Made available in DSpace on 2016-08-29T15:35:38Z (GMT). No. of bitstreams: 1 tese_8579_Débora Ker Palomino.pdf: 2473065 bytes, checksum: 34ec730616e5e96afa0326c96a502ec5 (MD5) Previous issue date: 2015-03-13 / A cristalização e formação de depósitos parafínicos é um problema operacional crítico na indústria do petróleo em todo o mundo e provoca grandes perdas econômicas na recuperação do óleo. São muitos os estudos que têm sido realizados para desenvolver modelos termodinâmicos de predição da precipitação de parafinas, sendo que boa parte deles utilizam a ressonância magnética nuclear (RMN) em alto ou baixo campo magnético juntamente com outras técnicas como calorimetria exploratória diferencial (DSC), análise elementar e cromatografia gasosa para caracterizar a fase sólida formada a partir do petróleo. Este trabalho busca um maior entendimento da cristalização de ceras parafínicas por meio de experimentos de espectroscopia de RMN de 1H e 13C conduzidos em temperaturas variáveis, o que pode auxiliar na previsão e remediação dos problemas causados pela sua deposição nas linhas de escoamento da produção. Para isso, o estudo desse fenômeno foi conduzido inicialmente em amostras de parafina comercial e, posteriormente, em uma amostra de petróleo parafínico com variação de temperatura sem extrair a fase sólida, garantindo a não interferência de solventes que podem influenciar no processo de cristalização. A metodologia desenvolvida demonstrou ser útil para determinar a temperatura inicial de aparecimento de cristais (TIAC), sendo obtida uma boa concordância com os resultados de DSC para a parafina comercial e petróleo. O registro de espectros em diferentes temperaturas permitiu também a identificação das variações de intensidade e largura de linha dos sinais associados aos diferentes grupos químicos presentes nos materiais estudados.

In this work the extraction of substances from the common melon (Cucumis melo var. Acidulus) was carried out, which has more specific application in both, the food industry, as in the pharmaceutical and cosmetic industry, becoming more valuable than the fruit in natura. The objective of this study was to extract, quantify, characterize and modify chemically by sulfation pectin the common melon (Cucumis melo var. acidulus). The extractions were performed in neutral, acidic and basic conditions, with yields of 8%, 10.8% and 14%, respectively. In addition to the Elementary Analysis, pectin extracted with acid, it was characterized by nuclear magnetic resonance of carbon (13C NMR) and Hydrogen (1H NMR), Potentiometric Titration, Spectroscopy in the Infrared (FT-IR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), hermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), Rheology and Zeta Potential. Some of these analyzes were not performed for samples extracted in alkaline, neutral and sulfated acid, as well as for commercial use sample, for which the analysis depended on the purpose for which it was proposed, is it to determine a specific feature the material and the degree of esterification (DE) or to identify overall change in polymer structure such as sulfation. The 13C-NMR showed peaks characteristic of galacturonic acid. The FT-IR and potentiometric titration permitted the calculation of the degree of esterification (DE) of acidic, basic, neutral and sulfated samples and also a commercial sample from Sigma Aldrich; GE results of the samples obtained by these techniques were compared, showing that the samples are acidic and neutral low GE. The result of GE