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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Dynamic Interleaved Imaging of Pyruvate Metabolism with Hyperpolarized 13C

Leung, Kevin Kai-Chi 24 May 2011 (has links)
Dynamic nuclear polarization and dissolution of 13C-labeled metabolite allows dynamic imaging of metabolism in-vivo. However, the spatial and temporal resolutions of magnetic resonance spectroscopic imaging are limited by the duration of free-induction decay acquisitions and the T1-based, non-recoverable polarization decay. This thesis describes the implementation of a spectral-spatial radiofrequency excitation pulse with a `flyback' echo-planar readout trajectory to dynamically image [1-13C]-pyruvate and [1-13C]-lactate in an interleaved manner. This technique excites a single resonance of either [1-13C]-pyruvate or [1-13C]-lactate and generates dynamic images with 5mm in-plane resolution. Metabolite dynamics extracted from the images and the corresponding non-localized spectroscopic data reveal similar kinetic rates upon fitting to a kinetic model. This demonstrates the feasibility of probing metabolism in heterogeneous tissues in-vivo with dynamic interleaved 13C MR imaging.
22

Dynamic Interleaved Imaging of Pyruvate Metabolism with Hyperpolarized 13C

Leung, Kevin Kai-Chi 24 May 2011 (has links)
Dynamic nuclear polarization and dissolution of 13C-labeled metabolite allows dynamic imaging of metabolism in-vivo. However, the spatial and temporal resolutions of magnetic resonance spectroscopic imaging are limited by the duration of free-induction decay acquisitions and the T1-based, non-recoverable polarization decay. This thesis describes the implementation of a spectral-spatial radiofrequency excitation pulse with a `flyback' echo-planar readout trajectory to dynamically image [1-13C]-pyruvate and [1-13C]-lactate in an interleaved manner. This technique excites a single resonance of either [1-13C]-pyruvate or [1-13C]-lactate and generates dynamic images with 5mm in-plane resolution. Metabolite dynamics extracted from the images and the corresponding non-localized spectroscopic data reveal similar kinetic rates upon fitting to a kinetic model. This demonstrates the feasibility of probing metabolism in heterogeneous tissues in-vivo with dynamic interleaved 13C MR imaging.
23

A Data-Based Practice Model For Pessary Treatment Of Pelvic Organ Prolapse: A Quality Improvement Project

Murray, Denise A. January 2014 (has links)
Background: Pelvic organ prolapse (POP) can be treated surgically or, more conservatively, with use of a pessary. Objective: To determine if the population of women treated for POP with the use of a pessary in one Nurse Practitioner's (NP) practice demonstrated health outcomes as better, same, or needing improvement through use of a data-based practice model from encounter data extracted from the electronic health record (EHR).Design: The project design was a quality improvement (QI) project, descriptive in nature. One Plan Do Study Act (PDSA) cycle was conducted for this QI project. Setting: NP managed specialty clinic in urban Southwestern Arizona that provides services to women with POP. Patients: Ten randomly selected women who had been treated conservatively for POP with use of a pessary were identified as two subpopulations and evaluated: women who received professional management of the pessary and women who were patient managed. Intervention: The intervention was the development of a data-based practice model, using patient profile data elements derived from the documented EHR encounters of the 10 women. Measurements: Twelve scales were developed to evaluate the patient profile data elements, generating numeric scores for each encounter. Two Decision Rules were then used to evaluate numeric scores by encounter, creating primary and secondary health outcomes. Limitations: Two limitations were identified. The QI project was limited by the small sample size of 10 patients. This is however, true to PDSA guidelines that recommend small scale cycles. The data were limited as only documented data were used. Conclusions: In general, the expected outcome was the outcome observed; the provider was unaware of any women in this QI Project who were not successfully treated with use of a pessary for treatment of POP. The value of this data-based practice model is that outcomes can be aggregated across populations rather than relying on recall of individual outcomes and therefore has potential to be used regularly and systematically as a quality feedback loop, as well as on a larger scale in future PDSA cycles to determine other outcomes beyond a single provider in this or other similar clinical populations.
24

