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1
Vasconcelos, Fernanda Nogales da Costa. "Caracterização dos genes phoA1, phoA2, phoB, phoU e PstS, membros do regulon PHO de Chromobacterium violaceum." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-24092014-161707/.
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Chromobacterium violaceum é uma bactéria de vida livre, móvel, que habita fontes de água e solos pobres de regiões tropicais e subtropicais. Nestes habitats, em que a concentração de fosfato é baixa, o regulon PHO encontra-se ativado. No laboratório, esta bactéria é capaz de crescer razoavelmente bem, apesar da limitação de fosfato, atingindo um rendimento celular similar ao observado na abundância deste nutriente. Mutações nos genes pstS, phoU, phoA1 e phoA2 foram construídas. As mutações pstS e phoU não causaram qualquer alteração no padrão de expressão da fosfatase alcalina, sugerindo que estes genes não participam da repressão dos genes de PHO. Porém, o mutante pstS mostrou-se deficiente na captação de Pi. Os mutantes phoA1 e phoA2 apresentaram, cada um, severa redução na atividade da fosfatase alcalina. Foi investigada a possibilidade de PhoA1 e PhoA2 formarem uma proteína heterodimérica. Fusões transcricionais entre phoU e phoB ao gene lacZ, revelaram que estes genes respondem à carência de Pi. Surpreendentemente, C. violaceum se mostrou pouco resistente a estresses ambientais.Chromobacterium violaceum is a free-living, mobile bacterium that inhabits water sources and soils of tropical and subtropical regions, where the phosphate concentration is low. The PHO regulon is activated in response to low phosphate concentration in the environment. Surprisingly, the growth yield of C. violaceum under phosphate excess or under phosphate limitation is very similar. Mutations in pstS, phoU, phoA1 and phoA2 genes were constructed. The expression of alklaine phosphatase was not affected by the phoU and pstS mutations, suggesting that these genes do not participate in the repression of the PHO regulon. However, the pstS mutant was deficient in the uptake of Pi. The phoA1 and phoA2 mutants presented each one a severe reduction in alkaline phosphatase activity. The hypothesis that PhoA1 and PhoA2 form a heterodimeric protein was investigated. Transcriptional fusions between the promoters of phoB and phoU to lacZ showed that these genes respond to Pi starvation. Stress resistance assays showed that C. violaceum is generally sensitive to environmental stresses.
2
Loney, Erica. "PhoR, PhoP and MshC: Three essential proteins of Mycobacterium tuberculosis." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1396606314.
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Le, Sage Valerie. "Ligand sensing and signal trasnduction by the two-component system PhoP/PhoQ." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95624.
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The Citrobacter rodentium genome sequence contains a phoPQ operonhomologous (~79% identity) to that of S. typhimurium. We report that C. rodentiumPhoQ senses fluctuations in Mg2+ concentrations and acidic pH. Surprisingly, PhoQwas not activated by the presence of AMPs. However, activation by AMPs is observedwhen C. rodentium PhoP/PhoQ was expressed in as. typhimurium background. Weidentified an outer membrane protease of the omptin family that was responsible forinhibiting PhoQ activation by AMPs. In stark contrast to S. typhimurium, which relieson LPS modifications to resist AMPs, our results suggest that C. rodentium promotesresistance through a PhoP/PhoQ-dependent OM protease to inhibit disruption of theouter membrane by AMPs .La séquence du génome de Citrobacter rodentium présente un opéron phoPQ(~79% identité) homologue à celui de S. typhimurium. Nous avons déterminé quePhoQ de C. rodentium perçoit les variations de pH et en Mg2+ du milieu environnant.De manière surprenante, les PAMs ne causent aucune augmentation d'activité dePhoQ. Néeanmoins, lorsque le système PhoP/PhoQ de C. rodentium est exprimé chezS. typhimurium les PAMs activent PhoQ. Nous avons identifié une protéine de lamembrane externe appartenant à la famille des omptin qui est responsable del'inactivité de PhoQ en présence des P AMs. Ces résultats suggèrent que le mécanismede résistance aux PAMs de C. rodentium serait régulé par le système PhoP/PhoQ et une protéase qui empêcherait la destruction de la membrane externe par les P AMs. Cemécanisme de défense est différent de celui du système PhoP/PhoQ de S. typhimuriumqui repose essentiellement sur des modification du LPS .
4
Salazar, Michael E. Jr (Michael Edward). "Induction kinetics of the PhoQ-PhoP two-component system in Escherichia coli." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104179.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Cells rely on signal transduction systems to sense and respond to changes in their enviroments. When a stimulus is present, the corresponding signal transduction system will activate and enact the appropriate biological response, often by modulating target gene expression. In many cases, the temporal dynamics of the activation of target gene expression in the presence of constant stimulus is complex, and often exhibits one or several pulses. How these complex temporal dynamics are regulated at the molecular level is unknown for many signal transduction systems. In this thesis, I discuss the molecular regulation of the temporal dynamics of PhoQ-PhoP induction in Escherichia coli. The PhoQ-PhoP pathway is a canonical two-component system that responds to low extracellular Mg'+, certain antimicrobial peptides, and potentially other unknown factors. Upon activation, the bifunctional histidine kinase PhoQ autophosphorylates and subsequently phosphotransfers to the response regulator PhoP, thereby activating it to increase transcription of PhoP target genes. Because PhoQ is bifunctional, PhoQ acts as a phosphatase on phosphorylated PhoP in the absence of stimulus, thereby keeping the system inactivated. When the PhoQ-PhoP system is strongly induced, PhoP target genes exhibit impulse kinetics, meaning gene expression increases to a maximal level and subsequently decreases to an eventual steady state. We discovered that this impulse response is caused by a negative feedback loop in which active PhoP transcribes mgrB, a gene encoding a small membrane protein that interacts directly with PhoQ to repress the output of the system. MgrB selectively inhibits the ability of PhoQ to phosphorylate PhoP, and permits PhoQ to act as a phosphatase on phosphorylated PhoP. This change in PhoQ activity causes a decrease in the level of active PhoP and the level of PhoP target genes. This thesis reveals how negative feedback loops and histidine kinase bifunctionality can drive the kinetics of two-component system induction in bacteria, and more generally explores how cells regulate changes in gene expression over time.
by Michael E. Salazar, Jr.
Ph. D.
5
Khan, Rizwan Ahmed. "Détection des émotions à partir de vidéos dans un environnement non contrôlé." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10227/document.
