Dissertations / Theses on the topic 'NMR spectroscopy of metabolites'
To see the other types of publications on this topic, follow the link: NMR spectroscopy of metabolites.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'NMR spectroscopy of metabolites.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Al-Busaidi, Harith N. K. "Secondary metabolites from Xylaria endophytes : the isolation and structure elucidation of secondary metabolites from Xylaria endophytes by chemical and spectroscopic methods." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5266.
Full text
2
Lenz, Eva-Maria. "Multinuclear NMR and HPLC-NMR spectroscopic studies on xenobiotic metabolism." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267785.
Full text
3
Asllani, Iris. "Anisotropic interactions of metabolites in skeletal muscle observed by dipolar coupling in ¹H NMR spectroscopy /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/8121.
Full text
4
Ehlers, Ina. "NMR studies of metabolites and xenobiotics: From time-points to long-term metabolic regulation." Doctoral thesis, Umeå universitet, Institutionen för medicinsk kemi och biofysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-97684.
Full textAbstract:
Chemical species carry information in two dimensions, in their concentrations and their isotopic signatures. The concentrations of metabolites or synthetic compounds describe the composition of a chemical or biological system, while isotopic signatures describe processes in the system by their reaction pathways, regulation, and responses to external stimuli. Stable isotopes are unique tracers of these processes because their natural abundances are modulated by isotope effects occurring in physical processes as well as in chemical reactions. Nuclear magnetic resonance (NMR) spectroscopy is a prime technique not only for identification and quantification of small molecules in complex systems but also for measuring intramolecular distribution of stable isotopes in metabolites and other small molecules. In this thesis, we use quantitative NMR in three fields: in food science, environmental pollutant tracing, and plant-climate science. The phospholipid (PL) composition of food samples is of high interest because of their nutritional value and technological properties. However, the analysis of PLs is difficult as they constitute only a small fraction of the total lipid contents in foods. Here, we developed a method to identify PLs and determine their composition in food samples, by combining a liquid-liquid extraction approach for enriching PLs, with specialized 31P,1H-COSY NMR experiments to identify and quantify PLs. Wide-spread pollution with synthetic compounds threatens the environment and human health. However, the fate of pollutants in the environment is often poorly understood. Using quantitative deuterium NMR spectroscopy, we showed for the nitrosamine NDMA and the pesticide DDT how intramolecular distributions (isotopomer patterns) of the heavy hydrogen isotope deuterium reveal mechanistic insight into transformation pathways of pollutants and organic compounds in general. Intramolecular isotope distributions can be used to trace a pollutant’s origin, to understand its environmental transformation pathways and to evaluate remediation approaches. The atmospheric CO2 concentration ([CO2]) is currently rising at an unprecedented rate and plant responses to this increase in [CO2] influence the global carbon cycle and will determine future plant productivity. To investigate long-term plant responses, we developed a method to elucidate metabolic fluxes from intramolecular deuterium distributions of metabolites that can be extracted from historic plant material. We show that the intramolecular deuterium distribution of plant glucose depends on growth [CO2] and reflects the magnitude of photorespiration, an important side reaction of photosynthesis. In historic plant samples, we observe that photorespiration decreased in annual crop plants and natural vegetation over the past century, with no observable acclimation, implying that photosynthesis increased. In tree-ring samples from all continents covering the past 60 – 700 years, we detected a significantly smaller decrease in photorespiration than expected. We conclude that the expected “CO2 fertilization” has occurred but was significantly less pronounced in trees, due to opposing effects. The presented applications show that intramolecular isotope distributions not only provide information about the origin and turnover of compounds but also about metabolic regulation. By extracting isotope distributions from archives of plant material, metabolic information can be obtained retrospectively, which allows studies over decades to millennia, timescales that are inaccessible with manipulation experiments.
5
Manton, David John. "Quantification of brain metabolites by in vivo proton MR spectroscopy : investigations into reproducibility and application to studies of intracranial tumours." Thesis, University of Hull, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321120.
Full text
6
Tolonen, A. (Ari). "Analysis of secondary metabolites in plant and cell culture tissue of Hypericum perforatum L and Rhodiola rosea L." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514271610.