Oxalates de calcium et hydroxyapatite : des matériaux synthétiques et naturels étudiés par techniques RMN et DNP / Calcium oxalates and hydroxyapatite : synthetic and natural materials studied by NMR and DNP techniques

Leroy, César 05 October 2016 (has links)
En France, environ 9,8% de la population souffre de lithiase urinaire. Nous proposons, ici, une nouvelle approche afin de caractériser ces matériaux et d'obtenir une meilleure compréhension de leur formation. Les médecins utilisent principalement des techniques FTIR pour déterminer les principales phases présentes dans une calcification pathologique donnée. Les méthodes de RMN semblent appropriées pour déterminer plus précisément la composition de ces calcifications pathologiques. Très peu d'analyses RMN de calculs rénaux et d'analogues synthétiques ont été réalisées à ce jour.Premièrement, les trois phases d'oxalate de calcium ont été synthétisées (CaC2O4?nH2O avec n = 1, 2, 3) en mettant en ¿uvre des protocoles originaux. L'analyse des spectres 1H, 13C CPMAS et 43Ca MAS à ultra-haut champ magnétique en abondance naturelle permet une identification précise des différentes phases et peut être interprétée en tenant compte du nombre d'inéquivalents des sites cristallographiques. L'hydroxyapatite a été étudiée en parallèle car pouvant également apparaître lors de lithiase urinaire.Enfin, nous montrons les résultats obtenus à partir de DNP MAS à 100 K sur les échantillons synthétiques. L'affinité de la combinaison biradical/solvant reste un facteur limitant pour les matériaux hétérogènes tels que ceux qui sont analysés dans cette étude. Nous devons être en mesure de trouver une combinaison appropriée pour les matériaux multi-composants complexes afin d'obtenir un gain équivalent sur tous les signaux. Finalement, il est démontré qu'il est possible de transposer l'approche méthodologique présentée ci-dessus à l'étude des calculs rénaux. / In France, about 9.8% of the population suffer from urolithiasis. The treatment of kidney stones, composed of 72% of hydrated calcium oxalates (CaC2O4∙nH2O) with n = 1, 2, 3, represents almost 900 million euros in annual spending and it is therefore necessary to understand the in vivo formation of these stones. Here we propose a new approach in order to characterize kidney stones and have a greater understanding of their formation. Physicians primarily use FTIR techniques to determine the major phases present in a given pathological calcification. NMR methods appears suitable to determine more accurately the composition of these pathological calcifications. Very few NMR analyzes of kidney stones and synthetic analogues were conducted to date. In a first step, the three phases of calcium oxalate were synthesized by implementing original protocols. Analysis of the 1H, 13C CP MAS and MAS 43Ca ultra-high magnetic field spectra at natural abundance allow precise identification of the different phases and can be interpreted by taking into account the number of inequivalent crystallographic sites. The hydroxyapatite was studied in parallel as it may also appear in urolithiase. Finally, we show results obtained from DNP MAS at 100 K on the synthetic samples. The affinity of the biradical/solvent combination remains a limiting factor for heterogeneous materials such as those analyzed in this study. We have to be able to find a suitable combination for complex multi-component materials and to obtain an equivalent gain on all signals. In a last step, it is demonstrated that it is possible to transpose the methodological approach presented above to the study of kidney stones.
25