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Dans notre communication quotidienne avec les autres, nous avons autant de considération pour l’interlocuteur lui-même que pour l’information transmise. En permanence coexistent en effet deux modes de transmission : le verbal et le non-verbal. Sur ce dernier thème intervient principalement l’expression faciale avec laquelle l’interlocuteur peut révéler d’autres émotions et intentions. Habituellement, un processus de reconnaissance d’émotions faciales repose sur 3 étapes : le suivi du visage, l’extraction de caractéristiques puis la classification de l’expression faciale. Pour obtenir un processus robuste apte à fournir des résultats fiables et exploitables, il est primordial d’extraire des caractéristiques avec de forts pouvoirs discriminants (selon les zones du visage concernées). Les avancées récentes de l’état de l’art ont conduit aujourd’hui à diverses approches souvent bridées par des temps de traitement trop couteux compte-tenu de l’extraction de descripteurs sur le visage complet ou sur des heuristiques mathématiques et/ou géométriques.En fait, aucune réponse bio-inspirée n’exploite la perception humaine dans cette tâche qu’elle opère pourtant régulièrement. Au cours de ces travaux de thèse, la base de notre approche fut ainsi de singer le modèle visuel pour focaliser le calcul de nos descripteurs sur les seules régions du visage essentielles pour la reconnaissance d’émotions. Cette approche nous a permis de concevoir un processus plus naturel basé sur ces seules régions émergentes au regard de la perception humaine. Ce manuscrit présente les différentes méthodologies bio-inspirées mises en place pour aboutir à des résultats qui améliorent généralement l’état de l’art sur les bases de référence. Ensuite, compte-tenu du fait qu’elles se focalisent sur les seules parties émergentes du visage, elles améliorent les temps de calcul et la complexité des algorithmes mis en jeu conduisant à une utilisation possible pour des applications temps réelCommunication in any form i.e. verbal or non-verbal is vital to complete various daily routine tasks and plays a significant role inlife. Facial expression is the most effective form of non-verbal communication and it provides a clue about emotional state, mindset and intention. Generally automatic facial expression recognition framework consists of three step: face tracking, feature extraction and expression classification. In order to built robust facial expression recognition framework that is capable of producing reliable results, it is necessary to extract features (from the appropriate facial regions) that have strong discriminative abilities. Recently different methods for automatic facial expression recognition have been proposed, but invariably they all are computationally expensive and spend computational time on whole face image or divides the facial image based on some mathematical or geometrical heuristic for features extraction. None of them take inspiration from the human visual system in completing the same task. In this research thesis we took inspiration from the human visual system in order to find from where (facial region) to extract features. We argue that the task of expression analysis and recognition could be done in more conducive manner, if only some regions are selected for further processing (i.e.salient regions) as it happens in human visual system. In this research thesis we have proposed different frameworks for automatic recognition of expressions, all getting inspiration from the human vision. Every subsequently proposed addresses the shortcomings of the previously proposed framework. Our proposed frameworks in general, achieve results that exceeds state-of-the-artmethods for expression recognition. Secondly, they are computationally efficient and simple as they process only perceptually salient region(s) of face for feature extraction. By processing only perceptually salient region(s) of the face, reduction in feature vector dimensionality and reduction in computational time for feature extraction is achieved. Thus making them suitable for real-time applications
6
Gardner, Stewart G. "Studies of PhoU in Escherichia coli: Metal Binding, Dimerization,Protein/Protein Interactions, and a Signaling Complex Model." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5685.
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Phosphate is an essential nutrient for all forms of life. Escherichia coli has a PhoR/PhoB two component regulatory system that controls the expression of various genes whose products allow the cell to thrive in low phosphate environments. The signaling mechanism of the PhoR/PhoB system has been studied and the phosphorylation cascade that controls gene expression is well understood. What is still unknown is how PhoR senses the phosphate level of the environment. The PstS, PstC, PstA, PstB, and PhoU proteins play a role in this signal sensing. This work confirms the hypothesis that the PstSCAB complex senses the environmental phosphate and that phosphate signal is passed through PhoU to PhoR. Further, this work characterizes residues important for interaction on PhoU and PhoR and identifies a structural model for interaction. This model points to a potential mechanism for PhoU mediated signaling to PhoR. We tested this model with direct coupling analysis and obtained further confirmation. Further use of these techniques may elucidate more of the interactions necessary for proper phosphate signaling.
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Politis, Panagiotis K. "The role of chromatin in the regulation of PHO5 and PHO3 genes in Saccharomyces cerevisiae." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343632.
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Münsterkötter, Martin. "Kooperative Wechselwirkungen von Transkriptionsfaktoren und Histonen mit Promotorelementen der Phosphatasegene PHO5 und PHO8 in Saccharomyces cerevisiae." Diss., lmu, 2001. http://nbn-resolving.de/urn:nbn:de:bvb:19-853.
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Gellatly, Shaan Lae. "Regulation of the PhoP-PhoQ two-component system in Pseudomonas aeruginosa and its role in virulence." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42991.
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Pseudomonas aeruginosa is an opportunistic bacterial pathogen that can cause severe
infections in individuals with underlying medical conditions. P. aeruginosa primarily infects at
epithelial surfaces where it interacts initially via type IV pili, flagella and LPS. Two component
regulatory systems control many aspects of pseudomonal physiology and mediate adaptation to
environmental changes including those that occur in the host. This thesis outlines the
contributions of these systems to the cytotoxicity to epithelial cells and sheds light on the
regulation mediated by the two-component sensor PhoQ. Systems that contributed to cytotoxicity
fell into several themes including motility, cyclic-di-GMP regulation, and carbon and nitrogen
utilization. Several genes controlled by PhoQ were shown to be dysregulated during infection of
lung epithelial cells, including upregulation of oprH-phoP-phoQ, the lipid A modification gene
arnB, and downregulation of a lipid A deacylase, pagL. Consistent with this, lipid A from a
phoQ mutant grown in varying magnesium concentrations displayed alterations. LPS of the
phoQ mutant revealed increased inflammatory properties as demonstrated by increased secretion
of the cytokines IL6, TNFalpha , and IL10 from PBMCs. The decrease in cytotoxicity of a phoQ
mutant correlated with a decrease in secretion of lipases and proteases when co-incubated with
cultured epithelial cells. These results suggest that the PhoP-PhoQ system might adapt the
bacterium to lung epithelia and that this might contribute to and be exacerbated by the selective
pressure of inhaled polymyxin therapeutics.
Unlike most sensor kinases that phosphorylate their cognate response regulators, PhoQ of P.
aeruginosa appears to act only as a phosphatase of its cognate regulator PhoP. Here it was
demonstrated that PhoP was not activated by PhoQ in a luminescence reporter screen. The sensor
kinase, RoxS, involved in regulation of the cyanide insensitive oxidase, was revealed as a
candidate phosphodonor to PhoP. Since mutation of roxS was able to reduce but not eliminate
expression from the oprH-phoP-phoQ operon, it is conceivable that other sensors contribute to
PhoP phosphorylation. It was also demonstrated that PhoP contributed to the known polymyxin
resistance of a phoQ mutant but only partially to cytotoxicity. These results emphasize the
complexity of the PhoP-PhoQ regulatory system.
10
Rodrigues, Alves Lucas Bocchini. "Patogenicidade de Salmonella Gallinarum com deleção dos genes phoP e phoQ (SG∆phoPQ) em aves comerciais." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/152283.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
RESUMO – Salmonella Gallinarum (SG) é um patógeno hospedeiro-específico que causa o tifo aviário, doença sistêmica severa que é considerada uma das principais preocupações da indústria avícola mundial. Quando infecta a ave, SG utiliza mecanismos de evasão para sobreviver e replicar no interior de macrófagos. Nesse contexto, os genes phoPQ codificam o sistema regulatório de dois componentes (PhoPQ) que regula genes de virulência responsáveis pela adaptação de Salmonella spp. a fatores antimicrobianos como baixo pH, peptídeos antimicrobianos e baixas concentrações de cátions bivalentes. No presente estudo, objetivou-se investigar a função desses genes para SG. Assim, uma estirpe de SG com genes phoPQ defectivos (SG ∆phoPQ) foi construída e sua patogenicidade avaliada em aves poedeiras de 20 dias de vida susceptíveis ao tifo aviário. SG ∆phoPQ não causou sinais clínicos nem mortalidade em aves desafiadas oralmente, sendo não-patogênica. Ademais, essa estirpe não foi recuperada de fígados e baços. Por outro lado, aves desafiadas subcutaneamente com a estirpe mutante tiveram alterações patológicas discretas a moderadas e baixas contagens bacterianas em tecidos de fígado e baço. A partir dos dados, observa-se que SG ∆phoPQ é atenuado para aves o que sugere que ambos os genes são importantes durante a infecção sistêmica em aves por SG.
