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La photocatalyse hétérogène est une technique d’oxydation utilisée pour l’élimination des Composés Organiques Volatils (COV). L’objectif est d’étudier la dégradation des COV initiaux et la production d’intermédiaires réactionnels lors de la mise en oeuvre de ce procédé dans des conditions proches de l’air intérieur (concentration des COV en mélange). TroisCOV modèles (toluène, décane, trichloréthylène) sont étudiés séparément puis en mélange dans un réacteurstatique puis dans un réacteur dynamique multi-pass. Les résultats obtenus montrent que (i) l’efficacité dedégradation dépend de la nature et du nombre de COV à traiter, des caractéristiques du média photocatalytiqueet des conditions opératoires, (ii) les intermédiaires majoritaires et les plus persistants sont les aldéhydeslégers, (iii) l’élimination des aldéhydes est inhibée lorsque les COV initiaux sont en mélange, (iv) l’augmentation du temps de résidence sur le matériau photocatalytique permet une élimination plus rapide des COV initiaux et des sous-produits. / Heterogeneous photocatalysis is a technique of oxidation used for the removal of Volatile Organic Compounds (VOCs). Aim is to study the degradation of initial VOCs and the production of reaction intermediates during this process in conditions close to the indoor air (VOC concentration in mixture). Three model VOCs (toluene, decane, trichloroethylene) are studied separately and then in mixture in a static reactor and in a dynamic multi-pass reactor. The obtained results show that (i) the degradation efficiency depends on the nature and the number of VOCs, on the photocatalyst characteristics and on process conditions, (ii) the major and the most persistent intermediates are light aldehydes, (iii) the elimination of aldehydes is inhibited when the initial VOCs are in mixture, (iv) increasing the residence time on the photocatalyst provides a higher removal rate of initial VOCs and of byproducts.

We report here the development of very efficient sulfonate based leaving groups, termed Nucleophile Assisting Leaving Groups (NALGs), to accelerate the rate of nucleophilic substitution reactions involving poor nucleophiles and/or substrates traditionally considered too hindered to undergo nucleophilic attack. Indeed NALGs have shown exceptional ability in improving rate of nucleophilic substitution reactions. New very mild stereoretentive halogenations and azidation reactions have also been developed for secondary cyclic alcohols using NALGs involving titanium(IV) reagents. This reaction is particularly significant since the carbon-halogen bond is found widely in natural products and is used extensively as a synthesis intermediate. Azide is also a synthetically important functional group from which a variety of biologically important functional groups are conveniently obtained. Though stereoretentive chlorination and bromination reactions are known, we have developed, for the first time, a stereoretentive azidation reaction using titanium(IV) azide, a reagent not previously used in organic synthesis. During our development of stereoretentive reactions, we eventually developed very efficient, mild, two-step one-pot stereoretentive halogenations (chlorination and bromination) using titanium(IV) halides as catalysts or stoichiometric reagents. These reactions were found to be particularly efficient for cyclic alcohols. An efficient one pot stereoretentive amidation reaction for secondary cyclic alcohols is also reported. The important features of this reaction are that, for the first time, chlorosulfite (prepared in situ from alcohol using thionylchloride) has been used as a leaving group and titanium(IV) fluoride as an activator. / Utilization of those two reagents is unique as thionylchloride has never been used for nucleophilic substitution reactions except in chlorination procedures. In addition, this work has found new and creative applications for titanium (IV) fluoride, a reactant rarely used in organic synthesis. Further exploiting the unique reactivity of titanium(IV), reactions of alkenes with various nucleophiles have been developed with this reagent in both catalytic and stoichiometric quantities. It was observed that a-substituted aromatic conjugated alkenes dimerize to generate important indan class of compounds which are very important in the polymer industry. In addition, non conjugated unactivated alkenes react with various nucleophiles to yield the adduct. / by Deboprosad Mondal. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

