Synthesis and complex self-assembly of AB and ABC amphiphilic block copolymers with a branched hydrophobic poly(2-oxazoline)

Amphiphilic block copolymers (ABPs) have been the focus of numerous studies thanks to their ability to self-assemble into materials with diverse applications, including drug delivery and nanocatalytic reactors. In order to increase the number of ABPs available and broaden the range of self-assembled structures and increase their morphological complexity, this work describes the synthesis of new families of linear AB and ABC amphiphilic block copolymers with a branched hydrophobic poly(2-oxazoline). First, we synthetized poly(ethylene oxide)-block-poly(2-(3-ethylheptyl)-2-oxazoline) (PEO-b-PEHOx), a new biocompatible amphiphilic AB diblock copolymer obtained in one step via microwave-assisted polymerization of EHOx using a new nosylated PEO macroinitiator. Kinetics of the polymerization in different solvents was crucial to optimize the synthesis and revealed a controlled, yet fast polymerization of the AB copolymer. Differential scanning calorimetry (DSC) proved that PEO-b-PEHOx shows glass transition temperatures below room temperature, making it suitable for a wide range of self-assembly method, especially in mild and solvent-free conditions. Self-assembly of PEO-b-PEHOx was then performed using film rehydration and solvent switch. In both cases, we were able to show the formation of various complex structures (multi-compartment micelles (MCMs), pseudo-vesicles and yolk/shell nanoparticles) by dynamic and static light scattering (DLS/SLS), transmission electron microscopy (TEM) and cryogenic transmission electron microscopy (Cryo-TEM). Our results show that PEO-b-PEHOx is a potent new AB copolymer due to its unique self-assembly behaviour. In the second part of this thesis, building upon the synthesis of PEO-b-PEHOx, we leveraged the living nature of the polymerization of oxazolines. Via sequential microwave-assisted polymerization, we synthetized in one-pot poly(ethylene oxide)-block-poly(2-(3-ethylheptyl)-2-oxazoline)-block-poly(2-ethyl-2-oxazoline) (PEO-b-PEHOx-b-PEtOz), a new biocompatible amphiphilic ABC triblock copolymer. Depending on the hydrophilic weight fraction of the copolymers, nanoscopic micelles, worms and polymersomes were formed as well as multicompartment vesicles (MCV). The self-assemblies were thoroughly analysed regarding their size and shape using dynamic and static light scattering, TEM and Cryo-TEM. By varying the ratio of PEO to PEtOz, we were able to drive the asymmetry of the polymersome membranes and proved it by two independent methods, bicinchoninic acid (BCA) assay and 2D-1H-NOESY NMR, which confirmed the presence of a longer PEO block (45 units) and the absence of a shorter PEtOz (less than 32 units) on the outer surface of the polymersomes. Thus, from this new family of ABC triblock copolymers, asymmetric polymersomes with a thin membrane (6-10 nm) can be obtained, justifying a potential future use in biomedical applications with the directed insertion of transmembrane proteins

MetExploreViz: web component for interactive metabolic network visualization

Summary: MetExploreViz is an open source web component that can be easily embedded in any web site. It provides features dedicated to the visualization of metabolic networks and pathways and thus offers a flexible solution to analyse omics data in a biochemical context. Availability and implementation: Documentation and link to GIT code repository (GPL 3.0 license) are available at this URL: http://metexplore.toulouse.inra.fr/metexploreViz/doc

Filmer les actions protestataires à Moscou

Cet article repose sur les enseignements d’une enquête filmique réalisée entre 2008 et 2011 sur des rassemblements de rue organisés par des coalitions protestataires à Moscou. Il s’agira d’une part de présenter ce que ce mode de connaissance qu’est la pratique filmique documentaire fait surgir en terme de précision empirique et d’aiguisement des sens dans l’étude des situations, et d’autre part, de réfléchir à l’expérience relationnelle singulière qu’est la relation documentaire.This article is based on teachings about film research conducted between 2008 and 2011 about street gatherings organised by protest coalitions in Moscow. It will firstly explain how this way knowing through documentary film practice gives rise to in terms of empirical precision and the sharpening in research contexts, and secondly will reflect on what makes the experience of the documentary relation distinctive.Este artículo se basa en una investigación fílmica realizada entre 2008 y 2011 sobre concentraciones de protesta en las calles en Moscú organizadas por diferentes agrupaciones. Se tratará, por un lado, de presentar lo que este modo singular de conocimiento que es la práctica fílmica o documental posibilita cuando pretende investigar el estudio de situaciones concretas. La práctica fílmica, en estos casos, aporta una mayor precisión empírica y exige una mayor articulación de los sentidos. Por otro lado, en este artículo se reflexionará sobre el tipo de experiencia relacional que implica la relación documental

