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Le tryptophane est un acide aminé essentiel qui, en plus de son rôle dans la biosynthèse des protéines, est le précurseur biochimique de nombreux composés. Beaucoup de peptides biologiquement actifs, qui possèdent dans leurs séquences cet acide aminé contenant un substituant indole, ont des propriétés physiologiques importantes. On peut citer par exemple des dérivés comme la sérotonine, le tryptamine, le sumatriptan qui ont des effets neurophysiologiques. Les analogues de tryptophane sont aussi des « building block » important pour la synthèse de peptidomimétiques, d'analogues de produits naturels et de composés biologiquement actifs. Une autre propriété importante du tryptophane et de ses analogues concerne la fluorescence du noyau d`indole qui peut être utilisée par exemple pour l`étude de changements conformationnels d'une protéine et aussi l'étude des interactions protéine-membrane.Dans ce contexte, cette thèse est consacrée à la mise au point d'une nouvelle stratégie de synthèse asymétrique permettant d'accéder efficacement à d`analogues énantiopurs du tryptophane : les beta 2-tryptophanes (2-indolyl-beta-alanines) ainsi qu'à la synthèse et l'étude de nouveaux analogues de peptides à activité opioïdes contenant ces analogues. Nous avons développé une nouvelle stratégie de synthèse asymétrique permettant d'accéder efficacement à des analogues de beta 2-tryptophane (2-indolyl-beta-alanines) énantiopurs. - Nous avons effectué la synthèse d`un auxiliaire chiral le (R)-4-(3-hydroxy-4,4-diméthyl-2-oxopyrrolidin-1-yl) benzoate de benzyle ainsi que celle du dérivé nitroacrylate correspondant : le (R)-4-(3-(3-nitroacryloyloxy)-4,4-diméthyl-2-oxo pyrrolidin-1-yl) benzoate de benzyle ((R)-10). Les composés racémiques ont également été synthétisés pour préparer les témoins racémique des molécules cibles.- Nous avons mis au point des conditions optimisées de la réaction d`alkylation de Friedel-Crafts entre ce nitroacrylate chiral et divers indoles.- Nous avons également étudié pour chaque produit ainsi obtenu les meilleures conditions de transformation conduisant à la synthèse des analogues des N-Fmoc-beta 2-tryptophanes racémiques et optiquement purs.- Nous avons contrôlé l'absence d'épimérisation pouvant se produire pendant les réactions de transformation des produits optiquement purs et déterminé sans ambiguïté la configuration absolue des 2-indolyl-beta-alanines isolées.- Nous avons synthétisé sur support solide par stratégie-(Fmoc) 4 nouveaux peptides potentiellement biologiquement actifs et 2 peptides de référence - analogues raccourcis de la nociceptine / Tryptophan, an essential amino acid, both functions as a building block in protein biosynthesis and as a biochemical precursor. It is abundantly found in most biologically active peptides that exhibit various physiological properties in particular hormonal and antimicrobial activities. Some of its natural derivatives like serotonin, tryptamine, and also unnatural derivatives such as sumatriptan, have neurophysiologic effects. Tryptophan analogues are also important building blocks for the synthesis of peptidomimetics, natural products and biologically active compounds. Another important property of tryptophan and tryptophan analogues is related to the fluorescence of the indole ring that can be used to study conformational changes in protein and in protein-membrane interactions. The asymmetric Friedel-Crafts alkylation of various indoles with a chiral nitroacrylate provides optically active beta-tryptophan analogues after reduction of the nitro group and removal of the chiral auxiliary. This reaction generally occurs in good yield and high diastereoselectivity (up to 90:10). We have established a new route to prepare enantiopure beta-tryptophan analogues ((S)-2-indolyl-beta-alanines). We showed that beta-nitroacrylate (R)-2 is a good chiral auxiliary for asymmetric Friedel-Crafts alkylation of indoles. (R)-2-indolyl--alanines were obtained by the same synthetic route by using the chiral compound (S)-2. beta-tryptophan analogues are delivered in their N-Fmoc-protected form, ready to use for instance in solid phase peptide synthesis, which is one of the most popular method for peptide synthesis. This study provides a new example of asymmetric beta-tryptophan analogues preparation and further studies concerning their applications in medicinal chemistry and in organic synthesis are now in progress.

