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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.
81

Análise reaxométrica para compostos de coordenação contendo íons paramagnéticos em solução / Relaxometric analysis for coordination compounds contaning paramagnetic ions in solution

Flávio Vinícius Crizóstomo Kock 06 April 2018 (has links)
Neste trabalho analisou-se por ressonância magnética nuclear em baixa (RMN-BR) e em alta resolução (RMN-AR), compostos de coordenação contendo íons paramagnéticos em solução. Demonstrou-se que estas são importantes ferramentas para o estudo destas espécies em meio aquoso, visando aplicações tanto em química analítica quanto em química inorgânica e bioinorgânica. Os estudos iniciais foram realizados com o ligante EDTA (Y4-), clássico agente quelante, e seus complexos com os íons Cu2+, Fe3+ e Mn2+. Os resultados demonstraram que a RMN-BR (20 MHz para o 1H) torna-se uma eficiente alternativa à espectrofotometria, principalmente para o estudo de complexos que não absorvem radiação no visível, como por exemplo, o quelato [Mn-Y]2-. A relaxometria por RMN-BR também foi usada para estudar soluções de quitosana (Chi) e seus complexos com os mesmos íons paramagnéticos previamente abordados para o EDTA. Os resultados demonstraram a eficiência da relaxometria tanto para os estudos de agregação polimérica em função do pH quanto para os estudos de complexação.<a name=\"_Hlk488851348\"> Foram também abordados complexos de sorbitol com íons Cu2+ tanto por relaxometria quanto por RMN-AR (600 MHz para o 1H). Neste caso, os resultados apresentaram uma alta complementariedade, permitindo inferir tanto acerca da troca de ligantes em solução e do pH ótimo para a complexação, quanto do surgimento de espécies macromoleculares com baixos coeficientes de autodifusão (D &asymp; 1,58 x10-10 mm2.s-1) em meio alcalino (pH &asymp; 12). Além do mais, foram avaliados novos complexos de Gd3+ com relevância biológica (agentes de contrastes), derivados do ligante AAZTA (6-amino-6-metilperhidro-1,4-diazepina). Os resultados demonstraram que as relaxividades paramagnéticas (r1p) foram de 7,44 mM-1.s-1 e 9,41 mM-1.s-1 para os derivados funcionalizados lateralmente com os ácidos propanoico e pentanoico, respectivamente, em comparação ao ligante precursor, 7,10 mM-1.s-1. Os estudos relaxométricos in vitro mostraram que estes novos derivados são menos susceptíveis à transmetalação com íons endógenos (Zn2+ e Ca2+), quando comparado ao AAZTA, possibilitando projetar o seu uso como agentes de contraste em tomografia por ressonância magnética (MRI). Aplicações relaxométricas in vivo foram realizadas utilizando o derivado contendo o ácido pentanoico conjugado ao peptídeo FibPep, apto a se ligar à proteína fibrina (presente em células tumorais). Os resultados demonstraram uma alta habilidade deste complexo para o assinalamento precoce e inequívoco do câncer de próstata (linhagem tumoral PC-3) em camundongos. / Low-resolution (LR) and high-resolution (HR) nuclear magnetic resonance (NMR) was used in this work for study coordination compounds containing paramagnetic ions in solution. It was demonstrated that these spectroscopies are important tools for the study of these species in aqueous medium, aiming applications in both, analytical chemistry and inorganic and bioinorganic chemistry. The initial studies were conducted using the EDTA (Y4-) ligand, classical complexant, and its chelate with the paramagnetic ions, among them Cu2+, Fe3+ and Mn2+. The results demonstrated that LR-NMR (20 MHz to 1H) becomes an efficient alternative to spectrophotometry, mainly for the study of complexes that do not absorb visible radiation, such as [Mn-Y]2- chelate. The LR-NMR relaxometry was also used to study chitosan (Chi) solutions and their complexes with the same paramagnetic ions previously discussed for EDTA. The results demonstrated the efficiency of the relaxometry for studies involving complexation and polymer aggregation as a function of the pH. Complexes of sorbitol with cupric ions were also addressed by relaxometry and HR-NMR (600 MHz to 1H). In this case, the results showed a high complementarity, allowing to infer about the ligand exchange and the optimum pH for the complexation reaction occurs. Besides, this study showed the appearance of species with low auto diffusion coefficients (D &asymp; 1.58 x10-10 mm2.s-1) in alkaline mediums (pH &asymp; 12), as consequence of the macromolecular character of this complex in this environment. In addition, new biologically relevant Gd3+ complexes (contrast agents) derived from AAZTA (6-amino-6-methylperhydro-1,4-diazepine) ligand were evaluated. The results demonstrated that the paramagnetic relaxivities (r1p) were 7.44 mM-1.s-1 and 9.41 mM-1.s-1 for derivatives laterally functionalized with propanoic and pentanoic acids, respectively, in comparison to precursor ligand, 7.10 mM-1.s-1. In vitro relaxometric studies demonstrated that these new derivatives are less susceptible to transmetallation reactions towards to endogenous ions (Zn2+ and Ca2+), in comparison to AAZTA (precursor ligand), becoming possible to design their use as contrast agents in magnetic resonance imaging (MRI) tomography applications. In vivo studies were conducted using the pentanoic acid derivative conjugated to FibPep peptide, able to bind to fibrin protein (present in tumor cells). The results for this study demonstrated a high ability of this complex for the early and unequivocal signaling for prostate cancer (PC-3 tumoral cell line) in mice.
82