ABSTRACT – Salmonella Gallinarum (SG) is a host-restrict pathogen that causes fowl typhoid, a severe systemic disease that is one of the major concerns to the poultry industry worldwide. When infecting the bird, SG makes use of evasion mechanisms to survive and to replicate within macrophages. In this context, phoPQ genes encode a two-component regulatory system (PhoPQ) that regulates virulence genes responsible for adaptation of Salmonella spp. to antimicrobial factors such as low pH, antimicrobial peptides and deprivation of bivalent cations. Herein, we aimed to investigate the role of the mentioned genes to SG. Thus, a phoPQ-depleted SG strain (SG ∆phoPQ) was constructed and its virulence assessed in twenty-day-old laying hens susceptible to fowl typhoid. SG ∆phoPQ did cause neither clinical signs nor mortality in birds orally challenged, being non-pathogenic. Furthermore, this strain was not recovered from livers or spleens. On the other hand, chickens challenged subcutaneously with the mutant strain had discreet to moderate pathological changes and also low bacterial counts in liver and spleen tissues. These findings show that SG ∆phoPQ is attenuated to susceptible chickens and suggest that both genes are important during chicken systemic infection by SG.
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Reinke, Hans. "Die Rolle des SAGA-Komplexes bei Aktivatorbindung und Chromatinöffnung am PHO5- und PHO8-Promotor in Saccharomyces cerevisiae." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-19064.
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Hertel, Christina. "In Vitro Studies of Nucleosome Positioning and Stability at the PHO5 and PHO8 Promoters in Saccharomyces cerevisiae." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-59424.
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Johns, Kristine Dawn. "Evidences for Protein-Protein Interactions Between PstB and PhoU in the Phosphate Signaling Complex of Escherichia coli." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3932.
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The PstSCAB2 complex serves the dual function of being a phosphate transporter as well as the primary sensor of phosphate for the Pho regulon. PhoU is an integral protein required for the signal from PstSCAB2 to be transmitted to PhoR. Our hypothesis is that conformational changes of PstSCAB2 during the phosphate transport process are the mechanism by which information about environmental phosphate levels are transduced to the cell. Additionally, we propose that direct protein-protein interactions between PhoU and the alternating conformations of PstSCAB2 mediate PhoU interactions with PhoR. By means of genetic and biochemical approaches, we have found substantial evidence supporting both these hypotheses.
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Munevar, Nicolas Federico Villamil. "Análise do metabolismo de polifosfato e do operon pst em Pseudomonas aeruginosa." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-10122015-101302/.
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O operon pst de P. aeruginosa codifica um transportador de fosfato de alta afinida-de e também a proteína PhoU que, em conjunto, atuam como repressores da ex-pressão do regulon Pho dessa espécie. A atividade de PhoU está também associada ao metabolismo de polifosfato (poliP), dado que mutantes phoU nulos apresentam um vasto acúmulo do biopolímero. Ensaios de β-galactosidase mostraram uma alteração na expressão dos genes ppk e ppx, envolvidos no metabolismo de poliP, no mutante phoU. Observou-se que na cepa selvagem, a transcrição de ppk e de ppx não responde às limitações de Pi ou de nitrogênio, sendo esses genes altamente expressos em condições normais de crescimento. Além disso, determinou-se que ppk é co-transcrito com o gene hemB, os quais formam, portanto, um operon. O operon pst também foi analisado. Foi identificado por ensaios de northern blot o transcrito do primeiro gene do operon, pstS, que codifica uma proteína periplasmática. Também, foi identificado um promotor imediatamente a montante de phoU, o gene mais distal do operon, que permitiria sua expressão em condições normais do crescimento bacteriano. Por fim, determinou-se por ensaios de EMSA que as duas sequências consenso Pho box presentes no operon pst são completamente funcionais.The pst operon in P. aeruginosa encodes a high-affinity phosphate transporter and the PhoU protein, which together act as repressors of Pho regulon of this species. The PhoU activity is also related with polyphosphate (polyP) metabolism, since phoU null mutants have a large accumulation of the biopolymer. β-galactosidase assays allowed to confirm a change in the expression of ppk and ppx genes, in-volved in PolyP metabolism, in the phoU mutant. It was also evidenced that in the wild type strain, the ppk and ppx transcription does not respond to Pi or nitrogen starvation, and that these genes are highly expressed under conditions of normal growth. In addition, it was determined that ppk is co-transcribed with hemB, a gene involved in the synthesis of porphyrins, and they constitute therefore an operon. The pst operon was also examined. Was identified by northern blot the transcript of the first gene in the operon, pstS, which encodes a periplasmic protein. Also, a promoter was identified immediately upstream of phoU, the most distal gene in the operon, allowing its expression in normal conditions of bacterial growth. Finally, it was determined by EMSA that the two consensus sequences Pho box present in the pst operon are fully functional.
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Boukhris, Ines. "Caractérisation, clonage, expression et étude de la régulation de gènes phytases de Streptomyces et Bacillus." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS274.
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Les phytases hydrolysent les phytates représentant la forme majeure de stockage du P dans les céréales. Ces phytates sont aussi des facteurs anti-nutritionnels qui chélatent les cations réduisant leur absorption. Dans le premier volet de cette thèse, une nouvelle souche bactérienne produisant une phytase extracellulaire a été isolée et identifiée comme Bacillus amyloliquefaciens US573. L’enzyme «PHY US573» a été purifiée et caractérisée en comparaison avec deux phytases commerciales Ronozyme PL et Natuphos. PHY US573 se distingue par sa forte thermostabilité en présence de calcium. En outre, PHY US573 se caractérise aussi par une tolérance remarquable aux sels comme le NaCl et LiCl. L’ensemble de ces propriétés montre que PHY US573 pourrait être une candidate intéressante pour des applications en alimentation animale ou en agriculture pour améliorer la biodisponibilité du P-phytique pour les plantes. Dans le deuxième volet, la souche Streptomyces sp. US42 produisant une activité phytase extracellulaire a été sélectionnée. L’enzyme «PHY US42» a été purifiée et caractérisée. PHY US42 est calcium dépendante également une grande stabilité en présence de sels biliaires et des protéases digestives. La modélisation moléculaire de PHY US42 indique qu'elle appartient au groupe des β-propeller phytases qui sont généralement calcium-dépendantes. Vu ses propriétés biochimiques intéressantes, PHY US42 constitue une bonne candidate comme additif dans les aliments pour animaux monogastriques en combinaison avec une histidine acide phytase. Enfin dans un troisième volet, nous nous sommes intéressés à l’étude de la régulation de l'expression du gène phytase de S. coelicolor M145 (sco7697) chez S. coelicolor M145, S. lividans TK24 ainsi que chez ses deux mutants ppk et phoP. Ainsi, en plus des boites pho localisées en amont de la région promotrice -35 siège de la régulation positive PhoP-dépendante, nous avons révélé pour la première fois que la RD localisée en aval de la région promotrice -10 est le siège d’une forte régulation négative par un répresseur inconnu. Ce dernier empêcherait l’activation PhoP-dépendante de l’expression du gène phytasePhytases hydrolyse phytate representing the major storage form of P in cereal. phytates are also anti-nutritional factors that chelate cations such as Ca²⁺, Mg²⁺, Fe²⁺, Z²⁺ reducing their absorption. The low bioavailability of phytic phosphorus in monogastric animals require their food supplementation with Pi to meet the needs of the animal in P. This