The thesis aims at methodological developments in Nuclear Magnetic Resonance (NMR) and study of oriented samples like liquid crystals and single crystals and powder samples. Though methodological development in solid state NMR (ss-NMR) has gone far ahead, this work attempts to contribute some novel methods in this direction. The work presented here falls into two categories (i) methodological developments for obtaining information on anisotropic interactions and (ii) experiments which utilize the existing methodologies to study systems of interest under static condition and also under sample spinning at the Magic Angle. In the solid state, dipolar couplings play a crucial role. On the one hand these couplings could be used to transfer polarization from an abundant nucleus to a rare nucleus and increase the sensitivity of the rare nucleus. On the other hand, the measurement of dipolar couplings itself is crucial for extracting structural and dynamic information. A third aspect is that dipolar couplings could be used to obtain correlation, say between two different nuclear species or between the same kind of nuclei as in an exchange experiment. A major part of this thesis deals with all three aspects mentioned above. The thesis presents a new heteronuclear polarization transfer scheme which is devoid of some of the short comings of the existing and well-known polarization transfer schemes. This pulse sequence has been found to be useful in different contexts involving both spin ½ and spin 1 nucleus. The use of dipolar couplings for obtaining correlation in both static oriented systems and in powder samples has been illustrated. In the case of the powder sample, the study has been useful in obtaining useful orientation information. Finally, chemical shifts are known to be indicators of finer structural features of molecules in solution and solid state. 13 C MAS NMR studies have been exploited in understanding these structural features of short peptides containing prolines in the solid state and for comparing with their structures in solution. Chapter 1 covers the theoretical aspects required for the experimental work described in the thesis. A brief description of NMR has been followed by the explicit description of various interaction Hamiltonian’s in ss-NMR. Subsequently the experimental and the theoretical tools needed for ss-NMR study like Magic Angle Spinning (MAS), Cross-Polarization, Homo/Heteronuclear decoupling schemes have also been discussed. Chapter 2, describes a new heteronuclear polarization transfer scheme for oriented samples – named DAPT (Dipolar Assisted Polarization Transfer) and its application to different systems. DAPT uses a homonuclear decoupling sequence such as BLEW-12 for effecting heteronuclear polarization transfer. The chapter has been divided into five related parts. Section 2(A) starts with an introduction to the existing heteronuclear polarization transfer schemes. Subsequently the theoretical background of the new sequence is presented. Experimental implementation of the sequence in an oriented system, liquid crystal is presented and is compared with the well-known polarization transfer scheme, Hartmann-Hahn Cross Polarization (HH-CP). In 2(B) the implementation of the sequence as a local field spectroscopy for measuring heteronuclear dipolar couplings is presented. After initial discussion about local field spectroscopy and its relevance in ss-NMR, the improvements made in the earlier mentioned sequence along with its 2D implementation in a liquid crystal sample are described. A comparative study is also presented using DAPT with various other homonuclear decoupling sequences. Chapter 2(C) deals with the extension of DAPT to spin-1 systems. The difficulties in setting up the HH-CP in spin-1 systems are highlighted. Experimental demonstrations on a test sample of oriented CD3 I and also on a deuterated liquid crystal is described. The sequence has been incorporated as part of a 2D correlation experiment, where the F1 dimension provides the quadrupolar couplings of deuterium and the F2 the chemical shifts of the attached carbons. The comparison of the sequence with HH-CP, its merits and demerits are discussed and the potential applications are highlighted. Chapter 2(D) deals with the relatively less studied transition in 14N nucleus, known as the Overtone-Transition (OT). An introduction to OT and its relevance is provided in the beginning followed by the extension of DAPT in exciting and detecting OT. The experiments have been done on a single crystal of a model peptide, N-Acetyl-DL-Valine and are compared with the conventional method. Amide proton chemical shifts are also measured using DAPT in an indirect way. The advantages and the future application