Full textAbstract:
Abstract
Sensitive chromatographic methods were developed for the quantitative analysis of secondary metabolites in Hypericum perforatum (St. John's wort) and Rhodiola rosea (Golden root, rose root) extracts. Sample preparation methods were developed for plant, cell culture and biotransformation suspension matrixes. High performance liquid chromatography (HPLC) was used for the separation of analytes, and chromatographic data was acquired using photodiode array (PDA) detection or atmospheric pressure ionization mass spectrometry (API-MS). Ionization efficiencies with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) were compared under different conditions. Specific mass spectrometric detection methods such as multiple reaction monitoring (MRM) and selective ion monitoring (SIM) were utilized. For identification of known and new secondary metabolites in plant tissues, mass spectrometric methods with triple quadrupole and time-of-flight mass spectrometers were used together with one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR).
7
Al-Busaidi, Harith. "Secondary Metabolites from Xylaria Endophytes: The isolation and structure elucidation of secondary metabolites from Xylaria endophytes by chemical and spectroscopic methods." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/17479.
Full textAbstract:
This thesis describes the isolation and structure elucidation of secondary metabolites from a number of endophytic Xylaria fungi. Six Xylaria endophytes were surface cultured on an aqueous malt extract-glucose medium. The fungus A311R, from a palm tree in Thailand, produced nonane-1,2,3-tricarboxylic acid, which was isolated for the first time as a natural product. Also isolated from the same fungus was spiculisporic acid; the first instance of isolation from a Xylaria fungus. The fungus 6RD12 produced cycloepoxydon, which was isolated for the first time from a Xylaria fungus, and 4,5,6-trihydroxy-3-propyl-3,4,6,7-tetrahydro-l//-isochromen- 8(5//)-one, which is a novel compound. The fungi A217R and A517R produced cytochalasin D, (S)-mellein and (3S,4S)-4-hydroxymellein as main secondary metabolites suggesting that the two fungi are the same species. The fungus X04 (Xylaria cf. juruensis) produced 2-Hydroxy-5-ethoxy-3-methylcyclohexa-2,5-dien- 1,4-dione as a novel compound, coriloxin as the main secondary metabolite in addition to (R)-mellein and a mixture of two stereoisomers of the 4-Hydroxymellein. The fungus 6RD8 produced (S)-Omethylmellein as the main secondary metabolite.
l
8
Alhaidari, Rwaida A. A. "Secondary metabolites from Xylariaceous fungi. The isolation and structure elucidation of secondary metabolites from Xylariaceous fungi by chemical and spectroscopic methods." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5705.
Full textAbstract:
This thesis describes the isolation and structure elucidation of secondary metabolites formed in static culture from a number of endophytic Xylariaceous fungi. Four Xylaria endophytes isolated from a palm tree in Thailand were surface cultured on an aqueous malt extract-glucose medium. They all produced cytochalasin D, coriloxin, (S)-mellein and (3R,4R)-4-hydroxymellein as the main secondary metabolites suggesting that the four endophytes could be the same species. The endophytic fungus A116 produced cytochalasin D as the main secondary metabolite. Another non-endophytic fungus B315, produced cytochalasin D, (R)-mellein, a mixture of two isomers of 4-hydroxymellein and phloroglucinol. X.62, an endophytic fungus, produced 19,20-epoxycytochalasin C from the mycelium as the main secondary metabolite. The fungus Engleromyces sinensis produced engleromycin acetate as the main secondary metabolite. Fungus X. polymorpha produced (3E)-4-(3¿-acetyl-2¿,6¿-dihydroxy-5¿-methylphenyl)-2-methoxybut-3-enoic acid.Ministry of Higher Education; Kingdom of Saudi Arabia.
9
Alhaidari, Rwaida Adel. "Secondary metabolites from Xylariaceous fungi : the isolation and structure elucidation of secondary metabolites from Xylariaceous fungi by chemical and spectroscopic methods." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5705.
Full textAbstract:
This thesis describes the isolation and structure elucidation of secondary metabolites formed in static culture from a number of endophytic Xylariaceous fungi. Four Xylaria endophytes isolated from a palm tree in Thailand were surface cultured on an aqueous malt extract-glucose medium. They all produced cytochalasin D, coriloxin, (S)-mellein and (3R,4R)-4-hydroxymellein as the main secondary metabolites suggesting that the four endophytes could be the same species. The endophytic fungus A116 produced cytochalasin D as the main secondary metabolite. Another non-endophytic fungus B315, produced cytochalasin D, (R)-mellein, a mixture of two isomers of 4-hydroxymellein and phloroglucinol. X.62, an endophytic fungus, produced 19,20-epoxycytochalasin C from the mycelium as the main secondary metabolite. The fungus Engleromyces sinensis produced engleromycin acetate as the main secondary metabolite. Fungus X. polymorpha produced (3E)-4-(3'-acetyl-2',6'-dihydroxy-5'-methylphenyl)-2-methoxybut-3-enoic acid.
