Current Biology: CB
Meizhi Xu, Fei Chen, Shilian Qi, Liangsheng Zhang, Shuang Wu
The stomatal complex is critical for gas and water exchange between plants and the atmosphere. Originating over 400 million years ago, the structure of the stomata has evolved to facilitate the adaptation of plants to various environments. Although the molecular mechanism of stomatal development in Arabidopsis has been widely studied, the evolution of stomatal structure and its molecular regulators in different species remains to be answered. In this study, we examined stomatal development and the orthologues of Arabidopsis stomatal genes in a basal angiosperm plant, Nymphaea colorata , and a member of the eudicot CAM family, Kalanchoe laxiflora , which represent the adaptation to aquatic and drought environments, respectively...
2018: Horticulture Research
Jompol Thongpaen, Thibault E Schmid, Loic Toupet, Vincent Dorcet, Marc Mauduit, Olivier Baslé
Cp*Rh(NHC) complexes with bulky chiral bidentate NHC-carboxylate ligands were efficiently synthesized and fully characterized including solid-state structures. These unprecedented rhodium(iii) complexes demonstrated high selectivity in pyridine-directed ortho-C-H borylation of arenes under mild conditions.
July 19, 2018: Chemical Communications: Chem Comm
Monisha Pathania, Silvia Acosta-Gutierrez, Satya Pratyusha Bhamidimarri, Arnaud Baslé, Mathias Winterhalter, Matteo Ceccarelli, Bert van den Berg
The outer membranes (OM) of many Gram-negative bacteria contain general porins, which form nonspecific, large-diameter channels for the diffusional uptake of small molecules required for cell growth and function. While the porins of Enterobacteriaceae (e.g., E. coli OmpF and OmpC) have been extensively characterized structurally and biochemically, much less is known about their counterparts in Vibrionaceae. Vibrio cholerae, the causative agent of cholera, has two major porins, OmpU and OmpT, for which no structural information is available despite their importance for the bacterium...
May 1, 2018: Structure
Judith E Unterlass, Arnaud Baslé, Timothy J Blackburn, Julie Tucker, Céline Cano, Martin E M Noble, Nicola J Curtin
3-Phosphoglycerate dehydrogenase (PHGDH) has recently been identified as an attractive target in cancer therapy as it links upregulated glycolytic flux to increased biomass production in cancer cells. PHGDH catalyses the first step in the serine synthesis pathway and thus diverts glycolytic flux into serine synthesis. We have used siRNA-mediated suppression of PHGDH expression to show that PHGDH is a potential therapeutic target in PHGDH -amplified breast cancer. Knockdown caused reduced proliferation in the PHGDH -amplified cell line MDA-MB-468, whereas breast cancer cells with low PHGDH expression or with elevated PHGDH expression in the absence of genomic amplification were not affected...
March 2, 2018: Oncotarget
Jin Li, Yoko Yamamoto, Jamison M Kinnane, Bree C Shugarts, Clarence K K Ho
Little research exists on how immigrant children develop their beliefs about school learning (BASLs) in their home and host cultures. We examined the BASLs and achievement children of Chinese immigrants' (CCI) and European American (EA) children. We followed longitudinally 120 middle-class children from age 4 to 5, balanced for gender. Children heard two story beginnings depicting a child eager to attend school and another not. Children completed the stories and were tested for math and literacy achievement...
March 7, 2018: Child Development
Didier Ndeh, Artur Rogowski, Alan Cartmell, Ana S Luis, Arnaud Baslé, Joseph Gray, Immacolata Venditto, Jonathon Briggs, Xiaoyang Zhang, Aurore Labourel, Nicolas Terrapon, Fanny Buffetto, Sergey Nepogodiev, Yao Xiao, Robert A Field, Yanping Zhu, Malcolm A O'Neill, Breeanna R Urbanowicz, William S York, Gideon J Davies, D Wade Abbott, Marie-Christine Ralet, Eric C Martens, Bernard Henrissat, Harry J Gilbert
This corrects the article DOI: 10.1038/nature21725.