in studying OT are also discussed. Chapter 2(E) discusses the extension of DAPT to the single crystal of NAV and in identifying the molecules in the unit cell. The SLF spectrum of NAV is complicated due to the presence of two magnetically in-equivalent molecules in the unit cell and with pairs of splitting for each C - 1H and C - 1H pairs. The dipolar couplings are extracted from the experiment and with the aid of a MATLAB program and by incorporating the crystal coordinates, identification of C-1H and C-1H pairs belonging to a particular molecule have been carried out. Chapter 3 describes a novel and useful modification of the well-known Separated Local Field (SLF) sequence in solid state known as PISEMA (Polarization Spin Exchange at the Magic Angle). PISEMA is a popular technique for measuring heteronuclear dipolar couplings in oriented in oriented biological membranes and in liquid crystals. While it has several advantages such as a large dipolar scaling factor, narrow line-widths in the dipolar dimension and ease of setting up etc it suffers from a major problem. The technique is highly sensitive to the proton off-sets which affect the measured dipolar couplings. In the present chapter the origin of this problem has been analyzed in detail and a solution has been proposed. The modification to the experiment has been implemented on a liquid crystal and the off-set independence of the new sequence has been demonstrated. Further studies on a more rigid system such as a solid single crystal has been used to verify the effect of the modification on homonuclear decoupling efficiency and the consequent effects on the line widths in addition to off-set independence. The advantages of the proposed method over the existing one in terms of line-width and robustness in measuring heteronuclear dipolar couplings are demonstrated. Chapter 4 presents a study of deuterium exchange on a di-peptide. Deuterium as well as carbon-13 NMR spectroscopy has been extensively used earlier on static powder samples for studying exchange phenomena. In the present study we have applied the methodology for obtaining relative N-D vector orientation in a di-peptide. The magnetization exchange between deuterium nuclei through the dipolar couplings between them has been monitored. The need to match the quadrupolar split energy levels of two different deuterium’s differently oriented in the magnetic field requires that the sample be spun slowly. Characteristic exchange powder patterns were obtained which were used to infer relative orientation information. Comparison with the crystal structure indicates that the magnetization is likely to be inter-molecular rather than intra-molecular. The chapter follows the following sequence. A brief description about the importance of exchange studies in ss-NMR is presented. A theoretical approach is followed by a discussion of the angular dependence of the frequencies and the visualization of the mutual re-orientation angles. The motivation of the project followed by the experimental techniques, especially the use of slow MAS ~ 100 Hz in exchange studies are also presented. Initial studies have been carried out on di-methyl sulphone to check the reproducibility of the earlier reported results and later the sequence is extended to amide proton deuterated di-glycine. The 2D exchange spectrum recorded under slow MAS is then discussed in the context of the crystal structure and possible amide deuteriums involved in the exchange process are inferred. Chapter 5 discusses the natural abundant 13C and 15N NMR spectroscopy in the solid state in designed tri-peptides containing prolines. Proline is a unique amino acid because of it torsion angle values and is responsible for the turns and the globularity of the proteins. The well studied SH3 domain protein often binds to short peptides containing prolines and hence these study gains importance. Three peptides containing prolines were taken up for study. For peptide (1), the conformation was observed as cis/trans in the solution state and for the other two peptides it was all trans. The X-ray studies showed that peptide (1) has two molecules in the unit cell with both cis conformation. This motivated us to look at the solid state spectra of the peptides. Chemical shifts are signatures of conformers and it was established from the chemical shift differences that there exist two molecules in the unit cell for peptide (1), both in cis conformation. The conformers for the other two peptides predicted by NMR chemical shifts also matched with those obtained from X-ray studies. This opens up the possibility of using simple NMR measurements in the solid state as tools for secondary structure determination in larger peptides and proteins.