10
Schilling, Franz [Verfasser]. "Novel Methods for NMR - Single-SHOT Correlation Spectroscopy and Diffusion of 13C-Metabolites utilizing both Hyperpolarization and Optimal Control / Franz Schilling." München : Verlag Dr. Hut, 2013. http://d-nb.info/1130261336/34.
Full text
11
Sjögren, Jörgen. "Bioassay-guided isolation and characterisation of antifungal metabolites : studies of lactic acid bacteria and propionic acid bacteria /." Uppsala : Dept. of Chemistry, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200517.pdf.
Full text
12
Lazariev, Andrii. "A quantum mechanics-based approach for optimization of metabolite basis-sets : application to quantitation of HRMAS-NMR signals." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00843311.
Full textAbstract:
From day to day, the role of HRMAS (High-Resolution Magic Angle Sinning) Nuclear Magnetic Resonance Spectroscopy (NMRS) in medical diagnosis is increasing. This technique enables setting up metabolite profiles of ex vivo pathological and healthy tissue. Automatic spectrum quantitation enables monitoring of diseases. However for several metabolites, the values of chemical shifts of proton groups may slightly differ according to the micro-environment in the tissue or cells, in particular to its pH. This hampers accurate estimation of the metabolite concentrations mainly when using quantitation algorithms based on a metabolite basis-set. The present word is devoted to the optimization of NMR metabolite basis set signals, particularly to the algorithms of chemical shift mismatch correction. Two sighal processing ("warping") methods were developed for simple and fast spectrum optimization : signal stretching/shrinking (resampling) and spectrum splitting. Then, another optimization method, QM-QUEST, coupling Quantrum Mechanical simulation and quantitation algorithms was implemented. The latter provides more robust fitting while limiting user involvement and respects the correct fingerprints of metabolites. Its efficiency is demonstrated by accurately quantitating signals from tissue samples of human brains with oligodendroglioma, obtained at 11.7 Tesla and spectra of cells acquired at 9.4T by HRMAS-NMR. As the necessity of fast NMR signal simulation based on quantum Mechanics is raised in the thesis, a part of the word is dedicated to an approximate method speeding-up the calculations. The algorithm based on spin-system fragmentation could become an important part of the QM-QUEST optimization method and will be implemented as an option of simulation in NMR-SCOPE, module of the jMRUI software package.
13
Schilling, Franz [Verfasser], Steffen J. [Akademischer Betreuer] Glaser, Silvio [Akademischer Betreuer] Aime, and Axel [Akademischer Betreuer] Haase. "Novel Methods for NMR - Single-SHOT Correlation Spectroscopy and Diffusion of 13C-Metabolites utilizing both Hyperpolarization and Optimal Control / Franz Schilling. Gutachter: Silvio Aime ; Steffen J. Glaser ; Axel Haase. Betreuer: Steffen J. Glaser." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1034420852/34.
Full text
14
Ojo, Catherine A. "Analysis & automatic classification of nuclear magnetic resonance signals." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4109.
Full textAbstract:
The human brain consists of a myriad of chemical compounds critical to its functioning. A group of these compounds, collectively known as metabolites, have been a research interest for years because the pathogenesis of neurodegenerative diseases, a tumours classification, the effectiveness of a drug, etc., can be investigated via variations in brain metabolite concentration levels. Nuclear Magnetic Resonance Spectroscopy (NMRS) enables investigators to conduct non-invasive in vivo studies of metabolites in the human brain and the rest of the body. However a number of problems have hindered the usage of NMRS as a clinical diagnostic tool. One is the non-uniqueness of the most widely used analysis methods, i.e. as the parameters and/or prior knowledge data of an analysis method are changed, the results also change. A second problem is the lack of a method that can automatically classify the signal components estimated via signal decomposition based signal analysis methods. Additionally, some of the most widely used analysis methods, by virtue of their algorithms, intrinsically assume the nature of NMRS signals, e.g. stationary, linear, Lorentzian, etc. Hence, this thesis explores a new analysis approach, based on a theoretical and practical understanding of NMRS, that (a) avoids making assumptions about the nature of experimentally acquired NMRS signals, (b) relies on a unique decomposition analysis method, and (c) automatically classifies the estimated peaks of an analysis. Unique decomposition analysis was conducted via the rarely used unique and non-linear signal decomposition method − the Fast Pad´e Transform (FPT). The FPT is compared with the main decomposition based NMRS analysis methods via a detailed mathematical analysis, and a comparative analysis. Automatic classification was conducted via a novel classification method, which is introduced herein, and which is based on quantum mechanical predictions of metabolite NMRS behaviour.