acid sample was also obtained by 1H NMR, confirming its low GE condition. The SEM of the sample showed particles with acidic spherical structure with surface flattening, typical drying spray dried, suggesting potential application in drug encapsulation. The XRD revealed that the material has amorphous character, an increase of crystallinity after chemical modification. The TGA technique revealed the pectin degradation in three stages. The DSC curve showed an endothermic peak at 150 ÂC and an exotherm at 245ÂC for the loss of water and the main step of breakdown of the material, respectively. The molecular weight of the acid sample, determined by GPC, showed values of typical polymeric materials 4.5 x 105 g/mol, consistent with pectins. The rheological study revealed the shear-thinning property of pectin solution. / Neste trabalho foi feita a extraÃÃo de substÃncias presentes no melÃo caipira (Cucumis melo var. acidulus) que tenham aplicaÃÃo mais especÃfica tanto na indÃstria alimentÃcia, quanto na indÃstria farmacÃutica e cosmÃtica, sendo, portanto, de maior valor comercial que os frutos in natura. O objetivo deste trabalho foi o de extrair, quantificar, caracterizar e modificar quimicamente por sulfataÃÃo a pectina do melÃo caipira (Cucumis melo var. acidulus). As extraÃÃes foram feitas em meio neutro, bÃsico e Ãcido, apresentando rendimentos de 8%, 10,8% e 14%, respectivamente. AlÃm da anÃlise elementar da pectina extraÃda em meio Ãcido, esta foi caracterizada por RessonÃncia MagnÃtica Nuclear do Carbono (RMN 13C) e do HidrogÃnio (RMN 1H), TitulaÃÃo PotenciomÃtrica, espectroscopia na regiÃo do infravermelho (FT-IR), Microscopia EletrÃnica de Varredura (MEV), DifraÃÃo de Raios-x (DRX), AnÃlise TermogravimÃtrica (TGA), Calorimetria ExploratÃria Diferencial (DSC), Cromatografia de PermeaÃÃo em Gel (GPC), Reologia e Potencial Zeta. Algumas dessas anÃlises nÃo foram realizadas para as amostras extraÃdas em meio bÃsico, neutro e a Ãcida sulfatada, bem como, para a amostra de uso comercial, para as quais, as anÃlises dependeram da finalidade a que se propunha, seja para determinar alguma caracterÃstica especÃfica do material como o Grau de EsterificaÃÃo (GE), seja para identificar mudanÃa geral na estrutura do polÃmero como a sulfataÃÃo. O RMN 13C revelou picos caracterÃsticos de Ãcido galacturÃnico. O FT-IR e a TitulaÃÃo PotenciomÃtrica permitiram o cÃlculo do Grau de EsterificaÃÃo (GE) das amostras Ãcida, bÃsica, neutra, sulfatada e tambÃm de uma amostra comercial da Sigma Aldrich; o resultado de GE das amostras, obtidos por essas tÃcnicas, foram comparados entre si, mostrando que as amostras Ãcida e neutra sÃo de baixo GE.O resultado de GE da amostra Ãcida tambÃm foi obtido por RMN 1H,confirmando sua condiÃÃo de baixo GE. O MEV da amostra Ãcida revelou partÃculas com estrutura esfÃrica com achatamentos superficiais, tÃpicos de secagem em spray dried, sugerindo potencial aplicaÃÃo em encapsulaÃÃo de fÃrmacos. A DRX revelou que o material apresenta carÃter amorfo, com aumento de cristalinidade apÃs modificaÃÃo quÃmica. A tÃcnica de TGA revelou os estÃgios de degradaÃÃo da pectina em trÃs etapas. A curva de DSC apresentou um pico endotÃrmico em 150 ÂC e um exotÃrmico em 245 ÂC, relativos à perda de Ãgua e à principal etapa de degradaÃÃo do material, respectivamente. A massa molecular da amostra Ãcida, determinada por GPC, apresentou valores tÃpicos de materiais polimÃricos 4,5 x 105 g/mol, condizentes com pectinas. O estudo reolÃgico revelou a propriedade pseudoplÃstica da soluÃÃo de pectina.