The aim of this thesis was the investigation of the mitochondrial response mechanisms upon apoptotic stimuli. The specific objectives were the biophysical characterization of membrane dynamics and the specific roles of lipids in the context of apoptotic regulation occurring at the mitochondrion and its complex membrane systems. The BH4 domain is an anti-apoptotic specific domain of the Bcl-2 protein. Solid phase peptide synthesis was used to produce large amount of the peptide for biophysical studies. A protocol has been established and optimized, guarantying the required purity for biophysical studies. In detail the purification by high performance liquid chromatography and the characterisation via mass spectroscopy are described. The secondary structure of BH4 changes significantly in the presence of lipid vesicles as observed by infrared spectroscopy and circular dichroism. The BH4 peptide aggregates at the membrane surface and inserts slightly into the hydrophobic part of the membrane. Using nuclear magnetic resonance (NMR) and calorimetry techniques, it could even be shown that the BH4 domain modifies the dynamic and organization of the liposomes which mimic a mitochondrial surface. The second study was on the first helix of the pro-apoptotic protein Bax. This sequence called Bax-α1 has the function to address the cytosolic Bax protein to the mitochondrial membrane upon activation. Once again a protocol has been established for the synthesis and purification of this peptide. The aim was to elucidate the key role of cardiolipin, a mitochondria-specific phospholipid, in the interaction of Bax-α1 with the mitochondrial membrane system. The NMR and circular dichroism studies showed that Bax-α1 interacts with the membrane models only if they contain the cardiolipin, producing a strong electrostatic lock effect which is located at the membrane surface. Finally, a new NMR approach was developed which allows the investigation of the lipid response of isolated active mitochondria upon the presence of apoptotic stimuli. The goal was there to directly monitor lipid specific the occurring changes during these physiological activities.

No description available.

Made available in DSpace on 2014-10-09T12:53:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:29Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

En dépit de l’importance considérable des matériaux alumino- et borosilicates pour la catalyse, l’origine moléculaire de leur activité demeure mal comprise. Ceci tient à la difficulté de caractériser le désordre structural local généré au sein du réseau silicaté par l’incorporation d’hétéroatomes. Le caractère local de la résonance magnétique nucléaire (RMN) à l’état solide en fait une technique adaptée pour résoudre cette question majeure. Les silicates en feuillés auto-assemblés en présence de surfactants sont d’excellents systèmes modèles pour l’étude de la structure locale autour d’hétéroatomes de B ou d’Al car la synthèse, la structure moléculaire et la signature RMN 29Si simple de leurs formes siliceuses sont parfaitement maîtrisées. L’incorporation dans leurs réseaux silicatés de différentes quantités d’Al ou de B et leurs conséquences ont été étudiées par des méthodologies avancées de RMN permettant de sonder les interactions à travers l’espace ou les liaisons chimiques entre noyaux de 29Si, 27Al, 11B et/ou 1H, une approche qui peut être étendue à la substitution atomique dans une argile aluminosilicate et un nouveau borosilicate de calcium. Ces résultats ont été combinés à la modélisation moléculaire pour construire et valider des modèles structuraux capables de décrire les distorsions et les réarrangements parfois profonds du réseau résultant de la substitution. Cela a révélé des différences frappantes entre les conséquences de l’incorporation d’Al ou de B dans deux matériaux de morphologie semblables mais de structures moléculaires différentes, et offre une occasion unique de comprendre les propriétés régissant l’incorporation d’hétéroatomes dans les silicates. / While alumino- and borosilicate materials have paramount importance in catalysis, the molecular origin of their activity is not completely understood. This is mainly because the incorporation of heteroatoms into the silicate framework deteriorates the molecular order by generating local disorder that is particularly difficult to establish. Because of its local vision of ordered and disordered environments, solid-state nuclear magnetic resonance (NMR) can play a key role to solve this long-standing issue. Surfactant-directed layered silicate materials with short-range molecular order are particularly interesting model systems to study the local structures around Al or B heteroatoms because the synthesis, molecular structures, and simple 29Si NMR signatures of their pure-silicate forms are well understood. Various amounts of Al and B atoms were incorporated into their frameworks, and their consequences on the local structure were investigated by state-of-the-art multidimensional NMR measurements probing spatial proximities or bonding interactions between 29Si, 11B, 27Al, and 1H nuclei, an approach that could be extended to atomic substitution in an aluminosilicate clay and a new calcium borosilicate. These results were combined with molecular modeling to build and evaluate structural models that capture the local framework distortions and sometimes profound rearrangements resulting from the atomic substitutions. This reveals remarkable differences between the consequences of the incorporation Al or B in two distinct frameworks of otherwise strongly-related materials, and offers a unique opportunity to understand the properties that drive heteroatom incorporation.

