Dissertations / Theses: 'Ligase IV'

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De, Melo Abinadabe Jackson. "Molecular basis for the structural role of human DNA ligase IV." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4040.

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Les défauts dans la réparation des cassures double-brin de l'ADN (DSBs) peuvent avoir d'importantes conséquences pouvant entrainer une instabilité génomique et conduire à la mort cellulaire ou au développement de cancers. Dans la plupart des cellules mammifères, le mécanisme de Jonction des Extrémités Non Homologues (NHEJ) est le principal mécanisme de réparation des DSBs. L'ADN Ligase IV (LigIV) est une protéine unique dans sa capacité à promouvoir la NHEJ classique. Elle s'associe avec deux autres protéines structuralement similaires, XRCC4 et XLF (ou Cernunnos). LigIV interagit directement avec XRCC4 pour former un complexe stable, tandis que l'interaction entre XLF et ce complexe est médiée par XRCC4. XLF stimule fortement l'activité de ligation du complexe LigIV/XRCC4 par un mécanisme encore indéterminé. Récemment, un rôle structurel non catalytique a été attribué à LigIV (Cottarel et al., 2013). Dans le travail de thèse présenté ici, nous avons reconstitué l'étape de ligation de la NHEJ en utilisant des protéines recombinantes produites dans des bactéries afin d’une part, d'explorer les bases moléculaires du rôle structural de LigIV, d’autre part de comprendre le mécanisme par lequel XLF stimule le complexe de ligation, et enfin de mieux comprendre comment ces trois protéines coopèrent au cours de la NHEJ. Nos analyses biochimiques suggèrent que XLF via son interaction avec XRCC4 lié à LigIV, pourrait induire un changement conformationnel dans la LigIV. Ce réarrangement de la ligase exposerait son interface de liaison à l'ADN ce qui lui permettrait alors de ponter deux molécules indépendantes d'ADN, une capacité indépendante de l'activité catalytique de LigIV
Failure to repair DNA double-strand breaks (DSBs) may have deleterious consequences inducing genomic instability and even cell death. In most mammalian cells, Non-Homologous End Joining (NHEJ) is a prominent DSB repair pathway. DNA ligase IV (LigIV) is unique in its ability to promote classical NHEJ. It associates with two structurally related proteins called XRCC4 and XLF (aka Cernunnos). LigIV directly interacts with XRCC4 forming a stable complex while the XLF interaction with this complex is mediated by XRCC4. XLF strongly stimulates the ligation activity of the LigIV/XRCC4 complex by an unknown mechanism. Recently, a structural noncatalytic role of LigIV has been uncovered (Cottarel et al., 2013). Here, we have reconstituted the end joining ligation step using recombinant proteins produced in bacteria to explore not only the molecular basis for the structural role of LigIV, but also to understand the mechanism by which XLF stimulates the ligation complex, and how these three proteins work together during NHEJ. Our biochemical analysis suggests that XLF, through interactions with LigIV/XRCC4 complex, could induce a conformational change in LigIV. Rearrangement of the LigIV would expose its DNA binding interface that is able to bridge two independent DNA molecules. This bridging ability is fully independent of LigIV’s catalytic activity. We have mutated this interface in order to attempt to disrupt the newly identified DNA bridging ability. In vitro analysis of this LigIV mutant will be presented as well as a preliminary in vivo analysis

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Nijnik, A. "ENU mouse mutant with a hypomorphic mutation in DNA ligase IV." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:5a8ae151-6261-4ad4-9541-d5c59ba654a7.

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Stiff, Thomas. "Characterisation of proteins that stimulate the DNA ligase IV/Xrcc4 complex." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249402.

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Wang, Yu. "Mismatch ligation during non-homologous end joining pathway kinetic characterization of human DNA ligase IV/XRCC4 complex /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1179947467.

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Amram, Jérémy. "Etude structurale et fonctionnelle des complexes multi-protéiques de la voie de réparation NHEJ chez l’homme." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA114822/document.

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La voie de réparation NHEJ (Non-Homologous End-Joining) est une voie majeure de réparation des cassures double-brin chez l’homme. Les protéines de cette voie interagissent et forment des complexes dynamiques dont les mécanismes moléculaires sont encore largement méconnus. Nous avons dans un premier temps mis au point des protocoles de production à l’échelle de plusieurs milligrammes des protéines cœur de la voie NHEJ en cellules d’insecte à l’aide du système MultiBac. Nous avons ainsi purifié les complexes Ku70/Ku80 et Ligase4/XRCC4 et les protéines Cernunnos et Artemis à homogénéité. Des essais de cristallisation, des études par SAXS et des analyses par microscopie électronique ont été réalisés sur différents complexes formés par ces protéines cœur du NHEJ. Nous avons également caractérisé par chromatographie d’exclusion de taille et calorimétrie, les interactions effectuées entre les protéines de la voie NHEJ. L’ensemble de ces travaux a permis d’établir des bases biochimiques solides en vue des études structurales et fonctionnelles de la voie NHEJ chez l’homme
Human DNA repair pathway NHEJ (Non-Homologous End-Joining) is a major pathway of double-strand breaks repair. The proteins involved in this pathway interact and form dynamic complexes whose molecular mechanisms are largely unknown. Firstly, we established protocols to be able to purify milligrams of those NHEJ pathway core proteins using MultiBac insect cells system. We then purified Ku70/Ku80 and Ligase4/XRCC4 complexes, Artemis and Cernunnos to homogeneity. Crystallogenesis assays, SAXS experiments and Transmission Electronic Microscopy experiments have been performed on several complexes formed by these core NHEJ proteins. We also characterized the interactions between these proteins by Size Exclusion Chromatography and Isothermal Calorimetry. These experiments have led to biochemical results sufficient to establish a solid basis to initiate the structural and functional study of the Human NHEJ Pathway

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Ochi, Takashi. "Non-homologous end-joining DNA double strand break repair : structural studies of the DNA ligase IV/XRCC4 complex." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609793.

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PATRIZI, LAURA. "ANALYSIS OF B LYMPHOCYTES IN MOUSE MODEL LIGASE IV WITH HYPOMORPHIC MUTATION IN VDJ RECOMBINATION ASSOCIATED WITH GROWTH DEFECT." Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150193.

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The major mechanism for the repair of DNA doublestrand breaks (DSBs) in mammalian cells is non-homologous end-joining (NHEJ), a process that involves the DNA-dependent protein kinase , XRCC4 and DNA ligase IV. Rodent cells and mice defective in these components are radiation-sensitive and defective in V(D)J-recombination, showing that NHEJ also functions to rejoin DSBs introduced during lymphocyte development. We have generated a knock-in mouse model with a homozygous Lig4 arginine to histidine (R278H) mutation that corresponds to the mutation identified in the first LIG4-deficient patient, who developed T cell leukemia associated with increased cellular radiosensitivity. The clinical presentation of the syndrome is complex and heterogeneous and may include varying degrees of lymphopenia, growth retardation and microcephaly. The phenotypic effects of the impaired repair of non programmed DNA damage are more diverse and difficult to study. Although such defects in cell survival and proliferation are likely to have an impact on the immune system, their contribution to the immunodeficiency of the LigIV syndrome remains unknown.

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Menchon, Grégory. "Criblage virtuel et fonctionnel sur le complexe XRCC4/ADN ligase IV/Cer-XLF de ligature des cassures double-brin de l'ADN : application en radiosensibilisation tumorale." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30395.

