Thèses sur le sujet « Paramagnetic solid state NMR »
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Kervern, Gwendal. « High-resolution solid-state NMR of paramagnetic molecules ». Lyon, École normale supérieure (sciences), 2008. http://www.theses.fr/2008ENSL0483.
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Cette thèse porte sur la RMN haute résolution de composés paramagnétiques solides. Elle présente de nouvelles méthodes permettant d'obtenir de tels spectres, ainsi que l'exploitation des spectres ainsi obtenus pour la caractérisation structurale de complexes paramagnétiques. Nous avons dans un premier temps développé des méthodes qui permettent de surmonter les difficultés liées au paramagnétisme. Ces méthodes inclues du transfert d'aimantation par recouplage dipolaire, l'adaptation d'impulsions adiabatiques pour les solides en rotation à très haute vitesse et la compréhension des phénomènes mis en cause dans leur efficacité. Nous présentons ensuite l'exploitation des données ainsi obtenues. Notamment pour la caractérisation de la structure électronique d'un catalyseur à base de fer à haut spin, la démonstration de l'absence de relaxation dite "de Curie" dans les solides ainsi que le développement d'un nouvel outil de cristallographie par RMN de poudresThis thesis is about high-resolution solid-state NMR of paramagnetic molecules. It exposes new methods to obtain high-resolution NMR spectra of paramagnetic solids. These methods gave us access to the structural information born by the electronic paramagnetism. In the first part, we propose new tools to overcome the difficulties associated with NMR of paramagnetic solids. These methods include proton to carbon magnetization transfer via dipolar recoupling, the use of adiabatic pulses with paramagnetic solids rotating at high MAS speeds, the development of a theory for a better understanding of the physics of such pulses. The second part exposes the interpretation of the high quality spectra obtained throught those methods. We characterized the electronic structure of high-spin iron (II) catalyst, we tackled the absence of the so-called "Curie relaxation" mechanism in the solid-state an we developed a new tool for crystallography thanks to proton NMR of paramagnetic powedrs
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Marsden, Ian. « Paramagnetic, diamagnetic and substituent chemical shifts in NMR spectroscopy ». Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317169.
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Sengupta, Ishita. « Solid State NMR Structural Studies of Proteins Modified with Paramagnetic Tags ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354321906.
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Mukhopadhyay, Dwaipayan. « Development of Solid-State NMR Methodologies for Protein Structure Determination based on Paramagnetic Tagging ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534438273233685.
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Ferrara, Chiara. « Solid State NMR studies of functional oxides ». Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2014. http://tel.archives-ouvertes.fr/tel-00956577.
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The functional oxides are performing materials showing interestant properties. The study of the local environment respect to the average struvture is essential for the deep understanding of the correlations between structure and properties ; this investigation of short and medium range can be performed with the use of solid state NMR techniques. In particular in this thesis three different classes of materials for applications in fields of optic and energy are considered : perovskite structure LaSrAlO4, the melilite system LaSr(Ga/Al)3O7 and the family of orthosylicates Li2(Fe/Mn)SiO4.
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jayasinha, arachchige Rajith Madushanka. « Solid-State NMR Structural Studies of Proteins Using Cyclen Based Paramagnetic Metal Chelating Probes ». The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461765391.
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Jayasinha, Arachchige Rajith Madushanka. « Development of New Paramagnetic Tags for Solid-State NMR Structural Studies of Natively Diamagnetic Proteins ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1388416184.
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Nadaud, Philippe S. « High-Resolution Structural Studies of Paramagnetic Proteins by Multidimensional Solid-State Nuclear Magnetic Resonance Spectroscopy ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268318234.
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Drew, Daniel L. Jr. « Investigating the Structure and Dynamic Properties of Bacteriophage S21 Pinholin Using Solid-State Nuclear Magnetic Resonance and Electron Paramagnetic Resonance Spectroscopy ». Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1610187893016095.
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Rankin, Andrew Gordon McLaughlin. « Applications of multinuclear solid-state NMR spectroscopy to the characterisation of industrial catalysts ». Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/12793.
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This thesis describes applications of advanced multinuclear solid-state nuclear magnetic resonance (NMR) experiments to the characterisation of industrially-relevant catalyst materials. Experiments on γ-Al₂O₃ introduce the use of solid-state NMR spectroscopy for the investigation of disordered solids. The existence of Al(V) sites on the surface of this material is demonstrated, showing that removal of adsorbed H₂O may facilitate a rearrangement effect in γ-Al₂O₃ that promotes the formation of these Al environments. A range of aluminium oxide-based supported metal catalysts has been investigated. Studies of these systems by ¹H and ²⁷Al solid-state NMR spectroscopy indicate that a metal-support interaction (MSI) exists between surface cobalt oxide crystallites and the γ-Al₂O₃ support, and is strongest for materials containing small, well dispersed Co oxide crystallites. It is shown that the hygroscopic nature of γ-Al₂O₃ allows the extent of the MSI to be visualised by ¹H MAS NMR, by observing the extent of the proton-metal oxide interaction resulting from the presence of adventitious adsorbed H₂O. The surface/bulk chemistry of Co spinel aluminate materials is also investigated. ¹H, ²⁹Si, ²⁷Al and ¹⁷O solid-state NMR techniques are used to gain insight into the structural nature of silicated alumina catalysts. The combination of isotopic enrichment and dynamic nuclear polarisation (DNP) surface-enhanced NMR spectroscopy can provide a definitive and fully quantitative description of the surface structure of Si-γ-Al₂O₃ (1.5 wt% Si), and the role of adventitious surface water is highlighted. Analysis of silicated aluminas prepared by “sequential grafting” and “single shot” approaches shows that silica growth on γ-Al₂O₃ follows two distinct morphologies. ¹⁷O gas exchange enrichment is also shown to be successful in facilitating ¹⁷O solid-state NMR studies of these materials. It is demonstrated that double (²⁹Si and ¹⁷O) enrichment of Si-γ-Al₂O₃ (1.5 wt% Si) can facilitate access to ²⁹Si-¹⁷O 2D correlation experiments, even at low silica loading. An exploratory investigation of Ti-alumina model catalysts has also been carried out using ¹H, ²⁷Al and ¹⁷O solid-state NMR spectroscopy. These studies indicate that Ti-γ-Al₂O₃ and Ti-Al M50 may be structurally distinct materials.
