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1
Nandakumar, Jayakrishnan. "Discrimination of RNA versus DNA by an RNA ligase and distinct modes of substrate recognition by DNA ligases /". Access full-text from WCMC:, 2007. http://proquest.umi.com/pqdweb?did=1428838891&sid=13&Fmt=2&clientId=8424&RQT=309&VName=PQD.
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2
Fan, Jun. "Investigating the crosstalk between Nedd4 ubiquitin ligases and PIAS3 SUMO ligase". Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/31791.
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Previously it has been shown that Rsp5p, a member of Nedd4 ubiquitin ligases in yeast, is modified by the ubiquitin-like protein SUMO and that this modification is performed by Siz1p, a member of PIAS SUMO ligases that are in turn substrates of Rsp5p-dependent ubiquitylation, thus defining a previously unidentified system of crosstalk between the ubiquitin and SUMO systems in yeast. This project aims to identify whether similar crosstalk pattern exists in human cells. In vitro ubiquitylation assays showed that some of the human Nedd4 family members (Nedd4.1, Nedd4.2, WWP1) are capable of ubiquitylating the human SUMO ligase PIAS3, while in contrast, Smurf2 does not appear to be able to modify this protein. This modification is partially WW-PY-motif-dependent as ubiquitylation level of PIAS3 mutants with altered PY motifs conducted by Nedd4.1 or Nedd4.2 was reduced, but not completely disrupted. Interestingly, in vitro SUMOylation assay revealed that Nedd4.1 is SUMOylated even in the absence of SUMO E3 ligases and an apparent interaction between the SUMO E2 (Ubc9) and Nedd4.1 was observed both in vitro and in vivo. I show that auto- SUMOylation of Nedd4.1 is accompanied with the formation of thioester-linked conjugates between Nedd4.1 and SUMO, but these do not involve cysteine residues (C867, C778, and C627) within the HECT domain itself and is not occurring at a predicted SUMOylation consensus site (K357). Furthermore, I have shown that Nedd4.1 and SUMO1/2 colocalize in HeLa cells, and that overexpression of epitope tagged Nedd4 and SUMO1/2, followed by denaturing pull-downs demonstrates that both Nedd4.1 and Nedd4.2 can be SUMOylated in vivo. Meanwhile, I have generated a SUMO trap based on SUMO interacting motifs (SIMs) and confirmed its ability of capturing SUMOylated proteins both in vivo and in vitro. Its use reveals that Nedd4 SUMO conjugates could be captured by SUMO trap when Nedd4 and SUMO were co-expressed in HeLa cells, again confirming Nedd4.1 as a substrate for SUMO1 or SUMO2. In conclusion, I show that SUMOylation of Nedd4.1 does exist in HeLa cells, and on the other hand, some of Nedd4 family members are responsible for PIAS3 ubiquitylation in vitro, providing evidence of a crosstalk between Nedd4 family of ubiquitin ligases and PIAS family of SUMO ligases in mammals.
3
Nakatsubo, Tomoyuki. "Characterization of O-methyltransferases and pinoresinol reductases involved in lignin and lignan biosynthesis". Kyoto University, 2008. http://hdl.handle.net/2433/123964.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第14173号
農博第1734号
新制||農||964(附属図書館)
学位論文||H20||N4412(農学部図書室)
UT51-2008-N490
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 梅澤 俊明, 教授 宮川 恒, 教授 矢﨑 一史
学位規則第4条第1項該当
4
Wang, Shao-Fang. "Biochemical and biophysical studies of MDM2-ligand interactions". Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/9527.
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MDM2, murine double minute 2, is a RING type-E3 ligase protein and also an oncogene. MDM2 plays a critical role in determining the steady levels and activity of p53 in cells using two mechanisms. The N-terminal domain of MDM2 binds to the transactivation domain of p53 and inhibits its transcriptional activity. The RING domain of MDM2 plays a role in the ubiquitination (and degradation) of p53. Several proteins are responsible for the ubiquitination mechanism including the ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2) and ubiquitin ligase (E3). Since the E2-E3 interaction is essential for ubiquitination, the protein-protein recognition site is a potential drug target. Two different MDM2 RING constructs were expressed and purified: MDM2RING (residues 386-491) and MDM2RING△C (residues 386-478). Both constructs were characterised using dynamic light scattering, size exclusion chromatography, mass spectrometry, NMR and electron microscopy. E3 ligase activity in vitro was also studied. Taken together these results showed that the MDM2RING construct formed a concentration-dependent oligomeric structure. In contrast, the MDM2RING△C construct formed a dimer at all concentrations. Both MDM2RING and MDM2RING △ C retain E3 ligase activity. However, the MDM2RING△C construct is less active. Full length E2 enzyme UbcH5a was also purified. Various biophysical techniques were used to study its interaction with MDM2 as well as with potential small molecule inhibitors as in principle, small molecules which disrupt the interaction between MDM2 and UbcH5a, could prevent/promote ubiquitination of p53. The dimerisation of MDM2 is important for its E3 activity and the C8-binding site potentially provides a second druggable site. In this work, peptide 9, which has the same sequence as the C-terminus of MDMX (an MDM2 homologue) was found to inhibit MDM2 E3 activity. Various biological techniques including NMR, fluorescence anisotropy, and electrospray mass spectrometry were used to investigate the interaction between two inhibitory peptides and MDM2. A major part of project involved virtual screening (VS) to search for small molecules which can affect MDM2-dependent ubiquitination. Three potential targets were considered: (1) the C8-binding site of MDM2; (2) the UbcH5a-binding site of MDM2; and (3) the MDM2-binding site of UbcH5a. Several small molecules were identified using our virtual screening database-mining and docking programs that were shown to affect MDM2-dependent ubiquitination of p53. In terms of understanding the complex biochemical mechanism of MDM2 this work provides two interesting and functionally relevant observations: (i) the MDM2 RING△C construct is a dimer as this would not be expected form the existing studies, and has less E3 ligase activity than MDM2RING; (ii) small molecules that bind MDM2 on the E2 binding site enhanced E3 ligase activity. One model to explain these observations is that binding of small molecule activators family to the RING induces a change in the conformation of the Cterminal tail residues which may enhance E2 binding.
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Lotte, Romain. "Caractérisation des interactions moléculaires entre la GTPase Rac1 et son régulateur HACE1 : perspectives en infectiologie et en cancérologie". Electronic Thesis or Diss., Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4087.
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La GTPase Rac1 est une protéine de signalisation intracellulaire qui joue notamment un rôle clé dans la prolifération cellulaire. Notre laboratoire a montré que la toxine CNF1, produite par les Escherichia coli pathogènes, catalyse l’activation de Rac1. Nous avons également identifié le rôle de la E3 ubiquitine-ligase HACE1, un suppresseur de tumeur avéré, dans la régulation par ubiquitylation de Rac1 actif. S’il est prouvé que la forme activée de Rac1 est une cible d’HACE1, le mode d’interaction de ces deux protéines reste à définir ainsi que le rôle de ces interactions dans l’infection et le cancer. L’objectif de mon travail a été de caractériser les interactions moléculaires entre HACE1 et Rac1. Nous avons testé l’hypothèse que des mutations ponctuelles d’HACE1 identifiées dans les cancers pourraient interférer avec son interaction avec Rac1 et sa capacité de contrôle de la croissance cellulaire. J’ai ainsi pu mettre en évidence que 13 mutations somatiques d’HACE1 issues de tumeurs séquencées altèrent sa fonction de contrôle de la croissance cellulaire. De plus, l’étude de ces mutations nous a permis d’identifier un groupe d’acides aminés, situés sur les ankyrin-repeats 5 à 7 d’HACE1, qui contrôle l’interaction d’HACE1 avec Rac1 et de ce fait son ubiquitylation. Enfin dans cette étude nous précisons le rôle du domaine intermédiaire d’HACE1 (MID) dans la spécificité d’interaction de la ligase avec la forme active de Rac1. In fine, la caractérisation de mutants d’interaction entre HACE1 et Rac1 ainsi que l’effet de la toxine CNF1 sur cet axe de signalisation doit nous renseigner sur l’importance de cette voie de régulation dans le cancer et l’infectionThe small GTPase Rac1 plays a key role in various intracellular signaling pathways including cell proliferation. Our laboratory has shown that the CNF1 toxin, produced by pathogenic Escherichia coli, catalyzes the activation of Rac1. We also identified the role of the E3 ubiquitin-ligase HACE1, a tumor suppressor, in the regulation by ubiquitylation of active Rac1. If the activated form of Rac1 is proved to be a target of HACE1, the mode of interaction between these two proteins remains to be define as well as the role of these interactions in infection and cancer. The aim of my work was to characterize the molecular interactions between HACE1 and Rac1. We tested the hypothesis that HACE1 point mutations identified in cancers could interfere with its interaction with Rac1 and its ability to control cell growth. We showed that 13 cancer-associated somatic mutations of HACE1, led to a defective control of cell proliferation. Moreover, the study of these mutations allowed us to identify a group of amino acids, located on the ankyrin-repeats 5 to 7 of HACE1, which controls the interaction of HACE1 with Rac1 and thus its ubiquitylation. We also identified a role for the intermediate domain of HACE1 (MID) in conferring the specificity of association of HACE1 to the active form of Rac1. Ultimately, the characterization of interaction mutants between HACE1 and Rac1 as well as the effect of the CNF1 toxin on this signaling axis will give us more insight on this regulatory pathway in cancer and infection
6
Lelievre, Chloé. "Formation de liaisons amides par réactions enzymatiques détournées ATP Regeneration System in Chemoenzymatic Amide Bond Formation with Thermophilic CoA Ligase". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF026.