Preserving hyperpolarised nuclear spin order to study cancer metabolism

Marco-Rius, Irene January 2014 (has links)
Monitoring the early responses of tumours to treatment is a crucial element in guiding therapy and increasing patient survival. To achieve this, we are using magnetic resonance imaging (MRI), which can provide detailed physiological information with relatively high temporal and spatial resolution. In combination with the dynamic nuclear polarisation (DNP) technique, high signal-to-noise is obtained, resulting in a powerful tool for in vivo 13C metabolic imaging. However, detection of hyperpolarised substrates is limited to a few seconds due to the exponential decay of the polarisation with the longitudinal relaxation time constant T1. This work aimed to improve the combination of hyperpolarisation and metabolic NMR/ MRI by extending the observation timescale of the technique. Working with quantum mechanical properties of the detected substrates, long lifetimes might be accessible by using the nuclear singlet configuration of two coupled nuclei. The singlet state is immune to intramolecular dipole-dipole relaxation processes, which is one of the main sources of signal decay in MRI. In favourable situations, the singlet relaxation time constant can be much longer than T1, so transfer of the polarisation into the singlet state may allow one to extend the usable time period of the nuclear hyperpolarisation. Here we studied the relaxation of hyperpolarised metabolites, including those found in the TCA cycle, and examined the possibility of extending their observation timescale by storing the polarisation in the long-lived singlet state. The polarisation remains in this state until it is eventually required for imaging. We also investigate how one may track polarised metabolites after injection into a subject due to the transfer of polarisation to the solvent by Overhauser cross-relaxation, so that the 13C polarisation remains untouched until imaging is required. In this way we should be able to interrogate slower metabolic processes than have been examined hitherto using hyperpolarised 13C MRS, and better understand metabolic changes induced in tumours by treatment.
26

Synthesis of chiral zirconium-based metal-organic frameworks as solid catalysts in asymmetric carbon-carbon coupling reactions

Nguyen, Khoa Dang 29 January 2020 (has links)
Comprehensive understanding of chirality has played a crucial role for ensuring safety and efficacy of drug products. In many cases, two optical configurations of a chiral molecule exhibit substantially different physiological behaviour, and thus the preparation of single enantiomers has become as an essential topic in the pharmaceutical industry.1-2 Enantiomerically pure compounds could generally be achieved by separation from racemic mixtures or direct synthesis of enantiopure molecules. Either way, chiral materials which are employed as stationary phase in chiral columns or chiral catalysis, are a basic condition to decide to enantiomeric excess of resulting mixtures. Despite obtaining high enantiomeric purity, the chiral separation of racemic mixtures is considered as an expensive and inefficient approach due to undesired enantiomers, while asymmetric synthesis, which enables dominant formation of the single enantiomers, is an atom-economical method. However, the development of efficient heterogeneous chiral catalysts has been still required further investigations to provide more potential options for asymmetric organic reactions, especially carbon-carbon bond formations, which are key steps in organic synthesis.1-3 In recent years, metal-organic frameworks have emerged as one of the most intriguing solid porous materials. Together with the highly active catalytic centers, wide structural and functional variations, MOFs have been successfully employed