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Xu, Bo. « Proton NMR relaxation investigations of particle exfoliation and distribution in polymer/clay nanocomposites ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42936.
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In the past two decades polymer/clay nanocomposites (PCNs) have emerged as promising materials that exhibit remarkably improved properties when compared to conventional composites and pristine polymers. Such improvements strongly depend on the dispersion of clay nanoparticles in the polymer matrix. In spite of great efforts expended in characterizing clay dispersion, effective, simple and quantitative techniques are still needed. This work addresses this challenge by presenting new aspects of 1H solid-state NMR for quantifying clay dispersion in PCNs filled with clay containing paramagnetic ions. Employing these 1H solid-state NMR methods, some structure-processing-deformation relationships of PCNs were derived, and basic insights into nuclear relaxation and spin diffusion in PCNs were gained as well.
Detailed models and analyses were described for 1H spin-lattice relaxation in the presence of paramagnetic clays in PCNs. Relaxation recovery was analytically correlated to clay dispersion in two ways: one is the initial relaxation recovery which is related to clay surface area, and the other is the spin-lattice relaxation time which is related to interparticle spacing. These two NMR observables were employed to quantitatively observe the evolution of clay morphology in poly(propylene)/clay (PP/MMT) nanocomposites upon equibiaxial stretching, as well as upon in situ uniaxial deformation. The initial relaxation recovery was independently utilized to determine the polymer-clay interfacial surface area and the degree of clay exfoliation. We demonstrated the capabilities of our models in quantitatively characterizing several materials, including poly(vinyl alcohol), nylon 6, poly(å-caprolactone) (PCL), poly(lactic acid) (PLA) and PP nanocomposites. These results were used to examine the dependence of clay morphology upon processing (strain ratio, strain rate, temperature), deformation (extension), component characteristics (polymer molecular weight, clay surface modification) and clay content. Effects of paramagnetic Fe3+ concentration and external magnetic field strength on 1H spin-lattice relaxation in PCNs were also investigated and discussed. In particular, low field separates the initial relaxation recovery into two stages: one related to clay content and the other related to the polymer-clay interfacial surface area. The low field was observed to enhance the paramagnetic contribution to the spin-lattice relaxation rate, increasing its sensitivity to clay morphology. In addition, measurements of long-distance spin diffusion coefficients for a variety of polymers and paramagnetic characteristics of organically modified clay were explored. Overall, the utility of NMR relaxometry in characterizing PCNs has been significantly expanded and successfully demonstrated in this dissertation.
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Xia, Yongjie. « Conformation of Y145Stop Prion Protein in Solution and Amyloid Fibrils Probed by Nuclear Magnetic Resonance Spectroscopy ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1493901910397545.
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Dawson, Daniel M. « Combined theoretical and experimental investigations of porous crystalline materials ». Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/7053.
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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.
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Heitjans, Paul, Sylvio Indris et Martin Wilkening. « Solid-state diffusion and NMR ». Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195770.
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Diffusion in solids, which requires the presence of crystal defects or disorder, has both microscopic and macroscopic aspects.
Nuclear magnetic resonance techniques provide access to microscopic diffusion parameters like atomic jump rates and activation
energies as well as to the tracer diffusion coefficient for macroscopic transport. Microscopic NMR methods include spin-lattice relaxation spectroscopy of stable and beta-radioactive nuclei, spin-spin relaxation or linewidth and spin alignment decay measurements, whereas macroscopic NMR methods are represented by the techniques of static and pulsed field gradient NMR. We recall some basic principles of the mentioned techniques and review case studies for their application to various solids like glassy and crystalline aluminosilicates, nanocrystalline composites, an intercalation compound and a simple bcc metal. Taken together, jump rates in solids are covered over about 10 decades by the microscopic, and diffusion coefficients over 3 decades by the macroscopic NMR methods.
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Heitjans, Paul, Sylvio Indris et Martin Wilkening. « Solid-state diffusion and NMR ». Diffusion fundamentals 2 (2005) 45, S. 1-20, 2005. https://ul.qucosa.de/id/qucosa%3A14378.
Texte intégralRésumé :
Diffusion in solids, which requires the presence of crystal defects or disorder, has both microscopic and macroscopic aspects.