creates an extra cost and increases the environmental pollution by the manure excretion highly charged phosphate. In the first part of this thesis, from soil samples taken near hot hydrothermal waters of the region Elhamma in southern Tunisian, a new bacterial strain producing extracellular phytase was isolated and identified as Bacillus amyloliquefaciens US573. The enzyme referred "PHY US573" was purified and characterized in comparison with two commercial acid histidine phytases Ronozyme PL and Natuphos. PHY US573 is calcium dependent and has an optimum activity at pH 7.5 (5 for Ronozyme and 5.5 for Natuphos) and 70°C (55°C for Ronozyme and Natuphos). PHY US573 is distinguished by its high thermostability, in fact, it keeps 93% of its activity after incubation for 10 min at 75°C in the presence of calcium while Ronozyme and Natuphos keep only 45% and 53% of their activity, respectively. This enzyme is specific for phytic acid and also has a very good stability at pH 3 to 9 and a perfect stability in presence of bile salts. In addition, PHY US573 is also characterized by a remarkable salt tolerance because it retains 80 to 95% of its activity in the presence of 20 g/l of NaCl and LiCl, respectively. All these properties shows that PHY US573 could be an interesting candidate for applications in feed industry alone or in combination with an histidine acid phytase. In a second part of this thesis, from the Streptomyces collection of LMB-CBS, a strain producing extracellular phytase activity was selected and identified as Streptomyces sp. US42. The enzyme "PHY US42" was purified and characterized. PHY US42 has a calcium-dependent activity (such as Bacillus phytases), optimally active at pH 7 and 65°C. PHY US42 is perfectly stable at pHs ranging from 5 to 10 and its thermal stability is greatly increased in the presence of calcium. Indeed, PHY US42 maintains 80% of its activity after 10 min of incubation at 75 °C in the presence of calcium. PHY US42 has also a high stability in the presence of bile salts and digestive proteases. Molecular modeling of PHY US42 indicates that it belongs to the β-propeller phytase group which are usually calcium-dependent. Given its interesting biochemical properties, PHY US42 which would operate mainly in the intestine, is a good candidate for use as an additive in agastriques fish food or in combination with an histidine acid phytase in feed industry. Finally in a third part, we are interested in studying the regulation of the expression of the phytase gene of S. coelicolor M145 (sco7697) in S.coelicolor M145, S.lividans TK24 and among its two mutants ppk and phoP. To do this, we merged the wild promoter regions (phyWT) or mutated (phym1, phym2, phym1+2) of sco7697 gene with the GUS reporter gene encoding ß-glucuronidase activity. Thus as expected, we demonstrated that the deletion of the PHO box located upstream of the -35 reduces the level of induction of sco7697 in conditions of Pi limitation. Moreover, we have revealed for the first time that the alteration of RD located downstream of -10 correlates with a dramatic increase of GUS expression when PhoP is present. Our results demonstrate that this RD is the seat of a strong negative regulation by an unknown repressor. This would prevent the PhoP-dependent activation of expression of the phytase gene
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Coornaert, Audrey. "Etude de la régulation post-transcriptionnelle de l'expression du système à deux composants PhoQ-PhoP par les ARN régulateurs chez Escherichia coli." Paris 7, 2012. http://www.theses.fr/2012PA077129.
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Les bactéries ont développé diverses stratégies leur permettant de survivre aux brusques changements de leur environnement. Par exemple, les systèmes à deux composants (SDC) sont des régulateurs transcriptionnels majeurs: souvent, une kinase, stimulée dans des conditions spécifiques, active le régulateur transcriptionnel qui lui est associé, afin de permettre la régulation de l'expression de ses gènes cibles. PhoQ-PhoP est un SDC central, activé dans des conditions de faible concentration de magnésium, d'acidification du milieu ou encore par les peptides antimicrobiens. En réponse, il active l'expression de nombreux gènes. Les ARN régulateurs sont aussi un moyen rapide d'adaptation. Chez les bactéries, l'action d'un grand nombre d'entre eux dépend de la protéine chaperon à ARN Hfq. Leur mode d'action consiste à s'apparier directement à l'ARNm cible par complémentarité imparfaite de séquence. Il en résulte une régulation, positive ou négative, de la traduction et/ou de la stabilité de l'ARNm cible. Nous avons montré que MicA et GcvB, deux ARN régulateurs Hfq-dépendants, réprimaient directement l'expression dephoPQ en se fixant à la région de démarrage de la traduction dephoP, entrant ainsi en compétition avec la fixation du ribosome. Etonnamment, ils affectent différemment l'expression des gènes cibles de PhoP : alors que MicA, contrôlé par sigma E, réprime l'expression du régulon, GcvB a un effet plutôt activateur. Ce résultat troublant attend encore une explication, même s'il semble lié à un effet pléiotropique de GcvB dans la cellule. Nous avons mis en évidence un lien entre trois systèmes d'adaptation bactériens différents: les ARNreg, les SDC et les facteurs sigmaBacteria have developed many strategies allowing them to adapt and live in ever changing environments. Among them, two- component Systems are key regulators of transcription: in most cases, a histidine kinase protein, stimulated by specific signals, activates its cognate response regulator, leading to regulation of the expression of target genes. PhoQ-PhoP is one of those two-component Systems, and is activated by low extracellular magnesium concentration, low pH or antimicrobial peptides. In response, it activates the expression of dozens of genes involved in magnesium import, bacterial virulence or response to acid stress. Small regulatory RNAs are also involved in the rapid adaptation of gene expression to the environment. In bacteria, there is a particular class, whose activity is dependent on the RNA chaperone Hfq. They act by pairing with target mRNA(s) via imperfect duplexes and modify, either positively or negatively, target mRNA translation and/or stability. We have showed that MicA and GcvB, two Hfq-dependent small regulatory RNAs, directly dowriregulate PhoQ-PhoP synthesis by pairing with the translation initiation region of the first cistron ofphoPQ mRNA, thereby inhibiting binding of the small ribosomal subunit. Surprinsingly, these regulations differently affect expression of the PhoP regulon: MicA has, as expected, a negative effet on the regulon, while GcvB seems to have a positive effect. This unexpected result is still under investigation but seems to be related to a pleiotropic effect of GcvB in the cell. More generally, we highlighted a link between three different bacterial adaptative regulatory Systems: sRNA, two-component Systems and sigma factors
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Johansson, Erik. "Phos Graphis." Thesis, Blekinge Tekniska Högskola, Sektionen för teknokultur, humaniora och samhällsbyggnad, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-1627.
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Phos Graphis är en mötesplats för fotografer och modeller. Denna mötesplats ska fungera som en grund för att hitta den medpart man söker, t.ex. en fotograf som letar efter en modell till ett projekt. Användarna erbjuds även egna gallerier och möjligheter att diskutera i forum samt privat meddelandefunktionalitet. Grundtanken är att Phos Graphis ska fungera som ett verktyg för att lättare kunna utvecklas inom sin roll.
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Gardner, Stewart G. "Genetic analysis of conserved residues in PhoU of Escherichia coli." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd934.pdf.
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Vlasic, Daniel 1979. "Fake Phong shading." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/87297.
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Ghorbel, Sofiane. "Caractérisation et régulation de l'expression de l'opéron phoR/phoP et du gène ppk qui jouent un rôle dans le contrôle de la biosynthèse d'antibiotiques chez Streptomyces lividans." Paris 11, 2004. http://www.theses.fr/2004PA112056.