Ambientes de coordenação de heteropolioxometalatos de Keggin em xerogeis fotocrômicos analisados por espectroscopia de RMN e RPE em sólidos / Keggin heteropolyoxometalates coordination environments in photochromic xerogels studied by solid state NMR and EPR spectroscopy

Oliveira Junior, Marcos de 24 February 2014 (has links)
Neste trabalho, é analisada a estrutura de materiais híbridos contendo poliânions de ácido 12-tungstofosfórico (H3PW12O40, HPW) inseridos em uma matriz de silicatos orgânico-inorgânica (ormosil). Estes materiais apresentam propriedade reversível de fotocromismo na faixa do UV (200-400nm), sendo cogitados como possíveis candidatos para aplicação como dosímetros pessoais UV. A metodologia sol-gel possibilita a obtenção destes compostos por vias relativamente simples e de baixo custo para a combinação dos componentes orgânicos e inorgânicos formadores da matriz ormosil. As propriedades do efeito fotocrômico, como intensidade e tempo de vida, ser alteradas variando-se a concentração e a natureza dos grupos presentes na matriz ormosil. Outras propriedades também podem ser ajustadas, como porosidade, adesão dos filmes, resistência mecânica, homogeneidade e transparência. No entanto uma correlação clara entre o processo de fotocromismo e a estrutura local ao redor do poliânion ainda não foi estabelecida. O objetivo geral da pesquisa é a caracterização estrutural e dinâmica destes compostos, a fim de se avançar no entendimento do processo fotocrômico e na otimização de métodos de preparação para o controle das propriedades fotocrômicas. Resultados preliminares mostram que o ambiente de coordenação do HPW nos ormosils é complexo, envolvendo diversas espécies de prótons, e os níveis de hidratação parecem desempenhar importante papel estrutural. Portanto, o objetivo específico deste trabalho é obter uma descrição da estrutura/dinâmica das espécies no ambiente de coordenação do poliânion, como espécies de hidratação e/ou grupos da matriz ormosil, e da interação entre estas espécies e o HPW. Para tal, foram utilizadas técnicas de ressonância magnética nuclear (RMN) para analisar amostras de composição simplificada, como uma amostra modelo HPW n6H2O e xerogeis contendo tetraetilortosilicato (TEOS) e no máximo dois organosilanos na composição, dentro do conjunto: 3-aminopropiltrietóxisilano (APTS), butironitrilatrietoxisilano (BUT) e 3 glicidoxipropilltrimetóxisilano (GLYMO). Embora a estrutura do HPW n6H2O seja extensamente discutida na literatura, ainda existem questões estruturais a serem discutidas, para as quais as técnicas de RMN podem fornecer importante contribuição. Diferentes tratamentos térmicos sobre o HPW nH2O foram testados para a obtenção do HPW n6H2O, e os resultados de RMN mostram que o controle de atmosfera durante o processo de secagem é determinante para a estrutura final das espécies de hidratação. No caso dos xerogeis, diferentes atmosferas foram testadas durante o preparo, estudando-se o efeito desta variável sobre a estrutura das espécies no ambiente de coordenação do HPW. Adicionalmente, tratamentos térmicos para a secagem das amostras também foram realizados. Após a irradiação das amostras com luz UV é formado um centro paramagnético WV no poliânion, que foi estudado por ressonância paramagnética eletrônica (RPE). A técnica de 31P permitiu avaliar a estrutura no ambiente mais local da molécula de HPW. Utilizando técnicas de 1H RMN, polarização cruzada (CP) {1H}-31P, correlação heteronuclear (HETCOR) {1H}-31P, {1H}-29Si e {1H}-13C, e medidas de tempos de relaxação spin-rede de 1H no sistema rotante (T1&rho;), foi constatado que o ambiente de coordenação do HPW nos xerogeis é basicamente constituído de espécies de hidratação, como H2O, H3O+, H5O2+ e H+(H2O)n, e espécies OH, que provavelmente pertencem a grupos na matriz de ormosil. Os experimentos de RPE permitiram identificar a existência de uma processo termicamente ativado, em que o elétron excitado realiza saltos entre os diferentes sítios WO6. Dois tipos de centros paramagnéticos WO6, ambos com simetria ortorrômbica, foram resolvidos em 20K. Um deles pôde ser atribuído