Nuclear magnetic resonance techniques provide access to microscopic diffusion parameters like atomic jump rates and activation
energies as well as to the tracer diffusion coefficient for macroscopic transport. Microscopic NMR methods include spin-lattice relaxation spectroscopy of stable and beta-radioactive nuclei, spin-spin relaxation or linewidth and spin alignment decay measurements, whereas macroscopic NMR methods are represented by the techniques of static and pulsed field gradient NMR. We recall some basic principles of the mentioned techniques and review case studies for their application to various solids like glassy and crystalline aluminosilicates, nanocrystalline composites, an intercalation compound and a simple bcc metal. Taken together, jump rates in solids are covered over about 10 decades by the microscopic, and diffusion coefficients over 3 decades by the macroscopic NMR methods.
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Kirby, Christopher William. « Solid-state NMR studies of cobalamins ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60546.pdf.
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Jackson, P. « Dipolar coupling in solid-state NMR ». Thesis, Durham University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379058.
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Heindrichs, Axel Stefan Dirk. « New methodologies in solid state NMR ». Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342111.
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Crockford, Charles. « New methodologies in solid state NMR ». Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289481.
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Stein, Robin Stephanie. « Structural studies using solid-state NMR ». Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612912.
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Portieri, Alessia. « Solid state NMR of sulfa-drugs ». Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3781/.
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This work has been a study of systems, mostly of sulfa-drugs, showing polymorphic behaviour. Using different means as solid state NMR, X-ray analysis, and theoretical calculations, we have seen how it is possible to understand results obtained from the different techniques, proving how the study of polymorphic systems needs cooperative advice from the different techniques that are able to detect polymorphic differences. Within the sulfa-drugs I have been mostly concentrating on sulfanilamide, studying (^13)C and (^15)N solid state NMR spectra of the different polymorphs. The NMR parameters that have been most interesting to study, have been the relaxation times that have revealed complicated motion of the molecule despite it being a small molecule. In order to obtain detailed information from (^15)N spectra it has been necessary to enrich the samples and this has enabled a study of the shielding tensors of the nitrogens in the molecule. (^13)C spectra were also recorded of systems studied sulfathiazole solvates that proved to show some of the same solid state effects in the NMR spectra as sulfanilamide. Shielding calculations have proved to be still limited in order to obtain reliable information on the shielding of both and (^13)C (^15)N nuclei but considering hydrogen-bonded molecules, as opposed to isolated molecules, seemed to have improved the calculations quite a lot, so that some idea of intermolecular effects could be deducted. Exact positions of the hydrogen has proved to be essential as well in order to improve the calculations. Finally a case study for the REDOR pulse sequence has been carried out. Different attempts to understand the effects influencing this particular experiment have been carried out on 20% and 99% doubly enriched glycine, as well as on a particular sample, doubly enriched BRL55834, but the internuclear distances measured with this technique still displayed some uncertainties that made results not thoroughly reliable.
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Likovec, Wayne Robert. « Solid state NMR studies of elastomers ». Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058875640.
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Bennett, David Alexander. « Structural methods in solid-state NMR ». Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13242/.
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New solid-state NMR experiments for measuring internuclear distances are designed using symmetry principles. The “recoupling” sequences described here are intended to reintroduce the MAS-averaged heteronuclear dipole-dipole coupling between a spin-1/2 nucleus (e.g. 1H) and a half-integer quadrupolar nucleus (e.g. 17O, I = 5/2). The magnitude of the dipolar interaction depends on the separation between the coupled nuclei, so the evolution of the spin system under the recoupled Hamiltonian can be used to measure the internuclear distance. Simulations of the spin dynamics are used initially to select candidate sequences and these are subsequently employed to measure both long-range and direct O–H distances in powdered L-Tyrosine.HCl (isotopically enriched with 17O at 20%to 30% at the O$^\eta$ site). Improvements to existing methods for the data analysis for this type of NMR experiment are also discussed, including the restriction and/or removal of certain fit parameters and the explicit inclusion of inhomogeneous radio-frequency fields as part of the fitting procedure. The effects of processing on the uncertainty of experimentally determined distances are considered, and a new analysis method which circumvents several of these effects is presented. Similar recoupling sequences can be used to measure the anisotropy of proton chemical shifts, and some preliminary results are also presented for this application. A systematic method for the assignment of congested spin-1/2 spectra resulting from molecules with large numbers of chemically similar sites is also described. This makes use of a comparison between the chemical shift tensor measured as usual by the 2D-PASS experiment and its principal components calculated from first principles using the density functional theory package CASTEP. The initial peak assignment is generated randomly and then varied using a steepest-ascent hill climbing algorithm with the square sum of the difference between the experimental and calculated principal values of the chemical shift tensor as the target function. The new method is tested on the 13C spectrum of the anti-inflammatory drug flufenamic acid and found to be superior to simple assignments using only the isotropic chemical shift.
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Telling, M. T. F. « Muon studies of paramagnetic spin fluctuations ». Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387708.
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Louie, Elizabeth April. « Solid-State NMR : investigations of biomolecular structure / ». Thesis, Connect to this title online ; UW restricted, 2005. http://hdl.handle.net/1773/8488.