Nesta tese, a ressonância magnética nuclear do estado sólido (SSNMR) foi utilizada para estudar a composição química e estrutura dos componentes da parede celular de plantas. Visando contribuir no desenvolvimento de estratégias de despolimerização da biomassa, SSNMR foi inicialmente utilizada para estudar efeitos dos pré-tratamentos químicos e físicos, e da ação de enzimas sobre algumas biomassas. Os resultados mostraram que, em baixas concentrações, tratamentos ácidos são altamente efetivos na remoção das frações de hemicelulose, com pouco efeito nas frações de lignina e celulose. Já tratamentos alcalinos promovem eficiente deslignificação da biomassa, sendo que a mínima concentração da solução alcalina necessária para obter a máxima deslignificação depende do tipo de biomassa e da temperatura do tratamento. Os estudos por SSNMR foram correlacionados com estudos por outras técnicas, contribuindo para um entendimento mais profundo sobre o efeito dos pré-tratamentos e da hidrolise enzimática em diferentes biomassas. Outra parte da tese aborda a determinação da cristalinidade de celulose nativa (não extraída) de biomassa de bagaço de cana-de-açúcar. Utilizando a técnica de polarização cruzada em múltiplas etapas (Multi-CP) e um procedimento de subtração espectral, foi possível isolar os sinais de RMN da celulose nativa e a partir daí avaliar o índice de cristalinidade (CI). Esse método foi utilizado para avaliar o CI da celulose nativa de bagaço de cana-de-açúcar submetido à pré-tratamentos com H2SO4 e NaOH e os resultados não mostraram variações significativas do CI da celulose nas concentrações utilizadas, apesar do aumento da eficiência da hidrólise. Assim, ao contrário de muitos trabalhos encontrados na literatura, não parece que a cristalinidade da celulose seja um fator primordial no aumento de eficiência da hidrólise enzimática. Na parte final da tese, as interações intermoleculares entre os dois principais polissacarídeos da biomassa: celulose e xilano foram investigadas utilizando uma variedade de técnicas avançadas de RMN bidimensional. Neste trabalho, a arquitetura molecular de hastes de plantas de Arabidopsis Thaliana, sem nunca serem seca foi estudada. Utilizando a técnica refocused J-INADEQUATE (Increadible Natural Abundance Double Quantum Transfer Experiment via J coupling) observamos dois conjuntos de deslocamentos químicos distintos para o xilano, sendo um deles coincidente com aquele observado em solução. Em seguida, utilizamos experimentos SSNMR com o intuito de investigar se algum desses domínios de xilano estaria vinculado com a celulose. Experimentos CP-PDSD (Proton Driven Spin Diffusion detected via 13C through Cross-Polarization) demonstram a existência de proximidade espacial entre o novo domínio do xilano e o domínio da celulose. A comparação de resultados entre as amostras de padrão e o seu mutante deficiente em celulose (irx3) indicaram que o xilano com novo deslocamento químico é fortemente dependente da presença de celulose. A análise da mobilidade molecular pela técnica Dipolar Chemical Shift Correlation (DIPSHIFT), mostrou que as moléculas do novo domínio do xilano são altamente rígidas - uma característica partilhada com a celulose. Combinados, esses dados fornecem evidências de uma arquitetura molecular específica entre os dois polissacarídeos majoritários da parede celular. / Solid-state nuclear magnetic resonance (SSNMR) was used to study the chemical composition and structure of plant cell wall components. Aiming the development of depolymerization strategies, SSNMR was initially used to study the effects of chemical and physical pre-treatments, as well as the enzymatic action on the structure and composition of biomasses. The results showed that, at low concentrations, pre-treatments with acids are highly effective for removal of hemicellulose without significant effect on lignin and cellulose. In turn, the alkaline pre-treatment promotes efficient delignification of the biomass. The minimum concentration of the alkaline solution required to achieve the maximum delignification depends on the type of biomass and treatment temperature. SSNMR studies were correlated with studies using other techniques, contributing to an in-depth understanding of the effect of pre-treatments and enzymatic hydrolysis in different biomasses. Another part of the thesis discusses is the determination