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La fonction amide est omniprésente dans les produits naturels et aussi dans de nombreux composés synthétiques comme des principes actifs et des polymères. De nombreuses approches ont été développées pour disposer de méthodes de synthèse efficaces. L'approche la plus courante en chimie conventionnelle est l'acylation d'une amine par un acide carboxylique activé. L'activation nécessite l'utilisation soit d'agents de couplage, résultant en une faible économie d'atomes, soit de catalyseurs couteux parfois utilisés dans des conditions drastiques. Les approches biocatalytiques sont donc des alternatives intéressantes pour des raisons économiques et environnementales. Différentes enzymes peuvent être utilisées comme des hydrolases, des nitrile hydratases et des transglutaminases qui activent l'acide sous forme acyl-enzyme pour favoriser l'addition nucléophile de l'amine. Depuis quelques années, l'intérêt pour les enzymes dépendantes de l'ATP s'est accru.Dans ce projet, nous nous sommes intéressés aux CoA ligases qui catalysent la formation d'acide activé sous forme d'acyl-adenylate puis acyl-thioester. Nous avons ainsi mis en évidence qu'en détournant la réaction par piégeage de l'intermédiaire activé par une amine, nous obtenons l'amide. L'utilisation de CoA ligases thermophiles permet de travailler à une température élevée et ainsi de faciliter l'addition non catalysée de l'amine. Ce système s'affranchit donc de l'utilisation de HSCoA onéreux. Pour un système efficace, nous avons aussi intégré avec succès un système de régénération de l'ATP comprenant une Polyphosphate Kinase 2 (Classe III) et une inorganique pyrophosphatase. L'efficacité de cette cascade a été illustrée par la synthèse chemo-enzymatique à l'échelle du laboratoire du N-méthylbutyrylamide avec un rendement de 77 % avec de faibles quantités en enzyme.L'exploration de la biodiversité par approche génomique basée sur la comparaison de séquence, nous a permis d'identifier plusieurs CoA ligases thermophiles actives sur des substrats ω-amino acides précurseurs de lactames. K6Q029 issue de Thermaerobacter subterraneus a fait l'objet d'études plus approfondies. Elle est notamment active sur des substrats ω-amino acides fonctionnalisés ou non, de chaines carbonées plus ou moins longues, mais aussi sur des acides carboxyliques variés tels que des aromatiques.Grâce à la résolution structurale d'A4YDT1, une CoA ligase promiscuitaire, nous avons identifié, en collaboration avec une équipe de cristallographes de l'université de Groningen (Pays Bas), les résidus impliqués dans sa spécificité de substrats pour les modifier par une approche rationnelle. Des mutants de cette enzyme ont ainsi permis l'obtention de δ-valerolactame et Ɛ-caprolactameThe amide function is widespread in nature and also in many synthetic products such as pharmaceuticals and polymers. Numerous approaches have been developed to provide reliable synthesis methods. The most common approach in conventional chemistry is the acylation of an amine by activated carboxylic acid. Activation requires the use of either coupling reagents resulting in low atom economy, or expensive catalysts sometimes used under drastic conditions. Biocatalytic approaches are therefore interesting alternatives for economic and environmental reasons. Different enzymes can be used such as hydrolases, nitrile hydratases and transglutaminases that activate the acid in acyl-enzyme form to promote the nucleophilic addition of the amine. In recent years, interest in ATP-dependent enzymes has increased.In this project, we focused on CoA ligases that catalyze the formation of activated acid as acyl-adenylate and then acyl-thioester. We have thus demonstrated that by diverting the reaction by scavenging activated intermediate with an amine, we obtain the amide. The use of thermophilic CoA ligases allows us to work at a high temperature and thus facilitate the uncatalyzed addition of the amine. This system therefore dispenses with the use of expensive HSCoA. For a better system, we have also successfully integrated an ATP regeneration system with a Polyphosphate Kinase 2 (Class III) and an inorganic pyrophosphatase. The efficiency of this cascade was illustrated by the lab-scale chemo-enzymatic synthesis of N-methylbutyrylamide in 77 % yield using low enzyme loading.Biodiversity exploration using a genomic approach based on sequence comparison allowed us to identify several thermophilic CoA ligases active towards ω-amino acid substrates. K6Q029 from Thermaerobacter subterraneus was further studied. In particular, this enzyme is active towards ω-amino acid substrates, functionalized or not, with more or less long carbon chains, as well as on various carboxylic acids such as aromatics.Thanks to the structural resolution of A4YDT1, a promiscuous CoA ligase from the literature, we have identified, in collaboration with a team of crystallographers from theUniversity of Groningen (Netherlands), the residues involved in its substrate specificity to modify them by a rational approach. Variants of this enzyme have thus allowed to obtain δ-valerolactam and Ɛ-caprolactam
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El, Hachem Najla. "Rôle pro-tumorigénique de HACE1 dans le mélanome". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4035.
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L’incidence du mélanome a augmenté de façon considérable lors des trente dernières années avec un doublement tous les dix ans. Le mélanome ne représente que 5% des cancers cutanés mais entraîne 80% de décès, ce qui constitue un problème majeur de santé publique. En effet, cette tumeur est extrêmement agressive et possède un fort potentiel métastatique. Dès l’apparition de métastases, le pronostic vital devient fortement défavorable. Malgré des avancées thérapeutiques majeures, de nombreux patients sont encore réfractaires à ces nouveaux traitements. La compréhension des mécanismes impliqués dans le développement de cette tumeur reste donc un enjeu de premier ordre. Le séquençage d'exomes a conduit à l'identification d'une mutation dans le gène RAC1 (la mutation P29S) constituant une des mutations somatiques les plus fréquentes dans le mélanome (après les mutations BRAFV600, NRASQ61 et NF1). RAC1 est une petite GTPase qui fonctionne dans plusieurs processus cellulaires. Dans des conditions physiologiques, l'activité de RAC1 est principalement contrôlée par des protéines activatrices de l'activité GTPase (GAPs) et des facteurs d'échange Nucléotidique (GEF). GAPs et GEFs contrôlent le niveau de RAC1-GTP et régulent donc son activité. L'activité de RAC1 est aussi dépendante de son niveau d'expression protéique qui est contrôlé par des E3 ubiquitine ligases, parmi lesquelles HACE1. HACE1 est considérée comme un suppresseur de tumeur. De façon inattendue, les données obtenues montrent clairement que HACE1 favorise les propriétés migratoires et tumorigéniques des cellules de mélanomeMelanoma incidence has considerably increased over the last thirty years, with a doubling every ten years. Melanoma accounts for only 5% of cutaneous cancers but causes more than 80% of deaths, which is a major public health problem. Indeed, this tumor is extremely aggressive and has a high metastatic potential. After the onset of metastases, the prognosis becomes highly unfavorable. Despite major therapeutic advances, many patients are still refractory to these new treatments. Understanding the mechanisms involved in the development of this tumor and the identification of new therapies remain a major issue. The sequencing of exomes led to the identification of a mutation in the RAC1 gene (P29S) constituting one of the most frequent somatic mutations in melanoma (after the BRAFV600, NRASQ61 and NF1 mutations). RAC1 is a small GTPase that is involved in several key cellular processes. Under physiological conditions, the activity of RAC1 is mainly controlled by GTPase activating proteins (GAPs) and Nucleotide Exchange (GEF) exchange factors. GAPs and GEFs control the level of RAC1- GTP and thus regulate its activity. The activity of RAC1 is also dependent on its protein level of expression which is controlled by E3 ubiquitin ligases, including HACE1. HACE1 is considered a tumor suppressor. Unexpectedly, our data clearly show that HACE1 promotes migratory and tumorigenic properties of melanoma cells. Indeed, inhibition of HACE1 alters migration of melanoma cells in vitro, as well as in vivo pulmonary colonization in mice. Transcriptomic analysis of 4 melanoma cell lines demonstrated that HACE1 suppression inhibits ITGAV and ITGB1 expression
8
El, Hachem Najla. "Rôle pro-tumorigénique de HACE1 dans le mélanome". Electronic Thesis or Diss., Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4035.
Texto completo da fonteResumo:
L’incidence du mélanome a augmenté de façon considérable lors des trente dernières années avec un doublement tous les dix ans. Le mélanome ne représente que 5% des cancers cutanés mais entraîne 80% de décès, ce qui constitue un problème majeur de santé publique. En effet, cette tumeur est extrêmement agressive et possède un fort potentiel métastatique. Dès l’apparition de métastases, le pronostic vital devient fortement défavorable. Malgré des avancées thérapeutiques majeures, de nombreux patients sont encore réfractaires à ces nouveaux traitements. La compréhension des mécanismes impliqués dans le développement de cette tumeur reste donc un enjeu de premier ordre. Le séquençage d'exomes a conduit à l'identification d'une mutation dans le gène RAC1 (la mutation P29S) constituant une des mutations somatiques les plus fréquentes dans le mélanome (après les mutations BRAFV600, NRASQ61 et NF1). RAC1 est une petite GTPase qui fonctionne dans plusieurs processus cellulaires. Dans des conditions physiologiques, l'activité de RAC1 est principalement contrôlée par des protéines activatrices de l'activité GTPase (GAPs) et des facteurs d'échange Nucléotidique (GEF). GAPs et GEFs contrôlent le niveau de RAC1-GTP et régulent donc son activité. L'activité de RAC1 est aussi dépendante de son niveau d'expression protéique qui est contrôlé par des E3 ubiquitine ligases, parmi lesquelles HACE1. HACE1 est considérée comme un suppresseur de tumeur. De façon inattendue, les données obtenues montrent clairement que HACE1 favorise les propriétés migratoires et tumorigéniques des cellules de mélanomeMelanoma incidence has considerably increased over the last thirty years, with a doubling every ten years. Melanoma accounts for only 5% of cutaneous cancers but causes more than 80% of deaths, which is a major public health problem. Indeed, this tumor is extremely aggressive and has a high metastatic potential. After the onset of metastases, the prognosis becomes highly unfavorable. Despite major therapeutic advances, many patients are still refractory to these new treatments. Understanding the mechanisms involved in the development of this tumor and the identification of new therapies remain a major issue. The sequencing of exomes led to the identification of a mutation in the RAC1 gene (P29S) constituting one of the most frequent somatic mutations in melanoma (after the BRAFV600, NRASQ61 and NF1 mutations). RAC1 is a small GTPase that is involved in several key cellular processes. Under physiological conditions, the activity of RAC1 is mainly controlled by GTPase activating proteins (GAPs) and Nucleotide Exchange (GEF) exchange factors. GAPs and GEFs control the level of RAC1- GTP and thus regulate its activity. The activity of RAC1 is also dependent on its protein level of expression which is controlled by E3 ubiquitin ligases, including HACE1. HACE1 is considered a tumor suppressor. Unexpectedly, our data clearly show that HACE1 promotes migratory and tumorigenic properties of melanoma cells. Indeed, inhibition of HACE1 alters migration of melanoma cells in vitro, as well as in vivo pulmonary colonization in mice. Transcriptomic analysis of 4 melanoma cell lines demonstrated that HACE1 suppression inhibits ITGAV and ITGB1 expression
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Orts, Julien. "Caractérisation des interactions entre ligands et protéines par RMN en solution". Grenoble, 2010. http://www.theses.fr/2010GRENY011.