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Saalwächter, Kay. « Heteronuclear recoupling methods in solid state NMR ». [S.l. : s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2000/0070/diss.pdf.
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Buda, Alina Reghina. « Solid state NMR for advanced materials characterization ». kostenfrei, 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972085459.
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Castro, Vasco. « Solid-state NMR characterization of lipid membranes / ». Stockholm : Department of Physical, Inorganic and Structural Chemistry, Stockholm university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7681.
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Barras, Jamie. « Solid-State NMR studies of inorganic materials ». Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339770.
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Parkinson, Matthew John. « Supramolecular interactions investigated by solid-state NMR ». Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429310.
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Brough, Adrian R. « Solid state NMR studies of inorganic materials ». Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239312.
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MariÌn, Montesinos Ildefonso. « New recoupling techniques in solid-state NMR ». Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438729.
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Jolly, Michael Matthew. « Method development in biological solid-state NMR ». Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/422129/.
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Solid-state nuclear magnetic resonance (ssNMR) has proved to be a useful tool in the analysis of structural and dynamic properties of proteins. However, the inherent low sensitivity of NMR hinders further advancements of the field. This thesis focuses on improving the sensitivity of ssNMR, be this through an improvement in signal to noise or an effective improvement in sensitivity by enhancing the information content. The mixed rotational and rotary resonance (MIRROR) sequence1 was employed to facilitate protein backbone assignment under moderate spinning speeds. Through the band selective nature of MIRROR, bidirectional transfer of magnetisation from the CCO site to the adjacent Cα and to the Cα of the next amino acid is possible. When applied to a 3D-NCOCA experiment this may be used to double the information content, providing correlations from CCO(i-1) to both Cα(i-1) and Cα(i). The MIRROR recoupling of CCO to Cα, is inherently low-power, allowing MIRROR to be utilised in a low-power experiment. Through this, greater enhancements in sensitivity per unit time can be realised. The longitudinal relaxation time (T1) limits the sensitivity per unit time at both room and cryogenic temperatures. To develop the use of relaxation agents for cryogenic NMR experiments, the room temperature relaxation properties and dynamics of the model protein, GB3, were explored. Site-specific relaxation measurements were used to understand the relaxation of residues in the protein and gain understanding into how this relates to the dynamics of the protein. In addition, low-temperature NMR measurements were used to investigate the effect temperature has on relaxation. The ongoing development of polarisation enhancement methods and machinery have made great progress in recent years particularly on the application towards biomolecules. However, arguably the most promising polarisation enhancement technique, dynamic nuclear polarisation (DNP) suffers from a variety of problems. Namely, line broadening effects as a result of the low-temperatures required and through doping with paramagnetic agents. Furthermore, the current method of sample preparation for DNP via the use of doping with exogenous radicals is not viable for all samples. Endogenous radicals for the DNP of large biomolecules may offer several advantages to their exogenous counterparts, including but not limited to, a greater understanding of quenching effects and polarisation transfer. This thesis explores the possibility of creating pseudo-biradicals bound covalently to a protein surface to elicit enhancements through the cross effect DNP mechanism. In summary, we have developed a range of methods that enhance the information content and sensitivity, which will provide new approaches for researchers investigating proteins using ssNMR.
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McDougal, Nicola. « Solid-state NMR studies of structural proteins ». Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619667.
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Nordon, Alison. « Solid-state NMR studies of inclusion compounds ». Thesis, Durham University, 1997. http://etheses.dur.ac.uk/4758/.
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The work contained within this thesis is a study of inclusion compounds using solid-state NMR. Such compounds typically exhibit static and/or dynamic disorder, which precludes the use of diffraction-based techniques to obtain detailed structural information. Hence, due to its ability to probe local environments, solid- state NMR can be used to provide information which would otherwise be inaccessible. However, the dynamic nature of the guest molecules within inclusion compounds can yield unusual results for routinely applied experiments, such as cross polarisation, heteronuclear dipolar decoupling and dipolar dephasing. Therefore, some of the more fundamental aspects of solid-state NMR have first been explored. The inclusion compounds of particular interest are those which contain urea or thiourea as the host species. The ordering of guest molecules and host dynamics have been investigated via both one- and two-dimensional (^13)C and (^1)H NMR experiments for the 2-hydroxyalkane/urea inclusion compounds. For the 1-fluorotetradecane/urea inclusion compound, an approach involving a combination of (^1)H→(^13)C and (^19)F→(^13)C cross-polarisation experiments, with both single-channel (^H) and double-channel decoupling ((^1)H,(^19)F) has been devised to assign (^13)C resonances and hence deduce guest ordering. Steady-state and transient (^19)F MAS NOE experiments have been used to probe the dynamics of the 1-fluorotetradecane/urea inclusion compound. Using the considerable sensitivity advantage of (^19)F NMR, over that of (^13)C, a detailed study of the conformational dynamics exhibited by fluorocyclohexane molecules included within thiourea has been performed via bandshape analysis, selective polarisation inversion and 2D exchange experiments. Intermolecular distance measurements have been determined for adjacent fluoroalkane molecules within urea tunnels using a series of static (^19)F NMR experiments. From the results obtained, conclusions regarding the mutual orientations of adjacent end-groups in such compounds have been made.