A agroindústria canavieira no Brasil é um setor de destaque por exercer papel fundamental na economia, sendo responsável pela geração de empregos, renda e produtos e subprodutos de interesse como, açúcar, etanol e energia. A clarificação do caldo de cana é um dos processos unitários mais críticos das usinas açucareiras. Atualmente, o açúcar brasileiro é clarificado utilizando-se o processo de contato com dióxido de enxofre, conhecido como sulfitação. Existe, porém, uma tendência mundial na redução do uso de compostos à base de enxofre nos alimentos, devido a possíveis efeitos nocivos à saúde. Além disso, a queima de enxofre elementar nas usinas é fonte de emissões de gases sulforosos, desconforto no ambiente de trabalho das fábricas e corrosão de metais nas instalações industriais. Dessa forma, alternativas à sulfitação têm sido avaliadas, entre as quais a ozonização, processo que carece de estudos fundamentais. No presente trabalho foram avaliados parâmetros de transferência de massa do ozônio, tanto em água como em solução modelo contendo sacarose e compostos fenólicos presentes no caldo de cana (ácidos ácido p-cumárico, cafeico, siríngico e clorogênico, além do flavonoide quercetina). A partir destes experimentos foi verificado que a ozonização da mistura de fenólicos é caracterizada por uma reação lenta devido à presença de ozônio dissolvido no meio. Observou-se que não houve degradação da sacarose e os principais intermediários identificados foram ácidos orgânicos, não ocorrendo, porém, mineralização completa dos compostos fenólicos. Após este estudo foram realizados experimentos de ozonização com caldo de cana seguindo um projeto experimental com o objetivo de verificar a remoção de cor ICUMSA e também de compostos fenólicos. Verificou-se importante remoção de cor (80%) após duas horas de ozonização a 40 oC, empregando-se 30 mg L-1 de ozônio no gás alimentado à vazão de 0,5 L min-1. Por outro lado, obtiveram-se 50% de remoção de compostos fenólicos para concentração de O3 no gás de 20 mg L-1, vazão de gás de 0,5 L min-1 e temperatura de 60 °C. Realizou-se por fim uma análise econômica preliminar para fins de comparação entre o processo de sulfitação e ozonização. O processo de ozonização demanda um investimento inicial maior que a sulfitação e à peroxidação. Quando os custos operacionais são comparados verifica-se que o custo operacional para a ozonização é 29% menor que a sulfitação e 43% menor que a peroxidação. Os resultados sugerem a possível aplicação da ozonização como tecnologia alternativa à utilização de enxofre no processo de clarificação. / The sugarcane agroindustry in Brazil currently stands out because it plays a major role in the economy, being responsible for generating jobs, income and products and by-products of interest, such as sugar, ethanol and power. The clarification of sugarcane juice is one of the most critical unit processes in sugar mills. Brazilian sugar is clarified using the sulphitation process. There is a worldwide trend in reducing the use of sulfur compounds in food because of its possible harmful effects on the consumer. In addition, burning elemental sulfur causes serious environmental problems, such as emissions of sulfurous gases, causing acid rain, discommodity in the working environment of plants and corrosion of metals in industrial facilities. Alternative treatments of sugarcane juice, replacing sulfur dioxide have been considered, among them ozonation. The main limitation of ozonation processes is gas-liquid mass transfer. In the present work, ozone mass transfer parameters were evaluated both in water and in model solutions of sucrose containing phenolic compounds present in the sugarcane juice. The main degradation products formed during the process were identified. From these experiments, ozonation of phenolic compounds in solution is characterized by a slow reaction due to the presence of dissolved ozone in the medium. The main intermediates identified were organic acids demonstrating that complete mineralization of the phenolic compounds does not occur. Ozonation experiments with sugarcane juice were carried out following an experimental design aiming at studying color and phenolic compounds removals. After two-hour experiments 80% color removal was achieved ozone concentration of 30 mg L-1, 0.5 L min-1 flow rate and 40 ° C. Moreover, 50% removal of phenolic compounds was achieved for 20 mg L-1 ozone concentration, 0.5 L min-1 flow rate and 60 ° C. The results confirm the efficiency of color removal, main target of the sugar industry. Finally, a preliminary economic analysis was carried out the purpose of comparing the sulphitation and ozonation process, and it was verified that ozonation requires an initial investment greater than sulphitation. Ozonation process requires an initial investment greater than sulphitation and peroxidation. On the other hand, operating costs were compared, the operating cost for ozonation is 29% lower than sulphitation and 43% lower than peroxidation. Results suggest the possible application of ozonation as an alternative technology to the use of sulfur in the clarification process.