a sítios WO6 interagindo fortemente com H2O, com a elongação da ligação W=O em WO6. Este sítio é dominante para amostras mais hidratadas. Além deste, outro sítio é observado em amostras mais secas, atribuído a centros WO6 interagindo mais fracamente com os H no ambiente do HPW. Estes resultados mostram que as espécies de hidratação desempenham um importante papel no processo de fotocromismo. / The local structure of hybrid organic-inorganic (ormosils) materials based on 12-phosphotungstic acid (H3PW12O40, HPW) was analyzed. These materials have reversible photochromic response in the range of ultraviolet (200 - 400 nm), and may found application in personal UV dosimeters. These ormosils can be prepared in a simple way using the sol-gel method, allowing the possibility of film depositions. It is known that properties such as the intensity of the photochromic response and the life-time in this state can be controlled changing the organic functional groups in the silane precursors. Other general properties can be also adjusted with these organic functionalities, such as film adhesion, mechanical response, homogeneity and transparency. However, the relation between the photochromic response, the chemical species (including water molecules) around the polyanion, and the local structure is still an open problem. The objective of this work was to analyze the effect of the preparation conditions of the ormosils (composition, atmosphere and thermal treatments) on the chemical environment around the polyanion and their possible influence in the photochromic response. The analysis of the interaction between the polyanion and the chemical species in the ormosil network and hydration species was carried out using nuclear magnetic resonance spectroscopy (NMR) in the solid-state for 1H, 31P, 13C, and 29Si. A set of simple photochromic ormosils were considered in this study, prepared with tetraethilorthosilicate (TEOS) and a maximum of two organosilane precursors from the set aminopropyltriethoxysilane (APTS), butyronitriletriethoxysilane (BUT) and 3-Glycidoxypropyltrimethoxysilane (GLYMO). Also, the HPW hexahydrate (HPW 6H2O) was analyzed as a model system to test the response of the NMR technique to the structural and dynamical process known in this crystal. The effects of thermal treatments and atmosphere in the preparation of the hexahydrate were analyzed. New information concerning the H dynamics and the thermal transformations observed in this system was gathered in this study. For the photochromic ormosils, preparations under three different atmospheres (uncontrolled ambient, N2 flow, and Ar glove-box) were carried out, as well thermal treatments to remove loosely bound water. Electronic paramagnetic resonance (EPR) experiments were carried out in UV-irradiated ormosils, were paramagnetic centers in WV, related with the photochromic process, were observed. The chemical environment around the polyanion was probed using the techniques of 1H-NMR, {1H}-31P cross-polarization, heteronuclear correlations {1H}-31P, {1H}-29Sie {1H}-13C, and the measurement of the proton spin-lattice relaxation in the rotating frame (T1&rho;). The results revealed the presence of close hydration species such as H2O, H3O+</sup), H5O2+ and H+(H2O)n, and OH groups from the ormosil network. No evidence of interaction between the polyanion and the organic functionalities was found. In the irradiated samples, the EPR experiments revealed a thermally activated hopping process for the excited unpaired electron between WO6 octahedra. Two kinds of paramagnetic sites at the WO6 octahedra, both with orthorrombic symmetry, were resolved at 20K. One of them corresponds to WO6 strongly interacting with water species, with an elongated W=O bond length. This site is dominant for higher hydrated samples. The other site corresponds to WO6 with a weak interaction with protons in the polyanion environment and is observed in higher amounts in less hydrated samples. These results show that the hydrate species in the polyanion coordination environment plays an important role in the photochromic process.
83