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Avalle, Paolo. « Solid state NMR of tin containing compounds ». Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4382/.
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A recent development in chemical research has been concerned with molecular assemblies, and all manner of structural aggregates, leading to the relatively new area of supramolecular chemistry. The systems under study are organometallic ion exchangers where the structural motif is [(Me(_3)Sn(^IV))(_4)M(^II)(CN)(_6)]=(_oo) (M=Fe, Ru, Os...). These 3D cyanides are not simply molecular crystals, and their chemistry and topology are more reminiscent of inorganic solids. By replacing the bridging unit (Me(_3)Sn(^IV)) with guests such as (nPr)(_4)N(^+) and (nBu)(_4)N(^+), new 3D structures can be engineered, leading to new compounds. Tin units show unchanged trigonal bypyramidal coordination upon variation of metal (M), guest size, hindrance by the ligands. Changes in the metal affect mainly the isotropic and anisotropic (^119)Sn shielding parameters. The interplay of the electronic nature of the metal(s) and the bonding capacity of the ligands is studied by (^59)Co NMR. Quadrupolar coupling constants and asymmetry parameters show how the coordinative bond is sensitive to spatial reorganisation. Shielding calculations for the [Me(_3)Sn(CN)(_2)]’ model and for different X-ray structures have been performed to reproduce trends in chemical shift changes. Relativity effects have been omitted from the computations. This approach had four major aims: (a) to establish the extent to which (^119)Sn isotropic chemical shifts can be computed by DPT methods with acceptable basis sets for model molecular fragments relevant to four selected compounds; (b) the computation of the U^Sn isotropic chemical shifts for different coordination geometries of the CN ligands; (c) the attempt to correlate between computed and observed isotropic chemical shifts for four selected compounds; (d) to ascertain whether such a correlation can be used to establish the assignment of three experimental (^119)Sn shifts in a predictive fashion.
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Goddard, Yanina Anatolievna. « Solid state NMR characterization of conductive polyanilines ». W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539623435.
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Different forms of ring deuterated polyaniline with different conductivity have been characterized by solid state deuteron nuclear magnetic resonance.;Quadrupole echo (QE) spectra of all forms of polyaniline consist of a superposition of lineshapes for nearly rigid aromatic rings and a small fraction of rings which undergo fast 180?? flips. The intensity of the fast flipping component is temperature dependent and different for conductive emeraldine salt (ES) and non-conductive emeraldine base (EB). This is a manifestation of the different structure and morphology of these polymers.;Simultaneous measurements of QE lineshapes and the relaxation time anisotropies allowed an accurate description of motion in polyanilines. Slow, small-angle libration in an asymmetric cone provided the best description for the "rigid" fractions of EB and ES. The broadening of deuteron QE lineshapes is consistent with the presence of a distribution of cone angles. Relaxation time measurements also reveal a relatively narrow distribution of librational rates for the EB sample. For ES, the magic angle spinning (MAS) spectra show the existence of two resolved signals with different relaxation rates, which are ascribed to microscopic domains with very different electrical properties. The unexpectedly short relaxation time found for nonconductive domains in ES can be explained by the presence of localized, unpaired electrons.;Spin count experiments proved that in highly conductive ES samples, loss of NMR signal intensity occurs not only because of high RF reflectance but also because of irreversible dephasing before signal acquisition due to interactions of nuclear spins with localized unpaired electrons.;Deuteron MAS spectra provided unique information about small frequency shifts. Compared to non-conductive EB, conductive emeraldine salts have an additional manifold of spinning sidebands, which is shifted ∼5.8 ppm towards higher frequencies. These shifted sidebands arise from quasi-metallic regions of the sample, where deuteron spins interact with delocalized electrons (Knight shift). The experimental temperature dependence of the intensity of the shifted peak can be explained using models developed for amorphous semiconductors. The observation of a Knight shift has an important consequence for the theory of electrical conduction in polyaniline: it implies that polarons are the charge carriers.
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Laage, Ségolène. « High-resolution solid-state NMR for proteins ». Lyon, Ecole normale supérieure, 2010. http://www.theses.fr/2010ENSL0583.
Texte intégralRésumé :
La RMN a récemment prouvé son potentiel en biologie structurale. Cette thèse décrit les méthodes que nous avons développées pour l’étude de protéines par RMN du solide à haute résolution. Après une présentation des récents progrès du domaine, nous présentons les améliorations liées à l’utilisation de la rotation à l’angle magique à très haute vitesse, notamment les techniques de découplage hétéronucléaire et de polarisation croisée à basse puissance, appliquées aux cas de la Superoxide Dismutase (SOD) et de la protéine GB1. Nous détaillons ensuite les perspectives émergeant dans l’utilisation des couplages J, avec trois nouvelles séquences. La J-CHHC renseigne sur les distances entre protons, le bloc S3E améliore résolution et sensibilité en effectuant du découplage J, et l’INADEQUATE-S3E combine transfert de polarisation par couplage J et découplage J. Nous donnons enfin des perspectives de mesure de longues distances par l’exploitation des propriétés paramagnétiques de la Cu(II) SODSolid-state NMR recently proved its potential for structural biology. This thesis details metods we developed for high resolution NMR of nanocrystalline proteins. After an introductory presentation of the recent advances in solid-state NMR of bio-systems, we present the improvements we proposed in the ultra-fast magic-angle spinning regime, notably low-field heteronuclear decoupling and low-field cross-polarization. We demonstrate them with the study of the Superoxide Dismutase (SOD) and the protein GB1. We then focus on the perspectives arising for J-couplings in proteins by presenting three new sequences. The J-CHHC sequence probes 1H-1H distances encoded in 13C-13C correlation experiments. The S3E block improves resolution and sensitivity by performing J-decoupling, and the INADEQUATE-S3E combines J-based transfer of polarization and J-decoupling. We finally give perspectives to probe long-range structural constraints with data exploiting the paramagnetic properties of Cu(II)-SOD
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Brown, Marco J. « Selective inversion in solid-state deuteron NMR ». W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539623900.