The thesis aims at developing techniques in solid state nuclear magnetic resonance (ssNMR) of paramagnetic metal-organic and inorganic systems in combination with electron paramagnetic resonance (EPR) spectroscopy and quantum chemical methods such as density functional theory (DFT).Solid state NMR signals of paramagnetic systems suffer from severe loss of sensitivity and resolution due to large hyperfine interactions. Among all the interactions seen in ssNMR, the interaction between the unpaired electron(s) and the observed nucleus leading to hyperfine interaction in paramagnetic solids is large in magnitude. Large broadening due to fast relaxation in paramagnetic systems on the one hand limits the excitation of the nuclei using conventional probes thereby causing severe loss in sensitivity and resolution of ssNMR signals. On the other hand the large shifts due to Fermi-contact interaction mask the diamagnetic chemical shifts (which are rich source of chemical group information) and make signal assignment difficult. The conventional techniques developed for solid state NMR of diamagnetic systems are inefficient for paramagnetic systems. These factors have led ssNMR of paramagnetic systems to be an unexplored topic for decades.Recently Ishii and co-workers have circumvented some of these problems using very-fast magic angle spinning (VFMAS).1 Spinning the sample at MAS frequencies >30 kHz drastically enhances the sensitivity and resolution of ssNMR signals in paramagnetic complexes. We have used the VFMAS approach and have shown how to cope with moderate hyperfine interactions in ssNMR of organic (cyclam and acetylacetonate) and inorganic (alkaline-copper pyrophosphates) systems with transition metal ions such as CuII, NiII and VIV as paramagnetic center. On the one hand Fermi-contact interaction which is responsible for large shifts up to 100 ppm in 1H and 1000 ppm in 13C and 31P cause severe problems for signal assignment. But on the other hand it also leads to better spectral dispersion and hence improve the resolution of the ssNMR signals. We were able to exploit this idea and a well resolved 13C and even 1H solid state NMR spectrum in paramagnetic metal-organic systems was obtained using a simple Hahn-echo experiment. This is usually not possible, since 1H NMR in diamagnetic solids suffer from large broadening of 100 kHz due to 1H-1H homonuclear dipolar coupling. Furthermore fast relaxation in paramagnetic systems allows one to reduce the interscan delay and thereby repeat the experiments several times in a given time and improve the signal to noise ratio. This compensates for loss in sensitivity more often due to fast relaxation in paramagnetic systems.Fermi-contact shifts are characteristics of unpaired electron spin density in a molecule. Using quantum chemical methods such as DFT one can calculate the theoretical Fermi-contact shifts.2 We have compared the experimental 13C ssNMR shifts with shifts from DFT calculation in paramagnetic metal –cyclam and –acetylacetonate complexes and have assigned the 13C signals. For assignment of 1H, a 2D version of dipolar INEPT (insensitive nuclei enhancement by polarization transfer) was used. In some cases such as the Cu-cyclam complex, a very well resolved 1H ssNMR spectrum motivated us to try 1H-1H homonuclear correlation experiment. We obtained several important cross peaks with a relatively simple pulse sequence. We used the dipolar connectivity information from it to complete the 1H assignment.One of the important aims of the thesis was to find a way to measure the metal-carbon distances using solid state NMR relaxation rates. In paramagnetic metal-organic complexes the carbon-13 relaxation caused by the dipolar interaction with the unpaired electron depends on the distance of the carbon atoms to the central metal ion, therefore its rates in principle contain structural information... / The thesis aims at developing techniques in solid state nuclear magnetic resonance (ssNMR) of paramagnetic metal-organic and inorganic systems in combination with electron paramagnetic resonance (EPR) spectroscopy and quantum chemical methods such as density functional theory (DFT).Solid state NMR signals of paramagnetic systems suffer from severe loss of sensitivity and resolution due to large hyperfine interactions. Among all the interactions seen in ssNMR, the interaction between the unpaired electron(s) and the observed nucleus leading to hyperfine interaction in paramagnetic solids is large in magnitude. Large broadening due to fast relaxation in paramagnetic systems on the one hand limits the excitation of the nuclei using conventional probes thereby causing severe loss in sensitivity and resolution of ssNMR signals. On the other hand the large shifts due to Fermi-contact interaction mask the diamagnetic chemical shifts (which are rich source of chemical group information) and make signal assignment difficult. The conventional techniques developed for solid state NMR of diamagnetic systems are inefficient for paramagnetic systems. These factors have led ssNMR of paramagnetic systems to be an unexplored topic for decades.Recently Ishii and co-workers have circumvented some of these problems using very-fast magic angle spinning (VFMAS).1 Spinning the sample at MAS frequencies >30 kHz drastically enhances the sensitivity and resolution of ssNMR signals in paramagnetic complexes. We