Caractérisation de CCX2, un élément de la super-famille des antiports cationiques CaCA et de son rôle dans l'homéostasie minérale

Caractérisation de CCX2, un élément de la super-famille des antiports cationiques CaCA et de son rôle dans l’homéostasie minérale.L'homéostasie des métaux est importante pour les fonctions cellulaires. Elle dépend de la régulation stricte des transports cellulaires d'ions métalliques et des espèces métalliques complexées. Nous rapportons ici l'analyse fonctionnelle chez Arabidopsis thaliana d'un élément de la superfamille CaCA, CCX2 (Calcium Cation eXchanger 2) qui n’est pas encore caractérisé dans les plantes. Nous avons pu observer en utilisant une fusion aves la protéine fluorescente GFP (Green Fluorescent Protein) que la protéine AtCCX2 était localisée dans le réticulum endoplasmique. L’expression de CCX2 est régulée par des traitements en métaux divers et par la carence en magnésium en particulier. De plus, l'expression du gène est régulée par la photopériode mais n’est probablement pas sous le contrôle de l'horloge circadienne. La caractérisation d'un mutant knock-out d’Arabidopsis a révélé que l’absence de l’activité CCX2 entrainait une meilleure croissance pendant la carence Mg (dans les conditions testées) mais pas de phénotype particulier sur les milieux aves excès de Zn ou de Cd ou induisant un stress osmotique. A ce stade, nous de pouvons apporter une explication au phénomène de tolérance pendant la carence Mg. Par ailleurs, le mutant ccx2 montre une réponse altérée à des hormones telles l’auxine et l’éthylène. Parce ce que le phénotype ccx2 mutant est relativement discret, des doubles mutants avec les gènes homologues les plus proches (CCX1 et CCX3) ont été créés. Alors que les mutants ccx1 et ccx3 sont plus résistants à la carence en Mg et ccx1 plus résistant à la déficience Zn, aucun effet additif de ces mutations avec la perte de fonction de CCX2 n’a été observé. Les profils en minéraux du mutant ccx2 ne permettent pas de confirmer des différences significatives dans les concentrations d’éléments minéraux mesurés. Des tendances pour le Ca2+ en particulier sont observées et devraient être confirmés par d’autres expériences. La surexpression hétérologue dans la levure ou dans une suspension de cellules BY2 de tabac, la surexpression dans la plante et la production de protéine pour des études d’activité de transport dans des vésicules n’ont pu être possibles pour la caractérisation de CCX2. L’expression de CCX2 semble toxique pour les bactéries, la levure et les cellules de plantes; en effet les organismes hôtes sont morts lors de l'induction de l'expression (testé au niveau de la levure). Cet effet pourrait être lié à la perturbation de l’homéostasie du Ca2+ qui joue un rôle très important comme messager secondaire lors de la perception d’un stimulus et en particulier lors de l’apoptose. L’Analyse AhCAX8/CCX2 AhCCX2 est constitutivement plus exprimé dans les racines de l’hyperaccumulatrice de Zn et Cd, Arabidopsis halleri (accession d’Auby) par rapport à sa parente proche non tolérante non accumulatrice A. lyrata ssp petraea. L'expression plus élevée pourrait être liée à l'adaptation aux hautes concentrations de zinc et de cadmium dans le sol. Nous avons pu observer qu’avec une protéine GFP, AhCCX2 est également localisée au niveau du réticulum endoplasmique comme son homologue AtCCX2. Puisque une haute expression de CCX2 est toxique pour les organismes, nous avons exprimé la protéine sous le contrôle de son propre promoteur dans A. thaliana. Cette expression faible et spécifique a pu être atteinte sans signe de toxicité. La caractérisation de A. thaliana exprimant AhCCX2 dans le type sauvage ou le mutant ccx2 a montré une meilleure croissance lors d’une déficience Mg et, dans les plantes ccx2 qui expriment AhCCX2, une moins bonne croissance lors d’une carence en Zn. Les analyses minérales des plantes exprimant AhCCX2 n’ont pas montré de différence au niveau des concentrations en minéraux. Cependant, certaines tendances ont été observées pour les concentrations en Ca, Fe et Zn qui doivent être confirmées. Nos données suggèrent pour AhCCX2 un rôle dans l'homéostasie du Zn. Un niveau d'expression élevé d’AhCCX2 a un impact négatif sur la croissance lors d’une carence en zinc et pourrait être une partie des adaptations à un approvisionnement en Zn élevé.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Organocatalytic synthesis of bio-based cyclic carbonates from CO2 and vegetable oils

Bio-based cyclic carbonates were synthesized by coupling CO2 with epoxidized linseed oil using a catalytic platform composed of a bicomponent organocatalyst. A screening of the catalytic activity of a series of organic salts and ionic liquids used in combination with (multi)phenolic or fluorinated hydrogen bond donors was realized before highlighting the synergistic effect between the organocatalyst and the most efficient cocatalysts. These kinetics studies, followed by IR spectroscopy under pressure, enabled to optimize the reaction conditions and to provide quantitative formation of the cyclocarbonated vegetable oil in short reaction time without using any organic solvent