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Un des buts de la recherche pharmaceutique est l'inhibition de protéines avec l'aide de petites molécules (ligands). L'une des phases clefs de ce procédé est la détermination du mode d'interaction entre un ligand et son récepteur. Cette tâche peut être entravée par l'absence de structure du complexe protéine-ligand. C'est pour répondre à ce besoin que nous présentons dans ce travail de thèse, une méthode capable de déterminer la structure de complexes protéine-ligands. Dans la méthode INPHARMA (Inter-ligands Nuclear Overhauser Effect for Pharmacophore Mapping), les inter-ligands NOEs (INPHARMA NOEs) sont utilisés pour déterminer l'orientation relative de deux ligands qui interagissent de manière compétitive avec un même récepteur. Cette nouvelle approche ouvre la voie à des applications pharmaceutiques, également au stade initial du développement, quand l'information structurale via la cristallographie par Rayons X est difficile d'accèsIn the process of structure-based drug design, the provision of the binding mode of ligands to the cellular receptor of interest is essential. This can suffer from limited access to protein/ligand structures, especially for the low affinity ligands that are commonly obtained from high throughput screening or fragment based lead discovery. In a common scenario crystal structures are available for one or several ligands but not for all chemical series of actual interest. Here, we present a new, NMR-based approach that allows overcoming this limitation. In the INPHARMA method interligand NOEs (Nuclear Overhauser Enhancement) are utilized to determine relative orientations of different chemical fragments binding competitively to a common receptor site. This novel methodology opens the way to the application of structure-based drug design already in an early stage of drug development, when structural information via crystallography is of difficult access
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Gupta, S. K. "Isolation, cloning and characterization of lignin biosynthesis pathway gene(s) 4-coumarate co a ligase (4cl) from leucaena leucocephala". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2008. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2705.
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Ndo, Gaetan. "Etude et optimisation de techniques de réduction de bruit impulsif pour transmissions haut débit sur lignes à courants porteurs en contexte résidentiel". Télécom Bretagne, 2010. http://www.theses.fr/2010TELB0153.
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Cette thèse a pour objectif l'étude et l'optimisation de quelques techniques de réduction de bruit impulsif de type asynchrone pour transmission large bande sur courants porteurs en lignes (PLC) en contexte résidentiel. En effet, outre les propriétés physiques assez particulières qui caractérisent ce type de canal de transmission, le bruit impulsif asynchrone demeure la cause principale de perte drastique de débit en PLC. Pour pallier à des dégradations de cette nature, les techniques dites de retransmission sont très souvent utilisées. Bien que robustes aux perturbations de nature impulsive, ces techniques de retransmission conduisent inévitablement à une réduction de débit et à l'introduction de délais de traitement supplémentaires pouvant être critiques pour des applications temps réel. D'un autre côté, plusieurs solutions alternatives sont proposées dans la littérature pour contrecarrer les effets nocifs du bruit impulsif sur les transmissions en PLC. Cependant, seules très peu d'entre elles présentent une complexité acceptable pour un récepteur PLC. En particulier, les techniques d'écrêtage et d'effacement sont d'une efficacité remarquable dans la mesure où elles offrent un très bon compromis entre complexité et amélioration des performances en présence de bruit impulsif. Dans cette thèse, une optimisation de la détermination du seuil de chacune des deux non-linéarités, qui se fait très souvent de manière empirique, est réalisée de manière analytique. Des structures adaptatives de réduction de bruit impulsif asynchrone sont également proposées au niveau du récepteur PLC. D'autre part, compte tenu de ses très bonnes propriétés de sélectivité fréquentielle et de son gain en efficacité spectrale par rapport à l'OFDM avec préfixe cyclique (CP-OFDM), l'OFDM/Offset QAM (OFDM/OQAM) peut être vue comme une modulation multiporteurse alternative pour les transmissions haut débit sur PLC. Cependant, aucune étude ne s'est réellement intéressée aux performances d'une telle modulation en environnement impulsif. Dans cette thèse, une analyse du comportement d'un système OFDM/OQAM en présence de bruit impulsif asynchrone est effectuée. Une évaluation théorique de l'expression du rapport logarithmique de vraisemblance (LLR) pour ce type de modulation, en transmission codée, est également proposée. Les performances en terme de taux d'erreur binaire sont évaluées en environnement PLC réalistes et comparées avec celles obtenues en CP-OFDM codé. Enfin, un nouveau point de vue sur une diversité supplémentaire de l'OFDM/OQAM est présentéThis thesis aims at improving some asynchronous impulsive noise reduction techniques for broadband transmissions over indoor power lines. Indeed, beside the particular physical properties of this type of medium, asynchronous impulsive noise remains one of the main causes of performance degradation in powerline communications (PLC). Such an impairment is usually coped with retransmission strategies at the price of a spectral efficiency loss. Although several other countering strategies are proposed in the literature, only very few of them exhibit a reasonable complexity. In particular, the clipping and the blanking approaches present a very good trade-off between the impulsive noise mitigation and the complexity of the implementation. In this thesis, an optimization of the threshold determination, which is usually empirically done, is performed analytically both for the clipping and the blanking non-linearities. Moreover, some adaptive receiver structures for asynchronous impulsive noise reduction over PLC are proposed. On the other hand, because of its good frequency selectivity features and its spectral efficiency gain compared to cyclic-prefix OFDM (CP-OFDM), the OFDM/Offset QAM (OFDM/OQAM) can be seen as an alternative multicarrier modulation scheme for transmission over power lines. Since no study was dedicated to analyze such a modulation in an impulsive environment, this thesis investigates the performance behavior of an OFDM/OQAM modulated system corrupted by asynchronous impulsive noise. Furthermore, a thorough Log-Likelihood Ratio (LLR) computation is derived for coded OFDM/OQAM transmissions under realistic PLC conditions, and the performance results are compared with those obtained with coded CP-OFDM. Finally, a new diversity of the OFDM/OQAM modulation is pointed out in this work
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Villa, Elodie. "Échapper à la mort cellulaire dans le cancer : mitophagie et régulation de la mort indépendante des caspases". Electronic Thesis or Diss., Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4109.
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Une des caractéristiques des cellules tumorales est leur habileté à échapper à la mort cellulaire. Pour y parvenir, elles ont développé une stratégie consistant à éliminer sélectivement les mitochondries endommagées par un processus de mitophagie. L’acteur principal de la mitophagie est l’ubiquitine ligase Parkin ; mais elle est mutée ou absente dans la majorité des cancers. Nous avons découvert qu’une autre ligase, ARIH1, appartenant à la même famille des RBR ligases que Parkin, est capable d’induire la mitophagie en réponse à un stress. Contrairement à Parkin, ARIH1 est surexprimée dans de nombreux cancers, notamment dans les cancers du poumon permettant ainsi une augmentation de la mitophagie conférant ainsi à ces cellules une résistance au stress induit par des agents chimiothérapeutiques. La mort cellulaire la mieux caractérisée est l’apoptose qui est directement liée à l’activation de caspases. Il a pourtant été établi qu’une inhibition des caspases ne permet pas d’empêcher la mort cellulaire car il existe la « mort cellulaire indépendante des caspases » ou CICD. Cependant, sa définition moléculaire précise reste toujours inconnue. Ainsi dans ce but, un criblage siRNA pan génomique a révélé l’importance de la voie ubiquitine/protéasome. Nous avons pu identifier en particulier une enzyme E3 ligase comme étant protectrice de la CICD. Cette enzyme est surexprimée dans de nombreux cancers et pourrait permettre aux cellules cancéreuses de résister à la CICD et favoriser la progression tumorale. En résumé, ce travail a permis de souligner l’importance des ubiquitines ligases dans les mécanismes d’échappement à la mort cellulaire mis en place par les cellules cancéreusesOne of the hallmarks of tumor cells is their ability to escape cell death.To achieve this, they have developed a strategy of selectively removing damaged mitochondria by a process of mitophagy. The main actor of mitophagy is the ubiquitin ligase Parkin; but it is mutated or absent in the majority of cancers. We have discovered that another ligase, ARIH1, belonging to the same family of RBR ligases as Parkin, is capable of inducing mitophagy in response to stress. In contrast to Parkin, ARIH1 is overexpressed in many cancers, especially in lung cancer, allowing an increase in mitophagy conferring resistance to stress induced by chemotherapeutic agents. The most characterized cell death pathway is apoptosis, which is directly related to caspases activation. However, it has been established, that caspase inhibition does not prevent cell death because there is another type of cell death called "caspase-independent cell death" or CICD. However, its precise molecular definition is still unknown. Thus for this purpose, pan-genomic siRNA screening was performed and revealed the importance of the ubiquitin / proteasome pathway. In particular, we have been able to identify an enzyme E3 ligase as being protective towards CICD. This enzyme is overexpressed in many cancers and could allow cancer cells to resist CICD and promote tumor progression. In summary, this work has highlighted the importance of ubiquitin ligases in the escape mechanisms to cell death implemented by cancer cells
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Thaler, Sebastian. "In vitro-Interaktion der E3-Ubiquitin-Ligase HectH7 mit dem potentiellen Tumorsuppressor CDX2 und Herstellung aufgereinigter polyklonaler Antikörper gegen HectH7 /". Berlin : Logos Berlin, 2005. http://deposit.ddb.de/cgi-bin/dokserv?id=2662618&prov=M&dok_var=1&dok_ext=htm.