Nesse trabalho obtiveram-se membranas de poli(imida) ramifricada com tamanho de poro ajustável usando melamina como agente de ramificação e indutor da formação de poros. Estas poli(imidas) foram sulfonadas usando-se ácido sulfúrico concentrado eficazmente. Finalmente, obtivemos membranas de carbono molecular por pirólise sob atmosfera inerte das poli(imidas) ramificadas. Estas membranas apresentam canais micrométricos paralelos à superfície e uma estrutura assimétrica constituída de uma camada densa filtrante e uma camada com canais micrométricos paralelos à superfície altamente ordenados. A membrana apresentou boa estabilidade química frente ao ataque por radicais hidroxila gerados via reação de Fenton. / In this work was obtained branched poly(imides) with tuned pore size using melamine as branching and pore induction agent. The poly(imides) with were efficiently sulfonated with concentrated sulfuric acid. Finally, the molecular sieve carbon membranes were obtained by pyrolysis under inert atmosphere of the branched poly(imides). These membranes have an asymmetric structure with a dense filtering layer and a porous layer with highly ordered channels standing parallel to the surface. These membranes display good chemical stability toward hydroxyl radical attack produced by Fenton reaction.

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Nesse trabalho obtiveram-se membranas de poli(imida) ramifricada com tamanho de poro ajustável usando melamina como agente de ramificação e indutor da formação de poros. Estas poli(imidas) foram sulfonadas usando-se ácido sulfúrico concentrado eficazmente. Finalmente, obtivemos membranas de carbono molecular por pirólise sob atmosfera inerte das poli(imidas) ramificadas. Estas membranas apresentam canais micrométricos paralelos à superfície e uma estrutura assimétrica constituída de uma camada densa filtrante e uma camada com canais micrométricos paralelos à superfície altamente ordenados. A membrana apresentou boa estabilidade química frente ao ataque por radicais hidroxila gerados via reação de Fenton. / In this work was obtained branched poly(imides) with tuned pore size using melamine as branching and pore induction agent. The poly(imides) with were efficiently sulfonated with concentrated sulfuric acid. Finally, the molecular sieve carbon membranes were obtained by pyrolysis under inert atmosphere of the branched poly(imides). These membranes have an asymmetric structure with a dense filtering layer and a porous layer with highly ordered channels standing parallel to the surface. These membranes display good chemical stability toward hydroxyl radical attack produced by Fenton reaction.

Des études moléculaires et génétiques ont montré qu'une empreinte épigénétique, située au niveau du locus sexuel (mat1) de la levure Schizosaccharomyces pombe, initie le changement de type sexuel. La réplication unidirectionnelle du locus mat1 permet la formation de l'empreinte sur le brin Watson. Les éléments moléculaires qui forment et protègent l'empreinte durant le cycle cellulaire restent peu connus. Afin de mieux comprendre le mécanisme de formation et de maintien de l'empreinte, j'ai caractérisé le recrutement au niveau du locus mat1 d'acteurs précoces dans le changement de type sexuel. J'ai montré que la protéine Sap1 (switch activating protein 1) est préférentiellement recrutée à l'intérieur de la séquence SS13, une séquence qui stabilise l'empreinte. Les protéines Lsd1/2 (lysine specific demethylases) qui contrôlent la pause de la fourche de réplication à mat1 et la formation de l'empreinte sont spécialement recrutées au niveau de mat1 indépendamment de l'allèle présent. La protéine Abp1 (homologue de CENP-B) est enrichie à côté de mat1 mais n'est pas impliquée dans la formation/maintien de l'empreinte. De plus, j'ai établi la signature de l'empreinte par séquençage à haut débit. En utilisant cette signature, j'ai mis en évidence que les protéines Lsd1/2 et Sap1 immunoprécipitent les deux côtés de la chromatide qui porte l'empreinte ce qui suggère la formation d'une structure protective définie comme l'imprintosome. / Genetic and molecular studies have indicated that an epigenetic imprint at mat1, the sexual locus of fission yeast, initiates mating type switching. The polar DNA replication of mat1 generates an imprint on the Watson strand. The process by which the imprint is formed and maintained through the cell cycle remains unclear. To understand better the mechanism of imprint formation and stability, we characterized the recruitment of early players of mating type switch at the mat1 region. We found that the switching activating protein 1 (Sap1) is preferentially recruited inside the mat1M allele on a sequence (SS13) that enhances the imprint. The lysine specific demethylases, Lsd1/2, that control the replication fork pause at MPS1 and the formation of the imprint are specifically drafted inside of mat1, regardless of the allele. The CENP-B homolog, Abp1, is highly enriched next to mat1 but it is not required in the process. Additionally, we established the computational signature of the imprint. Using this signature, we show that both sides of the imprinted molecule are bound by Lsd1/2 and Sap1, suggesting a nucleoprotein protective structure defined as imprintosome.