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En cancérologie, la radiothérapie est une des armes essentielles pour éradiquer les cellules tumorales. Les cassures des deux brins de l'ADN dites "double-brin" qu'elle induit sont particulièrement toxiques et constituent la principale cause de mort cellulaire. La NHEJ (Jonction d'Extrémités Non-Homologues) est la voie métabolique majeure de réparation de ces cassures double-brin de l'ADN et par ce mécanisme, les cellules humaines adoptent une résistance à la radiothérapie. Ce mécanisme de réparation constitue donc une cible de choix pour un traitement anticancéreux combiné en vue d'augmenter la sensibilité des cellules cancéreuses aux rayons ionisants (radiosensibilisation). Au cours du mécanisme NHEJ, la ligature finale des extrémités d'ADN est assurée par le complexe protéique tripartite: XRCC4/ADN Ligase IV/Cernunnos-XLF. Les interfaces protéiques concernées représentent toutes des cibles potentielles dans une stratégie rationnelle d'isolement de molécules inhibitrices, guidée par les structures tridimensionnelles de chaque protéine. A travers des expériences de criblage virtuel et de validation à la fois biophysique et biochimique, nous avons isolé les premières molécules capable de prévenir in vitro les interactions protéine-protéine pour les complexes XRCC4/Lig4 et XRCC4/Cer-XLF, respectivement. Ces composés sont des points de départ pour l'élaboration d'inhibiteurs potentiels de plus haute affinité grâce à l'apport de la biologie structurale, en vue d'un effet radiosensibilisant cellulaire
Radiotherapy is a major weapon used against cancer. Radio-induced DNA double strand breaks (DSB) are the main lesions responsible for cell death. Non-homologous end-joining (NHEJ) is a predominant DSB repair mechanism which contributes to cancer cells resistance to radiotherapy. NHEJ is thus a good target for strategies which aim at increasing the radio-sensitivity of tumors. Through in silico screening and biophysical and biochemical assays, our objective was to find specific ligands for the XRCC4/Lig4 and XRCC4/Cer-XLF protein-protein interactions involved in NHEJ. Here, we isolated the first compounds able to prevent their interaction in vitro. These early stage inhibitors are promising tools for cancer therapy with the hope to develop more specific compounds for cellular assays through the 3D structure of the protein/inhibitor complexes

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Tatavarthi, Haritha. "Action of Tyrosyl DNA Phosphodiesterase on 3'-Phosphoglycolate Terminated DNA Strand Breaks." VCU Scholars Compass, 2006. http://hdl.handle.net/10156/1799.

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Costa, Vânia Aparecida da. "Efeitos termoelétricos em ligas e nanoestruturas de semicondutores IV-VI." Instituto Nacional de Pesquisas Espaciais (INPE), 2015. http://urlib.net/sid.inpe.br/mtc-m21b/2015/01.30.11.47.

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Este trabalho apresenta um estudo teórico das propriedades termoelétricas de ligase nanoestruturas de semicondures IV-VI. Estes materiais têm sido muito estudados por possuírem altos valores de figura de mérito e por suas nanoestruturas (superredes, fios e poços quânticos) apresentarem possibilidades na melhora da resposta termoelétrica. Dentre os modelos teóricos desenvolvidos até o momento, pode-se observar que ainda não foi possível modelar quantitativamente os coeficientes mensurados e nem determinar o principal mecanismo responsável pela resposta termoelétrica. Para contribuir nessa área, foram estudados os coeficientes de transporte de ligas \emph{Pb$_{1-x}$Sn$_{x}$Te}, fios quânticos e super-redes de \emph{PbTe}. Partindo do modelo \emph{k . p}, conhecido como modelo de Dimmock, foi calculada a estrutura de bandas incluindo efeitos de não parabolicidade, anisotropia e múltiplos vales. Os coeficientes de transporte do \emph{bulk} e super-rede foram calculados dentro do formalismo semiclássico que utiliza a solução da equação de Boltzmann na aproximação do tempo de relaxação. No caso do fio quântico, foi utilizado o formalismo de Landauer, onde os coeficientes de transporte são dados em termos da probabilidade de transmissão de elétrons em movimento balístico entre contatos representados por reservatórios em equilíbrio. Com base na análise das variações de temperatura, concentração de portadores, percentual de estanho do \emph{bulk}, geometria e parâmetros das nanoestrururas, foram discutidos os mecanismos para o aumento da eficiência termoelétrica destes materiais. Os resultados indicam que o modelo utilizado para o \emph{bulk} possui um bom acordo com a experiência e que o aumento de estanho em ligas \emph{Pb$_{1-x}$Sn$_{x}$Te} melhoraos valores de figura de mérito. Um fator de ganho foi introduzido para avaliar a resposta termoelétrica devido à alteração na dimensionalidade e empacotamento de nanoestruturas no interior de um \emph{bulk} 3D finito. Alterações na eficiência termoelétrica de super-redes IV-VI podem ser obtidas explorando a sua anisotropia o que implica em novas possilibidades de aplicação em dispositivos termoelétricos.
This work presents a theoretical study of thermoelectric properties of IV-VI semiconductor alloys and nanostructures. These materials have a been widely studied because they have high figure of merit and their nanostructures (superlattices, quantum wires and quantum wells) are able to improving the thermoelectric response. The theoretical models, developed until now, either have not been able to model quantitatively the measured coefficients and neither to determine the main mechanism responsible for thermoelectric performance. To contribute in this area, the transport coefficients of \emph{Pb$_{1-x}$Sn$_{x}$Te} alloys, quantum wires and \emph{PbT} e superlattices were studied. From \emph{k . p} model, known as Dimmock model, it was calculated the band structure including non parabolicity, anisotropy and multiple valleys effects. The bulk transport coefficients and superlattice were calculated within the semiclassical formalism which uses the Boltzmann equation solution in the relaxation time approximation. In the quantum wire case, it was used the Landauer formalism, where the transport coefficients are given in terms of the transmission probability of electrons in the ballistic regime, between contacts represented by reservoirs in equilibrium. Based on the analysis of temperature variations, carrier concentration, percentage of tin percentage in bulk, geometry and parameters of nanostructures, were discussed the mechanism to increase the thermoelectric efficiency of these materials. The results indicate that the model used for the bulk has a good agreement with the experiment and the increase of tin in \emph{Pb$_{1-x}$Sn$_{x}$Te} alloys increase the figures of merit values. A gain factor has been introduced to study the thermoelectric performance due to changes in dimensionality and nanostructures packaging within a finite-3D bulk. Changes in the thermoelectric efficiency of IV -VI superlattices can be obtained exploiting its anisotropy, this implies new possilibidades of application in thermoelectric devices.

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Zheldakov, Igor. "Ultrafast Photophysics and Photochemistry Of Hexacoordinated Bromides of Pt(IV), Os(IV), and, Ir(IV) in the Condensed Phase Studied by Femtosecond Pump-Probe Spectroscopy." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1279998360.

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Yamamoto, Brent Joseph. "Norleual, an angiotensin IV receptor ligand and C-Met antagonist." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Summer2006/B%5FYamamoto%5F071206.pdf.

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Metz, Stefan. "Synthese neuartiger siliciumorganischer Riechstoffe sowie neutraler penta- und hexakoordinierter Silicium(IV)-Komplexe." kostenfrei, 2008. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2008/2959/.

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Audras, Matthieu. "Caractérisation structurale de complexes d'actinides (III) et (IV) par le ligand DOTA." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20096/document.