as heterogeneous catalysts for a variety of organic transformations.4-5 However, very few achievements relating to MOFs as asymmetric catalysts have been reported to date because of their low thermal and chemical stabilities. Such solid stable frameworks, the Zr-MOFs offers great opportunities for designing novel effective asymmetric catalysts.1, 6-9 This is an interesting, but also challenging topic with many open issues: • How can we introduce effectively enantiopure active sites into Zr-MOFs? • Are there any positive or negative impacts of Zr-nets on the performance of chiral catalytic sites? • If any, is it possible to control these effects during the reaction phase? • How is the recyclability of these chiral Zr-MOFs? Finding answers for these questions are the core of this thesis. In Chapter 3, DUT-67, an 8-connected zirconium and 2,5-thiophenedicarboxylate based MOF, was post synthetically functionalized by L-proline via solvent assisted linker incorporation to obtain a chiral base catalyst. The parent monocarboxylate could be almost completely exchanged by L-proline after 5 days of treatment. The resulting chiral DUT-67, DUT-67-Pro, was demonstrated to be a promising heterogeneous catalyst for the asymmetric Michael addition of cyclohexanone to trans-β-nitrostyrene with excellent yield (up to 96%) and enantioselectivity comparable to that of L-proline in homogeneous reaction (ee approximately 38%). The Zr-MOF could be reused at least 5 times without substantial degradation in crystallinity or catalytic activity. No leaching of catalytically active species into the liquid phase was detected over 5 cycles. A further understanding regarding the role of catalytic active sites, including Zr-clusters and L-proline, in asymmetric aldol addition of cyclohexanone and 4-nitro-benzaldehyde is investigated in Chapter 4 to clarify the predominant formation of syn-products as well as the absence of enantioselectivity in previous catalytic systems. The presence and location of L-proline into DUT-67 was confirmed by Solid-state MAS and DNP NMR data. The chiral DUT-67-Pro catalyst exhibits an excellent catalytic activity at low temperature (298 K) with an unprecedented syn-(S,S)-product selectivity in an asymmetric aldol addition reaction of cyclohexanone to 4-nitrobenzaldehyde (yield = 95%, ee = 96%). Comparative catalytic studies using a molecular Zr6-cluster model compound indicate the Zr6-moiety to be responsible for this inverse diastereoselectivity compared to well-established L-proline organocatalysis and a mechanism is proposed to explain the Zr6-cluster-mediated syn-selectivity. Masking residual acidic active sites in the cluster of the framework was found to be a key prerequisite to achieve the high enantioselectivity. The purely heterogeneous catalytic system based on DUT-67-Pro is highly stable and can be recycled several times. Lastly, a novel chiral diimine Zr-MOF, namely DUT-136, synthesized from one-pot reaction of ZrCl4 with 4-formylbenzoic acid, and (R,R)-1, 2-diphenylethylenediamine as an enantiopure core will be described in Chapter 5. Inspired from the versatile transformation of the C=N double bonds, a variety of post-synthetic methods, including oxidation, reduction, and metalation, was employed to modify DUT-136 for formation of the chiral amide-, amine-, and Ni-DUT-136, respectively. The catalytic behaviour of these post-synthetically modified materials was then evaluated in a wide range of asymmetric organic transformations, including the Friedel Craft alkylation, the Michael addition, the aldol reaction and the Ni-catalyzed C-C coupling. The research on synthesis of chiral Zr-MOFs and their catalytic behavior in this work are expected to provide a better understanding or at least give to other scientists open ideas for further deeper studies regarding this topic in the future.
27