have used the VFMAS approach and have shown how to cope with moderate hyperfine interactions in ssNMR of organic (cyclam and acetylacetonate) and inorganic (alkaline-copper pyrophosphates) systems with transition metal ions such as CuII, NiII and VIV as paramagnetic center. On the one hand Fermi-contact interaction which is responsible for large shifts up to 100 ppm in 1H and 1000 ppm in 13C and 31P cause severe problems for signal assignment. But on the other hand it also leads to better spectral dispersion and hence improve the resolution of the ssNMR signals. We were able to exploit this idea and a well resolved 13C and even 1H solid state NMR spectrum in paramagnetic metal-organic systems was obtained using a simple Hahn-echo experiment. This is usually not possible, since 1H NMR in diamagnetic solids suffer from large broadening of 100 kHz due to 1H-1H homonuclear dipolar coupling. Furthermore fast relaxation in paramagnetic systems allows one to reduce the interscan delay and thereby repeat the experiments several times in a given time and improve the signal to noise ratio. This compensates for loss in sensitivity more often due to fast relaxation in paramagnetic systems.Fermi-contact shifts are characteristics of unpaired electron spin density in a molecule. Using quantum chemical methods such as DFT one can calculate the theoretical Fermi-contact shifts.2 We have compared the experimental 13C ssNMR shifts with shifts from DFT calculation in paramagnetic metal –cyclam and –acetylacetonate complexes and have assigned the 13C signals. For assignment of 1H, a 2D version of dipolar INEPT (insensitive nuclei enhancement by polarization transfer) was used. In some cases such as the Cu-cyclam complex, a very well resolved 1H ssNMR spectrum motivated us to try 1H-1H homonuclear correlation experiment. We obtained several important cross peaks with a relatively simple pulse sequence. We used the dipolar connectivity information from it to complete the 1H assignment.One of the important aims of the thesis was to find a way to measure the metal-carbon distances using solid state NMR relaxation rates. In paramagnetic metal-organic complexes the carbon-13 relaxation caused by the dipolar interaction with the unpaired electron depends on the distance of the carbon atoms to the central metal ion, therefore its rates in principle contain structural information...

Les travaux de cette thèse portent sur la compréhension du processus du vieillissement des verres de phosphate à la base des études de résonance magnétique nucléaire (RMN) des solides. Le terme vieillissement se traduit dans ce cas par l’attaque aqueuse du verre sous atmosphère humide. Ce processus est d’un intérêt particulier dans tous les domaines où une haute résistance des verres de phosphate contre cette attaque constitue une propriété essentielle. Notamment c’est le cas pour la vitrification des déchets nucléaires. Dans le cadre de cette étude des systèmes modèles ont été étudiés (Na2O-P2O5 et Na2O-Al2O3-P2O5) pour obtenir une idée des changements structuraux qui ont lieu pendant l’attaque aqueuse. La résonance magnétique multinucléaire des solides (1H, 27Al, 31P et 17O) étant l’outil principal, des expériences en 1D et en 2D permettent de caractériser l’environnement proche des noyaux ainsi que leur environnement intermédiaire (connectivité hétéro- et homonucléaire). L’interprétation des données RMN de l’oxygène-17 est accompagnée d’une approche complémentaire. Des paramètres RMN calculés de l’oxygène-17 (DFT / GIPAW) des hydrogénophosphates cristallines ont été vérifiés et validés expérimentalement. Des corrélations entre les paramètres RMN de l’oxygène-17 (δCS, δiso, CQ, ηQ) et l’environnement structural du noyau ont été obtenu. Ces dernières permettent de caractériser les environnements du noyau oxygène-17 qui sont générés pendant le vieillissement d’un verre Na2O-P2O5 (NaPO3). / The present manuscript focuses on the investigation of phosphate glass weathering by multinuclear solid-state magnetic resonance. Weathering, that is aqueous attack and aging of the phosphate glass under humid atmosphere, becomes important in application domains where high resistance against aqueous attack is an essential property. In particular, this is the case for phosphate glass matrices for the immobilization of nuclear waste. In the frame of this work, binary (Na2O-P2O5) and ternary (Na2O-Al2O3-P2O5) model glass systems are considered. The aim is to obtain further insight into fundamental processes and structural changes that are taking place upon weathering attack on the glass. Solid-state nuclear magnetic resonance is used as the main tool for structural characterization. 1H, 27Al, 31P and 17O are employed as probe nuclei. A number of one- and two-dimensional techniques allows for insight into the glass structure on the low and intermediate range. The interpretation of 17O NMR data is accompanied by a complementary approach. Therefore, the reliability of calculated 17O NMR parameters of protonated crystalline phosphate phases has been validated for the first time. Relationships between 17O NMR parameters and the structural environment of the nucleus could be drawn. Those relationships prove to be helpful for the characterization of oxygen environments emerging in weathered NaPO3 glass based on the chemical shift (δCS, δiso) and the quadrupolar parameters (CQ, ηQ).