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Les anions polyaminocarboxylates ont été identifiés comme des composés d'intérêt pour les opérations de séparation des actinides, dans la migration des actinides dans l'environnement et dans la radiotoxicologie humaine. La caractérisation structurale de complexes formés entre les actinides et les ligands polyaminocarboxylates est essentielle pour une meilleure compréhension des interactions actinides – ligands. Parmi les anions polyaminocarboxylates, le macrocycle DOTA (acide 1,4,7,10-tétraazacyclododécane-tétraacétique) est décrit comme un agent complexant très fort des lanthanides(III), mais a été très peu étudié avec des actinides. L'objectif de ce travail de thèse est de décrire les complexes formés entre les actinides (III) et (IV) et le ligand DOTA et de les comparer avec les complexes de lanthanides(III). Pour cela, une approche a été mise en place afin de caractériser les complexes par des techniques analytiques complémentaires (spectrophotométrie, spectrométrie de masse à ionisation par électrospray, RMN, EXAFS, électrochimie) mais également par des calculs de chimie théorique pour aider à l'interprétation des données expérimentales.La formation d'un complexe de stœchiométrie 1:1 est observée avec les actinides(III) (américium et plutonium) comme dans le cas des lanthanides(III) : il y a formation rapide d'espèces intermédiaires qui évoluent lentement vers la formation d'un complexe limite. Au sein de ce complexe, le cation se trouve à l'intérieur de la cavité formée par le macrocycle DOTA, comme dans le cas des lanthanides(III). Quatre atomes d'azote et atomes d'oxygène des fonctions carboxylates sont impliqués dans la sphère de coordination du cation. Néanmoins, des différences sont observées sur les longueurs de liaisons formées entre le cation et les atomes d'azote (les liaison sont légèrement plus courtes dans le cas des complexes d'actinides) ainsi que sur la cinétique de complexation qui est légèrement plus rapide pour les actinides(III) que pour les lanthanides(III) de rayon ionique équivalent. Le même comportement en solution est observé lors de la complexation des actinides(IV) (uranium, neptunium et plutonium) à l'exception du thorium : il y a formation lente d'un complexe de stœchiométrie 1:1 (actinides(IV):ligand) dans lequel le cation se trouve à l'intérieur de la cavité formée par le ligand, bien que la cinétique de complexation des actinides (IV) soit plus lente que celle des actinides(III). L'étude des complexes thorium(IV)-DOTA montre la présence de complexes de stœchiométrie 1:1 et 1:2 en solution, pour lesquels seules les fonctions carboxylate du ligand seraient impliquées dans la complexation.Enfin, une première estimation de la constante de stabilité des complexes plutonium(IV)-DOTA, effectuée par des mesures électrochimiques, indique que les complexes d'actinides(IV) sont environ 10 ordres de grandeurs plus stables que les complexes d'actinides(III), comme ce qui a pu être observé avec d'autres polyaminocarboxylates
The polyaminocarboxylate anions have been identified as compounds of interest in the operations of actinide separation, in actinide migration in the environment and in human radiotoxicology. The structural characterization of complexes formed between actinides and polyaminocarboxylates ligands is essential for a better understanding of actinide-ligands interactions. Among the polyaminocarboxylate anions, the DOTA ligand (1,4,7,10-tetraazacyclododecane tetraacetic acid) is described as a very strong complexing agent of the lanthanides(III), but has been little studied with actinides. The objective of this thesis is to describe the complexes formed between the actinides (III) and (IV) and the DOTA ligand, and compare them with the lanthanide complexes. For this, an approach has been introduced to characterize the complex by complementary analytical techniques (spectrophotometry, electrospray ionization mass spectrometry, NMR, EXAFS, electrochemistry), but also by calculations of theoretical chemistry to help the interpretation of the experimental data. The formation of a 1:1 complex is observed with the actinides(III) (plutonium and americium) as in the case of lanthanides(III): rapid formation of intermediate species which evolves slowly towards the formation of a limit complex. Within this complex, the cation is located inside the cavity formed by the ligand. Four nitrogen atoms and oxygen atoms from the carboxylate functions are involved in the coordination sphere of the cation. However, differences were observed in the bond lengths formed between the cation and the nitrogen atoms (the bonds are somewhat shorter in the case of actinide complexes) as well as the complexation kinetics, which is slightly faster for the actinides(III) than for lanthanide(III) ions of equivalent radius. The same behavior was observed in solution upon complexation of actinides(IV) (uranium, plutonium and neptunium): slow formation of a 1:1 complex (actinide(IV):ligand) in wherein the cation is located inside the cavity formed by the macrocycle DOTA, although the kinetics of actinide(IV) complexation is slower than for the actinides(III) complexation. Nevertheless, the study of thorium(IV)-DOTA complexes shows differences since 1:1 and 1:2 complexes in solution are detected, and where only the carboxylate functions are involved in the coordination sphere of the cation. Finally, an initial estimate of the stability constant of the plutonium(IV)-DOTA complexes by electrochemical measurements indicates that complexes of actinide(IV) are approximately 10 orders of magnitude more stable than the complex of actinides(III), as previously observed with other polyaminocarboxylate anions

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Deak, Noémi. "Ligands soufrés (IV)/(VI) de type pince pour la stabilisation des métallylènes : synthèse, caractérisation et applications." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30393/document.

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Ce travail de thèse présente la synthèse, la caractérisation et la réactivité de métallylènes stabilisés par différents ligands pinces fonctionnalisés par des substituants soufrés à différents états d'oxydation. Les métallylènes, analogues lourds des carbènes, présentent dans leur état fondamental singulet une paire d'électrons et une orbitale p vacante. Ces caractéristiques donnent à ces espèces un comportement et une réactivité particulière. La littérature décrit de nombreux exemples de métallylène stabilisés par différents types de ligands, parmi lesquels les ligands de type pince gagnent actuellement en importance. Dans la chimie des complexes de métaux de transition, il a déjà été démontré que les ligands de type pince constituent un type de plateforme efficace grâce aux possibilités de modulation des propriétés des complexes liées à la modulation du squelette du ligand. Au cours des dernières décennies, ces ligands se sont révélés efficaces pour la stabilisation de métallylènes stables. Cependant, un seul exemple de métallylène stabilisé par un ligand de type pince contenant du soufre a été reporté dans la littérature. Au cours de cette étude, des ligands pinces O,C,O chélatants contenant des groupement sulfonyles et sulfinyles ont été conçus, synthétisés et complètement caractérise par les méthodes physico-chimiques et computationnelle et leurs effets sur la stabilisation des métallylènes ont été étudiés. Dans un premier temps, un ligand pince de type bis-sulfone a été obtenu et étudié pour la synthèse de nouveaux métallylènes. A partir de ce ligand, un germylène et un stannylène ont été caractérisés, le germylène étant le premier exemple dans la littérature d'une espèce de germanium divalente stabilisée par un ligand pince de donneur d'oxygène. La réactivité des métallylènes a été testée pour obtenir des produits de cycloaddition avec l'ortho-benzoquinone et des complexes des métaux de transition (fer et tungstène). Il a été démontré que la bis-sulfone se comporte comme un ligand ajustable de type pince O,C,O-chélatant, la coordination pouvant être possible par l'un ou l'autre des atomes d'oxygène des groupements sulfonyles. [...]
This work presents the synthesis, characterization and reactivity of metallylenes stabilized by different functionalized pincer ligands with substituents containing sulfur atoms in different oxidation states. Metallylenes, the heavier analogues of carbenes, have in their singlet ground state a lone pair of electron and a vacant p orbital. These features give the particular behavior and reactivity of these species. The literature describes many examples of metallylenes stabilized by different types of ligands, among which lately the pincer type ligands are gaining importance. In the chemistry of transitional metal complexes it was shown for a long time that the pincer-type ligands are a versatile ligand platform thanks to the possibilities of modulating the properties of the complexes through small changes of the ligand backbone. In the last few decades these ligands proved to be effective for obtaining stable metallylenes. However, in the literature there is one sole example of metallylene stabilized through sulfur containing pincer-type ligands. For this study, para substituted sulfonyl and sulfinyl containing O,C,O-chelating pincer ligands were designed, synthesized and completely characterized by the physico-chemical and computational methods and their effects on the stabilization of metallylenes was investigated. First, a bis-sulfone pincer ligand was obtained and studied for the synthesis of novel metallylenes. With this ligand a germylene and stannylene were obtained and characterized, the germylene being the first example in the literature of a divalent germanium species stabilized by an oxygen donor pincer ligand. The reactivity of the metallylenes was tested for obtaining cycloadducts with ortho-benzoquinone and transition metal complexes (iron and tungsten). It was shown that the bis-sulfone behaves as an adjustable O,C,O-chelating pincer type ligand, the coordination could be possible with either one of the oxygen atoms of the sulfonyl groups. [...]