Le processus conduisant à la prolifération et différenciation des cellules souches hématopoïétiques (CSH) en cellules de toutes les lignées sanguines s’appelle l’hématopoïèse. Bien que l'engagement des CSH soit régi par les cytokines, les facteurs de transcription, les modificateurs épigénétiques et la niche des CSH, notre groupe a constaté que leur engagement vers la lignée érythroïde dépendait aussi du métabolisme de la glutamine. La glutaminolyse contribue à la biosynthèse des nucléotides de novo ainsi qu’à la production de l'alpha-kétoglutarate (αKG), intermédiaire métabolique du cycle TCA (Oburoglu et al. 2014). Il est cependant important de noter que la différenciation érythroïde est un processus unique, où chaque cellule fille est structurellement et fonctionnellement différente de sa cellule mère. Chaque division définit un stade de différenciation précis avec un dernier cycle de division produisant un réticulocyte énucléé. Ainsi, nous avons émis l'hypothèse que les réseaux métaboliques mobilisés dans les progéniteurs érythroïdes changent en fonction du stade de différenciation et que ces réseaux régulent la transition des progéniteurs d'un stade à l'autre.Au cours de ma thèse, j’ai caractérisé les états métaboliques associés aux différents stades de différenciation des progéniteurs érythroïdes. Nous avons ainsi montré qu'aux stades précoces de différenciation érythroïde, avant la différenciation terminale, les progéniteurs hématopoïétiques présentent une activité métabolique accrue avec un niveau de phosphorylation oxydative (OXPHOS) plus élevé. Ces données sont en corrélation avec l'augmentation de la génération de l’αKG à ces stades de différenciation. De plus, nous avons constaté une augmentation de l’OXPHOS de ces progéniteurs en présence d’αKG exogène. Cependant, la différenciation terminale des précurseurs érythroïdes, caractérisée par la perte de la masse mitochondriale et de leur potentiel membranaire, est associée à une diminution du niveau d'OXPHOS. Ainsi, l'administration exogène d’αKG, a fortement atténué la différenciation érythroïde terminale et l'énucléation, sans affecter la différenciation des pro-érythroblastes. Inversement, un antagoniste de l’αKG (diméthyloxalylglycine, DMOG) n'a pas altéré la différenciation terminale ou l'énucléation, malgré l'abrogation de l'OXPHOS dans les érythroblastes.Ces données suggèrent que la production d’αKG et sa contribution à l’OXPHOS perturbent l'énucléation des globules rouges. C'est pourquoi, dans le but de réduire les niveaux intracellulaires d’αKG, nous avons inhibé l’expression de l'isocitrate déshydrogénase I (IDH1), enzyme cytosolique catalysant la conversion de l'isocitrate en αKG. Cependant, comme IDH1 peut catalyser les réactions dans les deux sens, la diminution de son expression pourrait également augmenter les niveaux d’αKG. En effet, nous avons constaté que le knockdown d'IDH1 entraînait une forte atténuation de la différenciation terminale et de l'énucléation des précurseurs érythroïdes. Cet effet est probablement dû à un déséquilibre de la disponibilité des substrats ; ainsi l’administration ectopique de l’αKG ainsi que du citrate renforce l’altération de la différenciation terminale des précurseurs érythroïdes IDH1-/- ainsi que leur énucléation. Cette étude identifie donc un rôle crucial pour le métabolite αKG dans la régulation de la fonction mitochondriale et de l’OXPHOS, processus qui sont une condition sine qua non pour la différenciation des précurseurs érythroïdes au stade proérythroblaste. Nous montrons en outre que la suppression d’OXPHOS et la catalyse d’intermédiaires du TCA, substrats d’IDH1, sont requis pour les phases terminales de la différenciation érythroïde et l'énucléation.En conclusion, les