La MAP kinase p38 régule la transduction du signal en réponse à un stress environnemental. Les inhibiteurs spécifiques de p38, qui sont connus pour bloquer la production de cytokines pro-inflammatoires, mais peuvent également intervenir sur le phénomène d'apoptose. C'est dans cette dernière optique que de nouvelles structures d'inhibiteurs, ont été synthétisées. Ces structures, après caractérisation par RMN, ont été ensuite évaluées en termes de mécanisme d'action et de disponibilité biologique. Outre les méthodes classiques cette évaluation a finalement fait appel aux techniques HR-MAS. Les sept molécules ainsi synthétisées ont été regroupées en trois famille (1a, 2a-c, 3a-c). Quoique les propriétés physico-chimique de ces motifs soient très différentes, il en ressort une potentialité d'action commune en tant qu'inhibiteur de la MAP kinase p38.

Le paramagnétisme des actinides en solution a été caractérisé par RMN selon deux approches, l'une macroscopique et l'autre moléculaire. Dans la première approche, les susceptibilités magnétiques des ions les plus stables en solution de l'uranium au californium, et ce pour différents degrés d'oxydation (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), ont été mesurées par RMN à l'aide de la méthode d'Evans. En milieu perchlorique, l'étude ducomportement paramagnétique des cations actinide a montré des déviations significatives par rapport à celui des lanthanides, particulièrement pour les ions actinide aux degré d'oxydation +III et +IV. En milieux chlorhydrique et nitrique, il a été observé que les comportements magnétiques des actinides suivaient l'ordre M(IV) > M(VI) > M(III) > M(V), correspondant à l'ordre généralement admis concernant le pouvoir complexant des ions actinide en solution aqueuse. Il a été démontré que la présence d'ions chlorure et nitrate en solution pouvait avoir un impact important sur le comportement magnétique de ces cations. Dans la deuxième approche, les déplacements chimiques des complexes paramagnétiques actinide(IV)-dipicolinate ont été étudiés et analysés en milieu diméthylformamide. Dans ces conditions expérimentales, il a été vérifié que le degré d'oxydation +IV des actinides en solution était stable en présence ou non de ligand ainsi que sur l'échelle de temps des analyses RMN. Les déplacements chimiques paramagnétiques des complexes limites 1 : 3 ont été étudiés à différentes températures. Les méthodes de séparation des contributions de contact et dipolaire habituellement utilisées pour les complexes de lanthanide(III) se sont avérées inapplicables dans le cas des complexes d'actinide(IV). / Paramagnetism of actinides in solution was characterized by NMR according to two approaches, a macroscopic one and a molecular one. In the first approach, magnetic susceptibilities of the most stable ions in solution from uranium to californium, for various oxidation states (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), were measured by NMR by using the Evans' method. In perchloric medium, the paramagnetic behavior of actinide cations showed significant deviations compared with lanthanides, particularly for cations at oxidation state +III and +IV. In hydrochloric and nitric media, it was observed that actinide magnetic behaviors followed the order M(IV) > M(VI) > M(III) > M(V), corresponding to the generally admitted order concerning the complexing power of actinide cations. It was demonstrated that the presence of chloride and nitrate in solution could have an large impact on the magnetic behavior of these cations. In the second approach, chemical shifts of actinide(IV)-dipicolinate paramagnetic complexes were studied and analyzed in dimethylformamide. In these experimental conditions, the only presence of the oxidation state +IV in solution as well as the stability of the latter on the NMR analysis timescale were verified, in presence or not of the ligand. Paramagneticchemical shifts of the 1 : 3 limit complex were studied at various temperatures. Themethod of separation of the contact and dipolar contributions usually used for lanthanide(III) complexes have proved not applicable in the case of actinide(IV) complexes.