Étude RMN du système de spins quantiques CuHpCl

Clémancey, Martin 30 April 2004 (has links) (PDF)
Cette thèse est consacrée à l'étude par résonance magnétique nucléaire (RMN) des propriétés magnétiques du composé Cu2(C5H12N2)2Cl4 (CuHpCl). Ce système de spins quantiques 1/2 a longtemps été considéré comme une réalisation expérimentale d'un système d'échelles de spins. Son diagramme de phase en fonction du champ magnétique est très riche, avec en particulier un état fondamental liquide de spin en champ nul et deux transition de phase quantique aux champ Hc1=7.5 Tesla et Hc2 = 13 Tesla. Le but premier de cette étude est une clarification de certaines zones de ce diagramme de phases, en particulier la phase basse température comprise entre Hc1 et Hc2 qui présente un ordre magnétique tridimensionnel. A travers l'étude d'un composé spécifiquement deutéré, nous avons montré la nature commensurable de cette phase ordonnée et étudié la nature de la transition en fonction de H et de T. Mais l'apport principal de cette étude, est la mise en évidence de l'apparition à basse température d'une aimantation transverse alternée due à des interactions anti-symétriques, similaire à celle observée dans d'autres composés liquide de spins tels que NENP ou SrCu2(BO3)2. Cette aimantation apparaît pour des champs inférieurs à Hc1 et persiste pour H> Hc2. CuHpCl semble être le seul composé à présenter la coexistence de cette aimantation alternée et d'une phase magnétique 3D. Cette aimantation alternée est également observée dans les mesures d'aimantations par couple menées sur ce composé. Enfin, dans le but de comprendre les chemins d'échanges dans CuHpCl, nous avons entrepris un étude préliminaire (RMN et mesures d'aimantation) de composés dérivés (méthylés) de CuHpCl.
84

Controle quantique grâce aux méthodes de RMN. Application à la simulation de systèmes quantiques

Negrevergne, C. 02 December 2002 (has links) (PDF)
Manipuler l'information selon les lois de la physique quantique permet d'ameliorer l'efficacite avec laquelle on traite certains problemes.<br> Les methodes de Resonance Magnetique Nucleaire en solution permettent d'initialiser, de manipuler et d'observer l'etat d'un systeme de spins 1/2 couples. ces methodes ont ete utilisees pour realiser experimentalement un petit processeur d'information quantique (QIP pour "Quantum Information processor") pouvant executer une centaine d'operations elementaires. un des themes principaux de ce travail a ete de concevoir, d'optimiser et de valiser des sequences d'impulsions necessaires pour "programmer" ce QIP.<br> ces techniques ont ete utilises pour executer un algorithme quantique de simulation des systemes anyoniques. des resultats experimentaux pour la determination des energies propres et de fonctions de correlation d'un systeme illustratif de fermions sur reseaux ont ete obtenus permettant de valider l'algorithme de simulation dans son principe et son execution experimentale.
85

Apport de l'Imagerie par Résonance Magnétique dans l'étude des mécanismes de structuration des matériaux cimentaires : application au suivi des modifications engendrées par le séchage

Magat, Julie 21 October 2008 (has links) (PDF)
L'objectif de ce travail est d'étudier les évolutions microstructurales des matériaux cimentaires au cours de l'hydratation et d'analyser les dégradations physico-chimiques de ces matériaux lorsqu'ils sont soumis au séchage. Ces évolutions sont caractérisées par les mesures de teneur en eau et de porosité qui sont des paramètres clés pour l'évaluation de la durabilité des matériaux. L'originalité du travail réside en l'utilisation de l'Imagerie par Résonance magnétique IRM. Nous présentons une synthèse bibliographique sur les matériaux cimentaires et sur l'IRM qui permet d'accéder à la densité protonique caractéristique de la teneur en eau et aux temps de relaxation qui donnent une information sur la distribution poreuse. Les résultats sont ensuite identifiés aux données obtenues par des techniques expérimentales du génie civil. Enfin deux problématiques inhérentes aux matériaux cimentaires qui sont l'analyse de l'hydratation et le couplage hydratation/séchage sont étudiées.
86

Disseny i avenços en nous agents de solvatació quiral: biantril i altres derivats tipus Pirkle