Texte intégralRésumé :
Deuteron NMR selective inversion (SI) is developed to study slow molecular motions in solids. Theoretical and practical aspects of selective inversion of spin-1 nuclei in solids are presented. Differences between powdered solids and liquids are considered. Double sideband modulated (DSBM) shaped pulses are shown to improve the performance of SI pulses. DSBM and DANTE selective pulses are compared for off-resonance SI applications. Common spin-{dollar}{lcub}1{rcub}\over{lcub}2{rcub}{dollar} shaped pulses are tested for suitability to solid state deuteron NMR. Simple, short pulses are shown to be most effective due to fast spin-spin relaxation and large underlying homogeneous linewidths in solids.;The power and utility of selective inversion is demonstrated by investigating the molecular dynamics of polycrystalline dimethylsulfone-{dollar}\rm d\sb6{dollar} (DMS). Quantitative information on the slow two-site jump motion in DMS is obtained. The complementary nature of selective inversion and quadrupolar echo lineshape (QELS) experiments is explored. Combination of QELS and SI extends the range of rates observed, increasing the accuracy of the information obtained. For DMS, motional rates were measured over a 80 K range (motional rates of {dollar}\rm 3\times 10\sp1{lcub}-{rcub}5\times 10\sp{lcub}4{rcub}\ s\sp{lcub}-1{rcub}),{dollar} permiting the barrier to slow rotation to be accurately characterized. SI was also used to observe the limiting homogeneous linewidth as a function of resonance offset and temperature. The temperature dependence of the homogeneous linewidth is shown to be sensitive to motion in the kilohertz range.;SI was used to quantify the molecular dynamics in some complex systems. SI and QELS experiments were performed on host urea-{dollar}d\sb4{dollar} in different urea inclusion compounds (UIC). Rotation rates about both the CO and CN bonds of urea-{dollar}d\sb4{dollar} in the UICs were determined as a function of temperature. Activation energies were obtained, and the results are discussed with respect to guest-host interactions in the UICs. Preliminary results are presented on quadrupolar echo lineshape simulations which include empirical, anisotropic homogeneous linewidth corrections. The modified simulations give significantly different best-fit motional rates than conventional QELS analysis. This allows some of the systematic errors of QELS analysis to be evaluated.;SI experiments were conducted, over a 125 K range, to study backbone motion in bisphenol-A polycarbonate. These experiments failed to detect the presence of any large angle slow motion of methyl groups in the isopropylidene moiety. This negative result suggests that cis-trans isomerization of the carbonate group is not the origin of the backbone motion.
40
Blackband, S. J. « NMR imaging of liquid-solid systems ». Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356019.
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Tsang, Eric P. K. « Aspects of quantitive analysis by electron paramagnetic resonance spectrometry ». Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334684.
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Iuga, Adriana. « Solid-state 31P NMR of nucleotide binding proteins ». [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973225238.
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Lim, Tang Kuan. « NMR studies of carbohydrates in the solid state ». Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/27129.
Texte intégralRésumé :
The work described herein entails the application of solid-state n.m.r. methods to both mono- and polysaccharide carbohydrates. Two major n.m.r. methods have been evaluated for studying these substances, namely, the carbon-13 cross-polarization-magic angle spinning method and the deuterium quadrupole echo method.
Heptakis-(2,6-di-O-methyl)- β-cyclodextrin and β-cyclodextrin peracetate were prepared and, together with α-and β-cyclodextrins as hosts, were used to encage a variety of organic guest molecules.
A number of metal sugar conjugates were prepared according to the procedures documented in this laboratory. Firstly, chelate coordination complexes were synthesized by forming salicylaldimine ligands derived from combinations of amino sugars (methyl 3,4,6-tri-O-acetyl-2-amino-2-deoxy-β-D-glucopyranoside or 1 , 3 , 4 , 6-tetra-O-acetyl-2-amino-2-deoxy-β-D-glucopyranose) and salicylaldehyde, with subsequent complexation of these to copper(II), zinc(ll), and cobalt(Il) ions. Similarly, chitosan Schiff's bases were prepared and complexed to copper(II) ion.