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J'ai étudié au cours de ma thèse les relations existant entre le métabolisme du phosphate et la production d'antibiotiques chez Streptomyces lividans. J'ai plus particulièrement cherché à élucider la dynamique de régulation du gène ppk et du système à deux composants phoR/phoP. On a observé qu' in vivo, Ppk joue un rôle crucial dans la régénération de l'ATP à partir de l'ADP et des polyphosphates. L'expression de ppk est induite en condition de limitation en phosphate d'une manière dépendante de PhoR/PhoP et réprimée en condition d'excès de phosphate et d'ATP par un répresseur putatif. Le phénotype de surproduction d'antibiotiques du mutant ppk est alors dû à un déficit énergétique conduisant à une stimulation des voies métaboliques centrales et à l'accumulation des précurseurs. J'ai étudié par des analyses transcriptionnelles, la régulation de l'expression de phoR/phoP et des gènes divergents phoU et psiA. J'ai démontré que l'expression de phoR/phoP, phoP et de phoU est induite en condition de limitation en phosphate, cette induction est plus importante chez le mutant ppk. J'ai parallèlement déterminé les sites de début de transcription de ces gènes (tsp) et étudié la force relative de leurs promoteurs à l'aide de fusion transcriptionnelle. J'ai démontré également que phoR/phoP, phoP et phoU sont sous le contrôle positif de PhoP. Les mutants phoP (régulateur) et phoR (kinase) sont caractérisés aussi par un phénotype de surproduction d'antibiotiques et de croissance limitée, par contre le rôle de phoU et psiA reste mystérieux. Enfin, j'ai découvert que psiA est aussi induit par la limitation en phosphate de manière dépendante de phoU mais indépendante de PhoR/PhoPI studied during my thesis the relations existing between the phosphate metabolism and the antibiotic production in Streptomyces lividans. I more particularly sought to elucidate the dynamics of regulation of the ppk gene and of the phoR/phoP two-component system. We have observed that in vivo, ppk play a crucial part in the regeneration of the ATP from the ADP and the polyphosphates. The expression of ppk is enhanced in condition of phosphate limitation in a PhoR/PhoP dependent manner and repressed in condition of phosphate and ATP excess by a putative repressor. The phenotype of antibiotic overproduction in the ppk mutant is then due to an energy deficit leading to a stimulation of the central metabolic pathways and to the accumulation of the precursors. I studied, by transcriptional analysis, the regulation of the phoR/phoP expression and the divergent genes phoU and psiA. I showed that the expression of phoR/phoP, phoP and phoU is induced in condition of phosphate limitation, this induction is more important in the ppk mutant strain. I, in parallel, determined the transcription start points (tsp) of these genes and studied the relative force of the various promoters using transcriptional fusion. I also showed that phoR/phoP; phoP and phoU are under the positive control of PhoP. The mutants phoP (response regulator) and phoR (sensor kinase) are also characterized by a phenotype of overproduction of antibiotics and limited growth. On the other hand the role of phoU and psiA remains mysterious. Lastly, I discovered that psiA is also induced by phosphate limitation in a phoU dependent but PhoR/PhoP independent way
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Hussaini, Muzhgan. "Luminous Land of Phon." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/91402.
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This thesis, Luminous Land of Phon, explores how architectural spaces, even interior spaces, interact with nature along different dimensions. Light and sound are the two very powerful elements of nature and are the focus of this study. Louis Kahn once said: "The sun does not realize how wonderful it is until after a room is made." (Source: https://www.quotetab.com/quotes/by-louis-kahn#GdaYdAIrZ8tmvcyh.97)
The question of nature is explored in an urban environment to challenge the tired dualistic division between the human and the natural world. This project transforms the way we think about the urban so that architecture and nature can have great harmony and elevate each other instead of canceling each other. The project is a school of architecture and landscape architecture that promotes fine spaces with desirable qualities of light and sound for the design professionals of the future. The project is sited in the University of the District of Columbia as an expansion of their existing campus and programs.Master of Architecture
The architecture is a school of Architecture and Landscape architecture consisting of a full scale natural water pool underneath the building, Gallery and shop space under the pool, studio spaces, class rooms, faculty offices, cafeteria, and ceremony halls for the University of the District of Columbia at its Van Ness Campus sited at the Connecticut Ave, NW Washington D.C. The thesis is an exploration of the concept of bringing nature into architecture and a formal study of their harmony with each other, Architecture, structure and construction of the building.
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Wu, Jesse 1972. "Towards a poly-phon-ic environment." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/70865.
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Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 96-99).
This thesis explores an architectural/landscape environment where polyphonic metaphors are the means for exploration and investigation. Polyphonic, as described in musical definitions/ terms, is the style of composition in which two or more distinctly independent but organically related parts sound against one another. This combination produces associations within the piece that relate to various time lengths and musical instruments when particular musical motives, specifically melodic lines, play against one another. An interdependent relationship between the lines, a vertical association, is referred as harmony, while an interdependent relationship within the lines, a horizontal relationship, is referred as melody. The significance of this metaphorical association with architectural form is the opportunity to create an architectural vocabulary that is exemplified by its richness and diversity of spatial, material, and subconsciousness qualities that moves beyond music's time sequential nature. It is an attempt to provide an environment that exhibits polyphonic qualities in a space-time sequence. Inherent to achieve these qualities, several issues must be considered. This includes; territorial definition and exchange (privacies vs. public), materiality decisions, physical reciprocity, lighting intentions ... etc. The vehicle for these studies will be a chamber music facility programmed for both practice and performance. It is a place where chamber groups or individual performers have decisions to select a place appropriate for their "style" of performance beyond the traditional enclosed concert hall.
by Jesse Wu.
M.Arch.
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Kolady, Krishnan V. "Phigs based phong rendering emulation Software." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41975.
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Discussed is the design, implementation and use of a graPHIGS (IBM PHIGS) based sub-system that provides for shading of graphical models using the Phong shading technique. The ISO standard for 3D graphics, PHIGS, provides for wireframe display and manipulation of graphics data. PHIGS + implementations, while providing this capability, will not be widely available for some time. This capability will provide a generally useful extension to PHIGS for use by PHIGS based applications. The software provides the applications programmer with a graPHIGS based instruction set which acts as a superset to the current graPHIGS calls. Using the provided functions the user can quickly do hidden surface elimination and Phong rendering of 3-D models in 3-D views. The program contains approximately 15,000 lines of C code and uses graPHIGS inquiries and calls for information retrieval and datastructure maintenance.
Master of Science
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Mcandrew, Peter Craig. "Characterisation of the Pho4 transcription activation domain." Thesis, Institute of Cancer Research (University Of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314104.
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Carvin, Christopher Dumas. "Transcriptional regulation and chromatin remodeling mechanisms at PHO5." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2193.
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Regulation of gene expression is vital for proper growth and prevention of disease states. In eukaryotes this regulation occurs in the context of chromatin which creates an inherent barrier for the binding of trans-acting factors, such as transcription factors and RNA polymerase. This dissertation focuses on the role of transcriptional activators and chromatin remodeling coactivators in the regulation of the repressible acid phosphatase gene PHO5. Our studies show that histone methylation at lysine 4 of histone H3 is required for the full repression of PHO5and GAL1-10. We show that bromodomains, a domain conserved in chromatin remodeling coactivators, may function to stabilize binding. Finally, we present a strategy using DNA methyltransferases as in vivo probes to detect DNA-protein interactions and examine chromatin structure. We extend this strategy to zinc-finger proteins which can be engineered to bind to any desired DNA sequence as a means of targeting methylation with potential use in epigenetic silencing.
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Jessen, Walter Joseph. "Chromatin dynamics at the Saccharomyces cerevisiae PHO5 promoter." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/3306.
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In eukaryotes, the organization of DNA into chromatin is a primary determinant of gene expression. Positioned nucleosomes in promoter regions are frequently found to regulate gene expression by obstructing the accessibility of cis-regulatory elements in DNA to trans-factors. This dissertation focuses on the chromatin structure and remodeling program at the S. cerevisiae PHO5 promoter, extending the use of DNA methyltransferases as in vivo probes of chromatin structure. Our studies address the diversity of histone-DNA interactions in vivo by examining nucleosome conformational stabilities at the PHO5 promoter. We present high-resolution chromatin structural mapping of the promoter, required to relate in vivo site accessibility to nucleosome stability and show that the PHO5 promoter nucleosomes have different accessibilities. We show a correlation between DNA curvature and nucleosome positioning, which is consistent with the observed differences in accessibility/stability. Kinetic analyses of the chromatin remodeling program at PHO5 show that nucleosomes proximal to the enhancer are disrupted preferentially and prior to those more distal, demonstrating bidirectional and finite propagation of chromatin remodeling from bound activators and providing a novel mechanism by which transactivation at a distance occurs.
