Les silicones auto-cicatrisants de façon autonome (sans stimulus externe) présentent de faibles propriétés mécaniques, limitant leur utilisation industrielle. L’objectif de cette étude était de dépasser cette limitation. Nos travaux se sont intéressés aux copolymères segmentés PDMS-urée constitués de blocs souples (SS) et rigides (HS). Tout d’abord, nous avons étudié la relation entre la structure des bis-urées et les propriétés macroscopiques. Nous avons ainsi montré que la symétrie des HS gouverne la rigidité de ces matériaux. Toutefois, la présence de HS symétriques inhibe la cicatrisation du matériau. Puis, nous avons développé un nouveau concept permettant d’accélérer leur cinétique de cicatrisation. Un stoppeur de chaine macromoléculaire a été ajouté à la formulation de ces silicones thermoplastiques, créant un défaut dans l’assemblage supramoléculaire, conduisant à des clusters organiques plus petits et plus dynamiques. Néanmoins, contrairement aux plastifiants, la chute du module de Young observée par rapport à la matrice est limitée. D’ailleurs, nous reportons la synthèse d’un copolymère PDMS-urée avec un module de traction de 1MPa dont 90% de la contrainte à rupture peut être récupérée après cicatrisation pendant 24h à 25°C. Ce concept a aussi été adapté à un thermoplastique commercial (GENIOMER80). Enfin, notre défi a été d’optimiser la balance entre rigidité et autocicatrisation. Dans ce contexte, nous avons synthétisé de nouvelles matrices plus rigides, ainsi que des additifs avec des groupements associatifs de plus grande énergie cohésive. Nous avons alors pu repousser la limite de rigidité accessible aux silicones auto-cicatrisants de façon autonome (3MPa). / Autonomous self-healable (without external stimulus) silicones exhibit too low mechanical properties restricting their use in industry. The aim of this study was to overcome this limitation. We focused our work on segmented PDMS-urea copolymers made of soft (SS) and hard segments (HS). First the investigation of the relationship between the bis-urea chemical structure and the macroscopic properties was made. Results shown that, the symmetry of HS governs materials rigidity. Moreover, with a too symmetrical HS, the material does not exhibit self-healing abilities. We have developed a new concept improving the healing efficiency of these materials. The idea was to add to the formulation of these silicone thermoplastics a macromolecular chain stopper. The new additive creates a defect in the supramolecular assembly which leads to smaller and more dynamic H-bonding clusters and hence a faster healing kinetic. Unlike plasticizers, this additive deteriorates the tensile modulus only marginally. We therefore report a stress at break recovery of 90% after 24 hours at room temperature for a PDMS-urea copolymer with a tensile modulus of 1MPa. The concept was also extented to a commercial thermoplastic (GENIOMER80). Finally, our last challenge was to manage the balance between rigidity and chains dynamics allowing self-healable materials with good mechanical properties. In this context we have synthesized new matrixes with higher HS percentage and additives with stickers with higher cohesive energy. These new syntheses have led to an improvement of the rigidity limit reachable by the autonomous self-healable silicones (3MPa).