Sánchez Aris, Marta 11 December 2001 (has links)
La present tesi doctoral es basa en la síntesi de nous agents de solvatació quiral (CSA) que siguin més eficaços i/o més versàtils que els existents al mercat actual. Per aconseguir aquest objectiu s'han introduït una sèrie de modificacions en les estructures dels CSA més comunament usats, com són l'alcohol de Pirkle i la 1-(1-naftil)etilamina, i s'ha avaluat l'efecte que aquests canvis confereixen a les noves molècules pel que fa a la seva capacitat d'acció com a agents de solvatació quiral. Així doncs en aquest treball:- S'han sintetitzat les amines, 1-adamantil-9-(9,10-dihidroantril)metilamina i la 1-(1-pirenil)etilamina però en cap cas s'ha pogut avaluar la seva capacitat com a agents de solvatació quiral degut a la dificultat per resoldre els seus enantiòmers.- S'han estudiat diverses rutes sintètiques per a l'obtenció del 2,2,2-trifluoro-1-(9-tripticil)etanol. Cap de les vies assajades ha donat lloc a l'alcohol desitjat amb rendiments acceptables. En la síntesi del 2,2,2-trifluoro-1-(9-tripticil)etanol via cicloaddició [4+2] el baix rendiment observat s'atribueix a l'electronegativitat del grup trifluorometil. Mentre que en el cas de l'obtenció de l'alcohol en estudi per reacció del 9-tripticil liti amb anhídrid trifluoroacètic i/o trifluoroacetat d'etil, aquesta no ha tingut lloc degut als impediments estèrics que apareixen en aproximar-se l'anió tripticil als diferents electròfils.- S'ha sintetitzat, amb molt bon rendiment, l'a,a'-bis(trifluorometil)-10,10'-(9,9'-biantril)dimetanol i s'han resolt els seus dos diastereoisòmers. S'ha demostrat l'eficàcia d'aquests compost com a CSA davant de diversos soluts quirals, superant en alguns casos i igualant en d'altres la capacitat solvatant de l'alcohol de Pirkle. S'ha determinat l'estequiometria dels complexos de solvatació formats entre l'lcohol en estudi i diferents soluts observant-se una certa tendència a la complexació 1:1. S'ha realitzat també estudi sobre la seva constant d'associació (K) a temperatura ambient i a baixa temperatura, d'on s'ha pogut concloure que la K augmenta en disminuir la temperatura.- S'ha aconseguit disposar d'un mètode de síntesi que ens permet obtenir el pirè perdeuterat en quantitats importants i a un cost relativament baix.- S'ha sintetitzat el macrocicle ciclobis[sulfit del (R,R)-a,a'-bis(trifluorometil)-9,10-antracendimetil]. Dades experimentals i càlculs teòrics han coincidit en afirmar que la cavitat que presenta aquest compost és massa petita com per permetre la inclusió de molècules orgàniques.- S'ha obtingut el precursor d'un nou macrocicle, el qual aportarà la mida necessària a la cavitat, per la posterior inclusió de molècules quirals en el seu interior.The present work is based on the synthesis of new chiral solvating agents which are more efficient and versatile than the ones in the current market. In order to reach this objective a number of modifications have been introduced in the structure of the common CSA, such as Pirkle's alcohol, and 1-(1-naphtyl)ethyilamine, and then been evaluated the effect of these changes in the behaviour of these new compounds as chiral solvating agents. From this work several facts and conclusions can be stated. The amines, 1-adamanthyl-9-(9,10-dihydroanthryil)methylamine and the 1-(1-pyrenyl)ethylamine, have been synthesized but their capacity as chiral solvating agents could not be evaluated due to the difficulty of resolving their enantiomers.Several synthetic methods to obtain 2,2,2-trifluoro-1-(9-tripticyl)ethanol have been studied. However, none of the routes has developed the expected alcohol efficiently. The synthesis of 2,2,2-trifluoro-1-(9-tripticyl)ethanol via cycloaddition [4+2] gives low yieds due to electronegativity of the group trifluoromethyl. On the other hand, the process of obtaining the studied alcohol to reaction of 9 tripticyl litium with trifluoroacteic anhydride and/or ethyl trifluoroacetate, did not work due to the steric effects found in the approach of the litium compound to the electrophil molecules The compound a,a'-bis(trifluorometihy)-10,10'-(9,9'-biantrhyl)dimethanol has been synthesized with a very good yield and have been separeted efficiently their diastereomers. The good behaviour of this product as a chiral solvating agent behind several enantiomeric molecules has been demostrated. This alcohol has showed a large capacity to induce chirality in racemic mixtures, which is the same, or sometimes even better than the assiciation capacity of Pirkle's alcohol. The stoichiometry of the association complexes has been determined concluding that the ratio is usually 1:1. A study of the equilibrium constant (K) has been carried out and has been demonstrated that K increases when temperature decreases.A synthetic method has been developed to obtain perdeuterio pyrene in quantity and low cost. A macrocycle ciclobis[(R,R)-a,a'-bis(trifluoromethyl)-9,10-anthracendimethyl sulphite]has been synthesized. Experimental results and theoretical calculations coincide to confirm that the cavity created in this molecule is too little to permit the inclusion of any organic compound.A precursor of a new macrocycle has been obtained, which will provide the appropiate size to the cavity in order to be able to include chiral molecules.
87

Estudi de nous agents de solvatació quiral: a,a'-bis(trifluorometil)-9,10-antracendimetanol i altres