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Cleary, Brian P. "Structural aspects of bis(quadridentate)zirconium(IV) complexes. Ligand motion and ligand exchange behavior of bis(N, N'-disalicylidene-1,2-phenylenediamino)zirconium(IV) and the two new complexes bis(N, N'-disalicylidene-cis-1,2-diamino-cyclohexane)-zirconium(IV) and bis(N, N''-disalicylidene-trans-1,2-diaminocyclhexane)zirconium(IV) /." Online version of thesis, 1989. http://hdl.handle.net/1850/11434.

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Chupin, Geoffroy. "Etude de la formation en solution de clusters de plutonium (IV) en présence du ligand acétate." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2022. http://theses.enscm.fr/ENSCM_2022_CHUPIN.pdf.

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Les clusters d’An(IV) sont des molécules à plusieurs centres métalliques reliés entre eux par des groupes oxo et/ou hydroxo en solution aqueuse (le ceur). Ces espèces se forment en présence d’eau par des réactions de condensation, et sont stabilisées par des ligands organiques ou inorganiques (en surface). Si les structures des clusters sont souvent décrites à l’état solide, elles le sont beaucoup moins en solution. La plupart des clusters observés en solution sont des clusters hexamèriques à géométrie octaédrique, complexés à des ligands à fonction carboxylate. Si quelques données existent pour les clusters hexamériques de Th(IV), U(IV) et de Np(IV) en solution, très peu d’informations sont rapportées sur le Pu(IV). Les données thermodynamiques et cinétiques sur la formation des clusters en solution sont rares. Il en résulte que les clusters ne sont pas pris en compte dans les modèles de spéciation. L’objectif de la thèse est l’étude en solution des clusters de Pu(IV) en présence d’un ligand carboxylate simple, le ligand acétate.Afin d’identifier l’ensemble des espèces susceptibles de se former en solution, le Pu(IV) en présence d’acétate a d’abord été caractérisé par spectroscopie d’absorption Vis-NIR. Huit espèces différentes ont pu être identifiées par spectroscopie Vis-NIR : trois cations aquo (Pu3+, Pu4+ et PuO22+) et cinq espèces d’acétate de Pu(IV). Ces cinq espèces ont ensuite été caractérisées en couplant des approches expérimentales (Vis-NIR, EXAFS et ESI-MS) et théorique par calcul de chimie quantique (DFT). Le cluster hexamérique octaédrique Pu6O4(OH)4(AcO)12(H2O)12 a été identifié en solution. Cette espèce était la structure manquante des clusters hexamèrique An6O6(OH)4(AcO)12 des An(IV). Les quatre autres espèces qui l’accompagnent sont proposées comme étant des complexes « classiques » monomériques. Connaissant les espèces d’acétates de Pu(IV) formées en solution, leurs fractions ont pu être évaluées par déconvolution et reportées sur un diagramme de distribution des espèces en pL
An(IV) clusters are multiple metallic centers molecules, were actinide atoms are linked by oxo or hydroxo groups. Those species are formed by condensation reactions with water. They are stabilized thanks to organic or inorganic ligands. If the structures of the clusters are well known at solid state, this is not the case in solution. Hexameric cluster with an octahedral shape core is the main structure detected in solution. This structure is stabilized by ligand with carboxylate functions. Information exists for Th(IV), U(IV) and Np(IV) hexanuclear in solution, but few studies are reported for Pu(IV). Thermodynamic and kinetic data on the formation and the stability of the cluster are scarce. Consequently, clusters are not taken into account for speciation diagram. The goal of this work is to study the plutonium clusters behavior in solution with a simple carboxylate ligand, acetate.In order to detect all potentially formed, plutonium with acetate species solutions were first characterized by Vis-NIR absorption spectroscopy. Large variations of pH and acetate concentrations were used and eight different species are identified : three aquo cations (Pu3+, Pu4+, PuO22+) and five plutonium complexes with acetate. Those five acetate complexes were characterized by coupling experimental (Vis-NIR and EXAFS spectroscopy and ESI-MS spectrometry) and theoretical approach through quantum chemistry. As a result, Pu6O4(OH)4(AcO)12(H2O)12 hexameric cluster has been identified, the missing bloc in the An(IV) series with formate, acetate ligands. The four other complexes are are attributed to plutonium acetate monomeric complexes. Species of Pu(IV) with acetate being described, their fractions in solution are evaluated and reported on a speciation diagram on the pL axis

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18

Loukova, G. V., V. V. Vasiliev, V. L. Ivanov, M. Ya Melnikov, V. A. Smirnov, and E. E. Melnichuk. "Two−photon Processes in Organometallic Molecules and Clusters: T−T Absorption of Group IV Metal Complexes." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35395.

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Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35395

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Patel, Dharmesh J. "Biomimetic Studies of Oxidation Reactions by Metalloporphyrins through Ligand Effect and Kinetic Studies of Photo-Generated Porphyrin-Iron(Iv)- Oxocompound II Models." TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2091.

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High-valent iron(IV)-oxo porphyrins are the central oxidizing species in hemecontaining enzymes and synthetic oxidation catalysts. Many transition metal complexes have been extensively studied as models of the ubiquitous cytochrome P450 enzymes to probe the sophisticated oxygen atom transfer (OAT) mechanism as well as to invent enzyme-like oxidation catalysts. In this work, two metalloporphyrin complexes have been successfully synthesized, and spectroscopically characterized. A new photochemical entry to porphyrin-iron(IV)-oxo derivatives, commonly referred to as compound II models, was also investigated in two porphyrin ligands that differ in electronic and steric environments. As determined by their distinct UV-vis spectra and kinetic behaviors, iron(IV)-oxo porphyrins [FeIV(Por)O] were successfully produced by visible light irradiation of highly photo-liable porphyrin-iron(III) bromates. The iron(IV)-oxo porphyrins investigated in this study include 5,10,15,20- tetra(pentafluorophenyl)porphyrin-iron(IV)-oxo (4a), and 5,10,15,20-tetra(2,6- difluorophenyl)porphyrin-iron(IV)-oxo (4b).