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Ribau, Humberto Miranda. "Soldadura laser pulsado Nd: YAG entre metais dissimulares". Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/23358.
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Mestrado em Engenharia MecânicaA presente investigação consiste no estudo experimental das propriedades mecânicas induzidas pela soldadura laser em chapas de materiais metálicos dissimilares, nomeadamente, aço de alta resistência dual-phase (DP) 600 com aço de alta resistência dual-phase (DP) 1000 e liga de alumínio AA6060-T6 com liga de titânio Ti-6Al-4V. No caso dos aços dual-phase, o estudo foi realizado em amostras de 0,8 mm de espessura, numa junta do tipo topo a topo. Após a seleção dos parâmetros mais adequados para a soldadura, foram efetuados ensaios de tração aos provetes soldados, com o objetivo de determinar as propriedades mecânicas e avaliar a influência dos parâmetros do laser. Em relação à ligação de alumínio com titânio, esta foi feita numa junta de sobreposição dupla em amostras de 1,9 e 0,9 mm de espessura, respetivamente. Do mesmo modo que os aços, foram também variados os parâmetros do laser, de modo a se obter os mais adequados, para posteriormente se efetuar ensaios de tração. Variou-se também o sítio onde o feixe laser incide na junta de sobreposição para melhor avaliar a soldadura.
The aim of this thesis consists of an experimental study of the mechanical properties induced by the laser welding in dissimilar metal, namely, dual-phase steel 600 with dual-phase steel 1000 and aluminium alloy AA6060-T6 with titanium alloy Ti-6Al-4V. In the case of the dual-phase steels, the study was carried out on 0,8 mm plates, in a butt joint type. After selecting the most appropriate parameters for the welding, tensile tests were performed on welded specimens with the purpose to find the mechanical properties and evaluate the influence of the laser parameters. The aluminium - titanium union was accomplished on a double-lap joint on 1,9 mm and 0,9 mm plates, respectively. Just like the situation of the steels, the laser parameters were too varied with aim to obtain the most appropriate parameters, to later perform tensile tests. It was also changed the place where the laser beam impacts on the specimen, to better analyse the welding.
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Wang, Peter Tien Chun. "Role and regulation of Gp78 E3 ubiquitin ligase and its ligand autocrine motility factor in mitochondrial dynamics and mitochondria-endoplasmic reticulum association". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54246.
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A ligand-receptor pair, autocrine motility factor (AMF) and Gp78, have been discovered to play multiple roles in mammalian cells. AMF functions as the essential glycolytic enzyme phosphoglucose isomerase in the cytoplasm, but when secreted acts a cytokine that stimulates cell motility, growth and survival. Gp78 serves as the cell surface receptor of AMF, and thus it is also known as AMFR. However, Gp78 can localize to the ER membrane and functions as an E3 ubiquitin ligase in the endoplasmic reticulum associated degradation (ERAD) pathway where it targets a wide variety of proteins for degradation. The concerted actions of AMF and Gp78 contribute to multiple aspects of cancer progression, and thus elevated levels of both proteins have been found in many types of cancers. Recently, it was discovered that AMF and Gp78 alter mitochondrial morphology and ER-mitochondria calcium coupling, processes that are essential in regulating mitochondrial metabolism and apoptosis. Furthermore, Gp78 has also been localized to ER-mitochondria contact sites where it targets the mitochondrial fusion proteins, mitofusin 1 and 2 (Mfn1/2), for degradation. In this dissertation, I show that during Gp78 induced mitophagy, autophagosome marker LC3 is recruited to mitochondria associated ER membrane. Moreover, I show that Gp78-dependent degradation of the mitofusins leads to diminished mitochondrial fusion and a perturbation of mitochondrial dynamics. I also report the ability of AMF to inhibit Gp78-induced mitochondrial fission. In my study of ER-mitochondrial association, I observed two types of ER-mitochondria contacts in HT-1080 fibrosarcoma cells: the rough and the smooth. Gp78 ubiquitin ligase activity selectively promotes rough ER-mitochondria association through the degradation of Mfn2. AMF treatment inhibits Gp78-dependent Mfn2 degradation and decreases rough ER-mitochondria contact sites. By dissecting the functions of AMF and Gp78 at the ER mitochondria contact sites, my thesis not only expands our understanding of the relationship between AMF and Gp78, it also provides novel insights into the intimate connection between the ER and mitochondria.Medicine, Faculty of
Graduate
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Chai, Jianfang. "Synthesis, structure and reactivity of manganese complexes supported by carbon or nitrogen donor ligands". Doctoral thesis, [S.l. : s.n.], 2004. http://webdoc.sub.gwdg.de/diss/2004/chai/chai.pdf.
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Pautler, Mark F. "The impediment of ligamen in multiple marriages". Theological Research Exchange Network (TREN), 2005. http://www.tren.com.
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Madikane, Mzekelo. "Biosulphidogenic hydrolysis of lignin and lignin model compounds". Thesis, Rhodes University, 2002. http://hdl.handle.net/10962/d1003976.
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Lignin degradation under biosulphidogenic conditions has not been extensively reported in the literature. Although aerobic degradation of lignin is well documented, anaerobic biodegradation has focused mainly on methanogenic systems with biosulphidogenic systems receiving less attention. Sulphate reducing bacteria are known to generate moderately high levels of both sulphide and alkalinity at room temperatures, and these conditions draw some comparison with the Kraft pulping process. In the Kraft pulping process, lignin is degraded chemically at ±170°C under high sulphide and alkaline conditions and may provide a model for understanding biosulphidogenic lignin degrading activity. The aim of this study was to investigate the biosulphidogenic hydrolysis of lignin within the context of the chemical and biological conditions generated by a mixed sulphate reducing bacteria consortia. Bioreactor studies with a mixed sulphate reducing consortia and pine wood powder (both untreated and depectinated) resulted in the generation of comparable levels of sulphide and alkalinity used in the chemical hydrolysis studies. Aromatic compound yields were between 20 to 50% of the chemical hydrolysis studies. This fluctuation may have been due to the utilization of these aromatic compounds as electron donors by the sulphate reducing consortia as evidenced by the high rate of sulphate reduction in both the untreated and depectinated wood bioreactors. Biodegradation of lignin model compounds was investigated in order to elucidate lignin degradation mechanisms. Both mono-aromatic and dimeric lignin model compounds were used as electron donors and carbon sources for the mixed sulphate reducing consortia. Biodegradation and mass spectrometer analysis of mono-aromatic compounds, ferulic acid and ferulic acid ethyl ester resulted in the production of intermediates such as catechol, cyclohexane carboxylic acid and adipic acid. These intermediates were also observed in the degradation of dimeric ferulic acid. Biodegradation of salicin resulted in the production of salicyl alcohol, ortho-cresol and acetate. Biodegradation of benzylic ether resulted in the production of vanillin and acetate as end products. The results of these studies provide evidence for a biosulphidogenic hydrolysis of lignin, and also the utilisation of lignin-derived aromatic compounds as electron donor sources, by a mixed sulphate reducing consortia.
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Betts, Walter B. "Microbial degradation of lignin and lignin related aromatic compounds". Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/12210.
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Galkin, Maxim. "Palladium-catalyzed lignin valorization : Towards a lignin-based biorefinery". Doctoral thesis, Uppsala universitet, Syntetisk organisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265315.
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The work described in this thesis focuses on the cleavage of the β-O-4′ bond, which is the most abundant interunit linkage in the lignin polymer. In the first part, three methods based on palladium catalysis have been developed and their applicability has been verified using lignin model compounds. A transfer hydrogenolysis of the β-O-4′ bond using formic acid as a mild hydrogen donor together with a base. An aerobic oxidation of the benzylic alcohol motif in the β-O-4′ linkage to generate a key intermediate in the cleavage reaction was performed. A redox neutral cleavage of the β-O-4′ bond was accomplished in which no stoichiometric reducing or oxidizing agents were added. In the second part of the thesis, a mechanistic study is presented. The corresponding ketone from a dehydrogenation reaction of the benzylic alcohol motif was identified to be the key intermediate. This ketone and its enol tautomer was found to be responsible for the β-O-4′ bond cleavage reaction under the employed reaction conditions. In the final part of this thesis, the methodologies have been applied to native lignin. The depolymerization reaction was combined with organosolv pulping. This approach was successful, and together with cellulose and hemicellulose, propenyl aryls were generated in excellent yields directly from wood. In this transformation, the lignin derived molecules have been reduced by an endogenous hydrogen donor from the wood.
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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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Lotte, Romain. "Caractérisation des interactions moléculaires entre la GTPase Rac1 et son régulateur HACE1 : perspectives en infectiologie et en cancérologie". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4087/document.