Du fait de leur difonctionnalités et, donc, de par leur réactivité particulière, les cétones alpha,beta-insaturées interviennent dans de nombreux schémas de synthèse de molécules complexes et le développement de nouvelles voies pour leur préparation est donc d'une grande importance. Ce travail consiste à développer la réaction d'hydroacylation carbonylante d'alcynes pour la synthèse d'énones. L'optimisation et le développement de ce système en utilisant les alcynes tenninaux simples a permis d'obtenir divers énones avec de bons résultats. De plus, l'application de la réaction à des alcynes particuliers, notmmnent les alcools propargyliques, a permis l'accès à des furanes. L'étude du mécanisme de la réaction a aussi été entrepris avec l'utilisation d'outils analytiques et, plus particulièrement, la RMN sous pression de monoxyde de carbone. Cette étude a permis de recueillir des informations quant au cycle catalytique engagé dans cette transformation. / By their difonctionnality and, then, by their special reactivity, alpha,beta-unsaturated ketones are involved in numerous synthesis to access complexe molecules. The development of new pathways for their fonnation is a major field of research interest. This work deals with the application of carbonyaltive hydroacylation reaction on terminal akynes for enones synthesis. After an optimisation step and the development of this system, we were able to obtain different enones in good yield and selectivities. ln addition, the use of propargyl alcohols as substrate leads to the fonnation of furane derivatives. A mecanistic investigation upon this reaction has been done with the help of analytical tools, especially NMR under high pressure of carbon monoxide. This study has brought several informations concerning the catalytic cycle of this transformation.

Neste trabalho, apresentamos um estudo por Ressonância Magnética Nuclear (RMN), Análises Termogravimétricas (DSC e TG) e Espectroscopia Infravermelho em cornplexos poliméricos formados entre poli(óxido de etileno), POE, e sais de lítio. Estes complexos tem mostrado uma grande potencialidade em aplicações tecnológicas (baterias, sensores, etc). Desenvolvemos e caracterizamos sensores de umidade e, discutimos como a umidade afeta a conformação do complexo e a mobilidade das espécies iônicas e da cadeia polimérica. Nossos resultados indicam que a hidratação afeta a conformação dos complexos poliméricos através do efeito plasticizante da água, o qual induz uma expansão volumétrica na cadeia do POE. Entretanto, para os níveis de hidratação utilizados, o processo mostrou-se completamente reversível. Através do estudo de RMN, conseguimos diferenciar os movimentos da cadeia polimérica daqueles das espécies iônicas (cátion e ânion). A análise do segundo momento das formas de linha de ressonância e os estudos de relaxação nuclear nos permitiu estimar distâncias médias entre as espécies iônicas e os prótons da cadela nestes complexos. Observamos também, que o comportamento da relaxação spin rede do hidrogênio e do flúor no P(OE)-LiBF4, em função da temperatura e da freqüência, reflete a natureza desordenada do material e a complexidade do processo de condução iônica nestes sistemas / In this work we report on a study using Nuclear Magnetic Resonance (NMR), Thermogravimetry Analysis (TGA), Differential Scanning Calorimetric (DSC) and Infrared Spectroscopy in polymeric complexes formed between poly(ethylene oxide), PEO), and lithium salts. These complexes have shown a large potential in for technological applications in batteries, sensors, etc. We