of native cellulose crystallinity (not extracted) of sugarcane bagasse biomasses. Using the cross-polarization technique in multiple blocks (Multi-CP) and a spectral subtraction approach, it was possible to isolate the NMR signals of the native cellulose and to evaluate the crystallinity index (CI). This method was used to accessof the CI of cellulose in sugarcane bagasse samples pre-treated with H2SO4 and NaOH. The results did not show significant variations of the cellulose CI, at the concentration used here, despite the increase in the hydrolysis efficiency. Thus, in contrast to some studies in the literature, it does not appear that the crystallinity of cellulose is a primary limiting factor concerning the enzymatic hydrolysis efficiency in biomasses. In the final part of this thesis, the intermolecular interactions between the two main polysaccharides of the plant cell wall, cellulose and xylan, were investigated using advanced two-dimensional NMR techniques. The molecular architecture of 13C labelled never-dried Arabidopsis Thaliana stems was studied. Using refocused J-INADEQUATE (Increadible Natural Abundance Double Quantum Transfer Experiment via J coupling) we observed two distinct chemical shifts in xylan, one of which coincides with that observed in solution. Next, we used SSNMR experiments toinvestigate the interaction between the novel xylan and cellulose domains. CP-PDSD (Proton Driven Spin Diffusion detected via 13C through Cross-Polarization) experiments demonstrated spatial proximity between the new xylan and cellulose domains. The same approach was used to study cellulose deficient (irx3) mutants and the comparison between the results indicate that the new xylan domain is cellulose-dependent. Dipolar Chemical Shift Correlation (DIPSHIFT) experiments were performed to analyse the molecular mobility of these polysaccharides showing that the novel xylan is highly rigid - a characteristic which is shared with cellulose. Combined, these data provide evidence for a specific molecular architecture between the two most common polysaccharides in plant cell walls.

Made available in DSpace on 2014-10-09T12:53:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:09:29Z (GMT). No. of bitstreams: 0 / No presente trabalho foi desenvolvida uma técnica radiográfica para a inspeção de amostras finas, que emprega feixes de partículas - ? como radiação penetrante e, detectores de traços nucleares de estado sólido para o registro da imagem. O feixe é gerado em uma tela de boro natural quando irradiada com nêutrons térmicos e o detector utilizado foi o CR-39. A interação das partículas - ? com o detector geram danos, os quais sob a ação de uma solução química adequada transformam-se em traços, as unidades básicas formadoras da imagem. Foi desenvolvido um sistema digital próprio para a aquisição, análise e processamento dos dados e das imagens registradas nos detectores. As condições ótimas de irradiação e de revelação para a obtenção de uma radiografia são 1,3 horas e 25 minutos a 70°C, respectivamente. Nestas condições a técnica é capaz de analisar amostras com até 10?m de espessura, com uma resolução espacial de 32?m. O emprego do sistema digital permitiu uma redução significativa no tempo despendido para a aquisição e análise de dados e, uma melhoria na visualização das imagens radiográficas registradas. Além disto permitiu acesso a novos dados referentes aos traços registrados, o que abriu novas perspectivas de pesquisa pois, tem-se acesso aos parâmetros fundamentais que norteiam a teoria da formação da imagem em detectores de traços nucleares utilizada neste trabalho. São apresentadas algumas radiografias que demonstram a potencialidade da técnica desenvolvida. Quando comparada com as outras técnicas radiográficas usuais, empregadas para inspecionar amostras finas, a desenvolvida no presente trabalho permite um menor tempo para a obtenção da imagem, não é necessário a manipulação de materiais radioativos líquidos e, o filme empregado é praticamente insensível às radiações ?, ?, raios - X e luz visível. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Neste trabalho apresenta-se a obtenção e caracterização de materiais luminescentes baseados em matrizes mesoporosas incorporadas com espécies moleculares altamente emissivas; o corante rodamina 6G (R6G) e o complexo de irídio (III) (N,N-trans-[Ir-(1-benzil-4-(2,4-difluorofenil)-1,2,3-triazol)2(4,4´-dimetil-2,2´-bipiridina)]+). Na incorporação da R6G foram explorados xerogéis mesoporosos sílica de composições puramente inorgânica e modificada com grupos aromáticos, além de vidros mesoporosos sódio aluminosilicato. O complexo de Irídio (III) foi incorporado somente aos vidros sódio aluminosilicato. As matrizes hospedeiras preparadas por metodologia sol-gel foram planejadas e desenvolvidas em consonância com as propriedades físico-químicas das espécies emissoras, a fim de promover maior incorporação e dispersão molecular via diferentes interações químicas. Por exemplo, no caso da sílica modificada com grupos aromáticos, espera-se que haja interação por afinidade química entre tais grupos e as ligações insaturadas das moléculas de R6G, resultando em maior taxa de incorporação e de retenção do centro emissor, bem como minimizando agregações moleculares. No caso dos vidros sódio aluminosilicato, a incorporação de ambas espécies catiônicas, o corante e o complexo de Ir(III), ocorre via troca iônica com íons Na+, que atuam como compensadores de carga dos sítios (AlO4)- da rede. Neste caso, um controle de dispersão molecular do centro emissor foi proposto variando-se a relação Si/Al na matriz (entre 2 e 9), a fim de promover a distribuição espacial dos sítios aniônicos ativos (AlO4)- entre os sítios neutros SiO4. A partir dessas abordagens foram obtidos materiais luminescentes quimicamente estáveis, com alto grau de dispersão molecular, fácil preparação, e excelentes propriedades fotofísicas. Previamente à incorporação, as matrizes foram caracterizadas do ponto de vista estrutural por diversas técnicas de RMN de estado sólido, DRX e sorção de N2. As propriedades fotofísicas dos emissores em solução e em estado sólido foram caracterizadas por medidas de absorção UV-Vis, espectroscopia óptica, tempo de vida de estado excitado e rendimento quântico absoluto. Adicionalmente, as matrizes contendo R6G foram submetidas a testes de ação laser e fotoestabilidade. Os resultados destes sistemas foram analisados com base na teoria do éxciton (em inglês, Single Exciton Theory). No que concerne os sistemas contendo o complexo de Irídio (III), suas propriedades fotofísicas foram relacionadas à eletrônica do centro emissor obtida por teoria do funcional de densidade (em inglês, Density Functional Theory, DFT). Neste caso, a partir do tratamento convencional realizado para moléculas em estado líquido, foram desenvolvidos e analisados métodos alternativos para tratar o problema em uma matriz hospedeira. O formalismo aplicado contribuiu para uma descrição detalhada da estrutura eletrônica do complexo, bem como mudanças devido à inserção deste na matriz. / This work presents the preparation and characterization of luminescent materials based on mesoporous host matrices loaded with highly emissive molecular species (the organic dye Rhodamine 6G (R6G), and the Iridium (III) complex (N,N-trans-[Ir-(1-benzyl-4-(2,4-difluorophenyl)-1,2,3-triazole)2(4,4´-dimethyl-2,2´-bipyridine)]+). In the case of R6G loading we have explored purely inorganic and organically modified silica compositions, as well as sodium-aluminosilicate glasses. The Ir(III) complex was loaded solely into the sodium-aluminosilicate glasses. The host matrices were designed and developed, via sol gel methodology, in consonance with the physicalchemical properties of the emitters aiming at improved molecular incorporation and dispersion through various chemical interactions. For instance, in the case of silica modified with aromatic groups, interaction among such groups with the unsaturated bonds of the R6G molecule is expected, resulting in higher molecular incorporation and retention efficiencies, as well as decreased aggregation. In the case of the sodium-aluminosilicate glasses, the loading of both cationic species, dye and Ir(III) complex, takes place via ionic exchange with Na+ at the (AlO4)- network sites. In this case, control of molecular dispersion of the emitting center was attempted by varying the Si/Al ratio in the matrix (between 2 and 9), so as to promote the spatial distribution of the active anionic sites among neutral SiO4 sites. Through these approaches, we were able to obtain materials with high chemical stability, high molecular dispersion, facile and low cost obtainment and excellent photophysical properties. Prior