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La GTPase Rac1 est une protéine de signalisation intracellulaire qui joue notamment un rôle clé dans la prolifération cellulaire. Notre laboratoire a montré que la toxine CNF1, produite par les Escherichia coli pathogènes, catalyse l’activation de Rac1. Nous avons également identifié le rôle de la E3 ubiquitine-ligase HACE1, un suppresseur de tumeur avéré, dans la régulation par ubiquitylation de Rac1 actif. S’il est prouvé que la forme activée de Rac1 est une cible d’HACE1, le mode d’interaction de ces deux protéines reste à définir ainsi que le rôle de ces interactions dans l’infection et le cancer. L’objectif de mon travail a été de caractériser les interactions moléculaires entre HACE1 et Rac1. Nous avons testé l’hypothèse que des mutations ponctuelles d’HACE1 identifiées dans les cancers pourraient interférer avec son interaction avec Rac1 et sa capacité de contrôle de la croissance cellulaire. J’ai ainsi pu mettre en évidence que 13 mutations somatiques d’HACE1 issues de tumeurs séquencées altèrent sa fonction de contrôle de la croissance cellulaire. De plus, l’étude de ces mutations nous a permis d’identifier un groupe d’acides aminés, situés sur les ankyrin-repeats 5 à 7 d’HACE1, qui contrôle l’interaction d’HACE1 avec Rac1 et de ce fait son ubiquitylation. Enfin dans cette étude nous précisons le rôle du domaine intermédiaire d’HACE1 (MID) dans la spécificité d’interaction de la ligase avec la forme active de Rac1. In fine, la caractérisation de mutants d’interaction entre HACE1 et Rac1 ainsi que l’effet de la toxine CNF1 sur cet axe de signalisation doit nous renseigner sur l’importance de cette voie de régulation dans le cancer et l’infectionThe small GTPase Rac1 plays a key role in various intracellular signaling pathways including cell proliferation. Our laboratory has shown that the CNF1 toxin, produced by pathogenic Escherichia coli, catalyzes the activation of Rac1. We also identified the role of the E3 ubiquitin-ligase HACE1, a tumor suppressor, in the regulation by ubiquitylation of active Rac1. If the activated form of Rac1 is proved to be a target of HACE1, the mode of interaction between these two proteins remains to be define as well as the role of these interactions in infection and cancer. The aim of my work was to characterize the molecular interactions between HACE1 and Rac1. We tested the hypothesis that HACE1 point mutations identified in cancers could interfere with its interaction with Rac1 and its ability to control cell growth. We showed that 13 cancer-associated somatic mutations of HACE1, led to a defective control of cell proliferation. Moreover, the study of these mutations allowed us to identify a group of amino acids, located on the ankyrin-repeats 5 to 7 of HACE1, which controls the interaction of HACE1 with Rac1 and thus its ubiquitylation. We also identified a role for the intermediate domain of HACE1 (MID) in conferring the specificity of association of HACE1 to the active form of Rac1. Ultimately, the characterization of interaction mutants between HACE1 and Rac1 as well as the effect of the CNF1 toxin on this signaling axis will give us more insight on this regulatory pathway in cancer and infection
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Schulz, Christoph [Verfasser], e Ingo [Akademischer Betreuer] Krossing. "Novel conducting salts for rechargeable lithium-ion batteries based on the difluorophosphato ligand = Neuartige Leitsalze für Lithium-Ionen Akkumulatoren basierend auf dem Difluorphosphat-Liganden". Freiburg : Universität, 2014. http://d-nb.info/1123480400/34.
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Villa, Elodie. "Échapper à la mort cellulaire dans le cancer : mitophagie et régulation de la mort indépendante des caspases". Thesis, Université Côte d'Azur (ComUE), 2017. http://www.theses.fr/2017AZUR4109.
Texto completo da fonteResumo:
Une des caractéristiques des cellules tumorales est leur habileté à échapper à la mort cellulaire. Pour y parvenir, elles ont développé une stratégie consistant à éliminer sélectivement les mitochondries endommagées par un processus de mitophagie. L’acteur principal de la mitophagie est l’ubiquitine ligase Parkin ; mais elle est mutée ou absente dans la majorité des cancers. Nous avons découvert qu’une autre ligase, ARIH1, appartenant à la même famille des RBR ligases que Parkin, est capable d’induire la mitophagie en réponse à un stress. Contrairement à Parkin, ARIH1 est surexprimée dans de nombreux cancers, notamment dans les cancers du poumon permettant ainsi une augmentation de la mitophagie conférant ainsi à ces cellules une résistance au stress induit par des agents chimiothérapeutiques. La mort cellulaire la mieux caractérisée est l’apoptose qui est directement liée à l’activation de caspases. Il a pourtant été établi qu’une inhibition des caspases ne permet pas d’empêcher la mort cellulaire car il existe la « mort cellulaire indépendante des caspases » ou CICD. Cependant, sa définition moléculaire précise reste toujours inconnue. Ainsi dans ce but, un criblage siRNA pan génomique a révélé l’importance de la voie ubiquitine/protéasome. Nous avons pu identifier en particulier une enzyme E3 ligase comme étant protectrice de la CICD. Cette enzyme est surexprimée dans de nombreux cancers et pourrait permettre aux cellules cancéreuses de résister à la CICD et favoriser la progression tumorale. En résumé, ce travail a permis de souligner l’importance des ubiquitines ligases dans les mécanismes d’échappement à la mort cellulaire mis en place par les cellules cancéreusesOne of the hallmarks of tumor cells is their ability to escape cell death.To achieve this, they have developed a strategy of selectively removing damaged mitochondria by a process of mitophagy. The main actor of mitophagy is the ubiquitin ligase Parkin; but it is mutated or absent in the majority of cancers. We have discovered that another ligase, ARIH1, belonging to the same family of RBR ligases as Parkin, is capable of inducing mitophagy in response to stress. In contrast to Parkin, ARIH1 is overexpressed in many cancers, especially in lung cancer, allowing an increase in mitophagy conferring resistance to stress induced by chemotherapeutic agents. The most characterized cell death pathway is apoptosis, which is directly related to caspases activation. However, it has been established, that caspase inhibition does not prevent cell death because there is another type of cell death called "caspase-independent cell death" or CICD. However, its precise molecular definition is still unknown. Thus for this purpose, pan-genomic siRNA screening was performed and revealed the importance of the ubiquitin / proteasome pathway. In particular, we have been able to identify an enzyme E3 ligase as being protective towards CICD. This enzyme is overexpressed in many cancers and could allow cancer cells to resist CICD and promote tumor progression. In summary, this work has highlighted the importance of ubiquitin ligases in the escape mechanisms to cell death implemented by cancer cells
25
Schulman, Cheryl Lutins. "Synthesis, Structure, and Solution Dynamics of Co₄(CO)₈(dmpe)(mu₄-PPh)₂". Thesis, University of North Texas, 1990. https://digital.library.unt.edu/ark:/67531/metadc501095/.
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Reaction of the tetracobalt cluster Co4(CO)10(t 4-PPh)2 with 1,2-bis(dimethylphosphino)ethane
(dmpe) affords the bis-substituted cluster Co4(CO)8(dmpe)(t 4-PPh)2. The bidentate dmpe ligand is
shown to bind to the cluster in a chelating fashion by IR, NMR, and X-ray diffractions analyses.
The fluxional nature of the ancillary carbonyl groups has been studied by variable temperature 13C
NMR measurements which reveal two distinct carbonyl scrambling pathways. The stability of the
phosphine-ligated cluster has been examined using in situ Cylindrical Internal Reflection (CIR)
Spectroscopy. The effect of the dmpe ligand on the cluster polyhedron will be discussed with
respect to the observed crystallographic and spectroscopic results
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Touzé, Elodie Giegé Richard. "Cristallogenèse et études structurales appliquées aux aminoacyl-ARNt synthétases". Strasbourg : Université Louis Pasteur, 2008. http://eprints-scd-ulp.u-strasbg.fr:8080/911/01/TOUZE_Elodie_2007.pdf.
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ANSELMO, George Carlos dos Santos. "Processo e caracterização de ligas Ti-Ni-Cu com efeito de memória de forma solidificadas rapidamente". Universidade Federal de Campina Grande, 2014. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/345.
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GEORGE CARLOS DOS SANTOS ANSELMO - TESE PPG-CEMat 2014..pdf: 19735821 bytes, checksum: c92e61b342c27548f43bd01d30640a96 (MD5)Made available in DSpace on 2018-04-06T20:54:52Z (GMT). No. of bitstreams: 1 GEORGE CARLOS DOS SANTOS ANSELMO - TESE PPG-CEMat 2014..pdf: 19735821 bytes, checksum: c92e61b342c27548f43bd01d30640a96 (MD5) Previous issue date: 2014-08-29
Ligas com efeito de memória de forma possuem grande potencial para aplicações nos setores da robótica, automotivo, aeronáutico, medicina e na produção de atuadores miniaturizados. O objetivo desse trabalho foi investigar e desenvolver materiais com efeito de memória de forma (Shape Memory Effect - SME) das ligas Ti-Ni-Cu na forma de fitas micrométricas produzidos por meio de Melt Spinning. A metodologia utilizada para produção das ligas Ti-Ni-Cu foi via fusão a plasma (Plasma Skull Push-Pull), e para fabricação de fitas utilizou-se a técnica de solidificação rápida por injeção de metal líquido em volante de cobre nas velocidades de 38 e 50 m/s, logos após as ligas e fitas Ti-Ni-Cu foram caracterizadas por: DSC, SMRT, DRX, MEV. Inicialmente barras prismáticas da liga Ti-Ni50-x-Cux (x=3,4,5,6,7%at.Cu) foram produzidas via fusão a plasma. Por meio solidificação rápida obteve-se fitas com espessuras de 30 a 45 µm com a variação da velocidade do volante de cobre de 38 e 50 m/s no Melt Spinning. Ensaios de DRX revelam à presença da fase B19’ nas ligas brutas de fusão a temperatura ambiente. As ligas apresentaram transformações de fase em único estágio B2↔B19`. As temperaturas de transformação As das ligas Ti-Ni-Cu decrescem com o incremento de Cu. Concluise que as temperaturas de transformação martensíticas (Ms) de fitas Ti-Ni-Cu decrescem com a diminuição do tamanho de grão, e os valores de histerese e entalpia decrescem quando altas taxas de super-resfriamento são alcançadas no Melt Spinnig.
Alloys with shape memory effect have immense potential for applications in robotics, automotive and aeronautics industry, medicine and in the production of miniaturized actuators. The aim of this study was to investigate, develop and manufacture materials with shape memory effect of Ti-Cu-Ni alloys in the form of micrometer tapes produced by Melt Spinning. The methodology used for the production of Ti-Cu-Ni alloys by fusion plasma (Plasma Skull Push-Pull), and manufacturing tapes used the technique of rapid solidification injection of liquid metal into the copper wheel speeds 38 and 50 m/s. alloy and Ti-Ni-Cu ribbons were characterization by: DSC, SMRT, XRD, SEM. Initially prismatic bars of Ti-Ni50-x-Cux (x = 3,4,5,6,7 at.Cu%) had been produced by plasma fusion. With the rapid solidification is obtained tapes with thicknesses between 30 to 45 µm with the variation of the speed of the wheel covers 38 and 50 m / s the melt spinning. XRD tests reveal the presence of the B19' in gross phase alloy melting temperature. The alloys showed phase transformations in single stage B2↔B19`. The transformation temperatures of the alloy Ti-Cu-Ni decrease with the increase of Cu. We conclude that the temperatures of martensitic transformation (Ms) of Ti-Ni-Cu ribbons decreases with decreasing grain size, and hysteresis values and enthalpy decreases when high rates of super-cooling are achieved in Melt Spinnig.