résultats obtenus au cours de ma thèse mettent en évidence la nature dynamique des réseaux métaboliques qui régulent la progression des précurseurs érythroïdes tout au long des différents stades de la différenciation érythroïde. / Hematopoiesis is the process whereby hematopoietic stem cells (HSCs) proliferate and differentiate to all blood cell lineages. While HSC commitment is known to be regulated by cytokines, transcription factors, epigenetic modifiers and the HSC niche, our group found that specification of HSCs to the red cell lineage is dependent on glutamine metabolism. Glutaminolysis contributes to de novo nucleotide biosynthesis and to the generation of the alpha-ketoglutarate (αKG) TCA cycle metabolite (Oburoglu et al. 2014). Importantly though, erythroid differentiation is a unique process as each daughter cell is structurally and functionally different from its parent cell. Each division defines a stage of differentiation with the final division cycle resulting in the production of an enucleated reticulocyte which further matures to a biconcave erythrocyte. Thus, we hypothesized that progenitor metabolic networks change as a function of the erythroid differentiation stage and moreover, that they regulate the transition of progenitors from one stage of differentiation to the next.During my PhD, I assessed the metabolic alterations that occur as a function of the erythroid differentiation stage. We showed that at early stages of human red cell development, prior to terminal differentiation, hematopoietic progenitors exhibited an increased metabolic activity with a significantly higher level of oxidative phosphorylation (OXPHOS). This correlated with the increased generation of αKG and indeed, we found that ectopic αKG directly augmented OXPHOS in these progenitors. However, the terminal differentiation of erythroid precursors, characterized by the loss of mitochondrial mass and membrane potential, was associated with a decreased level of OXPHOS. Notably, ectopic αKG, which did not alter pro-erythroblast erythroid differentiation, severely attenuated terminal differentiation and enucleation. Conversely, an αKG antagonist (dimethyloxalyl glycine, DMOG) did not negatively impact on terminal differentiation or enucleation despite abrogating OXPHOS in erythroblasts.These data suggested that the production of αKG and its subsequent contribution to oxidative phosphorylation perturb red cell enucleation. We therefore downregulated isocitrate dehydrogenase I (IDH1), the cytosolic enzyme that catalyzes the conversion of isocitrate to αKG, by an shRNA approach in an attempt to decrease αKG levels. However, because IDH1 can catalyze both the forward and reverse reactions, its downregulation could also increase αKG levels. Indeed, we found that IDH1 knockdown resulted in a severe attenuation of terminal erythroid differentiation and enucleation. This effect was likely due to an imbalance in substrate availability––both ectopic αKG as well as citrate further decreased polychromatic to orthochromatic erythroblast differentiation and the subsequent enucleation of IDH1-knockdown erythroid precursors. Thus, the present study identifies a crucial role for the αKG metabolite in regulating mitochondrial function and oxidative phosphorylation, processes that are a sine qua non for erythroid precursors at the pro-erythroblast stage. We further show that terminal erythroid differentiation and enucleation requires OXPHOS suppression and the IDH1-mediated enzymatic catalysis of its TCA substrates.To conclude, the results generated during my PhD highlight the dynamic nature of the metabolic networks that regulate the progression of erythroid precursors through the distinct stages of erythroid differentiation.