Estudo do metabolismo energético mitocondrial e sua relação com as crises epiléticas em Wistar audiogenic rats (WAR) / Study of mitochondrial energy metabolism and its relationship with epileptic seizures in Wistar audiogenic rats (WAR)

Dechandt, Carlos Roberto Porto 25 June 2018 (has links)
Introdução: Wistar Audiogenic Rats (WAR) é modelo experimental desenvolvido na Faculdade de Medicina de Ribeirão Preto, para estudo da epilepsia, entretanto, a seleção genética em resposta aos comportamentos de crises audiogênicas também trouxe à tona alterações no metabolismo energético nesses animais. Dois estudos são relevantes deste ponto de vista, no primeiro Botion e Doretto observaram que WAR após serem estimulados apresentam: (a) valores de glicemia maior em relação ao Wistar; (b) aumento no lactato circulante - o que pode indicar deficiência na fosforilação oxidativa (OXPHOS); (c) aumento da atividade adrenérgica, induzindo dessensibilização da via lipolítica ?-adrenérgica no tecido adiposo epididimal. Pereira e colaboradores investigando o metabolismo de carboidratos relataram: (a) aumento na via glicólica; (b) translocação de GLUT4 aumentada no músculo gastrocnêmico e (c) redução nos níveis de glicogênio muscular. Objetivo: Diante desses achados o presente estudo tem como objetivo elucidar o metabolismo energético mitocondrial e sua relação com as crises epiléticas induzidas por estímulos sonoros. Resultados: Através de analises comportamentais e calorimetria indireta, relatamos que WAR possui perfil ansiogênico e tem preferência em oxidar aminoácidos; utilizando biopsias de tecido hepático, musculo esquelético e cardíaco, observamos maior densidade mitocondrial, acompanhada de maior geração de H2O2 e como consequência maior estresse oxidativo; na busca para elucidar com maior destreza, realizamos isolamento da fração mitocondrial do tecido hepático, e concluímos que não há maior geração de H2O2 por mitocôndria, porém há um enriquecimento proteico (algumas proteínas funcionais - como as envolvidas na OXPHOS- e outras não-funcionais - como as UCPs), além de relatarmos maiores níveis de proteínas envolvidas na dinâmica mitocondrial, desse modo podemos concluir que WAR possuem maior densidade mitocondrial e mitocôndrias com maior eficiência; o mesmo perfil mitocondrial foi observado no tecido cerebral. Após tratamento com DNP e NAC, observamos redução do estresse oxidativo no tecido cerebral, porém apenas NAC reduziu a severidade da crise, assim concluímos que o suave desacoplamento induzido por DNP não é capaz de reduzir de forma significativa a severidade da crise, porém a inibição da glicólise pelo NAC, alterou a bioenergética cerebral é capaz a reduzir a severidade da crise, deixando evidenciado que o metabolismo energético tem papel essencial/relevante na crise epilética induzida por estímulos sonoros em WAR, enquanto o estresse oxidativo tem papel secundário. / Introduction: Wistar Audiogenic Rats (WAR) is an experimental model developed in the Ribeirão Preto Medical School, for the study of epilepsy, however, the genetic selection in response to the behaviors of audiogenic crisis also brought up changes in energy metabolism in these animals. Two studies are relevant from this point of view, in the first Botion and Doretto observed that WAR after being stimulated present: (a) higher blood glucose values in relation to the Wistar; (b) Increase in circulating lactatewhich may indicate deficiency in oxidative phosphorylation (OXPHOS); (c) Increased adrenergic activity. Pereira and collaborators investigating the metabolism of carbohydrates reported: (a) increase in glycolysis; (b) Translocation of GLUT4 increased in gastrocnemius muscle and (c) reduction in muscle glycogen levels. Objective: In the face of these findings, the present study aims to elucidate the mitochondrial energy metabolism and its relation to the epileptic crises induced by sound stimuli. Results: Through behavioral analysis and indirect calorimetry, we report that WAR has reduced exploratory activity and has preference to oxidize amino acids; Using biopsies of liver tissue, skeletal and cardiac muscles, we observe greater mitochondrial density, accompanied by greater generation of H2O2 and as a result of greater oxidative stress; in the search to elucidate with greater dexterity, we perform isolation of the mitochondrial fraction of the hepatic tissue, and we conclude that there is no greater generation of H2O2 by mitochondria, but there is a protein enrichment (some functional proteins - such as those involved in OXPHOS - and other nonfunctional ones - such as UCPs), in addition to reporting higher levels of proteins involved in mitochondrial dynamics, so we can conclude that WAR has greater mitochondrial density and mitochondria more efficiently; the same mitochondrial profile was observed in the brain tissue. After treatment with DNP and NAC, we observed reduction of oxidative stress in the brain tissue, but only NAC reduced the severity of the crisis, so we conclude that the smooth decoupling induced by DNP is not able to significantly reduce the severity of the crisis, however the inhibition of glycolysis by the NAC, altered the brain bioenergetics is able to reduce the severity of the crisis, leaving evidence that the energy metabolism has essential/relevant role in the epileptic crisis induced by sound stimuli in WAR, while oxidative stress has secondary role.
28

Sensitivity Enhancement of Liquid-State NMR and Improvement of the INPHARMA Method / Empfindlichkeitssteigerung der Flüssigkeits-NMR und Verbesserung der INPHARMA Methode

Reese, Marcel 08 April 2010 (has links)
No description available.
29

Estudo do metabolismo energético mitocondrial e sua relação com as crises epiléticas em Wistar audiogenic rats (WAR) / Study of mitochondrial energy metabolism and its relationship with epileptic seizures in Wistar audiogenic rats (WAR)