15
Salmon, Deborah Louise. "Metabolite profiling of the coccolithophore Emiliania huxleyi to examine links between calcification and central metabolism." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14932.
Full textAbstract:
Coccolithophores are single-celled marine phytoplankton, which produce intricate calcium carbonate platelets or ‘coccoliths’. Emiliania huxleyi is the most abundant and widespread coccolithophore, and is one of the most productive calcifying species on earth, playing a key role in global carbon, carbonate and sulphur cycles. Despite much research into coccolithophore biology, the underlying function of their coccoliths is still unknown. The main aim of the research reported in this thesis was to examine the impact of calcification on metabolism in coccolithophores. Calcification is a significant global process, so it is important to discover what effect it has on the metabolism of cells. The major metabolites each have different costs and benefits to the cell, which will vary depending on the habitat and environmental conditions the cell is in. By comparing the metabolite profiles of different strains, including calcifying, non-calcifying, haploid and diploid cells, differences in metabolite composition and potential patterns related to cell type were investigated. Low molecular weight (LMW) metabolites were characterised using a combination of metabolomic techniques. In agreement with previous research, dimethylsulphoniopropionate (DMSP) was the most abundant compound, followed by mannitol and glycine betaine (GBT). Less abundant sugars, polyols and amino acids were also identified. Environmental factors were manipulated to investigate how the principal metabolites were affected by salinity, different light intensities and nutrient (phosphate and nitrate) limitation. The data revealed a striking difference between haploid and diploid cells of the same strain, with the haploid containing lower concentrations of most of the major metabolites. Thus it is proposed that haploid cells have a different osmoregulatory strategy from the diploid cells. A negative correlation was found between DMSP and mannitol, suggesting that mannitol has a dual function, not only as a major storage compound but also as a principal compatible solute. Untargeted metabolite profiling is becoming a popular tool to investigate phenotypes and varying environmental conditions. LC-ESI-QTOF-MS/MS analyses of a wide range of metabolites showed that it is an effective method to identify differences and similarities between E. huxleyi strains grown in different conditions. Strain and growth phase appear to be the more important factors in differentiating metabolite profiles. Surprisingly there were no obvious metabolite profiling differences between calcifying and non-calcifying cells. Untargeted analysis can, however, be used to identify the compounds that did display differences, and which may be important biomarkers, so warrant further investigation. A range of metabolite profiling techniques highlighted important differences between strains, which will hopefully lead onto further research into the metabolome of E. huxleyi, and the unravelling of important metabolic pathways. There has been little research into the LMW metabolites of E. huxleyi, and especially comparisons between strains. Thus the use of metabolomics is a novel way to investigate the difference between cell types and the possible functions of calcification.
16
Bucur, Adriana. "Spectométrie de RMN quantitative in vivo pour la mesure des lipides hépatiques chez l'homme et des métabolites cérébraux chez un modèle murin de neuro-inflammation." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10094.