Application of the ¹³C-cross-polarization-magic angle spinning method in the spectral assignment of cyclodextrin inclusion complexes and metal sugar conjugates in the solid state has been demonstrated. In all cases, recourse to solution spectra was necessary for correct assignments of individual carbon resonances. The sugar resonances of cyclodextrins are relatively broad and are complicated by the substantial splittings. The rationales for such observations were drawn from comparative studies, based on closely related guest molecules. The smaller guest molecules were least affected by the cavity size of the host molecule heptakis-( 2 , 6-di-O-methyl) -β-cyclodextr in and the isotropic chemical shift values were similar to those measured for solutions. These values suggest that the guest molecules undergo anisotropic motion, which can be detected by the use of the dipolar dephasing technique. Studies of metal sugar conjugates by ¹³C n.m.r. revealed that paramagnetic ions have profound effects on the resolution obtained. The high concentrations of these ions result in broad featureless spectra. On the other hand, the diamagnetic ions proved to have little effect on the isotropic chemical shifts of the sugar chelates.
The deuterium quadrupole echo method has been used specifically to study the mobility of the guest molecules encaged in cyclodextrins. The "powder-type" spectra obtained were then compared with results reported in the literature in order to define the types of molecular motion.Science, Faculty of
Chemistry, Department of
Graduate
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Feng, Xiaolong. « Estimating molecular conformations by solid-state NMR spectroscopy / ». Stockholm : Eigenverl, 1998. http://www.gbv.de/dms/goettingen/265942721.pdf.
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Simpson, W. Mark. « Solid state NMR studies of molecular crystalline materials ». Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362006.
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Ball, Thomas James. « Development of new methods in solid-state NMR ». Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/385/.
Texte intégralRésumé :
Many chemically important nuclei are quadrupolar with half-integer spin (i.e., spin I = 1.5, 2.5, etc.) The presence of quadrupolar broadening for such nuclei can limit the information that may be extracted using NMR. MAS is able to remove first-order quadrupolar broadening but can only reduce the second-order contribution to the linewidth. The MQMAS and STMAS techniques have enabled high-resolution NMR spectra of half-integer quadrupolar nuclei in the solid state to be obtained by two-dimensional correlation under MAS conditions. Both of these experiments have several well-known limitations. One is that the conversion pulses in particular are very inefficient and the other is that the longer acquisition times required for two-dimensional experiments can be a limiting factor. Both of these disadvantages are addressed in this thesis. For the former case, existing composite pulse schemes designed to improve the efficiency of the conversion of multiple-quantum coherences are compared using 27Al and 87Rb MQMAS NMR of a series of crystalline and amorphous materials. In the latter case, a new experiment, named STARTMAS, is introduced that enables isotropic spectra of spin I = 1.5 spectra to be acquired in real time. The theoretical basis of the technique is explained and its applicability demonstrated using 23Na and 87Rb NMR of a wide range of solids. The nuclear Overhauser effect (NOE) is one of the most widely exploited phenomena in NMR and is now widely used for molecular structure determination in solution. NOEs in the solid state are rare and those to quadrupolar nuclei rarer still, this being due to the general absence of motion on the correct timescale and the usual efficiency of quadrupolar T1 relaxation, respectively. In this thesis, 11B{1H} transient NOE results are presented for a range of solid borane adducts. A comparison is made of the 11B NMR enhancements observed under MAS and static conditions and a rationale is proposed for the behaviour in the latter case.
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Orr, Simon Timothy. « Multinuclear solid-state NMR of fuel cell materials ». Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/35532/.
Texte intégralRésumé :
This thesis describes the application of multinuclear solid-state NMR to three materials systems: first, components of polymer-based proton-exchange fuel cells including the fluoropolymer membranes (Chapter 4) and the precious metal supported catalysts (Chapter 5); secondly, the formation of a complex bismuth niobium aluminoborosilicate glass-ceramic with novel dielectric properties (Chapter 6); finally, platinum (II) dialkyldithiophosphates which belong to a class of compounds (metal dialkyldithiophosphates) some of which are used in mineral separation processing (Chapter 7). A full investigation into the effects of different conditions during sample preparation and 19F NMR experiments on fluoropolymer membranes recommended unmilled preparation, dry storage and magic angle spinning below 24 kHz for the study of structural differences between membranes. The application of 19F NMR to a range of commercial and experimental fluoropolymer membranes revealed that the equivalent weight does not affect the mobility of the polymer molecules such that can be detected by this technique. Calculations of equivalent weight from 19F NMR differed with quoted values by up to 14%. Discrepancies were smallest in the short sidechain polymers, as low as 3%. The assignment of spectra was invariant with sidechain structure apart from a change in the number of ester links. The presence or absence of oxygen affected chemical shielding even around nuclei separated by several bonds. Differences in 1H linewidths between membranes could not be interpreted without the control and comparison of manufacturing techniques. It is desirable to remove the necessity for organic solvents in membrane casting. However, membranes cast from aqueous solution do not possess the same properties as those from propanol. It had been proposed that rapid drying of water cast membranes would result in a structure more similar to those from organic solvent. 1H NMR revealed that the opposite is the case, rapid drying makes the ordinarily more inhomogeneous aqueous membranes even more so. The application of both 19F and 1H NMR revealed that the monomolecular layers of fluoropolymer deposited on the surface of fuel cell catalysts to aid proton conductivity are categorically different in nature to the same materials in the bulk state. 19F NMR suggests a polymer structure either more disordered, greatly less mobile or both. 1H NMR displayed water environments that could not be reconciled to the standard model of rapid exchange between bulk water and water associated with acid groups. Spectral differences caused by solvent and polymer loading were discussed. The first complete and quantitative Fourier transformed 195Pt NMR spectra of platinum fuel cell catalysts, acquired using a field sweeping method, are analysed for deviation from the cubooctohedral particle model and surface oxidation. A combination of 11B, 27Al and 29Si studies of the BN1 ceramic system after different temperature heat treatments confirmed much of the previous work on phase evolution. However, it was shown that kyanite does not make up a significant proportion of the material until heat treatment reaches 1000 ºC and that aluminium impurities in bismuthbiobate crystals appear to increase with treatment temperature. The nature and abundance of glassy phases in the system are explored for the first time. Field sweep 195Pt NMR was employed to characterise the 195Pt chemical shift anisotropy of five platinum (II) dialkyldithiophosphates complexes. Additionally the 31P chemical shift anisotropies of two of the complexes, previously unpublished are presented.