developed and characterized humidity sensors and we discussed how the humidity affects the conformation of the complexes, the mobility of ionic species, and the polymeric chains. The results indicate that the hydration effects the conformation of polymeric complexes by plasticizing the water, which induces a volumetric expansion in the PEO chain. The process was completely reversible for the level of hydration studied. NMR was used to distinguish the movement of polymeric chains from the movement of the ionic species. From the analysis of the second moment of resonance lines and from the study of the nuclear relaxation we were able to estimate the average distance between the ionic species and the proton In the complexes chains. The behavior of spin-lattice relaxation of hydrogen and flurine in the P(EO) LiBF4 as a function of temperature and frequency reflects the nature of the disorder and the complexity of the ionic conduction process In these materials

Les recherches actuellement menées dans le domaine de l’Imagerie par Résonance Magnétique (IRM) s’orientent vers l’imagerie dite moléculaire, où l’agent de contraste interagit de manière non covalente avec une biomolécule exprimée dans des conditions pathologiques, modulant ainsi spécifiquement le contraste de la zone concernée. Dans ce but, l’évaluation de l’affinité du contrastophore pour sa cible potentielle est primordiale. Dans ce travail, la technique de « diffusométrie RMN » a été mise en œuvre pour évaluer les interactions non covalentes entre l’albumine sérique humaine (HSA) et différents agents de contraste potentiels pour l’IRM. La HSA présente en effet le double avantage de conférer aux agents de contraste une meilleure efficacité, qui se traduit par une augmentation plus marquée de la vitesse de relaxation des protons de l’eau, ainsi qu’un temps de rémanence vasculaire plus élevé, ce qui les rend propices à une utilisation en angiographie. Cette étude a été réalisée sur trois agents de contraste déjà largement décrits dans la littérature (Gd-DTPA, Gd-EOB-DTPA et MP2269) ainsi que sur trois nouveaux agents de contraste synthétisés dans le cadre de ce travail (Gd-C4-sulfadiméthoxin-DTPA, Gd-C4-sulfaphénazol-DTPA, Gd-C4-thyroxin-DTPA). Ces trois nouveaux contrastophores ont été caractérisés indépendamment en solution aqueuse et en présence d’albumine par deux autres techniques précédemment étudiés au sein de notre laboratoire : la relaxométrie protonique et la spectrométrie de masse electrospray. Les résultats obtenus ont révélé une bonne efficacité de deux des agents de contraste en solution aqueuse, ainsi qu’une affinité élevée pour la HSA dans le cas de ces deux mêmes contrastophores. La technique de diffusométrie RMN pour l’évaluation des interactions non covalentes repose sur la différence entre le coefficient de diffusion du ligand seul en solution (l’agent de contraste IRM dans notre cas) et du ligand lié à la macromolécule étudiée (la HSA). En effet, si le contrastophore se lie à l’albumine et que l’échange entre les deux partenaires est rapide sur les échelles de temps RMN, le coefficient de diffusion observé est une moyenne pondérée entre le coefficient de diffusion du ligand libre et le coefficient de diffusion du ligand lié à l’albumine. Les résultats obtenus ont confirmé les tendances observées lors de précédentes études réalisées avec d’autres techniques et nous ont apporté une information supplémentaire sur la cinétique d’échange entre les deux partenaires de l’interaction. Le travail a permis d’explorer les limites de validité de la méthode.

