Solid-state Nuclear Magnetic Resonance (NMR)is one of the premiere biophysical methods that can be applied for addressing the structure and dynamics of biomolecules, including proteins, lipids, and nucleic acids. It illustrates the general problem of determining the average biomolecular structure, including the motional mean-square amplitudes and rates of the fluctuations. Lineshape and relaxtion studies give us a view into the molecular properties under different environments. To help the understanding of NMR theory, both lineshape and relaxation experiments are conducted with hexamethylbezene (HMB). This chemical compound with a simple structure serves as a perfect test molecule. Because of its highly symmetric structure, its motions are not very difficult to understand. The results for HMB set benchmarks for other more complicated systems like membrane proteins. After accumulating a large data set on HMB, we also proceed to develop a completely new method of data analysis, which yields the spectral densities in a body-fixed frame revealing internal motions of the system. Among the possible applications of solid-state NMR spectroscopy, we study the light activation mechanism of visual rhodopsin in lipid membranes. As a prototype of G-protein-coupled receptors, which are a large class of membrane proteins, the cofactor isomerization is triggered by photon absorption, and the local structural change is then propagated to a large-scale conformational change of the protein. Facilitation of the binding of transducin then passes along the visual signal to downstream effector proteins like transducin. To study this process, we introduce 2H labels into the rhodopsin chromophore retinal and the C-terminal peptide of transducin to probe the local structure and dynamics of these two hotspots of the rhodopsin activation process. In addition to the examination of local sites with solid-state 2H NMR spectroscopy, wide angle X-ray scattering (WAXS) provides us the chance of looking at the overall conformational changes through difference scattering profiles. Although the resolution of this method is not as high as NMR spectroscopy, which gives information on atomic scale, the early activation probing is possible because of the short duration of the optical pump and X-ray probe lasers. We can thus visualize the energy dissipation process by observing and comparing the difference scattering profiles at different times after the light activation moments.

The main aim of this thesis is the development of $^{17}$O solid-state nuclear magnetic resonance (NMR) spectroscopic techniques to study the local structure and ion dynamics of functional oxide materials for applications in energy conversion, in particular as electrodes and electrolytes in solid oxide fuel cells (SOFCs). Broadly, the work comprises two related areas: (1) application of a combined experimental and computational methodology to enable the first $^{17}$O solid-state NMR studies of paramagnetic oxides, in particular a class of perovskite-derived structures used as mixed ionic-electronic conductors (MIECs) for SOFC cathodes, and (2) further uses of multinuclear variable-temperature NMR spectroscopy, with emphasis on $^{17}$O NMR results, to elucidate mechanistic details of oxide-ion motion and sublattice exchange in a novel family of promising SOFC electrolyte materials based on $\delta$-Bi$_{2}$O$_{3}$. In the first section, $^{17}$O magic-angle spinning (MAS) NMR spectra of the paramagnetic MIEC, La$_{2}$NiO$_{4+\delta}$, are presented and rationalized with the aid of periodic DFT calculations. Advanced NMR pulse programming and quadrupolar filtering techniques are coupled to extract high-resolution spectra. In particular, these data reveal local structural distortions in La$_{2}$NiO$_{4+\delta}$ that arise from incorporation of interstitial oxide defects. Moreover, variable-temperature spectra indicate the onset of oxide-ion motion involving the interstitials at 130 °C, which is linked to an orthorhombic$-$tetragonal phase transition. By analyzing the ion dynamics on the spectral timescale, specific motional mechanisms are elucidated that prove relevant to understanding the functionality and conductivity of this phase. Next, a similar methodology is applied to the Sr-doped analogues, La$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$, in an exploration of the defect chemistry and electronic structure of these phases (0 $\leq {x} \leq$ 1). By following the doping-induced evolution of spectral features assigned to interstitial and equatorial oxygen environments, changes in the ionic and electronic conductivity, respectively, are rationalized. This approach has been extended to the acquisition and assignment of $^{17}$O NMR spectra of isostructural Sm$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ and Pr$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ phases, promising SOFC cathode materials that exhibit paramagnetism on the A site (A = Sm, Pr). The final section details the characterization of oxide-ion motion in the fluorite-type phases Bi$_{1-x}$V$_{x}$O$_{1.5+x}$ and Bi$_{1-x}$P$_{x}$O$_{1.5+x}$ ($x$ = 0.087 and 0.148) developed as SOFC electrolytes. Variable-temperature NMR experiments between room temperature and 923 K reveal two distinct mechanisms. For the V-doped phases, an oxide-ion conduction mechanism is observed that involves oxygen exchange between the Bi-O sublattice and rapidly rotating VO$_{4}$ tetrahedral units. The more poorly conducting P-doped phase exhibits only vacancy conduction with no evidence of sublattice exchange, a result ascribed to the differing propensities of the dopants to undergo variable oxygen coordination. These initial insights suggest chemical design rules to improve the next generation of oxide-ion conducting materials.

No description available.

No description available.