Faune marine profonde des Antilles françaises : récoltes du navire Polka faites en 1993

Une collection de 107 organismes a été faite autour de la Guadeloupe, lors de pêches au casier entre 100 et 1000 mètres de profondeur environ. Cette collection a été étudiée par plusieurs taxonomistes confirmés. Les crustacés représentent à eux seuls, près de 75% des espèces. Pour l'essentiel (75 espèces), il s'agit de crustacés décapodes distribués en nombre égal entre les types macroure, anomoure et brachyoure. Les quelques crustacés non décapodes (seulement 5 espèces) appartiennent aux ordres des Stomatopodes, Amphipodes, Isopodes. Une liste détaillée de ces espèces est fournie, accompagnée de remarques surl'intérêt systématique, ou sur les potentialités de pêche. Pour faciliter le travail de détermination sur le terrain, lors des campagnes de pêche exploratoire qui sont réalisées aux Antilles françaises, 37 espèces sont illustrées en couleur. Deux espèces sont, pour l'instant, reconnues nouvelles pour la Science (#Paguristes sp. nov. et #Cymonomus sp. nov.); 5 autres, qui ne sont pas encore déterminées avec précision, pourraient également être nouvelles. Les rendements sont généralement faibles, et les perspectives de développement de la pêche profonde assez limitée

Plant-growth promotion by proteobacterial strains depends on the availability of phosphorus and iron in Arabidopsis thaliana plants

Phosphorus (as phosphate, Pi) and iron (Fe) are critical nutrients in plants that are often poorly available in the soil and can be microbially affected. This work aimed to evaluate how plant-rhizobacteria interaction changes due to different Pi or Fe nutritional scenarios and to study the underlying molecular mechanisms of the microbial modulation of these nutrients in plants. Thus, three proteobacteria (Paraburkholderia phytofirmans PsJN, Azospirillum brasilense Sp7, and Pseudomonas putida KT2440) were used to inoculate Arabidopsis seeds. Additionally, the seeds were exposed to a nutritional factor with the following levels for each nutrient: sufficient (control) or low concentrations of a highly soluble source or sufficient concentrations of a low solubility source. Then, the effects of the combinatorial factors were assessed in plant growth, nutrition, and genetic regulation. Interestingly, some bacterial effects in plants depended on the nutrient source (e.g., increased aerial zones induced by the strains), and others (e.g., decreased primary roots induced by Sp7 or KT2440) occurred regardless of the nutritional treatment. In the short-term, PsJN had detrimental effects on plant growth in the presence of the low-solubility Fe compound, but this was not observed in later stages of plant development. A thorough regulation of the phosphorus content was detected in plants independent of the nutritional treatment. Nevertheless, inoculation with KT2440 increased P content by 29% Pi-deficiency exposed plants. Conversely, the inoculation tended to decrease the Fe content in plants, suggesting a competition for this nutrient in the rhizosphere. The P-source also affected the effects of the PsJN strain in a double mutant of the phosphate starvation response (PSR). Furthermore, depending on the nutrient source, PsJN and Sp7 strains differentially regulated PSR and IAA- associated genes, indicating a role of these pathways in the observed differential phenotypical responses. In the case of iron, PsJN and SP7 regulated iron uptake-related genes regardless of the iron source, which may explain the lower Fe content in inoculated plants. Overall, the plant responses to these proteobacteria were not only influenced by the nutrient concentrations but also by their availabilities, the elapsed time of the interaction, and the specific identities of the beneficial bacteria. (Figure presented.)Fil: Orellana, Daniela. Universidad Adolfo Ibañez; Chile. Center Of Applied Ecology And Sustainability; Chile. Millennium Science Initiative Program; ChileFil: Machuca, Daniel. Universidad Adolfo Ibañez; Chile. Center Of Applied Ecology And Sustainability; ChileFil: Ibeas, Miguel Angel. Universidad Andrés Bello; Chile. Millennium Science Initiative Program; ChileFil: Estevez, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Millennium Science Initiative Program; Chile. Universidad Andrés Bello; ChileFil: Poupin Swinburn, María Josefina. Universidad Adolfo Ibañez; Chile. Center of Applied Ecology and Sustainability; Chile. Millennium Science Initiative Program; Chil