La memoria del trabajo describe en detalle la estrategia seguida para mejorar a nivel preclínico la detección temprana de respuesta a la terapia en modelos animales de cáncer cerebral, más concretamente de tipo glioma. Así, la evolución de un tumor de tipo glioblastoma (glioma astrocítico de grado IV) inducible mediante inyección estereotáctica intracerebral a ratones C57BL/6 de células de la línea GL261 de ratón, ha sido caracterizada de manera no invasiva (mediante imágenes por RM, IRM) en cuanto a su aumento de volumen durante el tiempo de vida de los animales. Además, las curvas de supervivencia y la supervivencia promedio de estos ratones en ausencia de terapia han demostrado ser reproducibles y han permitido establecer el grupo control con el cual comparar el efecto de diversos agentes terapéuticos en la evolución del tumor. De los agentes y protocolos terapéuticos investigados, el más efectivo resultó ser, como era de esperar por la experiencia clínica previa, un agente alquilante del DNA, la Temozolomida (TMZ). La TMZ, en un protocolo de tres ciclos de administración, aumentó significativamente la supervivencia de los animales tratados, produciendo además una ralentización del crecimiento de los tumores durante una semana aproximadamente. Una vez establecido el modelo de respuesta a terapia, se investigó si alguna estrategia de imagen molecular basada en RM podía detectar dicha respuesta transitoria de los tumores a la terapia. Las dos principales estrategias de perturbación del metaboloma del tejido cerebral investigadas fueron la retención diferencial de dimetilsulfóxido (DMSO) y la variación del patrón espectral global tanto en condiciones de euglicemia como en hiperglicemia transitoria. En ambos casos se adquirieron imágenes moleculares de los tumores cerebrales antes, durante la respuesta a la terapia y al manifestarse la recidiva tumoral mediante imagen espectroscópica de RM (IERM). Finalmente, la información de las imágenes moleculares basadas en la perturbación con DMSO, aplicada a las imágenes moleculares previas a la perturbación en condiciones de euglicemia, permitió desarrollar un clasificador matemático que genera imágenes nosológicas de zonas que muestran respuesta a la terapia de tumores GL261. Este clasificador fue validado con éxito en un conjunto de datos independiente (tumores no utilizados para desarrollar el clasificador). Además, la tesis ha permitido avanzar en paralelo con la caracterización mediante IRM/ERM/IERM de otros modelos preclínicos de glioma (ratones modificados genéticamente que desarrollan oligodedndrogliomas de manera espontánea, y glioblastomas humanos desarrollados en animales inmunodeprimidos, nude mice), para poder aplicar en un futuro estrategias de predicción y seguimiento de la respuesta a la terapia. / This work describes in detail the strategy followed for improving the early response to therapy detection in brain tumors at preclinical level. Animal models of brain tumors, specifically glioma models, have been used for this purpose. The evolution of a high grade glioma model (glioblastoma (GBM), IV grade), induced by estereotatic injection of GL261 cells into the striatum of C57BL/6 WT mice, has been characterized using a non-invasive technique, consisting on MR images (MRI). Tumor volume growth rate and animal survival curves have been proved to be reproducible and have been used for establishing a control group for comparing the effect of different therapeutic agents on tumor evolution. Among all the agents investigated, the most effective was Temozolomide (TMZ), an oral alkylating agent commonly used in clinical trials for GBM treatment. A three cycle protocol using TMZ improves the survival rate of treated animals in comparison with the control group. This protocol also affects tumor growth rate, slowing down tumor evolution for a seven days period. After developing the appropriate response to therapy model, different molecular imaging strategies based on MR were investigated to determine if any of them could detect the transitory tumor response to therapy. The main strategies studied were the differential retention of dimethyl sulfoxide (DMSO) and global changes detected in the spectral pattern of tumors in euglicemia and after a hyperglicemic challenge. In both cases, molecular images from the tumors were acquired before, during the response to therapy and at tumor recurrence, using MR spectroscopic imaging (MRSI). Finally, the information obtained from molecular images based on DMSO perturbation (perturbation enhanced MRSI) was applied in euglicemic conditions for developing a mathematical classification system which generates nosologic images for GL261 tumors that show response to TMZ treatment. This classification system was successfully validated with an independent test set of data (tumors that were not used previously for developing the system). In addition, this work has also advanced in the characterization by MRI/MRS/MRSI of other preclinical glioma models (genetically engineered mice which spontaneously develop oligodendrogliomas, and immunosuppressed mice which develop human GBM) for a possible application in the future in tumor response to therapy prediction and follow up strategies.