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Bach, Jason Samuel. "Design and evaluation of a prosthetic anterior cruciate ligament replacement medical device". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47580.
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Rupture of the anterior cruciate ligament (ACL) is a relatively common sports-related injury for which the current treatment is reconstruction with an autograft or allograft. Drawbacks associated with each of the current options would make a prosthetic alternative advantageous, however, artificial ligaments are not widely used, having failed due to lack of biocompatibility and mechanical insufficiencies. To develop the next-generation prosthetic ACL, design control principles were applied including specification of comprehensive design inputs, risk analysis, and verification testing. A design was proposed utilizing polyvinyl alcohol and ultrahigh molecular weight polyethylene, selected for good biocompatibility and mechanical strength and stiffness suitable for ACL replacement. A biomimetic fibrous rope pattern was designed for the intra-articular ligament section of the prosthetic that produced a close match the static tensile behavior of the native ACL and which also demonstrated good resistance to fatigue and creep. A calcium phosphate coating was recommended for the sections of the device lying within the bone tunnel to increase the rate of osseointegration. The proposed design was then evaluated in a computational simulation to assess functional restoration and the effects of installation parameters such as tension and tunnel orientation on knee kinematics. The encouraging results of preclinical verification testing support further in vivo evaluation of the proposed design.
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Johal, Amrit. "Chemicals from lignin". Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716671.
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This Thesis investigates the production of high-value chemicals, such as vanillin and guaiacol, by the decomposition and oxidation of lignin in high temperature water. Currently, there is significant global interest in developing chemical production methods that utilise biorenewable feedstocks in place of crude oil and natural gas. Lignin, a complex set of biopolymers found in wood, straw and similar plant materials, is a viable biorenewable raw material for the production of aromatic chemicals. However, currently lignin is mostly used as a low-value fuel in pulp mills. Chapter 1 highlights the concerns that have led to the current demand for greater utilisation of biomass. In that respect, the potential uses of lignin are described. Supercritical water is discussed in relation to green chemistry and specifically as a medium for carrying out oxidation reactions on methyl aromatics. The equipment and methodology used for carrying out experiments and the instruments used for product analysis are described in Chapter 2. Preliminary work that was carried out is described in Chapter 3. These experiments look at the stabilities and oxidation of monomeric aromatic aldehydes, acids and phenols in high temperature water. These substrates each contained either a p-hydroxyphenyl, guaiacyl or syringyl unit. The work in Chapter 4 examined the use of metal bromides and hydrobromic acid as catalysts in the oxidation of three lignin model compounds; 2-methoxy-4-methylphenol, 4-ethyl-2-methoxyphenol and eugenol. These reactions were performed in the near-critical to supercritical region of water. Lignin samples from both Kraft pulping and sulfite pulping sources were shown to breakdown to vanillin, vanillic acid and guaiacol through oxidative treatment in a high temperature water continuous-flow reactor. This work is described in Chapter 5. The overall conclusions of this Thesis are summarised in Chapter 6.
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Wade, R. C. "Ligand-macromolecule interactions". Thesis, University of Oxford, 1988. http://ora.ox.ac.uk/objects/uuid:576ce119-6a93-4eb0-a7e4-1f2513736dbd.
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The optimisation of ligand-macromolecule interactions is fundamental to the design of therapeutic agents. The GRID method is a procedure for determining energetically favourable ligand binding sites on molecules of known structure using an empirical energy potential. In this thesis, it has been extended, tested, and then applied to the design of anti-influenza agents. In the GRID method, the energy of a hydrogen-bond is determined by a function which is dependent on the length of the hydrogen-bond, its orientation at the hydrogen-bond donor and acceptor atoms, and the chemical nature of these atoms. This function has been formulated in order to reproduce experimental observations of hydrogen-bond geometries. The reorientation of hydrogen atoms and lone-pair orbitals on the formation of hydrogen-bonds is calculated analytically. The experimentally observed water structures of crystals of four biological molecules have been used as model systems for testing the GRID method. It has been shown that the location of well-ordered waters can be predicted accurately. The ability of the GRID method to assist in the assignment of water sites during crystallographic refinement has been demonstrated. It has also been shown that waters in the active site of an enzyme may be both stabilized and displaced by a bound substrate. Ligands have been designed to block the highly conserved host cell receptor site of the influenza virus haemagglutinin in order to prevent the attachment of the virus to the host cells. The protein was mapped energetically by program GRID and specific ligand binding sites were identified. Ligands, which exploited these binding sites, were then designed using computer graphics and energy minimization techniques. Some of the designed ligands were peptides and these were synthesised and assayed. Preliminary results indicate that they may possess anti-influenza activity.
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Peberdy, Jemma C. "Biomacromolecule-ligand interactions". Thesis, University of Warwick, 2004. http://wrap.warwick.ac.uk/4069/.
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The interactions and binding of various ligands to biomacromoleculcs e.g. DNA and proteins finds widespread application in the design and development of novel pharmaceuticals. DNA has been identified as the target molecule for a number of drugs and carcinogens and the supramolecular synthetic approach has led to the discovery of a range of bimetallo iron cylinders that bind to DNA inducing remarkable structural effects. The cylinders arc chiral and the enantiomers were separated on cellulose packed in paper or in a column. The optimum mobile phase for efficient separation was found to be 90% acctonitrilc: 10% 0.02 M NaCl. The (M)-enantiomers of the parent cylinder have been found to bind to DNA in the major groove. I Hydrophobic methyl groups were added at various positions on the ligand backbone. UV/visible absorbance, circular and linear dichroism were used to investigate any interactions of the metal complex with DNA with the aim of investigating any sequence preference or selectivity upon binding. Competitive binding studies and molecular dynamics simulations were used to probe the binding geometries of the enantiomers of the parent cylinder and two methylated cylinders to DNA as the exact site of interaction of the (P)-enantiomers of the parent cylinder was unclear. It was concluded that the methylated bimetallo iron cylinders bind to DNA and provide major groove recognition and may show some sequence preference. Circular dichroism was used to structurally characterise a range of buanosine-rich oligonucleotides (GRO's) and to investigate their interactions with a nucleolar protein - nucicolin. Biological/anti-proliferative activity has been related to the ability of the oligonucleotide to bind to this protein. It was found that nucleolin does bind to a biologically active GRO in the presence of K+ and induces a structural change in it.
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Kontopidis, George A. "Immunophilin ligand design". Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22386.
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The general aim of the project is predict and select small molecule ligands which may bind to 3D protein templates. Proteins from the Immunophilin family were used. The putative ligands were selected by two different methods, by structure similarity and using the docking program LIDAEUS, which was developed in house by Dr. P. Taylor. Twenty nine small molecules were selected from a small molecule database and were tested with a fluorescence assay, a PPIase assay and x-ray crystallography for binding activity. Six new ligands have been discovered which bind to Cyp-A. In this work the IC50 (concentration in which half inhibition occurred) of the putative ligands were determined by rotamase inhibition assay. In addition the binding of the ligands was also confirmed by crystallographic experiments. The X-ray structures of 3-acetyl-1 methyl piperidine, ethyl-piperidine glyoxylate, dimethyl sulfoxide, tetramethylene sulfoxide, cyclopentanone and 5,5-dimethyl-1,3-cyclohexanedione bound to Cyp-A have been solved and refined with Rfactor for each structure less than 20%. The structural analysis of the native and ligand structures revealed a hydrophobic pocket surrounded by residues Asn 102, Met 61, Arg 55 and His 122, a hydrogen bond donor site of the main chain nitrogen Asn 102, and another hydrogen bond donor site of the guanidinium of Arg 55. The six novel ligands have been classified into 3 different families of compounds, 3-Acetyl-1 methyl piperidine and ethyl-piperidine glyoxylate belong to the piperidine family and share structural similarities with a natural substrate of Cyp-A the dipeptide Ala-Pro. Dimethyl sulfoxide (DMSO), tetramethylene sulfoxide and cyclopentanone form the DMSO family and they do not share any similarities with known Cyp-A ligand. Only one compound has been discovered in the third family. This compound 5,5-dimethyl-1,3-cyclohexanedione also known as dimedone shows some structural similarities with the Val 11 residue of the Cyp-A ligand cyclosporin.
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Kvainauskas, Darius, e Martin Johansson. "Biodrivmedel från lignin". Thesis, KTH, Skolan för industriell teknik och management (ITM), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232835.