<p>Glutathione transferases (GSTs) are detoxication enzymes involved in the cellular protection against a wide range of reactive substances. The role of GSTs is to catalyze the conjugation of glutathione with electrophilic compounds, which generally results in less toxic products. </p><p>The ability to catalyze the denitrosation of the anticancer drug 1,3-bis(2-chloroethyl)- 1-nitrosourea (BCNU) was measured in twelve different GSTs. Only three of the enzymes showed any measurable activity with BCNU, of which human GST T1-1 was the most efficient. This is of special interest, since human GST T1-1 is a polymorphic protein and its expression in different patients may be crucial for the response to BCNU.</p><p>DNA shuffling was used to create a mutant library by recombination of cDNA coding for two different Theta-class GSTs. In total, 94 randomly picked mutants were characterized with respect to their catalytic activity with six different substrates, expression level and sequence. A clone with only one point mutation compared to wild-type rat GST T2-2 had a significantly different substrate-activity pattern. A high expressing mutant of human GST T1-1 was also identified, which is important, since the yield of the wild-type GST T1-1 is generally low. </p><p>Characterization of the Theta library demonstrated divergence of GST variants both in structure and function. The properties of every mutant were treated as a point in a six-dimensional substrate-activity space. Groups of mutants were formed based on euclidian distances and K-means cluster analyses. Both methods resulted in a set of five mutants with high alkyltransferase activities toward dichloromethane and 4-nitrophenethyl bromide (NPB). </p><p>The five selected mutants were used as parental genes in a new DNA shuffling. Addition of cDNA coding for mouse and rat GST T1-1 improved the genetic diversity of the library. The evolution of GST variants was directed towards increased alkyltransferase activity including activity with the anticancer drug BCNU. NPB was used as a surrogate substrate in order to facilitate the screening process. A mutant from the second generation displayed a 65-fold increased catalytic activity with NPB as substrate compared to wild-type human GST T1-1. The BCNU activity with the same mutant had increased 175-fold, suggesting that NPB is a suitable model substrate for the anticancer drug. Further evolution presented a mutant in the fifth generation of the library with 110 times higher NPB activity than wild-type human GST T1-1.</p>

The synthesis and reactions of hydrotris(pyrazolyl)borate, (TpR,R) supported ytterbium(II) borohydride and lanthanide(III) dialkyl (Ln = Yb, Lu) complexes were investigated. The lanthanide(III) dialkyl complexes were found to undergo both hydrogenolysis reaction and protonolysis reaction with terminal alkynes. Reaction of [(TptBu,Me)YbH]2 (1) with NH3BH3 and (TptBu,Me)YbI(THF) (2) with NaBH4 afforded the corresponding mono-ligand complexes, (TptBu,Me)Yb(BH4) (3) and (TptBu,Me)Yb(BH4)(THF) (4), respectively. Compounds 3 and 4 represent rare examples of lanthanide(II) tetrahydroborate complexes. IR spectroscopy data, in the B-H stretching region are consistent with the 3-BH4 bonding mode found in the solid state of compound 4 and the corresponding deuterium labelled BD4 analogue of 4 shows the expected IR isotope shifts. Mono-ligand lanthanide dialkyl complexes, (TpR,R)Ln(CH2SiMe2R)2(THF)0/1 (5-9) were synthesized from the homoleptic Ln(CH2SiMe2R)3(THF)2 (Ln = Yb, Lu; R = Me, Ph) complexes by two alternative and complementary methods: alkyl abstraction with the thallium salts of the ligands, TlTpR,R and protonolysis using the acid form of the ligands, HTpR,R. Hydrogenolysis of the dialkyl complexes (TpMe2)Ln(CH2SiMe3)2(THF) (7a, Yb; 8a, Lu) afforded the corresponding tetranuclear hydride complexes, [(TpMe2)LnH2]4 (11, Yb; 12, Lu). Similarly, hydrogenolysis of (Tp)Yb(CH2SiMe3)2(THF) (9) afforded the hexanuclear hydride [(Tp)YbH2]6 (13). When treated with a variety of terminal alkynes, the dialkyl complexes, (TpR,Me)Ln(CH2SiMe3)2(THF) (14a, Y; 8a, Lu), gave the corresponding bis-alkynide complexes, (TpR,Me)Ln(CCR)2 (15-27). The structures of the complexes depend on the steric size of both the alkyne substituents and the substituent on position 3 of the pyrazolyl ring. Except for the bulkiest substituents, the compounds are dimeric with two asymmetric 2-alkynide bridging groups and a coupled alkynide unit bridging the two lanthanide centers via an unusual enyne bonding motif. The synthesis of Lu(CH2Ph-4-R)3(THF)3 (R = H, 28a; R = Me, 28b) was achieved by salt metathesis reactions between KCH2Ph-4-R and LuCl3. Variable temperature NMR studies in THF shows that the formation of these complexes is accompanied by a small amount of the anionic ate K[Lu(CH2PH-4-R)4(THF)n] (30) complexes, which can be prepared independently by reaction of pure Lu(CH2Ph-4-R)3(THF)3 with one equiv. of KCH2Ph-4-R. One of the coordinated THF of 28a could be removed by trituration with toluene to give Lu(CH2Ph-4-R)3(THF)2 (29a). Protonolysis reaction with HTpR,R afforded the corresponding dibenzyl complexes, (TpR,R)Ln(CH2Ph-4-R)2(THF)n (31-33). X-ray crystal structures of complex 4, the dialkyl complexes 5b, 6b, 7 and 8; dihydride complexes 11, 12 and 13; bis-alkynide complexes 15, 16, 17, 21, 22 and 24 as well as the tribenzyl compounds 28a and 29a and dibenzyl complexes 31-33 were determined. The solution behaviour, solid state structures and structural diversity of these complexes are discussed.