August 31, 2017: Nature
Arnaud Baslé, Abdelnasser El Ghazouani, Jaeick Lee, Christopher Dennison
Methanobactins (Mbns) are modified peptides that sequester copper (Cu) methanotrophs use to oxidize methane. Limited structural information is available for this class of natural products, as is an understanding of how cells are able to utilize Mbn-bound Cu. The crystal structure of Methylosinus sporium NR3K CuI -Mbn provides further information about the structural diversity of Mbns and the first insight into their Cu-release mechanism. Nitrogen ligands from oxazolone and pyrazinediol rings chelate CuI along with adjacent coordinating sulfurs from thioamides...
March 26, 2018: Chemistry: a European Journal
Anuwat Aunkham, Michael Zahn, Anusha Kesireddy, Karunakar Reddy Pothula, Albert Schulte, Arnaud Baslé, Ulrich Kleinekathöfer, Wipa Suginta, Bert van den Berg
Chitin, an insoluble polymer of N-acetylglucosamine, is one of the most abundant biopolymers on Earth. By degrading chitin, chitinolytic bacteria such as Vibrio harveyi are critical for chitin recycling and maintenance of carbon and nitrogen cycles in the world's oceans. A decisive step in chitin degradation is the uptake of chito-oligosaccharides by an outer membrane protein channel named chitoporin (ChiP). Here, we report X-ray crystal structures of ChiP from V. harveyi in the presence and absence of chito-oligosaccharides...
January 15, 2018: Nature Communications
Nicolas Tokhadze, Philip Chennell, Yoann Le Basle, Valerie Sautou
Infliximab is a monoclonal antibody widely used for the treatment of inflammatory diseases. Over the past few years, many studies have assessed that monoclonal antibodies are prone to aggregation under stress conditions. The aim of this study was to investigate the stability of solutions of an infliximab biosimilar (Inflectra® ) at different concentrations (0.4, 2 and 10 mg/mL). These solutions were separately submitted to three temperature conditions that are likely to happen during the drug dispensing system: -20 °C, 5 °C and 25 °C...
February 20, 2018: Journal of Pharmaceutical and Biomedical Analysis
Judith E Unterlass, Robert J Wood, Arnaud Baslé, Julie Tucker, Céline Cano, Martin M E Noble, Nicola J Curtin
Cancer cells reprogram their metabolism and energy production to sustain increased growth, enable metastasis and overcome resistance to cancer treatments. Although primary roles for many metabolic proteins have been identified, some are promiscuous in regards to the reaction they catalyze. To efficiently target these enzymes, a good understanding of their enzymatic function and structure, as well as knowledge regarding any substrate or catalytic promiscuity is required. Here we focus on the characterization of human 3-phosphoglycerate dehydrogenase (PHGDH)...
November 28, 2017: Oncotarget
Ana S Luis, Jonathon Briggs, Xiaoyang Zhang, Benjamin Farnell, Didier Ndeh, Aurore Labourel, Arnaud Baslé, Alan Cartmell, Nicolas Terrapon, Katherine Stott, Elisabeth C Lowe, Richard McLean, Kaitlyn Shearer, Julia Schückel, Immacolata Venditto, Marie-Christine Ralet, Bernard Henrissat, Eric C Martens, Steven C Mosimann, D Wade Abbott, Harry J Gilbert
The major nutrients available to human colonic Bacteroides species are glycans, exemplified by pectins, a network of covalently linked plant cell wall polysaccharides containing galacturonic acid (GalA). Metabolism of complex carbohydrates by the Bacteroides genus is orchestrated by polysaccharide utilization loci (PULs). In Bacteroides thetaiotaomicron, a human colonic bacterium, the PULs activated by different pectin domains have been identified; however, the mechanism by which these loci contribute to the degradation of these GalA-containing polysaccharides is poorly understood...
February 2018: Nature Microbiology
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