Full textAbstract:
La SRM proton constitue un outil non invasif unique pour l'exploration biochimique quantitative des tissus vivants. Les deux études présentées dans cette thèse visent à maîtriser chacune des phases impliquées depuis l’acquisition des données jusqu’à l’estimation fiable et précise des profils métaboliques des tissus explorés. Des protocoles expérimentaux d’acquisition des signaux de spectrométrie de résonance magnétique proton in vivo à temps d’écho courts ont été définis puis optimisés pour une application pré-clinique (souris) sur un imageur 4.7T et pour une étude en environnement clinique menée à 1.5T. La première étude a permis de mesurer longitudinalement les altérations des métabolites cérébraux (N-acétyl-aspartate, choline, créatine, taurine) chez un modèle murin de neuro-inflammation sur un imageur 4.7T, et la seconde étude avait pour objectif la mesure de la quantité totale et la composition lipidique hépatique en environnement clinique à 1.5T chez des sujets stéatosiques. Des méthodes d’estimation des contributions métaboliques et lipidiques adaptées aux propriétés physiques de signaux ont été validées pour chacune de ces applications. Ces méthodes sont fondées sur des algorithmes de moindres carrés non linéaires. Des stratégies multi-tirages des valeurs initiales et des contraintes ont été favorablement validées. Les atouts et les originalités de ce projet reposent sur les développements synergiques des protocoles d’acquisitions et des méthodes de traitement du signal associées. Ces développements ont pour vocation d’enrichir la palette des informations biochimiques collectées pour l’aide au pronostic et diagnostic médicalThe proton MRS is a unique non-invasive method to quantitative biochemical exploration of living tissues. The studies presented in this thesis aim to handle each one of the involved steps, from data acquisition to reliable and precise metabolic profile estimation of explored tissues. Protocols for experimental acquisition of in vivo, short echo-time magnetic resonance signals were defined, and optimized for a pre-clinical application (mice) on a 4.7T scanner and for a clinical study at 1.5T. The first study allowed yo measuring cerebral metabolite (N-acetyl-aspartate, choline, creatine, taurine) alterations along time in a murine model of neuro-inflammation on a 4.7T scanner and the second study aimed to measure the total quantity and the composition of liver fat in patients with hepatic steatosis in a clinical environment at 1.5T. Signal processing methods for metabolite and fat contribution estimates, coping with physical signal properties were validated for both studies. These methods are based on non-linear least squares algorithms. Multiple starting values and constraints strategies were successfully validated. The assets and the originality of this project are based on the synergic developments of acquisition protocols and the associated signal processing methods. These developments were designed to enrich the list of the biochemical information non-invasively measured, in order to help medical prognostic and diagnostic
17
Chen, Kan. "Applications of Mass Spectrometry to Analysis of Prodiginines, Bioactivated Methylenedianiline Intermediates, and Hypoxia Induced Changes in the Zebrafish Skeletal Muscle Proteome." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/899.
Full textAbstract:
Mass spectrometry coupled with liquid chromatography and gel electrophoresis enables separation and detection of components in a complex mixture. During the last two decades, its applications were dramatically extended and remarkable progress has been made in many fields, in particular, environmental and biological analyses. This dissertation focuses on identification and characterization of biologically active compounds and comparative analysis of protein expression changes. The first two projects (Chapters 2 and 3) focus on the application of LC/MS approach to profile the bioactivated intermediates of 4, 4'-methylenedianiline (DAPM) from rat vascular smooth muscle cells (VSMCs) and bile. In our study, several DAPM metabolites were detected and characterized in detail by liquid chromatography-electrospray tandem mass spectrometry. The structural assignments of these metabolites from VSMCs and rat bile significantly improve our understanding of DAPM biotransformations and toxicity. The third project described in Chapter 4 focuses on using electrospray tandem mass spectrometry (ES-MS/MS) and theoretical calculation (GAUSSIAN 03 program) to investigate the unusual methyl radical loss and consecutive fragment ions that dominate the low-energy collision induced dissociation (CID) mass spectra of prodiginine compounds. Structures of the fragment ions are proposed and explanations are given to rationalize the observed competition between the formation of even-electron ions and radical ions. Our study shows that the lower apparent threshold associated with methyl radical loss points to a lower kinetic barrier. In Chapter 5, hypoxia-induced changes of zebrafish skeletal muscle were studied using two-dimensional difference in-gel electrophoresis (2D-DIGE) in vivo after 48 h in hypoxia vs. normoxia. The results showed that proteins involved in mitochondrial oxidative metabolism are down-regulated, whereas glycolytic enzymes are up-regulated to compensate for the loss of ATP synthesis in aerobic metabolism. The up-regulation of two spots identified as hemoglobin variants was also observed. These protein expression changes are consistent with a hypoxic response that enhances anaerobic metabolism or O2 transport to tissues.
18
MARCHETTI, LUCIA. "Tecniche innovative per la caratterizzazione di prodotti naturali quali fonti di composti attivi e valutazione della loro attività biologica." Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2022. http://hdl.handle.net/11380/1278348.