Carlos Roberto Porto Dechandt 25 June 2018 (has links)
Introdução: Wistar Audiogenic Rats (WAR) é modelo experimental desenvolvido na Faculdade de Medicina de Ribeirão Preto, para estudo da epilepsia, entretanto, a seleção genética em resposta aos comportamentos de crises audiogênicas também trouxe à tona alterações no metabolismo energético nesses animais. Dois estudos são relevantes deste ponto de vista, no primeiro Botion e Doretto observaram que WAR após serem estimulados apresentam: (a) valores de glicemia maior em relação ao Wistar; (b) aumento no lactato circulante - o que pode indicar deficiência na fosforilação oxidativa (OXPHOS); (c) aumento da atividade adrenérgica, induzindo dessensibilização da via lipolítica ?-adrenérgica no tecido adiposo epididimal. Pereira e colaboradores investigando o metabolismo de carboidratos relataram: (a) aumento na via glicólica; (b) translocação de GLUT4 aumentada no músculo gastrocnêmico e (c) redução nos níveis de glicogênio muscular. Objetivo: Diante desses achados o presente estudo tem como objetivo elucidar o metabolismo energético mitocondrial e sua relação com as crises epiléticas induzidas por estímulos sonoros. Resultados: Através de analises comportamentais e calorimetria indireta, relatamos que WAR possui perfil ansiogênico e tem preferência em oxidar aminoácidos; utilizando biopsias de tecido hepático, musculo esquelético e cardíaco, observamos maior densidade mitocondrial, acompanhada de maior geração de H2O2 e como consequência maior estresse oxidativo; na busca para elucidar com maior destreza, realizamos isolamento da fração mitocondrial do tecido hepático, e concluímos que não há maior geração de H2O2 por mitocôndria, porém há um enriquecimento proteico (algumas proteínas funcionais - como as envolvidas na OXPHOS- e outras não-funcionais - como as UCPs), além de relatarmos maiores níveis de proteínas envolvidas na dinâmica mitocondrial, desse modo podemos concluir que WAR possuem maior densidade mitocondrial e mitocôndrias com maior eficiência; o mesmo perfil mitocondrial foi observado no tecido cerebral. Após tratamento com DNP e NAC, observamos redução do estresse oxidativo no tecido cerebral, porém apenas NAC reduziu a severidade da crise, assim concluímos que o suave desacoplamento induzido por DNP não é capaz de reduzir de forma significativa a severidade da crise, porém a inibição da glicólise pelo NAC, alterou a bioenergética cerebral é capaz a reduzir a severidade da crise, deixando evidenciado que o metabolismo energético tem papel essencial/relevante na crise epilética induzida por estímulos sonoros em WAR, enquanto o estresse oxidativo tem papel secundário. / Introduction: Wistar Audiogenic Rats (WAR) is an experimental model developed in the Ribeirão Preto Medical School, for the study of epilepsy, however, the genetic selection in response to the behaviors of audiogenic crisis also brought up changes in energy metabolism in these animals. Two studies are relevant from this point of view, in the first Botion and Doretto observed that WAR after being stimulated present: (a) higher blood glucose values in relation to the Wistar; (b) Increase in circulating lactatewhich may indicate deficiency in oxidative phosphorylation (OXPHOS); (c) Increased adrenergic activity. Pereira and collaborators investigating the metabolism of carbohydrates reported: (a) increase in glycolysis; (b) Translocation of GLUT4 increased in gastrocnemius muscle and (c) reduction in muscle glycogen levels. Objective: In the face of these findings, the present study aims to elucidate the mitochondrial energy metabolism and its relation to the epileptic crises induced by sound stimuli. Results: Through behavioral analysis and indirect calorimetry, we report that WAR has reduced exploratory activity and has preference to oxidize amino acids; Using biopsies of liver tissue, skeletal and cardiac muscles, we observe greater mitochondrial density, accompanied by greater generation of H2O2 and as a result of greater oxidative stress; in the search to elucidate with greater dexterity, we perform isolation of the mitochondrial fraction of the hepatic tissue, and we conclude that there is no greater generation of H2O2 by mitochondria, but there is a protein enrichment (some functional proteins - such as those involved in OXPHOS - and other nonfunctional ones - such as UCPs), in addition to reporting higher levels of proteins involved in mitochondrial dynamics, so we can conclude that WAR has greater mitochondrial density and mitochondria more efficiently; the same mitochondrial profile was observed in the brain tissue. After treatment with DNP and NAC, we observed reduction of oxidative stress in the brain tissue, but only NAC reduced the severity of the crisis, so we conclude that the smooth decoupling induced by DNP is not able to significantly reduce the severity of the crisis, however the inhibition of glycolysis by the NAC, altered the brain bioenergetics is able to reduce the severity of the crisis, leaving evidence that the energy metabolism has essential/relevant role in the epileptic crisis induced by sound stimuli in WAR, while oxidative stress has secondary role.
30