Glutathione transferases (GSTs) are detoxication enzymes involved in the cellular protection against a wide range of reactive substances. The role of GSTs is to catalyze the conjugation of glutathione with electrophilic compounds, which generally results in less toxic products. The ability to catalyze the denitrosation of the anticancer drug 1,3-bis(2-chloroethyl)- 1-nitrosourea (BCNU) was measured in twelve different GSTs. Only three of the enzymes showed any measurable activity with BCNU, of which human GST T1-1 was the most efficient. This is of special interest, since human GST T1-1 is a polymorphic protein and its expression in different patients may be crucial for the response to BCNU. DNA shuffling was used to create a mutant library by recombination of cDNA coding for two different Theta-class GSTs. In total, 94 randomly picked mutants were characterized with respect to their catalytic activity with six different substrates, expression level and sequence. A clone with only one point mutation compared to wild-type rat GST T2-2 had a significantly different substrate-activity pattern. A high expressing mutant of human GST T1-1 was also identified, which is important, since the yield of the wild-type GST T1-1 is generally low. Characterization of the Theta library demonstrated divergence of GST variants both in structure and function. The properties of every mutant were treated as a point in a six-dimensional substrate-activity space. Groups of mutants were formed based on euclidian distances and K-means cluster analyses. Both methods resulted in a set of five mutants with high alkyltransferase activities toward dichloromethane and 4-nitrophenethyl bromide (NPB). The five selected mutants were used as parental genes in a new DNA shuffling. Addition of cDNA coding for mouse and rat GST T1-1 improved the genetic diversity of the library. The evolution of GST variants was directed towards increased alkyltransferase activity including activity with the anticancer drug BCNU. NPB was used as a surrogate substrate in order to facilitate the screening process. A mutant from the second generation displayed a 65-fold increased catalytic activity with NPB as substrate compared to wild-type human GST T1-1. The BCNU activity with the same mutant had increased 175-fold, suggesting that NPB is a suitable model substrate for the anticancer drug. Further evolution presented a mutant in the fifth generation of the library with 110 times higher NPB activity than wild-type human GST T1-1.

This work comprises two main parts. The first part outlines our efforts to expand on the recent work of Gütlich et.al. by synthesizing Co(II) based spin crossover systems within a dendritic framework. We wanted to investigate the possibility of synthesizing different first generation, triazole containing dendrimers using “click” type reactions and their coordination ability with Co(II) ions. To this end we have had limited success mainly due to the numerous challenges in synthesizing a pure dendrimer product. The second part details our efforts in the synthesis of a mononuclear Co(II) based single molecule magnet. This comes as an extension to recent reports by Chang and Long where they have successfully obtained mononuclear Fe(II) single molecule magnets by inducing structural distortions within the complexes to amplify the spin-orbit coupling. We postulated that the use of Co(II) in conjunction with a bulky ligand framework would lead to desirable magnetic properties. We chose the known bis(imino)pyridine ligand scaffold due to its rich chemistry and its interesting and unexpected coordination behaviour, as we have seen in previous research efforts by our lab. To this end we were successful in isolating and characterizing 4 compounds, and we have carried out detailed magnetic measurements on the two most magnetically interesting species.