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Marden, Chloe Maria. "Functional analysis of the P47 PHOX gene promoter." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392359.
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Gomes, Sara Maria Zago. "Expressão e atividade da NAD(P)H-oxidase de membrana nas células trofoblásticas de camundongos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/42/42134/tde-09092008-173354/.
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As células trofoblásticas provenientes de cones ectoplacentários na fase de pós-implantação expressam as subunidades do complexo NAD(P)H-oxidase de membrana p22-phox, gp91-phox, p47-phox, p40-phox, p67-phox e Rac1 previamente descritas em fagócitos e envolvidas com a atividade fagocitária destas células. Ocorre modulação da expressão das subunidades do complexo enzimático NAD(P)H-oxidase sob o estímulo com PMA, agente capaz de fosforilar a subunidade p47-phox e ativar esta enzima em fagócitos profissionais. Nossos ensaios experimentais indicam que as células trofoblásticas são capazes de gerar espécies reativas de oxigênio dependente da atividade do complexo NAD(P)H-oxidase de membrana de baixa intensidade quando não estimuladas e de forma muito mais intensa quando estimuladas pelo PMA. As características de expressão e atividade do complexo enzimático NAD(P)H-oxidase de membrana encontradas neste estudo sugerem que esta enzima é semelhante a encontrada em outros fagócitos e, desta forma possa talvez estar também envolvida com processos de defesa da interface materno-fetal.In macrophages and neutrophils, the activation of the phagocytosis is defined by the acquisition of competence for microbicide, tumoricide and cytolytic functions resultant of generation and release of oxygen reactive species, besides the phagocytic process per se. Like these phagocytes, trophoblast cells in many species are also phagocytic. This cellular population involves completely the embryo and exhibits different and specific characteristics along the gestation. In rodents and primates, these cells are strategically positioned between maternal and fetal circulation and exhibit invasive and phagocytic activity, respectively responsible for anchorage of the embryo into the endometrium and uptake of an adequate nutritional supply for the embryo development. In rodents, these activities present a maximum degree during the implantation period, gradually declining, as the placenta develops. In the presence of strange particles at the maternal-placental interface, however, this process can be reactivated and, in this case, may be related to defense\'s mechanisms. Previous studies performed in our laboratory showed the potential of the trophoblast in producing and releasing reactive species of oxygen/nitrogen, in a very similar manner to that observed in macrophages and neutrophils. The production of such molecules is associated to different enzymes, but the localization of hydrogen peroxide on trophoblast cell surface has suggested a NAD(P)H-oxidase activity. NAD(P)H-oxidase is formed by the cytochrome b558 associated to the cellular membrane (subunits p22-phox + gp91-phox), the cytosolic subunits p47-phox, p67-phox and p40phox and, the GTPases Rac1 and Rac2 in an electron generator system that uses NADH or NADPH as substratum. Once activated, the enzymatic complex is responsible for the electron inflow to the molecular oxygen, yields superoxide anion. Thus, based on the literature and results previously obtained by our group, this study analyzed the protein and gene expression of the NAD(P)H-oxidase complex subunits respectively by immunolocalization and Westernblotting and rt-PCR, in the mouse trophoblast stimulated with PMA. Rt-PCR semi-quantitative analyses showed increase expression of the subunits p22-phox, gp91-phox, p47-phox, p67-phox, p40phox and Rac1 in PMA-treated in comparison with non treated ectoplacental cones. The expression of the subunits gp91-phox, p47-phox and p67-phox were confirmed by Western blotting and, like gene expression also increased in the presence of PMA. These subunits were mostly located in the trophoblast giant cell population, associated to the phagocytic process at the maternal-placental interface. Increased expression of such subunits may be related to an increase in the NAD(P)H-oxidase activity. To analyze this possibility and to determine the role played by NAD(P)H-oxidase activity in the reactive oxygen species produced by trophoblast cells, cellular assays were performed using the oxyethidium fluorescence, a product of dihydroethidium oxidation by superoxide anion. Thus, under PMA stimulus and antimycin A that blocks the mitochondrial NAD(P)H-oxidase activity and, apocynin and allopurinol, respectively blocking the membrane NAD(P)H-oxidase and xhantine oxidase and, still, using specific superoxide and hydrogen peroxide scavengers (superoxide dismutase enzyme and catalase) we showed the generation of reactive species of oxygen-NAD(P)H-oxidase dependent by trophoblast cells, mostly when stimulated. These results come to add important information about the potential of the trophoblast in producing reactive species at the maternal-fetal interface and, open a new investigation interest on the NADPH-oxidase regulatory processes and its involvement in defense functions of the embryo in both healthy and pathological processes that can determine the failure of the gestation.
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Bélanger, Étienne. "Synthèse asymétrique par voie catalytique d'alpha-fluorocétones et développement de dérivés de l'i-PR-PHOX comme équivalents pratiques du t-BU-PHOX." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28320/28320.pdf.
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Bélanger, Etienne. "Synthèse asymétrique par voie catalytique d'alpha-fluorocétones et développement de dérivés de l'iota-PR-PHOX comme équivalents pratiques du tau-BU-PHOX." Doctoral thesis, Université Laval, 2011. http://hdl.handle.net/20.500.11794/22782.
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Tableau d'honneur de la Faculté des études supérieures et postdoctorales, 2011-2012Cette thèse porte sur le développement de nouvelles méthodologies de synthèse asymétrique permettant l'accès aux ct-fluorocétones. Deux nouvelles méthodes de synthèse énantiosélectives par voie catalytique d'a-fluorocétones ont été développées. La stratégie employée implique l'utilisation de précurseurs d'énolates fluorés comme nucléophiles prochiraux dans la réaction d'alkylation allylique catalysée par le palladium. En premier lieu, les éthers d'énol silylés ont été examinés dans cette réaction et une grande variété d'a-fluorocétones a pu être synthétisée avec de très bonnes énantiosélectivités. Ensuite, une méthode alternative utilisant les carbonates d'énol allylés fluorés a également été développée dans le but de simplifier les conditions réactionnelles et de pallier aux problèmes de stabilité observés pour certains éthers d'énol silylés. En plus de remédier à ces problèmes et de permettre l'accès aux mêmes oc-fluocétones, l'élément clé de cette deuxième approche est l'utilisation de moins de ligand chiral que de catalyseur de palladium. Cet important effet du ratio ligand/palladium, très peu documenté dans la littérature, a démontré la différence de réactivité entre les précurseurs d'énolates fluorés et les composés non fluorés. Finalement, la dernière partie de cette thèse met l'emphase sur le design, la synthèse et l'application de nouveaux ligands chiraux phosphinooxazolines (PHOX) en catalyse asymétrique. Le but visé est de généraliser les deux méthodes précédentes en permettant l'accès aux deux séries d'énantiomères des a-fluorocétones. La synthèse de plusieurs nouveaux ligands PHOX dérivés de la valine, de la leucine et de l'isoleucine a été réalisée et leur efficacité a été démontrée dans diverses réactions énantiosélectives.
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Lefevere, Vincent. "Architectures spécialisées pour l'éclairement de Phong en temps réél." Lille 1, 1994. http://www.theses.fr/1994LIL10017.