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20

Haas, Isabelle [Verfasser], and Rhett [Akademischer Betreuer] Kempe. "Novel N-Ligand Stabilized Transition Metal Complexes of the Group IV Triad as Efficient Catalysts for Polymerization and Oligomerization / Isabelle Haas. Betreuer: Rhett Kempe." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/106000948X/34.

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21

Bion, Lionel. "Étude de la stabilisation de l'uranium (IV), par formation d'un complexe avec un ligand hétéropolyanion, en vue de son analyse différée dans le temps /." Gif-sur-Yvette : Service de documentation et d'édition multimédia, Centre d'études de Saclay, 1995. http://catalogue.bnf.fr/ark:/12148/cb35814052v.

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22

Aydin, Juhanes. "Novel Pincer Complex-Catalyzed Transformations : Including Asymmetric Catalysis." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8524.

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This thesis is focused on the development of new pincer complex-catalyzed transformations. Optimization of the catalytic properties (fine-tuning) was directed to increase the catalytic activity as well as the chemo-, stereo- and enantioselectivity of the complexes. This was achieved by varying the heteroatoms in the terdentate pincer ligand, by changing the electronic properties of the coordinated aryl moiety and by implementing chiral functionalities in the pincer complexes. In the cross-coupling reaction of vinyl epoxides and aziridines with organoboronic acids the chemoselectivity of the reaction could be increased by employment of pincer complexes instead of commonly used Pd(0) catalysts. Furthermore, the introduction of a methoxy substituent in the aromatic subunit of the complex considerably increased the activity of the pincer complex catalyst. Fine-tuning of the enantioselectivity in electrophilic allylation reactions was achieved by using a wide variety of new BINOL- and biphenanthrol-based pincer complexes. The highest enantioselectivity (85% ee) was obtained by applying biphenanthrol-based pincer complexes. Stereoselective pincer complex-catalyzed condensation of sulfonylimines with isocyanoacetate could be achieved under mild reaction conditions. By application of chiral PCP catalysts, 2-imidazolines could be obtained with up to 86% ee. A new pincer complex-catalyzed C-H bond functionalization based reaction between organonitriles and sulfonylimines affords homoallylic amines and beta-aminonitriles in high yields. The asymmetric version of this process affords beta-aminonitriles with up to 71% ee. In the last chapter, a pincer complex-catalyzed redox coupling reaction is described. In this highly regio- and stereoselective process the integrity of the pincer catalysts is fully retained. This catalytic reaction proceeds with a high level of functional group tolerance, as allylic acetate and aryl halide functionalities are retained.

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23

Charbonnel, Marie-Christine. "Extraction de l'uranium (vi), du plutonium (iv) et des produits de fission par les n,n'-tetraalkyldiamides." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21116.

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Etude des proprietes extractives de r::(2)nc(o)(ch::(2))::(3) c(o)nr::(2). Ces composes extraient u(vi) et pu(iv), les actinides et lanthanides trivalents restant en phase aqueuse. Mise en evidence des 3 complexes 2l. Hno::(3), l. Hno::(3) et l. 2hno::(3) (l-glutaramide). A faible acidite, on a pu observer les complexes l. Uo::(2)(no::(3))::(2) et l. Pu(no::(3))::(4) et a forte acidite l. Uo::(2)(no::(3))::(3)h et l. Pu(no::(3))::(6)h::(2)

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Iraqi, Ahmed. "Nouveaux complexes d**(0)-d**(8) zirconium(iv)-rhodium(i) catalyseurs d'hydroformylation des olefines : composes hydrures et composes cationiques." Toulouse 3, 1988. http://www.theses.fr/1988TOU30055.

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25

Darbieu, Marie-Hélène. "Complexes modeles de la methylcobalamine (meb12) : comportement de la liaison co-c en presence de derives de l'etain iv." Toulouse 3, 1987. http://www.theses.fr/1987TOU30148.

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26

Canete, Kausel Elisa. "Centro Penal Femenino en Vicuña-IV región: lugar, recursos, trabajo y rehabilitación : propuesta para mitigar el modelo tradicional de arquitectura penal ligado al castigo y marginación : Vicuña, Provincia Del Elqui, Coquimbo, Chile." Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/150018.

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27

Mathieu, Ludovic. "Cycle thorium et réacteurs à sel fondu : exploration du champ des paramètres et des contraintes définissant le "Thorium Molten Salt Reactor"." Phd thesis, Grenoble INPG, 2005. http://tel.archives-ouvertes.fr/tel-00010791.

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Le recours à l'énergie électronucléaire pour diminuer les émissions anthropiques de CO2 nécessite des avancées technologiques majeures. Les réacteurs nucléaires de IVe génération doivent répondre à plusieurs contraintes, telles qu'une sûreté améliorée, la régénération du combustible et la minimisation de la production de déchets radioactifs. De ce point de vue, l'utilisation du Cycle Thorium en Réacteurs à Sel Fondu semble prometteuse. Cet axe de recherche, étudié dans le passé, avait cependant débouché sur un concept dont les défauts ont empêché la réalisation. Une nouvelle réflexion est menée afin de trouver des solutions et d'aboutir au concept de Thorium Molten Salt Reactor. Le couplage d'un code de transport de neutrons avec un code d'évolution des matériaux permet de simuler le comportement d'un coeur nucléaire, et de suivre son évolution tout au long de sa vie. Par cette méthode, nous avons étudié un large éventail de configurations de réacteurs. Les performances de ces systèmes ont été évaluées, grâce à un jeu de contraintes qu'ils doivent satisfaire au mieux. Ce travail a permis de comprendre bon nombre de phénomènes physiques régissant le comportement de ces réacteurs. Grâce à cette nouvelle compréhension, la recherche de configurations acceptables a pu aboutir à des solutions satisfaisantes, apportant un souffle nouveau dans le domaine des Réacteurs à Sel Fondu.

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28

Lachkar, Mohammed. "Contribution a l'etude de nouveaux complexes sandwich a base de phtalocyanines et de porphyrines de cerium trois et quatre." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13074.

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Synthese et caracterisation du premier biplan mixte phtalocyamine porphyrine de cerium. Etude de ce compose par voltammetrie cyclique. Synthese du premier triplan mixte phtalocyamine bis-porphyrines-bis cerium, et de la bis -phtalocyamine de cerium

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29

Andreae, Jörn [Verfasser]. "Molekulargenetische Analyse des DNA-Ligase IV-Gens bei Kindern mit akuter lymphoblastischer Leukämie / von Jörn Andreae." 2006. http://d-nb.info/981858953/34.

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30

Lun, Melody. "Regionalized choroid plexus-cerebrospinal fluid factors and effect of DNA Ligase IV deficiency in the developing mammalian brain." Thesis, 2016. https://hdl.handle.net/2144/19054.