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Lignin är en molekyl som finns i alla växter och kan användas för att framställa nya generationens biodrivmedel. Ligninbaserade biodrivmedel är bra från en miljöaspekt för att det minskar växthuseffekten, men också för att utvinningen av svartlut kan effektivisera tillverkning av pappersmassa. Vid tillverkning av massa fås en restprodukt vid namnet svartlut. Svartlut har ett högt energiinnehåll och kan vara ganska besvärlig att hantera. Det kan användas till värme eller energi internt i massabruken, men fås ofta i större mängder än massa- och pappersbrukens sodapannor kan ta hand om. Det är från svartlut som lignin kan utvinnas. Idag finns det processer som bland annat LignoBoost som utvinner lignin från svartlut. Lignin behöver därefter omvandlas till en flytande form för att sedan blandas in som en komponent i bensin och diesel. Detta kandidatexamensarbete utforskar möjligheter att använda svartlut för utvinning av lignin till ligninbaserade biobränslen. Utöver det har hela råvaruflödet av lignin kartlagts. Kartläggningen av råvaruflödet har utförts med hjälp av en litteraturstudie och intervjuer. Vidare har uppskattningar gjorts på hur stor del av energianvändningen i transportsektorn som kan ersättas med energi från lignin. Energipotentialen från ligninet har baserats på tre olika fall där olika stora andelar av det tillgängliga ligninet används. För Fall 2, där 50% av ligninet utvinns, beräknades även kostnaden för en energikälla (skogsflis) som kan ersätta den energi i svartlutet som annars används som bränsle i massa- och pappersbruken. Från litteraturstudien och intervjuerna är slutsatsen att det i nuläget inte finns ett färdigt råvaruflöde för lignin, däremot är det tre steg som behöver gå ihop för att ett fungerande råvaruflöde ska skapas; utvinning av lignin, omvandling till flytande lignin och distribution. Samtliga aktörer i detta råvaruflöde behöver samarbeta för att hitta en lösning alla kan dra fördel av och subventioner kan behövas för att drivmedlet ska ha ett rimligt pris. Resultatet visar att det finns 3,1 miljoner ton lignin tillgängligt under ett års tid från massa- och pappersbruken i Sverige. Från detta lignin är energipotentialen 12,81 TWh ifall det antas att 30% av allt svartlut används. Detta motsvarar 13,6 % av energibehovet i transportsektorn och räcker till bränsle för 1,56 miljoner personbilar årligen. Ifall 50 % av svartluten används är energipotentialen 21,34 TWh, vilket motsvarar 22,7 % av energibehovet i transportsektorn. I detta fall skulle 25 miljoner ton trädbränsle behöva användas för att ersätta energin, med ett beräknat pris på 1,56 miljarder SEK.Lignin is a molecule found in all plants and can be used to produce new generation biofuels. Lignin-based biofuels are beneficial from an environmental aspect because they help to reduce the greenhouse effect, but also because the extraction of black liquor can streamline the production of pulp. In the manufacturing process of pulp, a residual product is obtained by the name of black liquor. Black liquor has a high energy content and can be quite difficult to handle after extraction. It can be used for heat or energy internally in the pulp mill, but it is often available in larger quantities than infrastructure at the pulp- and paper mills can handle. It is from black liquor that lignin can be extracted. Today, there are processes such as LignoBoost that extract lignin from black liquors. The lignin then needs to be converted into a liquid form and then mixed as a component of gasoline and diesel. This Bachelor's Degree Project explores the possibilities of using black liquor and making ligninbased biofuels. In addition, the entire raw material flow of lignin has been mapped. The mapping of the raw material flow has been carried out using a literature study and interviews. Furthermore, estimates have been made of how much of the energy consumption in the transport sector that can be replaced by the energy that is obtainable from lignin. The energy potential of the lignin is based on three different cases, with different proportions of available lignin. For Case 2, where 50% of the lignin is recovered, the cost of a replacement source (wood chips) is also calculated. This energy source can replace the energy in black liquor that is used as fuel in the pulp- and paper mills. From the literature study and the interviews, it is concluded that there is currently no raw material flow for lignin, but there are three steps that need to work together to create a functioning one; recovery of lignin, conversion into liquid lignin and distribution to consumers. All stakeholders in this raw material flow need to work together to find a solution everyone can benefit from and subsidies may be needed for the fuel to have a reasonable price. The result shows that there are 3.1 million tonnes of lignin available for one year from pulp and paper mills in Sweden. From this lignin the energy potential is 12.81 TWh if it is assumed that 30% of all black liquor is used, which is equivalent to the energy used by 1.56 million cars. This corresponds to 13.6% of the energy demand in the transport sector. If 50% of the black liquor is used, the energy potential is 21.34 TWh, which corresponds to 22.7% of the energy demand in the transport sector. In this case, 25 million tons of wood fuel would need to be used to replace energy, which costs 1.56 billion SEK.
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Delance, Cécile. "Analyse des mécanismes assurant la robustesse d’un événement de transdifférenciation : rôle de l’ubiquitine ligase E3 SEL-10". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAJ027.
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Les cellules différenciées peuvent changer de destin cellulaire de manière induite ou naturelle. Afin de comprendre et connaître les acteurs et mécanismes contrôlant les processus de reprogrammation, notre laboratoire étudie le changement d'identité (ou transdifférenciation, Td) naturel d’une cellule épithéliale rectale (nommée Y) en motoneurone (nommé PDA) chez Caenorhabditis elegans. Les travaux préliminaires ont montré qu’il existe une synergie entre les modifications d’histone (jmjd-3.1 et wdr-5.1) et l’ubiquitination (sel-10). SEL-10 est une ubiquitine ligase E3 possédant un domaine Fbox et une répétition de domaines WD40. Dans cette étude, nous avons pu mettre en évidence : i) une implication du domaine Fbox, des indications sur la localisation intracellulaire de SEL-10 et un rôle inattendu du protéasome au sein de la Td. ii) un rôle de SEL-10 dans la robustesse de la Td (résistance aux stress environnementaux). iii) sel-10, jmjd-3.1 et wdr-5.1 agissent sur la transcription de gènes impliqués dans la transdifférenciation (testé par smFISH). Ainsi qu’une caractérisation du motif d’expression marqueur de Td cog-1 au cours de la redifférenciationDifferentiated cells can change their cellular fate induced or naturally. In order to understand the mechanisms controlling reprogramming processes, our laboratory is studying the natural change in identity (or transdifferentiation, Td) of a rectal epithelial cell (named Y) and motor neuron (named PDA) in Caenorhabditis elegans.Preliminary work has shown that there is a synergy between histone modifications (jmjd-3.1 and wdr-5.1) and ubiquitination (sel-10). SEL-10 is an E3 ubiquitin ligase with a Fbox domain and WD40 repeat domain.In this study, we highlight: i) the Fbox domain involvement in the Td, indications about the intracellular localization of SEL-10 and an unexpected role of the proteasome within TD. ii) a role of SEL-10 in the robustness of the Td. iii) sel-10, jmjd-3.1 and wdr-5.1 act on gene transcription in transdifferentiation. This one was tested by smFISH and allowed the characterization of the cog-1 transdifferentiation marker expression pattern during redifferentiation
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Deeth, R. J. "Redirected ligand-field analysis : applications of the cellular ligand-field model". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355257.
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Freundlich, Joel Stephen. "Metal-ligand multiple bonds in organometallic complexes containing triamidoamine ligand systems". Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38782.
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Jackson, Alicia M. "Investigation of the ligand shells of homo-ligand and mixed-ligand monolayer protected metal nanoparticles : a scanning tunneling microscopy study". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39548.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references.
Monolayer Protected Metal Nanoparticles have recently found widespread use in and are the focus of intensive study in many areas of scientific research ranging from biology to physics to medicine. Consisting of a nanoscale, crystalline, metallic core surrounded by a self-assembled monolayer of ligands (a 3-D SAM or ligand shell), their appeal and utility stem from their numerous unique properties-many of which arise and are modulated by the intimate spatial and electronic contact between core and shell. The ligand shell controls the particle's interactions with its environment (e.g. sensing, assembly, and electron transfer ability). Furthermore, the ability to manipulate and assemble such nanomaterials through the ligand shell is paramount to their incorporation into and the development of new nanoparticle based materials and devices. However, little is known of the exact composition and packing arrangements of molecules within the ligand shell, and even less so on how to control the resulting nanostructuring. In this thesis we present a Scanning Tunneling Microscopy investigation of the ligand shells of homo- and mixed-ligand metal nanoparticles.
(cont.) We develop an understanding and model of the ligand arrangements around the nanoparticle core, showing that the multifaceted, high curvature, and topologically spherical nature of the core results in a 3-D SAM that has many differences from its 2-D SAM counterparts. We show that the core curvature (and correspondingly, the changing facet to edge ratio on the core surface) of the particles is the dominant driver for the packing and behavior of the ligand shell. Most interestingly, we find that when certain two-component, mixed SAMs are assembled around the particle core, the ligands phase-separate into ordered, ribbon-like domains, only a few molecules in width-a behavior never before seen on flat surfaces. We show that both the domain morphology and width can be controlled through the ligand shell composition and the particle core size, and that the observed phase-separation is a general phenomenon across nanoparticle compositions. We present these studies as a first step towards developing a complete model of and control over the ligand shell structure of nanoparticles.
by Alicia M. Jackson.
Ph.D.
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Auguste, Tiphanie. "Implication de ROQUIN dans la physiopathologie du lymphome T angio-immunoblastique". Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST0076.
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Implication de ROQUIN dans la physiopathologie du lymphome T angio-immunoblastique. Le T-LAI est un lymphome T périphérique qui de part sa rareté bénéficie de peu d'études contrairement aux lymphomes B. En France, le T-LAI est le PTCL le plus fréquemment rencontré. Malgré une évolution clinique variable, le T-LAI reste une tumeur agressive dont la survie globale est inférieure à 3 ans. Un des objectifs de notre équipe est donc de mieux comprendre la physiopathologie de ce lymphome et d'identifier des évènements oncogéniques conduisant à son développement. Dans le cadre de ce projet, notre étude s'est portée sur le gène ROQUIN qui code une E3 ubiquitine ligase de la famille RING et dont la mutation est associée à l'apparition d'un syndrome proche du T-LAI chez la souris sanroque.Bien que nous n'ayons détecté aucune mutation dans la séquence codante de ROQUIN nous avons identifié un nouveau transcrit alternatif appelé ROQUIN ØE17. Celui-ci code une protéine qui, comme la forme sauvage, se localise dans les granules de stress et les corps P et interagit avec certains ARNm et micro-ARN. Néanmoins il est le seul à inhiber l'expression de la molécule de costimulation ICOS. ROQUIN ØE17, qui est présent en concentrations variables dans les différentes populations lymphocytaires T n'est quasiment pas exprimé dans les T-LAI. De ce fait, la perte du transcrit ROQUIN ØE17 pourrait participer à la genèse et/ou développement de ce lymphomeImplication of ROQUIN in the physiopathology of angio-immunoblastic T cell lymphoma. AITL is a peripheral T cell lymphoma, poorly studied compared to B cell lymphomas due to its rarity. In France, AITL is the PTCL the most frequently encountered. Despite a variable clinical course, AITL is an aggressive tumor with an overall survival lower than 3 years. One of our goal is to better understand the physiopathology of this lymphoma and identify oncogenic events that lead to its development. In this project, our study was focused on ROQUIN gene that encodes a RING E3 ubiquitin ligase and whose mutation induces an AITL-like syndrom in sanroque mice.Although we did not detect any mutation in ROQUIN coding sequence, we identified a novel alternative transcript referred as ROQUIN ØE17. It encodes a protein that, like wild type protein, localizes to stress granules and P bodies and interacts with mRNAs and microRNAs. However, only ROQUIN ØE17 inhibits the expression of the costimulatory molecule ICOS. This transcript, whose expression varies between T cell populations, is hardly expressed in AITL. Consequently, the loss of ROQUIN ØE17 could be involved in the genesis and/or development of this lymphoma
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Schupp, Michael. "Identifizierung und Charakterisierung von AT1-Antagonisten als PPAR[gamma]-Liganden [PPARgamma-Liganden]". [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2005/134/index.html.