A computational solution to automatically map metabolite libraries in the context of genome scale metabolic networks

This article describes a generic programmatic method for mapping chemical compound libraries on organism-specific metabolic networks from various databases (KEGG, BioCyc) and flat file formats (SBML and Matlab files). We show how this pipeline was successfully applied to decipher the coverage of chemical libraries set up by two metabolomics facilities MetaboHub (French National infrastructure for metabolomics and fluxomics) and Glasgow Polyomics (GP) on the metabolic networks available in the MetExplore web server. The present generic protocol is designed to formalize and reduce the volume of information transfer between the library and the network database. Matching of metabolites between libraries and metabolic networks is based on InChIs or InChIKeys and therefore requires that these identifiers are specified in both libraries and networks. In addition to providing covering statistics, this pipeline also allows the visualization of mapping results in the context of metabolic networks. In order to achieve this goal, we tackled issues on programmatic interaction between two servers, improvement of metabolite annotation in metabolic networks and automatic loading of a mapping in genome scale metabolic network analysis tool MetExplore. It is important to note that this mapping can also be performed on a single or a selection of organisms of interest and is thus not limited to large facilities

Temperature and nutrient effects on the relative importance of brown and green pathways for stream ecosystem functioning: A mesocosm approach

In addition to global warming, aquatic ecosystems are currently facing multiple global changes among which include changes in nitrogen (N) loads. While several studies have investigated both temperature and N impacts on aquatic ecosystems independently, knowledge on their interactive effects remains scarce. In forested headwater streams, decomposition of leaf litter represents the main process ensuring the transfer of nutrients and energy to higher trophic levels, followed by autochthonous primary production, mainly ensured by phototrophic biofilms. The main aim of this study was to disentangle the independent and combined effects of temperature increase and nutrient availability on the relative importance of brown and green processes involved in stream functioning. We hypothesised that water temperature and nutrients would lead to a general increase in leaf‐litter decomposition and primary production, but that the intensity of these effects would be largely modulated by competitive interactions arising between microorganisms as well as by the top‐down control of microorganisms by macro‐invertebrates. Macro‐invertebrates would, in turn, be bottom‐up controlled by microbial resources quality. To test these hypotheses, we conducted a 56‐day experiment in artificial streams containing leaf litter, microbial decomposers and biofilm inoculum, and an assemblage of macro‐invertebrates. Two water inorganic N:phosphorus (P) ratios (33 and 100, molar ratios) and two temperatures (ambient, +2°C) were manipulated, each treatment being replicated three times. Fungal and biofilm growth as well as leaf‐litter decomposition and primary production were quantified. Top‐down impacts of invertebrate primary consumers on brown and green compartments were evaluated using exclosures while bottom‐up control was evaluated through the measurement of resource stoichiometry and fatty acid profiles, as well as quantification of macro‐invertebrate growth and survival. Contrary to expectations, microbial decomposition was not significantly stimulated by nutrient or temperature manipulations, while primary production was only improved under ambient temperature. In the + 2°C treatment with high N:P, greater biofilm biomass was associated with lower fungal development, which indicates competition for nutrients in these conditions. Temperature increased macro‐invertebrate growth and leaf‐litter consumption, but this effect was independent of any improvement of basal resource quality, suggesting that temperature mediated changes in consumer metabolism and activity was the main mechanism involved. Most of our hypotheses that were based on simplified laboratory observations have been rejected in our semi‐controlled mesocosms. Our study suggests that the complexity of biological communities might greatly affect the response of ecosystems to multiple stressors, and that interactions between organisms must be explicitly taken into account when investigating the impacts of global change on ecosystem functioning