Pomares Marco, Marta 05 February 2002 (has links)
El present treball es basa en la síntesi de nous agents de solvatació quiral els quals són més eficients i versàtils que els ja existents en el mercat. Per tal d'assolir aquest objectiu s'han realitzat diverses modificacions a l'estructura dels CSA més habituals, tal i com els comercials alcohol de Pirkle i la 1-(1-naftil)etilamina. Posteriorment s'ha avaluat l'efecte d'aquestes modificacions en front del comportament d'aquests nous agents de solvatació quiral. A partir d'aquest treball s'han pogut establir diversos fets i conclusions. L'alcohol 2,2-dimetil-1-(1-naftil)propanol s'ha sintetitzat i els seus enantiomers s'han resolt però la seva capacitat com a agent de solvatació quiral sembla presentar una capacitat no tan bona com la proporcionada per l'alcohol de Pirkle. El compost a,a'-bis(trifluorometil)-9,10-antracendimetanol ha estat sintetitzat i els seus diastereoisòmers s'han separat eficientment. S'ha demostrat el bon comportament com a CSA en front de diversos soluts racèmics. Aquest alcohol presenta una gran capacitat per induir enantiodiferenciació amb mescles racèmiques, la qual cosa h a permès demostrar un millor comportament si es compara amb els resultats obtinguts a partir de l'alcohol de Pirkle. S'ha determinat l'estequiometria dels complexos d'associació formats, la qual cosa ha permès determinar que en tots els casos estudiats la relació és 1 a 1; encara que l'alcohol presenta a la seva estructura dos grups funcionals. S'ha dut a terme l'estudi de les constants d'equilibri (K). S'ha observat que les constants (K) augmenten en disminuir la temperatura.A més, s'ha estudiat la síntesi per tal d'obtenir l'alcohol (R,R)-a,a'-bis(trifluorometil)-9,10-antracendimetanol de forma enantiopura de forma molt exitosa.Aquest alcohol s'ha utilitzat a com a auxiliar quiral en una reacció de Diels-Alder. S'ha sintetitzat el mono-acrilat d'aquest alcohol i s'ha fet reaccionar amb ciclopentadiè per formar els respectius adductes diastereoisomèrics. El e.d. obtingut és del 70%. És el mateix resultat que quan s'utilitza l'acrilat de l'alcohol de Pirkle.S'ha desenvolupat una metodologia per obtenir el perdeutero-a,a'-bis(trifluorometil)-9,10-antracendimetanol i s'exposen les avantatges d'utilitzar CSA perdeuterats quan es realitzen experiments de RMN per tal de determinar l'e.e de les mostres. Els propis senyals del CSA en 1H i 13C NMR desapareixen.Múltiples mètodes sintètics s'han desenvolupat per tal d'obtenir l'a,a'-diamino-9,10-antracendietà. Només utilitzant 9,10-antracendicarboxaldehid, com a reactiu de partida, i realitzant una reacció de Mitsunobu del derivat alcohol proporciona l'amina. El producte s'obté amb baix rendiment. Aquest és el motiu pel qual és rebutja l'ús d'aquesta amina com a CSA / The present work is based on the synthesis of new chiral solvating agents which are more efficient and versatile than the ones in the current market. In order to reach this objective a number of modifications have been introduced in the structure of the common CSA, such as Pirkle's alcohol, and 1-(1-naphtyl)ethylamine, and then the effect of these changes in the behaviour of these new compounds as chiral solvating agents has been evaluated. From this work several facts and conclusions can be stated. The alcohol, 2,2-dimethyl-1-(1-naphthyl)propanol, has been synthesized and its enantiomers have been separated but its capacity as chiral solvating agent seem to be not as good as the capacity of Pirkle's alcohol.The compound a,a'-bis(trifluoromethyl)-9,10-anthracenedimethanol has been synthesized and their diastereoisomers have been separated efficiently. The good behaviour of this product as a chiral solvating agent (CSA) towards several enantiomeric molecules has been tested. This alcohol has showed a large capacity to induce enantiodifferentiation in racemic mixtures, which shows, in all cases, a much better capacity than using Pirkle's alcohol. The stoichiometry of the association complexes has been determined concluding that the ratio is usually 1:1, although this alcohol presents two functional groups. A study of the equilibrium constant (K) has been carried out and has been demonstrated that K increases when temperature decreases.Furthermore, it has been developed a synthesis to obtain enantiopure (R,R)-a,a'-bis(trifluoromethyl)-9,10-anthracenedimethanol in a very good yield.This alcohol has also been tested as a chiral auxiliary in a Diels-Alder reaction. The mono-acrylate of this alcohol has been obtained and it has reacted with cyclopentadiene to form distereoisomeric adducts. The d.e obtained is 70%. It is the same as the one obtained when Pirkle's acrylate is used.A synthetic method has been developed to obtain perdeuterio--a,a'-bis(trifluoromethyl)-9,10-anthracenedimethanol and the advantages of using a perdeuterated CSA are clearly showed when NMR experiments are made to determine e.e of the samples. The own signals of the CSA in 1H and 13C NMR disappear.Several synthetic methods have been developed to obtain a,a'-diamino-9,10-anthracenediethane. But only using 9,10-anthracendicarboxaldehide, as starting material, and making the Mitsunobu reaction of its alcohol derivative afforded the amine. The compound is obtained in low yield, so that is the reason why the use of this amine as CSA is rejected.
88