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Fundamental to mammalian brain development is the integration of cell intrinsic and extrinsic signals that direct the proliferation and differentiation of neural stem cells. Precise expression of transcription factors together with other intracellular components instruct progenitor cell fate, whereas interaction with extracellular signaling factors refines this process. We have elucidated the composition of the cerebrospinal fluid that is the source of multiple extrinsic cues during brain development. The choroid plexus, a highly vascularized tissue located in each ventricle of the brain, actively secretes cerebrospinal fluid. By RNA sequencing, we obtained transcriptome data on the choroid plexi from lateral and fourth ventricles of the mouse brain and discovered that they include transcripts unique to each tissue. Transcription factor expression in the macaque and human choroid plexi suggests that positional identities of these tissues are conserved in the primate brain. Based on transcriptional results, we defined the choroid plexus secretome, a prediction of secreted factors from the choroid plexus. By quantitative mass spectrometry, we detected proteins secreted by each choroid plexus, and comparison of these proteomic results with transcriptional profiling suggests that choroid plexus transcriptomes contribute to availability of regionalized cerebrospinal fluid factors during development. In the second part of my dissertation research, I studied the role of DNA repair mechanisms in regulating neural stem cells. These studies focused on DNA LigaseIV, an essential component of DNA double-stranded break repair, during cerebral cortical development. Deficiency of LigaseIV activity caused by a missense mutation leads to LigaseIV syndrome, in which a key clinical feature is microcephaly. Using the Lig4 R278H mouse mutant, we found increased cell death in the developing cortex, contributing to reduced cortical thickness and cellularity in the anterior cerebral cortex. These results indicate that DNA LigaseIV is essential for proper cortical development. Together, these findings illustrate the complexity of regulatory mechanisms that guide brain development, requiring the integration of mechanisms from within and outside the cell. We have investigated two such mechanisms, extrinsic cues from regionalized cerebrospinal fluid and DNA LigaseIV. These results should provide greater insight into mechanisms of normal brain development and neuropathological states.
2017-11-02T00:00:00Z

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31

Lemos, Sónia Cristina Gaspar de. "Imunodeficiências primárias e neoplasias hematológicas: quando investigar?" Master's thesis, 2014. http://hdl.handle.net/10316/37429.

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32

Wong-Foy, Antek Golangco. "Ancillary Ligand Effects in Zirconium(IV) Aminoborollide and Nitrogen Chelated Pt(II) Complexes." Thesis, 2002. https://thesis.library.caltech.edu/6900/1/Wong-Foy_ag_2002.pdf.

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The preparation of new chloro derivatives of pentamethylcyclopentadienyl aminoborollide complexes of Zr are described. Treatment of the dianions 1.9-1.12 with Cp*ZrCl_3 yields Cp*{η^5-C_4H_4BN(Si(CH_3)_3)_2}ZrCl•LiCl (1.13), Cp*{η^5-C_4H_4BNC(CH_3)_3Si(CH_3)_3}ZrCl•Li•CI (1.14). |Cp*{η^5-C_4H_4BN(Et)CH_2CH_2Net_2}ZrCl_2Li]_2 (1.15), and Cp*{η^5-2,5-Ph_2C_4H_2BNMe_2}ZrCl•LiCl (1.16). The electronic spectra of these complexes were measured and compared to the parent complex Cp*{η^5-C_4H_4BN(CHMe_2)_2}ZrCl•LiCl (1.17a) in THF solvent. In general, as the substituents directly bonded to nitrogen increase in size, a blue shift of the low energy, aminoborollide to zirconium charge transfer band (LMCT), occurs. λ_(max) decreases in the order 1.16 > 1.17a > 1.14 > 1.15 ~ 1.13. The anionic portions of complexes 1.13-1.16 have also been structurally characterized by x-ray crystallography. Although the changes are very small, in general a lengthened B-N bond correlates linearly with the observed blue shift of the LMCT band.

Studies directed towards the development of a Pt(II)-catalyzcd oxidation of ethylene to ethylene glycol based on the Shilov system for alkane functionalization is described. The first step is the activation of ethylene towards nucleophilic attack by water to generate a Pt(II) β-hydroxyalkyl intermediate that is oxidized in a second step to the Pt(IV) β-hydroxyalkyl. Reductive elimination via an S_N2-type mechanism at the α-C of the Pt(IV) β-hydroxyalkyl liberates the oxidized product leaving the reduced Pt(II) center to bind another equivalent of olefin. The first system examined was the methyl ethylene complex [(tmeda)PtMe(η^2-C_2H_4)][SbF_6,], 2.2. Nucleophilic attack at the bound ethylene was not observed: instead displacement of ethylene occurred. The bound ethylene in the neutral complexes cis-Cl_2PtL(η^2-C_2H_4), (L =PPh_3 (2.23), AsPh_3 (2.24), Me_2SO (2.25)) and trans-Cl_2Pt(η^2-C_2CH_4)(C_5H_5N). 2.26 arc susceptible towards attack by OH-. Under catalytic conditions (excess ethylene and H_2O_2) decomposition of 2.23, 2.24, and 2.25 was observed. In 2.26, 1 turnover was observed before decomposition occurred. The hound ethylene in the complex [(tmeda)PtCl(η^2-C_2H_4)][ClO_4] is activated towards nucleophilic attack by water and OH-, allowing the isolation of the Pt(II) β-hydroxyalkyl. This is rapidly oxidized to the Pt(IV) β-hydroxyalkyl by hydrogen peroxide. In the presence of HCl, it undergoes reductive elimination to yield 2-chlorocthanol and (tmeda)PtCl_2. Unfortunately, this system also showed no catalytic activity.

The dicationic complexes (|(ArN=C(Me)-C(Me)=NAr)Pt(solv)_2 |X_2. (Λr = 2.6-(CH_3)_2C_6,H_3: 3.5a: solv = CH_3CN, X = CF_3SO_3-, BF_4-, SbF_6-; 3.5b: solv = (CH_3)_2CO, X = BF_4-, SbF_6-,) and 3.6 [(CyN=C(H)-C(H)=NCy)Pt(CH_3CN)_2]X_2, (Cy = C_6H_(11) , X= OTf, BF_4-, Pf_6-, SbF_6-) were synthesized from the corresponding Pt dichlorides with 2 equiv. of AgX. The reaction of 3.5a with 1-phenylpyrazole, 2-phenylpyridine, 2-vinylpyridine, and 2-(2-thienyl)pyridine in acetone affords the cyclometalation products 3.11-3.14 via intramolecular C-H activation of an sp^2 C-H bond of the unsaturated sidegroup. Pyridines with saturated groups at the 2-position do not undergo a similar cyclomctalation reaction. 3.6 undergoes cyclometalation of one of the cyclohexyl groups, an example of sp^3 C-H bond activation. The later reaction proceeds only partway to completion, implying that an equilibrium has been reached: in the case where X = OTf, the equilibrium favors the starting dication. Furthermore, the intramolecular C-H activation occurs in trifluoroethanol but not in acetone under comparable conditions in contrast to the reactions of 3.5a with the substituted pyridines.

The diaqua complexe [(ArN=C(Me)-C(Me)=NAr)Pt(H_2O)_2]X_2, 4.3. (Λr = 2.6-(CH_3)_2C_6H_3; X = OTf^-, BF_4^-) decompose in aqueous solution to yield a red-orange precipitate. Spectroscopic characterization of the precipitate by ^1H, IR, and conductivity measurements is consistent with C_(2v), symmetric structure containing hydroxo groups. Confirmation of the dicationic, dinuclear Pt(II) complex, 4.4, where the two Pt centers are bridged by two OH groups was revealed by x-ray crystallography.

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33

Hatwell, Karen Rachel. "The kinetics of ligand exchange of seven-coordinate molybdenum(IV) and eight-coordinate europium(III) compounds." 1999. https://scholarworks.umass.edu/dissertations/AAI9950158.