This work comprises two main parts. The first part outlines our efforts to expand on the recent work of Gütlich et.al. by synthesizing Co(II) based spin crossover systems within a dendritic framework. We wanted to investigate the possibility of synthesizing different first generation, triazole containing dendrimers using “click” type reactions and their coordination ability with Co(II) ions. To this end we have had limited success mainly due to the numerous challenges in synthesizing a pure dendrimer product. The second part details our efforts in the synthesis of a mononuclear Co(II) based single molecule magnet. This comes as an extension to recent reports by Chang and Long where they have successfully obtained mononuclear Fe(II) single molecule magnets by inducing structural distortions within the complexes to amplify the spin-orbit coupling. We postulated that the use of Co(II) in conjunction with a bulky ligand framework would lead to desirable magnetic properties. We chose the known bis(imino)pyridine ligand scaffold due to its rich chemistry and its interesting and unexpected coordination behaviour, as we have seen in previous research efforts by our lab. To this end we were successful in isolating and characterizing 4 compounds, and we have carried out detailed magnetic measurements on the two most magnetically interesting species.

ABSTRACT SYNTHESIS AND ELECTROCHROMIC PROPERTIES OF CONDUCTING POLYMERS OF SUCCINIC ACID BIS-(2-THIOPHEN-3-YL-ETHYL) ESTER AND THEIR USE IN ELECTROCHROMIC DEVICES Sa&ccedil / an, Lale M.Sc., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare June 2006, 59 pages A new monomer / succinic acid bis-(2-thiophen-3-yl-ethyl)ester (SATE) was synthesized through the esterification reaction of 2-thiophen-3-yl-ethanol and succinyl chloride. The chemical structure of monomer was characterized via Nuclear Magnetic Resonance Spectroscopy (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Electrochemical behaviors of SATE alone and SATE in the presence of thiophene were studied by cyclic voltammetry (CV). The synthesis of homopolymer and copolymer were achieved via constant potential electrolysis. Both homopolymer (PSATE) and copolymer [P(SATE-co-Th)] were characterized by various techniques including cyclic voltammetry, FTIR, Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermal Gravimetry Analysis (TGA) and UV-VIS Spectrophotometer. Conductivities of samples were measured by four probe technique. The electrochromic properties of the polymers were investigated via spectroelectrochemistry, colorimetry and switching studies. In addition, dual type electrochromic devices (ECDs) composed of PSATE, P(SATE-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) were constructed and evaluated. Spectroelectrochemistry, switching ability and stability of the devices were investigated by UV-Vis Spectrophotometer and Cyclic Voltammetry. They have shown to possess good switching times, reasonable contrasts, high stabilities and optical memories.

Adaptation to any undesirable change in the environment dictates the survivability of many microorganisms. Such changes generate a quick and suitable response, which guides the physiology of bacteria. Stringent response is one of the mechanisms that can be called a survival strategy under nutritional starvation in bacteria and was first observed in E. coli upon amino acid starvation, when bacteria demonstrated an immediate downshift in the rRNA and tRNA levels (Stent and Brenner 1961). Mutations that rendered bacteria insensitive to amino acid levels were mapped to an ‘RC gene locus’, later termed relA because of the relAxed behavior of the bacteria (Alfoldi et al. 1962). Later on, Cashel and Gallant, showed that two “magic spots” (MSI and MSII) were specifically observed in starved cells when a labeled nucleotide extract of these cells was separated by thin layer chromatography (Cashel and Gallant 1969). These molecules were found to be polyphosphate derivatives of guanosine, ppGpp and pppGpp (Cashel and Kalbacher 1970; Sy and Lipmann 1973), and were shown to be involved in regulating the gene expression in the bacterial cell, demonstrating a global response, thus fine-tuning the physiology of the bacterium. Two proteins in E. coli, RelA and SpoT, carry out the synthesis and hydrolysis of these molecules, respectively, and maintain their levels in the cell (Cashel et al. 1996; Chatterji and Ojha 2001). On the other hand, Gram-positive organisms have only one protein Rel carrying out the functions of both RelA and SpoT (Mechold et al. 1996; Martinez-Costa et al. 1998; Avarbock et al. 1999). Although Rel or RelA/SpoT has been studied from several systems in detail pertaining to the physiological adaptation, less information is available