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Petrescu, Anca Daniela. "Ligand binding proteins: roles in ligand transfer and activation of nuclear receptors". Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/290.
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Cholesterol and fatty acyl-coenzymeA thioesters are signalling molecules with role in regulation of genes involved in lipid and glucose transport and metabolism. The studies described herein focused on three proteins that bind lipids and have different cellular functions: steroidogenic acute regulatory protein (StAR), hepatocyte nuclear factor-4a (HNF-4a) and acyl-CoA binding protein (ACBP). First, StAR mediates delivery of cholesterol to inner mitochondrial membrane in steroidogenesis by a poorly understood mechanism. In our studies, fluorescent NBD-cholesterol binding assays demonstrate that StAR binds cholesterol at two binding sites with 32 nM Kds and circular dichroism spectra show that cholesterol binding results in changes of StAR secondary structure. Fluorescent sterol exchange assays between donor and acceptor mitochondrial membranes indicate that StAR significantly increased the formation of rapidly transferable cholesterol domains. Second, HNF-4a, a nuclear receptor, had been shown to bind fatty acyl-CoAs as natural ligands with apparent low affinities obtained with radiolabeled ligand binding assays. Our fluorescence spectroscopy studies demonstrate that HNF-4a ligand binding domain (HNF-4aLBD) binds acyl-CoAs at a single binding site with Kds of 1.6-4 nM. Fluorescence resonance energy transfer (FRET) between HNF-4aLBD tryptophan residues and cis-parinaroyl-CoA yielded an intermolecular distance of 42 Â thus pointing to direct molecular interaction. Third, although ACBP has been detected in the nucleus, it is not known whether ACBP may directly and/or functionally interact with a nuclear acyl-CoA binding protein such as HNF-4a to regulate transcription. Our present studies in vitro and in intact cultured cells, including circular dichroism of HNF-4a in the presence of ACBP, coimmunoprecipitation of HNF-4a/ACBP complexes, ACBP and HNF-4a colocalization in nuclei of cells by confocal microscopy demonstrate a physical association of ACBP and HNF-4a. FRET microscopy data indicated an intermolecular distance of 53 Â between ACBP and HNF-4a in rat hepatoma cells. Functional assays (transactivation of an HNF4a-dependent reporter gene) showed significant increase in the presence of ACBP in two different cell lines. Expression of ACBP anti-sense RNA decreased HNF-4a-mediated transactivation, pointing to a role of ACBP in co-regulating HNF-4a-dependent transcription.
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Dodson, A. P. J. "The use of lignin peroxidases to degrade lignin in plant cell walls". Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46747.
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Tan, Xin. "Effect of Organosolv Lignin and Extractable Lignin on Enzymatic Hydrolysis of Lignocelluloses". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752000022518.
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Jennings, John Adam. "HETEROGENEOUS BASE METAL CATALYZED OXIDATIVE DEPOLYMERIZATION OF LIGNIN AND LIGNIN MODEL COMPOUNDS". UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/81.
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With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions.
Alternatively, selective benzylic oxidation strategies have recently been explored for lignin and lignin models. In this work, heterogeneous catalytic methods using supported base metals and layered-double hydroxides were evaluated for the oxidation of lignin models both before and after benzylic oxidation. Additionally, by studying putative reaction intermediates, insights were gained into the mechanisms of oxidative fragmentation of the model compounds.
Generally, it was found that after benzylic oxidation models were more susceptible to oxidative fragmentation. Indeed, several heterogeneous oxidation systems were found to convert lignin models to oxygenated aryl monomers (mainly benzoic acids and phenols) using inexpensive primary oxidants (i.e., hydrogen peroxide and molecular oxygen). Reactions were conducted at relatively mild temperatures and at low oxygen concentrations for the purpose of an easy transition to large-scale experiments. Finally, the catalytic systems that resulted in significant cleavage of lignin models were applied to a Kraft lignin. Oxidation of Kraft lignin resulted a mixture of products for which analytical data and increased solubility are consistent with interunit cleavage within the lignin macromolecule.
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Dodge, Luke A. "FRACTIONATION OF LIGNIN DERIVED COMPOUNDS FROM THERMOCHEMICALLY PROCESSED LIGNIN TOWARDS ANTIMICROBIAL PROPERTIES". UKnowledge, 2018. https://uknowledge.uky.edu/bae_etds/54.
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The overuse of antibiotics in agriculture is an emerging concern, due to their potential detrimental impact to the environment. This study focuses on exploring antimicrobial properties of lignin derived compounds. Lignin is of interest as a feedstock to replacing some petroleum-based chemicals and products because it is the most abundant source of renewable aromatic compounds on the planet. Two lignin rich streams, residues from the enzymatic hydrolysis of dilute acid and alkaline pretreated corn stover, were decomposed via pyrolysis and hydrogenolysis, respectively. The resulting liquid oils were subjected to sequential extractions using a series of solvents with different polarities. Chemical compositions of the extracted fractions were characterized through HPLC and GC/MS. These extracted compounds were screened against Saccharomyces cerevisiae (S. cerevisiae), Escherichia coli, and Lactobacillus amylovorus for antimicrobial properties. Six lignin model monomers: guaiacol, vanillin, vanillic acid, syringaldehyde, 2,6-dimethoxyphenol, and syringic acid were compared to the oils and extracted fractions for antimicrobial properties. Development of lignin-derived chemicals with antimicrobial properties could provide a novel use for this underutilized natural resource.
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Bourgeois, Yannick. "Modélisation des perturbations électromagnétiques générées sur un réseau de télécommunications par une agression de type foudre". Limoges, 2009. https://aurore.unilim.fr/theses/nxfile/default/ecc54aba-2824-4378-9858-a6928f3bb547/blobholder:0/2009LIMO4004.pdf.
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La foudre par ses effets directs et indirects peut engendrer des dégâts importants sur un réseau de télécommunications. Cette thèse aborde la modélisation des mécanismes de couplage d'une décharge orageuse sur une structure constituée d’un réseau filaire et d’un bâtiment. A l’aide d'un code de calcul basé sur la théorie des lignes de transmission et associé à une approche topologique, l’étude de l'efficacité d'une protection contre la foudre, réalisée grâce à un conducteur nu placé au dessus d'un câble enterré, est effectuée de manière exhaustive en s'appuyant sur des résultats expérimentaux obtenus à l'aide d'éclairs déclenchés. De plus, la thèse aborde, à l’aide de la théorie des antennes dans le domaine temporel (FDTD), le calcul des courants induits simultanément sur un bâtiment et son réseau d'adduction lors d'un impact direct sur un pylône. L'application pratique visée par l'ensemble de ces travaux est l'amélioration de la protection contre la foudre des sites de radiodiffusionsLightning by its direct and indirect effects may engender important damages on a telecommunications network. This thesis approaches the modeling of the coupling of a lightning stroke with a structure composed of a building associated to a wired network. By means of a formalism based on the transmission line theory associated to a topological approach, a study of the efficiency of a lightning protection device, composed of a shielding wire installed in the ground above the underground cable, is made in a exhaustive way by using experimental data obtained by means of triggered lightning. Furthermore, thanks to the antenna theory in the time domain (FDTD), the thesis also approaches the calculation of the currents generated simultaneously on a building and its wired network when the lighting stroke occurs on the considered structure. The practical application aimed by all these works being the improvement of the lightning protection of the radio-sites
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Labisch, Oliver. "Offenkettige Monosaccharide als Liganden". Diss., [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00006050.
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Luo, Jie. "Lignin-Based Carbon Fiber". Fogler Library, University of Maine, 2010. http://www.library.umaine.edu/theses/pdf/LuoJ2010.pdf.
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Nguyen, Nhung Phuong. "Axial ligand mutant H229A /". unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-08082008-134926/.
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Thesis (honors)--Georgia State University, 2007.Title from file title page. Under the direction of Dabney White Dixon. Electronic text (88 p. : col. ill.) : digital, PDF file. Description based on contents viewed Sept. 30, 2008. Includes bibliographical references (p. 46-47).
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Nguyen, Nhung Phuong. "Axial Ligand Mutant: H229A". Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/honors_theses/1.
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Many pathogenic bacteria use their iron acquisition mechanisms to live inside hosts. Streptococcus pyogenes is a pathogenic bacterium that uses streptococcal iron acquisition ABC transporter to obtain heme. SiaA (HtsA, spy1795), a lipoprotein located on the cell surface, serves as a heme binding protein. To understand the iron-uptake mechanism, histidine 229, one of the two proposed axial ligands in SiaA, was mutated to alanine. SiaA H229A was expressed in E. coli, lysed by French Press, and purified by fast protein liquid chromatography (FPLC). SDS-PAGE indicated that pure protein was isolated. Nickel affinity FPLC gave purer H229A when 0.5 M imidazole was added to the binding buffer. Overall, histidine 229 is likely to be an axial ligand in wild type SiaA, as shown by the fact the mutant readily lost heme as evidenced by UV-vis spectra.
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Brown, C. A. "Ligand field spectral intensities". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377247.
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