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Apres une breve introduction de l'infographie et des diverses techniques d'eclairement et d'ombrage, nous etudions differentes architectures en vue de la realisation d'une unite calculant l'eclairement de phong en temps reel. Nous montrons rapidement que cela reclame une puissance de calcul importante. La complexite de chacune des formules d'eclairement est ensuite examinee afin de determiner la meilleure optimisation selon la position de la source et de l'observateur, pour une ou plusieurs sources. Par la suite, nous restreignons notre etude a la conception d'une unite d'eclairement pour des sources de lumiere situees a l'infini dans une scene visualisee en projection perspective. Lors de la conception, deux points attirent notre attention du fait de leur complexite importante. Il s'agit de la normalisation et de l'elevation a la puissance. Afin d'optimiser la complexite du premier des deux modules, nous determinons les tailles utiles des chemins donnees grace a une etude theorique. Cela nous permet d'introduire l'unite de pre-normalisation. Pour resoudre le second point, plusieurs solutions sont proposees dont l'utilisation d'approximations. Les architectures correspondantes sont presentees aboutissant ainsi a une solution finale permettant d'obtenir un rendu du speculaire tres proche de celui propose par phong pour un prix tres abordable. Enfin nous detaillons le reste de la version restreinte du processeur d'éclairement.
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Baker, Sarah Jane. "Molecular characterisation of Salmonella typhi PhoP/Q regulated genes /." Title page, abstract and contents only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phb1683.pdf.
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Karathanassis, Dimitrios. "Structural insights into membrane binding by phox homology (PX) domains." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619724.
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Pereira, Alexandre. "Processus physico-chimiques de contamination moléculaire phot-assistée sur satellites." École nationale supérieure de l'aéronautique et de l'espace (Toulouse ; 1972-2007), 2004. http://www.theses.fr/2004ESAE0010.
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Le contrôle du vieillissement des satellites est un enjeu économique très important pour l’industrie spatiale. La contamination moléculaire des surfaces externes des satellites est un problème majeur rencontré en orbite, directement lié à cette dégradation des matériaux. Le travail présenté dans cette thèse concerne ainsi l’étude des processus physico-chimiques de la contamination moléculaire photo-assistée des revêtements de contrôle thermique, des optiques et des générateurs solaires des véhicules spatiaux. Le but était de comprendre et de modéliser les processus essentiels régissant la photo-déposition de contaminants afin de développer un modèle physique prédictif. Pour valider ce modèle, nous avons élaboré un moyen d’essai expérimental visant à simuler d’une part la condensation de contaminants purs et d’autre part leur photo-déposition, et de comparer les cinétiques de déposition et de réémission dans les deux cas. Nous avons ainsi pu mettre en évidence différents régimes de déposition suivant la température du substrat, le flux de contaminants incident, la durée d'irradiation UV, et caractériser les dépôts polymères par spéctrométrie FTIR et microscopie optique. Le modèle développé nous permet de modéliser la croissance d’un dépôt par condensation sur une surface froide, l'équilibre entre l'adsorption et la désorption de molécules transitoirement adsorbées, la croissance d’un film polymère par photo-déposition sur une surface chaude ainsi que la réémission des molécules qu’elles soient simplement condensées ou polymérisées.
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Raad, Houssam. "Etude de la régulation de l'activation de la NADPH oxydase : phosphorylation de la GP91 phox / NOX2 et de la P67 phox dans les polynucléaires neutrophiles humains." Paris 11, 2008. http://www.theses.fr/2008PA11T056.
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Kriegl, Lydia. "Chromatinstruktur und Regulation der Genexpression des Phosphatasegens PHO3 in Saccharomyces cerevisiae." Diss., [S.l.] : [s.n.], 2005. http://edoc.ub.uni-muenchen.de/archive/00004720.
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Schermer, Ulrike. "Mechanism of chromatin reassembly at the yeast PHO5 promoter upon repression." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-64228.
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Bui, Thanh Phong [Verfasser]. "Theoretical and Numerical Analysis of Broadband Combustion Noise / Thanh Phong Bui." Aachen : Shaker, 2008. http://d-nb.info/1162793031/34.
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Erasmus, Jennifer Carr. "Small Pho GTPase Signalling Downstream of E-cadherin." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503823.
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Khong, Phong [Verfasser], Peter [Akademischer Betreuer] Mutschler, and Mario [Akademischer Betreuer] Pacas. "Magnetic Guidance for Linear Drives / Phong Khong. Betreuer: Peter Mutschler ; Mario Pacas." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2011. http://d-nb.info/1105563898/34.
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Nguyen, Thanh Phong [Verfasser]. "Greenhouse Gas Emissions from Composting and Anaerobic Digestion Plants / Phong Nguyen Thanh." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/104305586X/34.
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Almeida, Luiz Gustavo de. "Acúmulo de polifosfato e o papel do gene phoU em Pseudomonas aeruginosa." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-26062014-163027/.
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Polifosfato inorgânico (PPi) é um polímero linear formado por diversas moléculas de ortofosfato (Pi) unidas por ligações fosfoanidridas de alta energia. Bactérias da espécie Pseudomonas aeruginosa acumulam grandes quantidades de PPi. Moléculas de Pi são captadas do meio através de dois sistemas de transporte. O principal deles é o sistema Pst, que possui alta afinidade por seu substrato. Pst é codificado por um operon de mesmo nome, formado por cinco genes. Os quatro primeiro genes codificam para as proteínas envolvidas no transporte de Pi, sendo que o último gene do operon, phoU, codifica para uma proteína cuja exata função é desconhecida. Com o objetivo de elucidar o papel deste gene e avaliar a sua relação com o acúmulo de PPi, foi construída uma mutação phoU na cepa PA14 de P. aeruginosa. O mutante não só apresentou uma maior capacidade de acumular PPi mas também se mostrou mais sensível a estresses ambientais e a antibióticos. Os resultados obtidos indicam que o gene phoU possui uma função regulatória sobre o acúmulo de PPi. O mutante phoU também apresentou níveis mais altos da molécula de alarme guanosina tetrafosfato (ppGpp). Foi proposto um modelo que explica a relação entre o gene phoU, o acúmulo de polifosfato e ppGpp. O mutante phoU foi também cultivado em cultura contínua em um quimiostato limitado em Pi por 13 dias. Diversos ensaios fenotípicos foram realizados com bactérias isoladas do quimiostato. Estes apresentaram algumas características fisiológicas distintas da cepa ancestral.Inorganic polyphosphate (PPi) is a linear polymer composed of several molecules of orthophosphate (Pi) linked by energy-rich phosphoanhydride bonds. Bacteria of the species Pseudomonas aeruginosa accumulate large amounts of PPi. Pi molecules are captured via two trasport systems. The main one is the Pst system, which has high affinity for its substrate. Pst is encoded by an operon of the same name, consisting of five gene. The first four genes encode proteins involved in the transport of Pi and the last gene of the operon, phoU, encodes a protein whose exact function is unknown. To elucidate the role of phoU and its relation to PPi accumulation, a phoU mutant was constructed in strain PA14 of P. aeruginosa. The mutant accumulated high levels of PPi but was more sensitive to environmental stresses and antibiotics. The results indicate that phoU plays a regulatory role in the accumulation of PPi. The phoU mutant also displays high levels of the alarmone guanosine tetraphosphate (ppGpp). A model that explains the relation between phoU, ppGpp and polyphosphate accumulation is proposed. The phoU mutant was grown under steady-state conditions in a chemostat limited Pi for 13 days. Phenotypic assays performed with the bacteria isolated from the chemostat showed they acquired some distinct physiological characteristics.
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Anba, Jamila. "Biosynthese et exportation d'une proteine periplasmique, phos, chez escherichia coli k-12." Aix-Marseille 2, 1987. http://www.theses.fr/1987AIX22062.