on the egulation of the protein activity under different conditions. Our studies show that the RelMsm is composed of several domains (HD, RSD, TGS and ACT) with distinct function. HD and RSD domains, present in the N-terminal half of the protein, harbor catalytic sites for the hydrolysis and the synthesis of (p)ppGpp, respectively. TGS and ACT domains, on the other hand, are present at the C-erminal half of the protein and have regulatory function. It, therefore, appears that a communication exists between these domains, to regulate protein activity. It was shown earlier, while studying Rel from S.equisimilis, that there exists an interaction between the C-terminal and the N- terminal of the protein which determines the kind of activity (synthesis/hydrolysis), the protein should demonstrate (Mechold et al. 2002). Later, the N-terminal half crystal structure of the same protein suggested an inter-domain “cross-talk” between the HD and the RSD domain that controls the synthesis/hydrolysis switch depending on cellular conditions (Hogg et al. 2004). In the present work, studies have been carried out to understand a Gram- positive Rel in greater detail and to find out how the opposing activities of Rel are regulated so that a futile cycle of synthesis and hydrolysis of (p)ppGpp, at the expense of ATP, can be avoided. The work has been divided into several chapters describing studies on various aspects of the protein. Chapter 1 outlines the history of the stringent response and summarizes the information available about the stringent response in various systems including plants. Several roles that (p)ppGpp plays in different bacteria have been examined. A special mention on the crystal structure of RelSeq has been made with respect to the regulation of activity. Also, the information available regarding the effects of (p)ppGpp on RNA polymerase has been documented. Role of ppGpp in plants has been discussed in great detail with special emphasis on abiotic stresses. Since different functional domains have been identified in RelMsm, the protein has been divided into two halves and they have been discussed separately in the form of two chapters. Chapter 2 describes the N-terminal half of the Rel protein of M. smegmatis in greater detail. Out of the several domains identified, the role of the two domains present in the N-terminal half of the protein has been studied. The N-terminal half shows both synthesis and hydrolysis activities. Importantly, we find that the protein is active even in the absence of accessory factors such as ribosome and uncharged tRNA, unlike RelA of E. coli. Moreover, deletion of the C-terminal half of the protein leads to a much higher synthetic activity, clearly indicating that the C-terminus is involved in regulating the activity of the protein. Both TGS and ACT domains (the two domains found in the C-terminal half of the protein) have been found to play a regulatory role. The results also indicate that all the deleted constructs are active both in vitro and in vivo. Chapter 3 discusses the C-terminal half of the protein and its role in the multimerization observed in RelMsm. We show that multimerization of Rel protein is due to the inter-molecular disulfide cross-linking. Furthermore, we find that the monomer is the active species in vivo. One of the fascinating points about the C- terminal half is that it is largely unstructured. Additionally, the C-terminal half cannot complement the N-terminal part of the protein when provided in trans, demonstrating further, the requirement of an intact protein for bringing about regulation of Rel activity. This requirement in cis suggests the presence of an intra-molecular communication between the N- and the C-termini, as a mediator of protein regulation. Further, presence of uncharged tRNA increases pppGpp synthesis and down-regulates its hydrolysis in the wildtype protein. However, the uncharged tRNA-mediated regulation is absent in the deleted construct with only the N-terminus half, indicating that uncharged tRNA binds to the C-terminal half of the protein. Several cysteine mutants have been constructed to understand their role in the regulation of Rel activity. The results suggest that one cysteine, present at the C-terminus, is required for intra-molecular cross-talk and the uncharged tRNA-mediated regulation. A detailed characterization of the communication between the two halves of the protein has been attempted in Chapter 4. Surface plasmon resonance experiments carried out on the different cysteine mutants discussed in Chapter 3, for uncharged tRNA binding indicate that all the mutants bind to uncharged tRNA with near-equal affinities as the wildtype protein. This study suggests that the non-responsiveness for tRNA seen in one of the