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Bhattacharya, Prodipta. « Solid state NMR studies of ferroelectric relaxor materials ». Thesis, University of Warwick, 2005. http://wrap.warwick.ac.uk/66666/.
Texte intégralRésumé :
Multi-nuclear solid state nuclear magnetic resonance has been used to investigate the local atomic structure of the relaxor ferroelectric materials, lead magnesium niobate titanate (PMN-PT) and sodium potassium bismuth titanate (NKBT). In addition to these two series of materials, numerous precursor and model niobate compounds have also been analysed in order to gain a insight into the structures and phases present in these materials. The PMN-PT series was investigated using 93Nb, 207Pb and 170 NMR techniques. A total of 14 PMN-PT samples, from pure PMN to PMN-90PT, were investigated in order to fully understand the transitions taking place over the entire compositional range. 9~b proved to be the most informative nucleus, owing to its high sensitivity to the changes occurring at the B-site of the perovskite structure. We discovered three distinct niobium environments. We then proposed a new randomsite random-layer model explaining the distribution of the cations among two different layers ß' and ß". The high level of correlation between the theoretical predictions and the experimental results suggests that there are actually two different ways that PMN-PT behaves, one for titanium concentrations less than 25% and the other for concentrations over 25%. This was also clearly visible in our PMN-PT spectra, as a sharp line present in titanium concentrations below 25%, that disappears in the concentrations above 25%. We have also tied in our results with the existing literature on PMN-PT to identify possible links to the dielectric response and phase transitions in the material. NKBT was investigated using both 23Na and 39K MAS NMR techniques. The 23Na data proved most informative and results were obtained at different fields and different spinning speeds. We were then able to extract calculated isotropic chemical shift values and quadrupolar parameters to understand the subtle changes taking place. The preliminary results hint that there are some interesting changes taking place around the morphotropic phase boundary in the material.
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Christopher, Elizabeth Anne. « Solid-state NMR study of polymorphism in pharmaceuticals ». Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5752/.
Texte intégralRésumé :
This thesis is concerned with attempts to establish solid-state NMR as a complementary technique to X-ray crystallography for providing information on crystal structure, i.e. information regarding conformation, packing and inter- or intra-molecular interactions. Methods of assigning the solid-state NMR spectrum have been used which rely upon (^1)H-(^13)C dipolar interactions and upon the shielding anisotropy experienced by the nuclei. Single pulse experiments have also been used to identify solvate molecules. Of particular importance, the anisotropy and asymmetry have been found for a number of steroids, and the values used to assign the high frequency region of the spectrum. This has enabled chemical shifts to be linked to the hydrogen bonds that are present. Thus, the mode of hydrogen bonding can be predicted in forms of cortisone acetate for which the crystal structure is not available. Chemical shifts have also been linked with the conformation of the D ring. In this way, important crystallographic information has been gleaned from the solid-state NMR spectrum. The effect of the formation of hydrogen bonds upon the shielding tensor components of carbonyl and ester carbons has been studied, and found to cause a high frequency shift in δ22, which is probably oriented along the C=0 bonds. This leads to a high frequency shift in the isotropic chemical shift. The effect of the spinning speed upon the centreband intensity of a peak as the anisotropy and asymmetry are varied has been investigated. It has been found that at low spiiming speeds, the centreband intensity does not vary in a simple fashion. Thus it is recommended that full shielding tensor analysis is performed. The effect of the spinning speed on the sample temperature has also been studied. Results show that at low spinning speeds (up to 2 kHz) there is sample cooling as the spinning speed increases (attributed to the Joule -Thompson effect). But at higher spinning speeds (above 2 kHz) then there is sample heating as the spinning speed increases. The importance of this result is discussed. The effect of quadrupolar nuclei (35C1 and (^14)N) upon the spectrum of a spin-(^1)(_2) nucleus ((^13)C) has been studied. In favourable cases, the anisotropy in the spin-spin coupling constant has been found, whilst in other cases, the sign and magnitude of the quadrupolar coupling constant have been obtained. The broadening of resonances of carbon atoms adjacent to quadrupolar nuclei has been valuable in assigning the solid-state NMR spectra. The broadening effect has also been observed at more distant sites. It has not been possible to distinguish the effects of (^37)C1 and (^35)C1 on the carbon spectra of chlorine containing steroids.
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Gomez, Ruben. « Solid-state NMR studies of lithium nitrido-metallates ». Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430515.
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