CO2-sourced non-isocyanate poly(urethane)s with pH-sensitive imine linkages

Carbon dioxide is a renewable C1‐feedstock that is exploited for the production of polymers. In this work, we report on the conversion of CO2 into novel bis(oxo‐carbamate)s that are then exploited for the synthesis of degradable non‐isocyanate polyurethanes (NIPUs) bearing acid‐sensitive imine functions within the polymer backbone. Two CO2‐sourced bis(oxo‐carbamate)s were first prepared by the facile catalyst‐free and regioselective aminolysis of an α‐alkylidene cyclic carbonate (prepared by carboxylative coupling of CO2 with a propargylic alcohol) with two secondary diamines, piperazine and N,N’‐dimethyl‐1,6‐hexanediamine. A large diversity of poly(urethane‐co‐ imine)s (PUIs) with molar masses ranging from 4500 to 8500 g/mol were then prepared by polycondensation of bis(oxo‐carbamate)s with various primary diamines, and by using Ti(OEt)4 as catalyst and drying agent. Finally, the pH‐responsiveness of PUIs was demonstrated by immersing a representative polymer in aqueous solutions at different pH. This work illustrates that hydrolytically degradable NIPUs can be constructed by polycondensation of novel CO2‐sourced monomers with diamines

CO2-sourced non-isocyanate polyurethanes: from the monomer synthesis to the elaboration of polymeric materials

Due to problems related to the rarefaction of fossil resources and the global warming that comes from CO2 emissions, new carbon feedstocks that are abundant, renewable, non-toxic, inexpensive and environmentally friendly must be explored to produce chemicals. Besides the valorization of bio-based raw materials, the use of CO2 as a C1 carbon source into added-value products has gained interest in both academic and industrial fields. One promising way to valorize CO2 relies on its chemical fixation onto epoxides to produce cyclic carbonates that find applications as electrolytes in lithium ion batteries, as aprotic polar solvents or as useful intermediates for polycarbonates. Cyclic carbonates also react with primary amines to produce 2-hydroxyethylurethane. This reaction can be extrapolated to the synthesis of non-isocyanate polyurethanes (NIPU) by polyaddition of bifunctional cyclic carbonates with diamines.5 This study focusses on (i) the synthesis of cyclic carbonates using new highly efficient organocatalysts and (ii) their valorization as monomers to produce non-isocyanate polyurethanes. First, we have identified a bicomponent organocatalyst for the very fast synthesis of cyclic carbonates from CO2 and epoxides under very mild reaction conditions. Kinetics of reactions were followed by online Raman spectroscopy. NMR titrations were realized to evidence the mechanism of activation of this novel organocatalytic system that will be discussed in detail this talk. The second objective relies on the development of new efficient organocatalysts for the synthesis of high molar masses NIPUs in short reaction times. Organic compounds interacting with the cyclic carbonate by hydrogen bonding were identified and their catalytic activity was highlighted by a model reaction between ethylene carbonate and a primary amine before extrapolation to the synthesis of NIPUs that find applications as coatings or foamed materials

Chemical fixation of CO2 with epoxides: towards the synthesis of cyclic carbonates, precursors of CO2-based polyurethanes

Due to concerns about global warming combined with the decrease of fossil resources, the chemical transformation of carbon dioxide into added-value products has gained interest in both academic and industrial fields. To date, the chemical fixation of CO2 onto epoxides is one of the most promising ways to valorize carbon dioxide at an industrial scale . Indeed, cyclic carbonates are useful intermediates for polycarbonates and polyurethanes synthesis or can be used as electrolytes in lithium ion batteries. Although fixation of carbon dioxide onto epoxides has been extensively studied, the design of highly effective catalysts still remains a challenge. Here, we present a new highly efficient biocomponent organocatalyst based on the use of an ammonium salt (TBAI) in combination with single or double hydrogen bond donors activators (typically fluorinated alcohols)

Study of Cd hypertolerance in Arabidopsis halleri

info:eu-repo/semantics/publishe

Ecobiogaz Projet - Biogas as a prerequisite to reduce both greenhouse gas and agriculture’s energy dependence: is it a profitable alternative ?

Ecobioga

Advances in the use of CO2 as a renewable feedstock for the synthesis of polymers

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds.The Excellence of Science (EOS) program in the frame of the NECOPOL project; BIODEC and PROSTEM projects; the Spanish CERCA progra

Upgrading CO₂ into novel families of regioregular and functional polymers

Polycarbonates (PCs) and polyurethanes (PUs) belong to some of the world-leading polymers found in many of our daily life applications. PCs are mainly produced by polycondensation of alkylcarbonates/phosgene derivatives with diols at high temperature, or by ring-opening polymerization of 5- or 6-membered cyclic carbonates while PUs are industrially made by polyaddition of diisocyanates with diols. Recent developments in the PUs field deal with the polyaddition of 5-membered dicyclic carbonates with diamines, but this polymerization is much slower compared to the isocyanate route and gave regio-irregular polymers of low molar mass due to the asence of selective ring-opening and the occurrence of side reactions. The polyaddition of dicyclic carbonates with diols would also be attractive to prepare PCs but is challenging due to the poor reactivity of the 5-membered cycles towards alcoholises. Until very recently, using a single 5-membered dicyclic carbonate platform to access various polymer families remained an elusive endeavour. In this talk, we will describe an innovative approach for the preparation of new families of PCs and PUs, by the facile room temperature polyaddition of novel activated CO2-sourced 5-membered biscyclic carbonates with diols (for PCs) or diamines (for PUs). These novel cyclic carbonates are prepared by organocatalyzed carboxylative coupling of CO2 with dialkynols. Although PCs require some organocatalyst to be produced, PUs synthesis do not require any activation. Moreover, this process allows for the synthesis of regioregular functional polymers free of defects and displaying high molar masses (Mn up to 100 kg/mol in some cases). The origin of this unprecedented reactivity will be explained as well as its impact on the polymer structure. We will also show that these novel CO2-sourced monomers can also be exploited to expand their scope of valorization to a fourth family of novel functional polymers, by tuning the nature of the comonomer. We believe that this platform of novel monomers is opening new perspectives in the facile production of novel and/or existing world-class relevant polymers by valorizing CO2 as a renewable feedstock