Estudi de la significació cel·lular dels "lípids mòbils" visibles per RMN en cèl·lules C6 de glioma de rata

Quintero Bernabeu, Maria Rosa 12 February 2007 (has links)
Els lípids mòbils visibles per RMN (ML) ressonant a 1,28 i 0,9ppm han estat descrit en el patró espectral de tumors cerebrals agressius I en diversos tipus cel·lulars en cultiu. Els ML provenen principalment de triacilglicerols (TAG) continguts en gotícules lipídiques (1-10 ?diàmetre) i han estat relacionats a necrosi i hipòxia en tumors, i a la velocitat de proliferació en cultius cel·lulars. Entendre l'origen bioquímic I biofísic dels ML pot ser ajuda a la MRS de tumors cerebrals humans en el diagnòstic, pronòstic i planificació de la teràpia.Els senyals de lípids visibles per RMN (ML) de les cèl·lules C6 han estat monitorats a 9,4 i 11,7 T (pols i adquisició i 136 ms temps d'eco) en sediments cel·lulars per espectroscòpia de 1H NMR. S'ha trobat un comportament reproduïble amb el creixement. Els ML augmenten de fase log (dia 4 de cultiu) a fase postconfluent (dia 7 de cultiu). Aquest comportament es correspon amb el percentatge de cèl·lules que contenent gotícules citosòliques detectables per tinció amb Nile Red i epifluorescència. (rang 23% -60% de cèl·lules). El nombre de cèl·lules positives augmenta després de la sembra (dia 0-1), disminueix a fase log (dia 2-4), augmenta altre cop amb la confluència (dia 5) i encara més en post-confluència (dia 7). L'aturada de la proliferació induïda per deprivació de factors de creixement indueix una major acumulació de gotícules citosòliques (fins a 100%) i un major augment en els ML ( fins a 21 vegades respecte de les cèl·lules de fase log de dia 4 de cultiu).La quantificació del lípids neutres en extractes lipídics totals de cèl·lules C6 per cromatografia en capa prima (TLC) mostra que no hi ha canvis significatius amb el creixement o l'aturada de proliferació en els principals tipus de lípids neutres presents (triacilglicerols, TAG; diacilglicerols, DAG; esters de colesterol, ChoEst) excepte pels DAG, els quals decreixen en cèl·lules de dia 7.La quantificació per 1H-13C HMQC dels extractes de cèl·lules C6 (cèls. dia 4, fase log, n=3; i dia 7, post-confluenst, n=3) i and {1}-13C-glucosa enriquida 99% (cèls. dia 4, , n=3, incubació 2h4; i dia 7, n=3, incubació 48h) va mostrar que no hi havia diferències significatives en el contingut de TEG entre cèl·lules de dia 4 i de dia 7. La distribució del marcatge obtinguda suggereix una compartimentalització de la síntesi de PL i TAG a partir de DAG, i un origen diferent de glucosa per la síntesi de TAG en les condicions experimentals.L' aparent discrepància entre els resultants d'RMN, microscòpia òptica I TLC pot ser explicada si es tenen en compte canvis biofísics en el pool de lípids neutres i els resultants de marcatge. Es proporciona una explicació cel·lular pels resultats obtinguts: la hipòtesi de la llançadora de TAG. / NMR-visible mobile lipids (ML) resonances at 1.28 and 0.9ppm have been described in the spectral pattern of aggressive tumours and in cultured cell types. These ML mostly originate from triacylglicerol (TAG) in droplets (1-10 micrometers of diameter) and have been related to necrosis and hypoxia in tumours and proliferation rate in cultured cells. Proper understanding of the biochemical and biophysical origin of these ML could help MRS of human brain tumours to provide useful information for diagnosis, prognosis and therapy planning. NMR-visible mobile lipid (ML) signals of C6 glioma cells have been monitored at 9.4 and 11.7 T (single pulse and 136 ms echo time) from cell pellets by 1H NMR spectroscopy. A reproducible behavior with growth has been found. ML signals increase from log phase (4 day of culture) to postconfluence (7 day of culture). This ML behavior is paralleled by the percentage of cells containing epifluorescence detectable Nile Red stained cytosolic droplets (range 23% - 60% of cells). The number of positive cells increases after seeding (day 0-1), decreases at log phase (day 2-4), increases again at confluence (day 5) and even further at post-confluence (day 7). C6 cells proliferation arrest induced by growth factors deprivation induces an even higher accumulation of cytosolic droplets (up to 100% of cells) and a large ML increase (up to 21 -fold with respect to 4 day log phase cells)When neutral lipid content is quantified by thin-layer chromatography (TLC) on total lipid extracts of C6 cells, no statistically significant change can be detected with growth or growth arrest in major neutral lipid containing species (triacylglycerol, TAG, diacylglycerol, DAG, cholesterol esters, ChoEst) except for DAG, which decreased in post-confluent, 7 day cells. Quantitation of C6 lipid extracts of cultured cells (day 4 cells, log phase, n=3, and day 7 cells, postconfluent, n=3) and {1}-13C-glucose 99% enriched grown cells (day 4 cells, n=3, 24h incubation with 13C enriched glucose, day 3-day 4, and day 7 cells,n=3, 48h incubation with 13C enriched glucose, day 5-day 7) by 1H-13C HMQC showed no statistically significant changes in TAG content between day 4 and day 7 cultured cells. The labelling distribution obtained suggests a cellular compartimentalization of the synthesis pathway for PL and TAG from DAG, and an origin different from glucose for TAG synthesis under the experimental conditions (log phase and post-confluence).The apparent discrepancy between NMR, optical microscopy and TLC results can be reconciled if possible biophysical changes in the neutral lipid pool with growth and labeling results are taken into account. A cellular explanation for the observed results is proposed: the TAG-droplet-size-change hypothesis.
89