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La surproduction par escherichia coli de la proteine periplasmique affine pour le phosphate (phos) provoque l'accumulation du precurseur de phos a la fois dans la membrane interne et le cytoplasme. Seul le precurseur membranaire peut etre mature et exporte, alors que le precurseur cytoplasmique subit une coupure lente de sa sequence signal et donne naissance a une forme "pseudo-mature" cytoplasmique. Existence d'un captage entre la synthese et l'exportation. Une application du systeme phos a ete realisee pour la production du facteur de liberation de l'hormone de croissance humaine (hgrf) chez e. Coli. En carence de phosphate, la proteine hybride phos-hgrf est synthetisee et exportee vers le periplasme
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Anba, Jamila. "Biosynthèse et exportation d'une protéine périplasmique, PhoS, chez Escherichia coli K-12." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602327q.
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Lubin, Emma A. (Emma Alexandra). "Global characterization of the Pho regulon in Caulobacter crescentus." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87463.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
Bacteria must sense and respond to their environment in order to survive and proliferate. Adapting to phosphate-limited conditions is particularly critical, as phosphate is a central component of many important biomolecules. Most bacteria respond to phosphate limitation through a widely conserved pathway, composed of the phosphate transport Pst system, and downstream signal transduction pathway, PhoR-PhoB, termed the Pho system. In this thesis, I use the model organism Caulobacter crescentus to characterize the response to phosphate limitation. I use ChIP-Seq on the transcriptional regulator PhoB to globally map the Pho regulon in Caulobacter in both phosphate-starved and -replete conditions. I find that the regulatory regions of over 50 genes are bound by PhoB following phosphate limitation, and I identify a consensus PhoB binding motif in Caulobacter. I then examine the function of PhoU, which is a putative negative regulator of the Pho regulon in Caulobacter and many other bacteria. I use morphological and microarray data to demonstrate that PhoU is not a negative regulator of the Pho regulon, and that it instead acts outside the PhoR-PhoB pathway. I find that the function of PhoU is tightly linked to cellular phosphate metabolism. This work offers insight into how Caulobacter responds to nutrient stress, as well as a better understanding of the connectivity and output of the phosphate limitation response pathway.
by Emma A. Lubin.
Ph. D.
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Ghimire, Jenisha. "Role of Ime4 Protein in PHO Regulon of S.cerevisiae." ScholarWorks@UNO, 2015. http://scholarworks.uno.edu/td/2037.
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In the yeast Saccharomyces cerevisiae, the IME4 methyltransferase, interacts genetically with methyl binding protein, Pho92, to affect the expression of PHO regulon target genes. Cells mutant in IME4 or PHO92 show increases in the RNA abundance of PHO regulon target genes. The increase in the RNA abundance of the PHO regulon target genes is not additive in the cells double mutant in IME4 and PHO92. Hence, Ime4 and Pho92 interact in a single pathway in PHO regulon. Surprisingly, cells overexpressing IME4 and MUM2 shows increase in some PHO regulon target genes, indicating that IME4 affects the PHO regulon target genes through multiple mechanisms in different conditions. A promoter swap experiment revealed that one of the PHO regulon mRNAs that codes for phosphatase, PHO5, is a direct target of Ime4. Further experiments are required to examine whether the same is true for all PHO regulon mRNAs.
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Martel, Alexandre. "Caractérisation de la position 48 du récepteur phoQ de Salmonella enterica serovar typhimurium." Mémoire, Université de Sherbrooke, 2001. http://savoirs.usherbrooke.ca/handle/11143/3284.
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La première partie de cette étude décrit la mise au point d'un test in vivo . Ce test utilise la luciférase comme gène rapporteur et permet de quantifier l'activité du récepteur PhoQ. Ce test est idéal pour la mesure de l'activité globale et de la régulation par le magnésium des différents mutants du récepteur PhoQ de Salmonella enterica serovar typhymurium obtenus par mutagenèse dirigée. De plus, cette étude démontre que l'ajout d'extension dépassant 8 acides aminés en C-terminal du récepteur PhoQ peut amener une plus grande phosphorylation de PhoP. La seconde partie de cette étude traite de la caractérisation de la position 48. Des études in vivo et in vitro démontrent que la mutation de la thréonine 48 du récepteur PhoQ conduit à la modification de l'équilibre kinase/phosphatase, et affecte le degré de phosphorylation de PhoP. Finalement, la cartographie par formation de ponts disulfures de la région environnant le résidu 48 suggère que ce dernier est positionné vers l'intérieur de l'interface de dimérisation."--Résumé abrégé par UMI
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Kativhu, Chido L. "PhoP-regulated genes contribute to Mycobacteria tuberculosis-induced burst size necrosis in macrophages." eScholarship@UMMS, 2021. https://escholarship.umassmed.edu/gsbs_diss/1120.
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Tuberculosis (TB) is primarily a pulmonary disease caused by Mycobacterium tuberculosis (Mtb). Mtb is highly infectious, but studies have shown that only 5–15% of Mtb-infected individuals develop TB disease. The Bacille Calmette-Gu.rin (BCG) vaccine is the only commercially available Mtb vaccine, but its efficacy varies based on the strain used. The Mtb PhoPR-mutant variant, MTBVAC, has been tested as a possible attenuated live vaccine against Mtb. Although it has successfully conferred durable CD4+ T-cell responses in infants, it has also resulted in adverse effects. Our goal is to identify PhoPR-regulated gene(s) that mediate Mtb-induced burst size necrosis in infected cells. PhoPR is a two-component system in mycobacteria. PhoR responds to environmental cues, such as changes in pH, and phosphorylates the PhoP transcription factor, which then activates or suppresses the expression of approximately 40 Mtb genes. The Mtb PhoPR-mutant strain is able to replicate in infected macrophages, but it does not induce the horizontal spread of Mtb to other immune cells. Our lab has previously shown that virulent, cytopathic strains of Mtb, such as H37Rv, suppress early apoptosis, have faster replication rates in macrophages, and trigger cell death at a lethal load threshold of approximately 25 bacteria. Cell death of infected macrophages primarily occurs via necrosis, which involves nuclear pyknosis without DNA fragmentation and general disruption of lipid bilayer membranes. Viable bacilli are released to infect other macrophages and neutrophils recruited to the developing TB lesion. Here, we show that PhoP contributes to burst size necrosis in macrophages and that the PhoP-regulated genes, fadD21 and pks3, are potential drivers of this necrosis. FadD21 and pks3 are involved in the generation of diacyl trehalose/penta-acyl trehalose (DAT/PAT) for cell wall synthesis, suggesting that Mtb cell wall composition may determine virulence. Therefore, we have uncovered potential targets for early intervention or vaccinations to avoid granuloma formation or tissue damage in response to Mtb-induced macrophage necrosis.
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Martel, Alexandre. "Caractérisation de la position 48 du récepteur phoQ de Salmonella enterica serovar typhimurium." Sherbrooke : Université de Sherbrooke, 2001.
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Conesa, Balbastre Gustavo. "Identification de particules et de processus durs dans le spectromètre PHOS de l'expérience ALICE." Phd thesis, Université de Nantes, 2005. http://tel.archives-ouvertes.fr/tel-00084765.
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Les collisions d'ions lourds sont un outil unique pour étudier la matière nucléaire dans des conditions extrêmes de densité et de température, comme celles présents peu après le Big Bang, où la matière nucléaire aurait été composé d'un plasma de quarks et de gluons quasi-libres. Sa production à l'aide de collisions Pb-Pb à 5.5A TeV est le thème central de l'expérience ALICE-LHC. Les photons émis dans ces collisions sont des signatures très intéressantes parce qu'elles apportent des informations non perturbées sur le plasma. Le détecteur PHOS de l'expérience ALICE est dédié à leur détection. Cette thèse présente une étude des performances de PHOS et décrit les algorithmes d'identification de particules. Les photons de haute énergie sont produits associés à un jet émis l'opposé qui subira des modifications causées par le plasma. Une méthode d'identification de ces processus et une estimation des modifications du jet par le plasma sont explicitées.