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This research involves three projects. The first area includes research on the kinetics of ligand exchange for three molybdenum(IV) compounds. The second area entails the kinetics and mechanisms of the dissociation of tetradentate Schiff-base compounds with europium(III). The third area shows attempts of the polymerization of Na[Eu(dshp)2]. The molybdenum(IV) compounds studied contained the ligands 5,7-dicholor-8-hydroxyquinolinol and the chloride ion. The compounds were reacted in methylene dichloride with either more 5,7-dicholoro-8-hydroxyquinolinol or picolinic acid. The kinetics of the ligand exchange reactions were followed using absorption data following changes in the spectra. Reaction rates and activation parameters were found for the three reactions studied. Studies of the reaction rate as a function of concentration show that the reactions are dissociative in nature. The second part of this research involved the dissociation of europium(III) and yttrium(III) coordination compounds with salen and its derivatives in dimethyl sulfoxide. This reaction is followed by monitoring the decrease of europium(III) compound emission peaks and the growth of ligand emission as well as by absorption spectral changes. The reaction rates, activation energy, and reaction mechanism information were obtained for this exchange using the emission and absorption data. Several conclusions were made for this study of solvent insertion into the compound. Firstly, this reaction is not affected by light. Secondly, the solvent can affect the kinetics in that dimethyl formamide and dimethyl sulfoxide are rate increasing solvents compared to water. Thirdly, the 2 to 3 compounds have generally a faster rate than the 1 to 2 compounds and the reactions. And fourthly, the compounds with a six-member chelating ring and an electron-withdrawing hydroxyl group are more kinetically stable than those with five member chelating rings. The final part of this research involved the polymerization of Na[Ln(dshp)2], where Ln = Y, Eu, with isophthalolyl chloride and terephthalolyl chloride. The resulting compounds were then analyzed and emission data measured for the europium species. However, the results did not support the formation of polymers.

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Hsu, Jia-Wei, and 許家緯. "Croup IV Metal Complexes Containing Symmetric and Asymmetric Pincer Type Tridentate Ligand. Synthesis, Characterization and Ethylene Polymerization Studies." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/31544915293707922851.

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碩士
國立彰化師範大學
化學系
99
A series of zirconium and hafnium complexes containing symmetric and asymmetric tridentate substituted pyrrolyl ligand have been synthesizd and characterized. The zirconium compounds Zr[C4H2N(2-CH2NtBu)(5-CH2NMe2)](NR2)2 (4, R = Me；5, R = Et) have been prepared by reacting M(NR2)4(1, M = Zr，R = Me；2, M = Zr，R = Et) with 1 equiv of [C4H2NH(2-CH2NHtBu)(5-CH2NMe2)] in heptane via deamination. MCl[C4H2N(2-CH2NHtBu)(5-CH2NMe2)][C4H2N(2-CH2N-tBu)(5-CH2NMe2)](6, M = Zr；7, M = Hf) have been prepared by reacting M(NEt2)4 (2, M = Zr 3, M = Hf) with 2 equiv of [C4H2NH(2-CH2NHtBu)(5-CH2NMe2)] in CH2Cl2 via deamination, and Zr[C4H2N(2-CH2NtBu)(5-CH2NHtBu)](NMe2)2(12) have been prepared by reacting 1 with 1 equiv [C4H2NH(2,5-CH2NHtBu)] in ether via deamination. The insertion reaction of PhNCO, PhNCS and CS2 with complexes 4, 5 and 12 have been studied. The zirconium compounds Zr[C4H2N(2-CH2NtBu)(5-CH2NMe2)][PhNC(NR2)O](NR2)(8, R = Me；9, R = Et) have been prepared by reacting 4 and 5 with 1 equiv PhNCO in ether. Zr[C4H2N(2-CH2NtBu)(5-CH2NMe2)][PhNC(NMe2)S](NMe2)(10) have been prepared by reacting 4 with 1 equiv PhNCS in ether. Zr[C4H2N(2-CH2NtBu)(5-CH2NHtBu)][CS(NMe2)C](NMe2)(13) have been prepared by reacting 12 with 1 equiv CS2 in ether, and Zr[C4H2N(2-CH2NHtBu)(5-CH2NMe2)][PhNC(NEt2)O]3(11) have been prepared by reacting 5 with 2 equiv PhNC(NEt2)OH in ether. All the new compounds were characterized by 1H and 13C NMR spectroscopy and the structures of 6, 7 , 10, 11 and 13 have also been determined by X-ray crystallographic studies. Complexes 5, 6, 8 and 12 have been studied as olefin polymerization of ethane.

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35

Zhong, Hong A. "Ancillary ligand effects : from zirconium(IV)-catalyzed homogeneous propylene polymerization to platinum(II)-mediated C-H bond activation." Thesis, 2001. https://thesis.library.caltech.edu/8167/1/ZHONG%202001.pdf.

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A series of C_s- and C₁-symmetric doubly-linked ansa-metallocenes of the general formula {1,1'-SiMe₂-2,2'-E-('ƞ⁵-C₅H₂-4-R¹)-(ƞ⁵-C₅H-3',5'-(CHMe₂)₂)}ZrC₂ (E = SiMe₂ (1), SiPh₂ (2), SiMe₂ -SiMe₂ (3); R¹ = H, CHMe₂, C₅H₉, C₆H₁₁, C₆H₅) has been prepared. When activated by methylaluminoxane, these are active propylene polymerization catalysts. 1 and 2 produce syndiotactic polypropylenes, and 3 produces isotactic polypropylenes. Site epimerization is the major pathway for stereoerror formation for 1 and 2. In addition, the polymer chain has slightly stronger steric interaction with the diphenylsilylene linker than with the dimethylsilylene linker. This results in more frequent site epimerization and reduced syndiospecificity for 2 compared to 1.

C₁-Symmetric ansa-zirconocenes [1,1 '-SiMe₂-(C₅H₄)-(3-R-C₅H₃)]ZrCl₂ (4), [1,1 '-SiMe₂-(C₅H₄)-(2,4-R₂-C₅H₂)]ZrCl₂ (5) and [1,1 '-SiMe₂-2,2 '-(SiMe₂-SiMe₂)-(C₅H₃)-( 4-R-C₅H₂)]ZrCl₂ (6) have been prepared to probe the origin of isospecificity in 3. While 4 and 3 produce polymers with similar isospecificity, 5 and 6 give mostly hemi-isotactic-like polymers. It is proposed that the facile site epimerization via an associative pathway allows rapid equilibration of the polymer chain between the isospecific and aspecific insertion sites. This results in more frequent insertion from the isospecific site, which has a lower kinetic barrier for chain propagation. On the other hand, site epimerization for 5 and 6 is slow. This leads to mostly alternating insertion from the isospecific and aspecific sites, and consequently, a hemi-isotactic-like polymers. In comparison, site epimerization is even slower for 3, but enchainment from the aspecific site has an extremely high kinetic barrier for monomer coordination. Therefore, enchainment occurs preferentially from the isospecific site to produce isotactic polymers.

A series of cationic complexes [(ArN=CR-CR=NAr)PtMe(L)]⁺[BF₄]⁺ (Ar = aryl; R = H, CH₃; L = water, trifluoroethanol) has been prepared. They react smoothly with benzene at approximately room temperature in trifluoroethanol solvent to yield methane and the corresponding phenyl Pt(II) cations, via Pt(IV)-methyl-phenyl-hydride intermediates. The reaction products of methyl-substituted benzenes suggest an inherent reactivity preference for aromatic over benzylic C-H bond activation, which can however be overridden by steric effects. For the reaction of benzene with cationic Pt(II) complexes, in which the diimine ligands bear 3,5-disubstituted aryl groups at the nitrogen atoms, the rate-determining step is C-H bond activation. For the more sterically crowded analogs with 2,6-dimethyl-substituted aryl groups, benzene coordination becomes rate-determining. The more electron-rich the ligand, as reflected by the CO stretching frequency in the IR spectrum of the corresponding cationic carbonyl complex, the faster the rate of C-H bond activation. This finding, however, does not reflect the actual C-H bond activation process, but rather reflects only the relative ease of solvent molecules displacing water molecules to initiate the reaction. That is, the change in rates is mostly due to a ground state effect. Several lines of evidence suggest that associative substitution pathways operate to get the hydrocarbon substrate into, and out of, the coordination sphere; i.e., that benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway.