Depuis 1949, date à laquelle Bloembergen en introduisit le concept, la diffusion de spin nucléaire suscite un vif intérêt en résonance magnétique. La diffusion de spin, qui peut être définie comme le transfert de polarisation de spin induit par l’interaction dipolaire, est un mécanisme omniprésent dans les solides. Les mesures expérimentales de ce phénomène contiennent des informations sur la structure du système étudié. La diffusion de spin est cependant un problème quantique à N corps, ce qui rend sa description ab initio relativement difficile. L’objectif principal de cette thèse est d’obtenir une description quantitative et ab initio de la diffusion de spin, en modélisant de manière adéquate la dynamique à N corps sous-jacente. Tout d’abord, nous exploitons une approche existante, reposant sur l’utilisation d’une équation maître pour les polarisations, dans le cas de la diffusion de spin entre carbones permise par les protons (PDSD). Ensuite, nous introduisons une méthode permettant de simuler l’évolution temporelle d’un ensemble d’observables pour un système de spins nucléaires fortement couplés, en utilisant les corrélations de petit ordre dans l’espace de Liouville (LCL). Le modèle LCL fournit une description précise du transfert de polarisation pour les systèmes polycristallins soumis à la rotation à l’angle magique. Après avoir décrit le modèle, nous analysons plus en détail la réduction de l’espace de Liouville pour les solides, afin d’identifier les conditions dans lesquelles l’approximation LCL est valide. Enfin, nous effectuons des simulations de la diffusion de spin entre pro- tons (PSD) et entre carbones (PDSD), à partir de la structure des cristaux étudiés et sans aucun paramètre libre, et nous constatons pour des solides organiques polycristallins que leur accord avec les mesures expérimentales est excellent. / Since its introduction by Bloembergen in 1949, nuclear spin diffusion has been a topic of significant interest in magnetic resonance. Spin diffusion, which can be defined as the transfer of spin polarisation induced by the dipolar interaction, is a ubiquitous transport mechanism in solids. Experimental observations of spin diffusion contain structural information. However, the many-body nature of the problem makes it difficult to describe from first principles. The central goal of this thesis is to obtain a quantitative description of the spin diffusion phenomenon from first-principles, through the development of suitable models of the underlying many-body dynamics. To that end we first consider an extension of an existing approach that relies on a master equation to describe the polarisations, for the case of proton-driven carbon-13 spin diffusion (PDSD). Second, a novel approach is introduced for the simulation of the time evolution of selected observables for large strongly coupled nuclear spin systems, using low-order correlations in Liouville space (LCL). Following the introduction of this new simulation method, Liouville-space reduction in solids is analysed in more detail, in order to identify the conditions under which the LCL approximation is valid. Finally, using the LCL model, simulations of proton spin diffusion (PSD) and PDSD are performed, directly from crystal geometry and with no adjustable parameters, and are found to be in excellent agreement with experimental measurements for polycrystalline organic solids.

Since its introduction by Bloembergen in 1949, nuclear spin diffusion has been a topic of significant interest in magnetic resonance. Spin diffusion, which can be defined as the transfer of spin polarisation induced by the dipolar interaction, is a ubiquitous transport mechanism in solids. Experimental observations of spin diffusion contain structural information. However, the many-body nature of the problem makes it difficult to describe from first principles. The central goal of this thesis is to obtain a quantitative description of the spin diffusion phenomenon from first-principles, through the development of suitable models of the underlying many-body dynamics. To that end we first consider an extension of an existing approach that relies on a master equation to describe the polarisations, for the case of proton-driven carbon-13 spin diffusion (PDSD). Second, a novel approach is introduced for the simulation of the time evolution of selected observables for large strongly coupled nuclear spin systems, using low-order correlations in Liouville space (LCL). Following the introduction of this new simulation method, Liouville-space reduction in solids is analysed in more detail, in order to identify the conditions under which the LCL approximation is valid. Finally, using the LCL model, simulations of proton spin diffusion (PSD) and PDSD are performed, directly from crystal geometry and with no adjustable parameters, and are found to be in excellent agreement with experimental measurements for polycrystalline organic solids.