cysteine mutants is due to the loss of inter-domain interaction, while the binding of protein to accessory factors is unaffected. Fluorescence resonance energy transfer has been carried out to observe domain movement in the presence of accessory factors. Distances between the different domains scattered in this ~90 kDa protein, measured by FRET technique, are suggestive of an inter-domain cross-talk, specifically between C338 and C692, thereby regulating the activity of this enzyme. We show, for the first time, that the product of this protein, (p)ppGpp can bind to the C-terminal half making it unstructured, and can, therefore, regulate the protein activity. Chapter 5 is an effort to characterize the promoter of rel from M. tuberculosis. This study was undertaken in order to develop an expression system in mycobacteria. The +1 transcription and the translation start sites have been identified. The –10 hexamer for the RNA polymerase binding has also been mapped using site-directed mutagenesis and is found to be TATCCT. This promoter is also unusually close to the +1 transcription start site. The promoter is specific for mycobacteria and does not function in E. coli. Additionally, the promoter is found to be constitutive in M. smegmatis; however, the possibility of it being regulated in M. tuberculosis cannot be ruled out. Appendix section discusses, in short, the phylogenetic analysis of the mycobacterial Rel sequences. Diagrams of the plasmids used in this study have been provided. Mass spectra recorded for the in vitro synthesized and purified pppGpp and the trypsin digest of the full-length Rel protein have also been given. O O O O

L'Ellipticine, alcaloïde représentatif des composés de type pyrido[4,3-b] carbazole, est un<br />puissant cytotoxique de part ses propriétés intercalantes mais également du fait de son<br />aptitude à inhiber l'activité de religation de l'ADN de la topoisomérase II. De nombreux<br />laboratoires se sont attachés à réaliser des synthèses efficaces de l'ellipticine mais également<br />de ses analogues structuraux.<br />Dans la première partie, en s'appuyant sur des travaux antérieurs du laboratoire, nous avons<br />développé une voie de synthèse d'un nouvel analogue benzoxazinique de l'Ellipticine, en 9<br />étapes, avec un rendement global de 4%. L'étape clé de notre stratégie, permettant la<br />construction du squelette tétracyclique, consiste à condenser la benzoxazine protégée par un<br />groupement N-Boc sur le N,N-diéthyl-4-formylnicotinamide suivant une double réaction de<br />metallation. Une réaction de couplage palladiée est ensuite utilisée afin d'introduire de<br />manière judicieuse les substituants désirés.<br />Dans une deuxième partie, nous avons préparé des dérivés 1,4-dihydropyridiniques originaux<br />substitués en positions 2 et 6 par divers groupements alkyles, allyles, aryles ou hétéroaryles ;<br />nous avons réalisé des réactions de couplage palladié de type Suzuki-Miyaura ou Stille à<br />partir de bis-vinylphosphates obtenus à partir de glutarimides commerciaux. Nous avons<br />ensuite mis au point les conditions d'alkylation de ces composés en position 4. Le traitement<br />acide des diverses dihydropyridines ainsi obtenues a ensuite permis d'accéder, suivant les<br />conditions expérimentales, à des pyridines diversement substituées ou à des composés<br />dicétoniques.

In der vorliegenden Arbeit werden bi- und oligometallische Komplexe, die auf Bis(alkinyl)titanocen-Bausteinen (Metallorganische pi-Pinzetten) basieren, beschrieben. Dabei stehen Synthesestrategien und Untersuchungen zum Reaktionsverhalten sowie elektrochemische Eigenschaften der mehrkernigen Komplexe im Vordergrund. Bimetallische Ti-M-Systeme (M = Cu, Ag) können als Vorstufen zu höhernuklearen Spezies dienen. Die oligometallischen pi-Pinzetten-Komplexe sind entweder durch organische Ligandsysteme oder über anorganische Bausteine wie Halogenide oder Pseudohalogenide miteinander verknüpft. Über entsprechende Kupfer(I)- und Silber(I)-Pseudohalogenid-Komplexfragmente können Bis(akinyl)titanocen-M-Komplexe (M = Cu, Ag) mit bis zu neun Metallzentren in einer Verbindung realisiert werden. Je nach verbrückender Einheit werden dabei gewinkelte, lineare oder sternförmige Strukturen gebildet. Die gegenseitige elektrochemische Beeinflussung verschiedener Metallzentren in ausgewählten Komplexen wird cyclovoltammetrisch orientierend untersucht. Ein weiterer Schwerpunkt der vorliegenden Arbeit liegt in der Synthese und der Untersuchung thermischer Eigenschaften von Kupfer(I)-Alkin-Komplexen, die präparativ und finanziell mit moderatem Aufwand zugänglich sind. Über thermogravimetrische Untersuchungen können Rückschlüsse auf die Eignung solcher Verbindungen für den MOCVD-Prozeß getroffen werden.