Détermination de la structure par RMN d'une protéine impliquée dans la biosynthèse de centres [Fe-S]: SufA

Duraffourg, Nicolas 21 December 2006 (has links) (PDF)
La protéine SufA d'Escherichia coli est une protéine homodimérique, dite d'échafaudage, qui permet l'assemblage de centres [Fe-S] avant de les transmettre à une protéine cible possèdant une fonction biologique. Elle appartient à un ensemble de protéines organisées en opéron (SUF) qui semble activé dans le cadre de stress oxydatif. Afin de mieux comprendre le mode de fixation du centre [Fe-S] par la protéine SufA, la détermination de la structure tridimensionnelle par RMN a été entreprise. Nous avons obtenu la structure monomérique de la protéine sans son centre [Fe-S] (forme apo) et effectué des études de résonance magnétique nucléaire (RMN) préliminaires de la protéine SufA avec son centre métallique reconstitué. Nous avons pu ainsi observer trois résidus cystéine, que des études biochimiques ont montré comme étant impliqués dans la chélation du centre [Fe-S], et affirmer qu'ils étaient proches du site métallique sans toutefois définir exactement le mode de coordination du centre [Fe-S]. La détermination de la structure du dimère, en cours, et des études RMN complémentaires sur l'holoprotéine (avec son centre [Fe-S]) devrait nous permettre de répondre à ces questions toujours en suspens. D'autre part nous avons observé des différences structurales par rapport aux structures cristallographiques (publiées au cours de ce travail de thèse), particulièrement dans la partie C-terminale de la protéine où se situent deux des cystéines observées.
90

Magnétisme nucléaire de l'3He liquide : nouvelle détermination du paramètre de Landau F0a

Goudon, Valérie 24 October 2006 (has links) (PDF)
L'3He est un liquide de Fermi modèle, isotrope, pur, de température de Fermi accessible, et dont les interactions sont aisément contrôlées en faisant varier la pression du liquide. Ce manuscrit présente des mesures précises de susceptibilité magnétique nucléaire par RMN continue de l'3He liquide en fonction de la température et de la pression. Les principaux efforts expérimentaux sont portés sur la thermométrie, la mesure de la pression de l'3He in situ pour étendre les mesures jusqu'à la pression de solidification, ainsi qu'une caractérisation soigneuse du spectromètre RMN. <br /><br />Nos mesures remettent en cause d'environ 5% les résultats de référence pour la température de Fermi effective en fonction des interactions. L'extraction du paramètre de Landau F0a dépend aussi de la masse effective déterminée par des mesures de chaleur spécifique, et par conséquent de l'échelle de température. La ré-analyse des mesures de chaleur spécifique dans l'échelle PLTS-2000 implique une augmentation de la masse effective de 4,5%. F0a est donc déterminé dans ce manuscrit pour deux échelles de température (PLTS-2000 et Greywall). Contrairement aux résultats antérieurs, la dépendance en densité de F0a ne montre pas de saturation vers les hautes pressions.

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