Etudes de cinétiques enzymatiques par polarisation dynamique nucléaire avec dissolution (D-DNP) : application à l'étape oxydative de la voie des pentoses phosphates (PPP) / Enzymatic kinetic studies by nuclear dynamic polarization with dissolution (D-DNP) : application to the oxidative step of the pentose phosphate pathway (PPP)

Sadet, Aude 09 October 2017 (has links)
L'une des voies principales du métabolisme cellulaire est la voie des Pentoses Phosphates (PPP). Cette voie métabolique est composée de deux cascades enzymatiques, une voie oxydative et une voie non oxydative. La voie oxydative de la PPP produit un cofacteur, le NADPH, qui est responsable du processus de détoxification de la cellule par son activité réductrice et un précurseur de diverses biosynthèses comme la lipogenèse. Un dysfonctionnement des trois enzymes qui composent cette étape de la PPP peut engendrer la mort cellulaire. Grâce à une nouvelle technique, la Polarisation Dynamique Nucléaire suivie par Dissolution (D-DNP), qui permet d’obtenir un gain de sensibilité par un facteur > 10 000, la quantification des paramètres cinétique dans les conditions physiologiques in cell est possible.Dans ce travail de thèse, nous utilisons un nouveau modèle de quantification des paramètres cinétiques qui offre la possibilité d’étudier une cascade enzymatique composée de 3 enzymes par D-DNP. Grâce à ces expériences, la sélectivité de la première enzyme de la voie oxydative, la G6PD, pour l’un des deux anomères de glucose-6-phosphate, ainsi que le rôle antioxydant de la deuxième enzyme de la PPP, la 6PGL, ont été observés. Pour réaliser ces études, une méthode de synthèse et de purification des différents substrats de chaque enzyme a été développée. Le tout premier inhibiteur de la 6PGL a été testé. Des études préliminaires réalisées sur des Trypanosoma brucei, parasite responsable de la maladie du sommeil, indiquent que la pénétration du glucose dans les cellules est l'étape cinétiquement limitante pour sa conversion enzymatique. / The Pentose Phosphate Pathway (PPP) is one of the main pathways of cellular metabolism. This metabolic pathway is composed of two enzymatic cascades: one is an oxidative pathway, and the other is non-oxidative. The oxidative branch of PPP produces a cofactor, NADPH, which is responsible for the detoxification process of the cell due to its reducing activity, and is also a precursor of various biosynthesis such as lipogenesis. A dysfunction of one of the three enzymes that make up this step of PPP can lead to cell death. Thanks to a new method, Dissolution Dynamic Nuclear Polarization (D-DNP), which features a sensitivity gain by a factor 10,000 compared to standard liquid-state NMR, the quantification of kinetic parameters under physiological conditions, in cell, becomes possible.In this thesis, we add to the scientific library a new model of quantification of kinetic parameters, and the possibility of studying an enzymatic cascade composed of 3 enzymes by D-DNP measurements. Based on these experiments, the selectivity of the first enzyme in the oxidative pathway, G6PD, for one of the two glucose-6-phosphate anomers, was confirmed. The antioxidant role of the second PPP enzyme, 6PGL, was equally studied. To carry out these studies, a method of synthesis and purification of the different substrates of each enzyme has been developed. The very first inhibitor of 6PGL has also been tested. Preliminary experiments on Trypanosoma brucei, a parasite responsible for sleeping sickness, indicate that glucose penetration inside cells is the limiting kinetic step for its conversion.

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