to loading, the matrices were characterized from the structural point of view through several solid state NMR techniques, XRD and N2 sorption. The photophysical properties of the emitters in solution and in the solid state were characterized and compared through UV-Vis absorption and emission, excited state lifetimes and absolute quantum yields measurements. Moreover, the R6G loaded materials were tested in a laser cavity with respect to their laser efficiencies and photo stabilities. The results of these systems were analyzed in terms of the Single Exciton Theory. As for the materials loaded with Ir(III) complex, the photophysical studies were complemented by a theoretical approach though Density Functional Theory, DFT. From the conventional treatment performed for iridium (III) complexes in liquid state, alternative methods were developed and analyzed for treating the problem in the host matrix. The applied formalism contributed to a detailed description of the electronic structure of the complex, as well as of the changes perceived due to insertion in the matrix.

L’estimation du délai post mortem est une étape fondamentale en anthropologie médico-légale. À ce jour, peu de méthodes précises et fiables existent. Les objectifs de notre travail étaient d’étudier le tissu osseux et son évolution dans les années et siècles suivant le décès en développant la Résonance Magnétique Nucléaire (RMN) des solides du carbone13C et du proton1H. Nous avons analysé une centaine d’os humains et animaux pour lesquels nous connaissions l’âge au décès, le sexe, la date de décès et les conditions de conservation. Nous avons caractérisé les os au niveau moléculaire en identifiant le collagène, les lipides et l’hydroxyapatite constitutifs du tissu osseux. Nous avons développé une méthode RMN permettant de distinguer des altérations de certains échantillons attestant de la présence d’adipocire au sein du tissu osseux, ou des dégradations sur des échantillons très anciens. L’étude de l’âge au décès et du sexe des sujets n’a pas mis en évidence une grande influence de ces facteurs sur les données RMN même si, pour des délais post mortem de 0 ou 1 an, les sujets féminins présentent quantitativement plus de lipides que les sujets masculins. L’analyse des conditions de conservation des individus montre un développement plus important d’adipocire pour les os laissés à l’air libre comparés aux os enterrés. Enfin, nous rapportons une décroissance quantitative du collagène et des lipides présents au sein du tissu osseux lorsque l’intervalle post mortem augmente. Cette décroissance est beaucoup plus rapide pour les lipides (quelques années) que pour le collagène (plusieurs millénaires) alors que l’hydroxyapatite présente une relative stabilité dans les premiers siècles suivant le décès. / The post mortem interval estimation is a fundamental step in forensic anthropology and up to now there are little accurate and reliable methods to do so. The objectives of our study were to investigate the bone composition and its evolution over years and centuries following the death by developing carbon 13C and proton 1H solid-state nuclear magnetic resonance (NMR). We analyzed about one hundred human and animal bones for which the age at death, sex, date of death and the storage conditions were known. Bones were characterized at the molecular level by identification of collagen, lipids and hydroxyapatite embedded in the bone matrix. We have designed a NMR-based method that allows determining alterations on some samples, evidencing the presence of adipocere (bone wax) within the bone, or finding bone tissue deterioration on some very old samples. Subject age at death and sex did not reveal significant changes on NMR data, except for post mortem interval ranging between 0 to 1 year, where female subjects had quantitatively more lipids in their bones than males. Storage conditions may promote a greater development of adipocere especially for bones left in the open air compared to those buried. Finally, we report a quantitative decrease of collagen and lipids present in the bone tissue when the post mortem interval increases. This decrease is much faster for lipids than for collagen where as the hydroxyapatite has a relative stability in the first centuries after the death. Decreases occur with very different time constants, ranging from years to millennia.