The main objects of this diploma thesis are basic trends in the mortgage market in the United States and their role in the current mortgage crisis. As a theoretical background in the first part of this work are mentioned asymetric information with the optimal consumer choice regarding mortgage product and the general theory of the securitization. Practical part continues from the description of the main characteristics of the mortgage to the whole mortgage market and the role of government agencies. Following analysis is concerning the significant tendencies in the past years, which dominates in the mortgage market in the USA. The focus is mainly aimed at the growth of alternative mortgage products in connection with strong home price apreciation. Then the position of mortgage brokers and their role in the subprime sector are discusssed. Subprime sector is analysed as well and then the securitization of mortgages as the main trend in the past years is investigated. The development of the current crisis is the object of the last chapter.

This diploma thesis discusses the problem of asymmetrically distributed information between economic agents who interact with each other. It describes the historical development of asymmetric information in economic theory. It mainly focuses on possible emergence of inefficiencies due to asymmetrically distributed information. It describes the model of adverse selection. The thesis also points out how it is possible to apply this model of adverse selection together with knowledge of contract theory to partly overcome these inefficiencies. The aim of the study is to show on concrete examples how to design optimal contract and how these optimal contract can minimize the impact of asymmetric information on economic efficiency.

The desire to use more energy efficient heavy equipment in the earth-moving industry has rapidly increased due to higher environmental awareness. Studies within electrification and new types of hydraulic circuit architecture has shown great potential regarding energy savings. The advantages of implementing a closed, pump-controlled, hydraulic system for controlling the boom cylinder on the back-hoe of an articulated backhoe loader is evaluated in this thesis. The possibilities of electric energy regeneration is investigated and to what extent energy savings can be expected for the complete hydraulic system during normal operation. In order for pump-controlled systems to even be conceivable alternatives to conventional valve-controlled system, they must be able to achieve the same characteristics and driveability as the original valve-controlled systems. The possibilities of imitating the characteristics of a valve-controlled hydraulic system with hydro-mechanical pressure feedback is also investigated in this thesis. The original characteristic is able to be imitated with the implemented pump-controlled system with simple means by defining the current characteristic as the relationship between the operator input, cylinder load and cylinder flow. The evaluated sectioned hydraulic system demonstrates energy savings of 30% during both a light and a heavy duty cycle. With components more suitable for this type of system and an improved control strategy, energy savings of over 50% compared to the original system is believed to be possible.

Les hélicènes sont des composés polyaromatiques générant un squelette hélicoïdal. Si ces structures ont trouvé de nombreuses applications en chimie des matériaux, les résultats en catalyse asymétrique sont moins nombreux, surtout en ce qui concerne les hélices phosphorées. Au cours de cette thèse, nous avons développé des nouvelles voies d'accès à des phosphines possédant une chiralité hélicoïdale, et où le phosphore est inclus dans l'hélice elle-même, à son extrémité. Les structures hélicoïdales souhaitées ont été synthétisées par deux méthodologies différentes, faisant intervenir soit une étape de photocyclisation diastéréosélective ou soit une réaction de cyclotrimérisation [2+2+2] d'alcynes. Les deux voies synthétiques développées font intervenir le même motif phosphindole. Les phophahélicènes synthétisés ont été évalués en tant que ligand en catalyse énantiosélective à l'or. Une bonne activité catalytique et des excès énantiomériques atteignant 96% ont été mesurés dans des réactions de cycloisomérisation d'énynes ou de cycloadditions [2+2] et [4+2].Les phosphahélicènes ont aussi été testés dans des réactions d'organocatalyse par les phosphines. Dans ce cas, des excès énantiomériques allant jusqu'à 97% ont été obtenus dans une réaction de cyclisation [3+2] entre une oléfine activée et un allénoate. / Helicenes are ortho-fused polyaromatic compounds in which benzene rings are angularly annulated to give helically-shaped molecules.Molecular scaffolds with helical chirality have been rarely used for building phosphorus ligands and catalysts. In this context, with the purpose of accessing unprecedented chiral auxiliaries for organo- and organometallic catalysis, we have synthesized new series of phosphahelicenes. These compounds have been prepared via two differents procedures: a diastereoselective photochemical cyclization and a [2+2+2] cyclotrimerisation of alkynes, starting from phosphindole as a key building block. These phosphahelicenes have been evaluated as chiral ligand in gold promoted cyclisation reactions. These helical gold complexes proved to be highly efficient both in terms of catalytic activity and enantioselectivity in enyne cycloisomerizations, [2+2] and [4+2] cycloaddition reactions. Phosphahelicenes have also been used in phosphine organocatalysis. Good yields and enantiomercic excesses up to 97% have been obtained in [3+2] cyclizations between olefins and allenoates.