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Šormová, Lucie. "Analýza mutací v oblastech MLBR /Major Ligand Binding Regions/ genu COL1A1 u českých osob s diagnózou Osteogenesis imperfecta, typ I-IV." Master's thesis, 2010. http://www.nusl.cz/ntk/nusl-301857.

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Osteogenesis imperfecta is an inherited disorder caused mainly by collagen type I genes mutations, COL1A1 and COL1A2. These mutations affect especially connective tissue. Disease is characterized by fragile bones, deformations and increased frequency of fractures. It's worldwide extensive disorder regardless of age, sex, nationality or races. The incidence is 1: 16 - 20 000 births. Currently, we described nine clinically distinct forms of Osteogenesis imperfecta. Only the first four types OI, type I-IV, are caused by collagen type I genes mutations . In these nine types there are distinguished mild and severe forms. Type II and III are lethal forms, death occur offen during prenatal period or in the first days of the life affected individuals. Characteristic clinical features of collagen forms OI are an increased incidence of fractures, deformations of bones, blue sclera, hearing loss, Dentinogenesis imperfecta small or subnormal growth (Marini, 2010). This study alignment is mainly the description of the clinical forms, exploring the molecular basis of disease and determine the relationship between the type and position of the mutation and the resulting phenotype of affected individuals. We have analysed exons 31-40, including associated non-coding regions, of the COL1A1 gene (so-called MLBR =...

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Ménard, Liliane. "Effet du CP-3(iv), un ligand du récepteur CD36, sur le stress oxydatif suite à une ischémie cardiaque transitoire chez la souris." Thèse, 2015. http://hdl.handle.net/1866/14043.

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Le récepteur éboueur CD36 facilite l’internalisation des acides gras libres non estérifiés (AGNE) au niveau des tissus cardiaque et périphériques. Lors d’une ischémie-reperfusion du myocarde (MI/R), les dommages produits sont en partie liés à l’internalisation des AGNE et à la production d’espèces réactives de l’oxygène, contrairement à ce qui est observé chez des souris déficientes en CD36 (CD36-/-). Nous avons émis l’hypothèse selon laquelle le CP-3(iv), un ligand synthétique du récepteur CD36, exercerait un effet cardioprotecteur en réduisant la taille de la zone myocardique infarcie lors d’une ischémie transitoire du myocarde. Nos objectifs étaient 1) de déterminer l’effet cardioprotecteur du CP-3(iv) et 2) de définir son mécanisme. Pour cela, des études in vivo et ex vivo ont été faites. Des souris de type sauvage ont été traitées avec le CP-3(iv) (289 nmol/kg) par voie sous-cutanée pendant 14 jours avant d’être soumises à 30 minutes d’ischémie suivant la ligature de l’artère coronaire gauche descendante et de sa reperfusion pendant une période de 6 ou 48 heures. De plus, des coeurs isolés de souris ont été perfusés 30 minutes, suivi de 40 minutes à faible débit (10%) et de 30 minutes de reperfusion pendant laquelle le coeur est perfusé avec le CP-3(iv) à une concentration de 10-6 M. Nos travaux ont montré que l’effet cardioprotecteur d’un traitement préventif par le CP-3(iv) permet de diminuer la taille de l’infarctus et préserve l’hémodynamie cardiaque de façon dépendante du CD36 puisque cet effet est non visible chez les souris CD36-/-. De plus, le CP-3(iv) exerce non seulement un effet systémique, mais aussi un effet cardioprotecteur direct sur le coeur isolé.
The scavenger receptor CD36 facilitates the internalization of non-esterified fatty acids (NEFA) on cardiac and peripheral tissues. During myocardial ischemia and reperfusion (MI/R), the damage induced is in part related to the internalization of NEFA and the production of reactive oxygen species, in opposition to what is observed in CD36-deficient mice (CD36-/-). We hypothesized that CP-3(iv), a synthetic ligand of the CD36 receptor, provides a cardioprotective effect by reducing the infarct area during a transient myocardial ischemia. Our objectives were 1) to determine the cardioprotective effect of CP-3(iv) and 2) to define its mechanism. For this, in vivo and ex vivo studies have been done. Wild-type mice were treated with CP-3(iv) (289 nmol/kg) subcutaneously during 14 days before being submitted to 30 minutes of ischemia following left anterior descending coronary artery ligature and reperfusion for a period of 6 to 48 hours. In addition, isolated mouse hearts were perfused 30 minutes, followed by 40 minutes with low flow (10%) and 30 minutes of reperfusion during which the heart is perfused with CP-3(iv) at a concentration of 10-6 M. Our work has shown that the cardioprotective effect of preventive treatment with CP-3(iv) reduces the infarct size and preserves cardiac hemodynamics in a CD36-dependent manner because this effect is not visible in CD36-/- mice. In addition, CP-3(iv) not only exerts a systemic effect, but also a direct cardioprotective effect on the isolated heart.

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Harp, John Robert. "Naive and memory T cell trafficking in selectin ligand-deficient mice: the role of fucosyltransferase –IV and –VII in the differential migration of T cell populations." 2010. http://trace.tennessee.edu/utk_gradthes/714.

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The correct and timely delivery of immune cells is critical for protection against foreign antigen. In order for cells to access most organs, there are requirements that must be met to facilitate exit from the blood into extravasculature. The initial requirement is selectin-selectin ligand interactions that mediate tethering and rolling to allow shear resistance. For proper selectin-selectin ligand interaction, glycoproteins must be modified by fucosyltransferases –IV and –VII, which adds fucose to an acceptor substrate to form the sialyl-LewisX moiety. Using fucosyltransferase –IV and –VII double knockout (FtDKO) mice, we made several novel observations. Our first observation showed increased numbers of naïve T cells in non-lymphoid organs. To support this observation, we blocked chemokine-mediated entry into lymph nodes (LNs) with pertussis toxin and L-selectin mediated entry with anti-CD62L antibody in WT mice. We also treated WT mice with the S1P1 agonist, FTY720, to retain lymphocytes in LNs. Our results suggested that when access to LN is perturbed, lymphocytes accumulate in non-lymphoid organs. Our second observation showed an enrichment of effector/memory T cells in FtDKO LNs. To determine if effector/memory CD8 T cells were retained in LNs, we transferred naïve and memory CD8 T cells into WT mice then treated the recipient mice with anti-CD62L. We found that LN exit rates of naïve and memory CD8 T cells were similar, but slowed as T cell density decreased. To understand if memory CD8 T cells were using selectin ligand independent mechanisms, we transferred naïve and memory CD8 T cells into WT or FtDKO mice. We found reduced numbers of memory CD8 T cells in LNs, however, their frequency was increased. We explored this result by transferring CFSE labeled memory CD8 T cells. We found that memory CD8 T cells divide more in FtDKO mice compared to WT. These experiments suggested that selectin ligand deficiencies cause increased frequency of effector/memory T cells in LNs due to low density and increased emptiness induced proliferation. Taken together, these findings reveal how selectin ligand deficiencies contribute to T cell accumulation in non-lymphoid organs and elucidate mechanisms of retention in LNs.

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