L’objectif des travaux est de mieux comprendre durant la torréfaction de différentes biomasses l’évolution chimique à la fois des phases solide et gaz. Des expériences de torréfaction ont été menées selon un profil de température dynamique entre 200 et 300°C, sous atmosphère inerte, sur du pin, du frêne, du miscanthus et de la paille de blé. La perte de masse et la formation des espèces condensables ont été analysées par ATG-GCMS, et l’évolution chimique de la phase solide par RMN du solide 13C CP/MAS. Trente espèces condensables ont été détectées ; la moitié a été formée dans l’ensemble de la gamme de température explorée et un tiers l’a été par toutes les biomasses. Les principaux phénomènes qui semblent associés à la dégradation du solide sont la décristallisation de la cellulose, une sévère dégradation de l’hémicellulose, la dévolatilisation des groupes acétyles, la conservation des groupes méthoxys et la formation d’un résidu solide. Il a été par ailleurs montré que perte de masse et évolution chimique du solide n’étaient pas directement corrélées pour différentes biomasses. A partir de ces résultats expérimentaux, un modèle conceptuel a été développé pour décrire la dégradation de la biomasse. Trente réactions ont été associées aux trois constituants macromoléculaires principaux que sont la cellulose, l’hémicellulose et la lignine, respectivement représentées par deux sucres en C5 et C6 et par trois unités detype H, G et S. Ce modèle présente l’originalité de s’appuyer sur une description détaillée de ces deux derniers constituants et de prévoir la formation de seize espèces condensables, cinq gaz permanents et six formes de char solide, grâce à des réactions ayant un sens chimique et équilibrées d’un point de vue stoechiométrique. / The objective of the present work is to better understand chemical evolution of both solid and gaseous phases during torrefaction of various biomasses. Torrefaction experiments were carried out with a dynamic profile of temperatures between 200 and 300°C, under inert atmosphere, for pine, ash-wood, miscanthus and wheat straw. Mass loss and formation of condensable species were analyzed by TGA-GC-MS, and chemical evolution of solid phase was characterized by 13C CP/MAS solid-state NMR. Thirty condensable species could be detected; a half of these species were formed during the whole temperature range, and a third were formed by all biomass types. The main phenomena that occurred in solid phase were found to be decrystallization of cellulose, severe degradation of hemicellulose, devolatilization of acetyl groups, conservation of methoxyl groups and charring. It was also found that mass loss and chemical evolution of solid were not directly correlated for different biomasses. Based on the experimental results, a conceptual model was developed to describe biomass degradation duringtorrefaction. Thirty reactions were determined for the three major macromolecular constituents, namely cellulose, hemicellulose – represented by C5 and C6 sugars – and lignin – represented by H, G and S units. The main innovations of this model are in thedetailed approach of hemicellulose and lignin compositions, as well as in the prediction of sixteen condensable and five permanent species, and six forms of solid char, through chemically meaningful and stoichiometrically valid reactions.