Les protéines prions sont associées à une classe de maladies neurodégénératives, dont l'encéphalopathie spongiforme transmissible (EST) est la mieux connue. La protéine prion Sup35p représente un tel modèle car elle est non associée à une maladie. Sup35p se compose de trois domaines : un domaine N-terminal qui est responsable de la formation de prion, d'un domaine de milieu (M) qui affiche un degré élevé de flexibilité, et un domaine C-terminal fonctionnel et globulaire. Le fragment Sup35pNM est souvent utilisé comme modèle pour documenter l'assemblage et les propriétés infectieuses de Sup35p. Les études de Sup35p et Sup35pNM par RMN du solide ont révélé d'étonnantes différences structurelles entre les deux cœurs amyloïdes de Sup35p et Sup35pNM. Nos résultats sur Sup35p apportent un nouvel éclairage sur le monde étonnamment diversifié des prions où la variabilité conformationnelle joue un rôle énorme et perturbant. Ils reflètent l'image émergente que les prions sont des unités structurelles complexes. En effet, même s'il affiche une structure très définie, un domaine donné peut adopter des conformations différentes selon les circonstances (en isolation, dans le contexte d'un fragment ou la protéine entière) ou de l'environnement (conditions de tampon, présence de chaperonnes). Nos résultats donnent une explication au niveau moléculaire pour la contractante propension à l'assemblage et l'infectiosité de Sup35pNM et Sup35p, et soulignent l'importance primordiale d'une caractérisation structurale au niveau moléculaire des agrégats utilisés dans des études fonctionnelles / Prion proteins are associated with a class of neurodegenerative diseases, including transmissible spongiform encephalopathy (TSE) which is the best known. The prion protein Sup35p displays a model system because it is not associated with disease. Sup35p consists of three domains: an N-terminal domain which is responsible for the prion formation, a middle domain (M) that displays a high degree of flexibility, and a functional C-terminal domain. Sup35pNM the fragment is often used as a model to document for the assembly and infectious properties of Sup35p. Solid-state NMR studies of Sup35p and Sup35pNM fibrils showed amazing structural differences between the two amyloid cores. Our results shed new light on the surprisingly diverse world of prions where conformational variability plays a huge role. They reflect the emerging picture that prions are complex structural units. Even if it displays a very defined structure, a given field may adopt different conformations depending on the circumstances (in isolation, in the context of the whole protein or fragment) or the environment (buffer conditions, presence of chaperones). Our results provide an explanation at the molecular level for the contrasting propensity assembly and infectivity Sup35pNM and Sup35p, and emphasize the central importance of a structural characterization at the molecular level

No description available.

Nuclear Magnetic Resonance (NMR) and computational methods increasingly play a predominant and indispensable role in modern chemical research. The insights into the local nuclear environment that NMR can provide is unique information which allows the structural characterization of novel materials, as well as the understanding and explanation of their relevant properties on an atomic scale. Computational methods, on the other hand, can be used to support experimental findings, providing a rigorous theoretical basis. Furthermore, when more complex chemical systems are considered, calculations can prove to be invaluable for the interpretation of experimental data and often allow an otherwise impossible spectral assignment. This thesis presents a series of studies in which NMR spectroscopy, in combination with computational methods, is utilized to investigate a variety of chemical systems both in solution and the solid state. An overview of the thesis and experimental and computational details are given in Chapter 1. In Chapter 2, the quantum mechanical basis necessary for the description of the NMR phenomenon is presented. Chapter 3 explores the main experimental techniques employed routinely for the acquisition of NMR spectra in both solution and the solid state. Chapter 4 describes the main features of density functional theory (DFT) and its implementation in computational methods for the calculation of relevant NMR parameters. Chapter 5 reports an experimental solution-phase NMR study and a parallel computational investigation of the poly(CTFE-co-EVE) fluoropolymer. In Chapter 6, the combination of [superscript(14/15)]N solution-phase NMR techniques and DFT methods for the study of alkylammonium cationic templates used in the synthesis of microporous materials is presented. The characterization of a boroxoaromatic compound in the solid state and the study of its reactivity are described in Chapter 7. In Chapter 8, two experimental NMR methods for the study of the anisotropic chemical shift interaction in the solid state are compared and used to characterize a range of materials. Cross-polarization and nutation of quadrupolar nuclei are computationally investigated under both static and spinning conditions in Chapter 9. A general conclusion and a summary are given in Chapter 10.

This thesis combines solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), chemical synthesis, isotopic enrichment and density-functional theory (DFT) calculations to provide insight into a number of microporous materials. The first class of materials studied is metal-organic frameworks (MOFs), where the presence of paramagnetic ions has a range of effects on the ¹³C NMR spectra, depending on the nature of the ligand-metal interactions. For the Cu²⁺-based MOFs, HKUST-1 and STAM-1, the assignment of the NMR spectra is non-intuitive, and unambiguous assignment requires specific ¹³C labelling of the organic linker species. It is shown that ¹³C NMR spectra of these two MOFs could act as a sensitive probe of the nature of “guest” molecules bound to the Cu²⁺. The second class of materials is aluminophosphates (AlPOs). It is shown that, using a series of relatively simple linear relationships with the crystal structure, the NMR parameters calculated by DFT (with calculation times of several hours) can be predicted, often with experimentally-useful accuracy, in a matter of seconds using the DIStortion analysis COde (DISCO), which is introduced here. The ambient hydration of the AlPO, JDF-2, to AlPO-53(A) is shown to occur slowly, with incomplete hydration after ~3 months. The resulting AlPO-53(A) is disordered and some possible models for this disorder are investigated by DFT. The final class of materials is gallophosphates (GaPOs), particularly GaPO-34 and related materials. The two as-prepared forms of GaPO-34 are characterised by solid-state NMR, and their calcination investigated by TGA and in-situ powder XRD. An unusual dehydrofluorinated intermediate phase is isolated and characterised for the first time by solid-state NMR. The fully calcined material is shown to be stable under anhydrous conditions, but hydrates rapidly in air. The hydrated material is stable under ambient conditions, but collapses upon heating. Partial dehydration without collapse is achieved by gentle heating or room-temperature evacuation. The impurity phases, GaPO₄ berlinite and GaPO-X are investigated by solid-state NMR and, while the structure of GaPO-X remains unknown, much structural information is obtained.