Full textAbstract:
Gli estratti ottenuti da piante medicinali sono costituiti per lo più da miscele complesse di composti attivi chimicamente differenti, anche conosciuti come metaboliti secondari. L’attività biologica dei prodotti naturali non è da attribuire a un singolo composto, ma piuttosto alla moltitudine di molecole che agiscono in sinergia tra loro. Per questa ragione la determinazione di tutti i costituenti attivi rappresenta un punto cruciale per assicurare l’efficacia, attendibilità e sicurezza nell’uso dei prodotti medicinali a base di piante. Ancora oggi, il controllo di qualità ed autenticità delle materie prime vegetali è ostacolato dalla mancanza di metodi analitici validati e dalla limitata disponibilità di standard di riferimento. I metodi di analisi per gli estratti vegetali e per i prodotti nutraceutici devono essere costantemente messi a punto ed aggiornati, dal momento che sempre nuove combinazioni di sostanze vengono impiegate in nuove formulazioni. Questo progetto di Dottorato di ricerca si è basato sullo sviluppo e successiva applicazione di metodi innovativi per l’analisi di metaboliti secondari di origine vegetale. Particolare attenzione è stata rivolta all’analisi di piante di interesse farmaceutico (Cannabis sativa L., and Spathodea campanulata P. Beauv.) e nutraceutico (Morus alba L., Aloysia polystachya Griseb. et Moldenke). Oggetto di questa dissertazione sono anche i diversi saggi in-vitro, messi a punto per valutare l’attività biologica degli estratti in analisi.
Nel primo Capitolo, è stata applicata la spettroscopia NMR per la determinazione dei principali cannabinoidi non psicoattivi presenti nelle infiorescenze femminili di Cannabis da fibra. Il metodo analitico è stato sviluppato e validato in conformità alle linee guida internazionali. Questa tecnica trova applicazione nel monitoraggio del materiale vegetale di partenza, per garantire una migliore riproducibilità nei test biologici e per assicurare efficacia e sicurezza nell’uso di prodotti farmaceutici derivati. Come proseguimento del lavoro, metodi separativi e non separativi per l’analisi dei cannabinoidi sono stati discussi e messi a confronto per comprenderne potenzialità e svantaggi. Alcune varietà di C. Sativa sono state selezionate per la preparazione di estratti ricchi in cannabinoidi non psicoattivi, di cui è stata valutata l’attività antiproliferativa su modelli cellulari.
Nel secondo Capitolo, è presentato uno studio di caratterizzazione della composizione chimica di varietà di gelso Italiane, quali fonti di principi attivi nel contesto di nuovi approcci terapeutici per il diabete mellito. Questo studio, primo nel suo genere, prevede di selezionare le cultivar più idonee alla produzione di estratti standardizzati a base di attivi ipoglicemizzanti. Le proprietà antiglicative e antidiabetiche di estratti di foglie di gelso sono state testate e diverse strategie per ritardare il rilascio dei componenti attivi sono state sviluppate al fine di potenziarne le capacità terapeutiche.
Nel terzo Capitolo è stata analizzata la composizione chimica di S. campanulata, mediante HPLC-ESI-MS2. L’obiettivo principale è stato quello di individuare i composti responsabili della documentata inibizione di H. pylori e fare luce sui meccanismi alla base dell’attività biologica.
Nel quarto Capitolo è stata indagata la composizione fenolica di A. polystachya, mediante tre differenti tecniche MS accoppiate all’HPLC. Il metodo di analisi è stato sviluppato e validato per l’identificazione dei principali metaboliti, e alcuni di essi sono stati identificati per la prima volta in questa pianta.Plant extracts mainly consist in complex mixtures of chemically different bioactive compounds also known as secondary metabolites. In most cases, the bioactivity of natural products is not ascribable to a single compound, but rather to a multitude of them acting in a synergistic way. In this view, the complete definition of all the phytochemical constituents represents a key point to ensure the efficacy, reliability, and safety in the use of herbal medicines. Even today, the quality and authenticity assessment of herbal raw materials is frequently impaired by the lack of validated analytical methods and by the limited availability of certified references. Techniques for the analysis of herbal extracts and nutraceuticals need to be developed and upgraded continuously since different combinations of ingredients are employed in new formulations. In view of the above, the current PhD project was focused on the development and application of innovative analytical methods for the analysis of plant bioactive secondary metabolites. Particular attention was paid to plants of pharmaceutical (Cannabis sativa L., and Spathodea campanulata P. Beauv.) and nutraceutical interest (Morus alba L., Aloysia polystachya Griseb. et Moldenke). Different in-vitro assays for the bioactivity evaluation of these plants’ extracts were also the object of this PhD Thesis. In Chapter 1, the NMR technique was applied for the determination of the main non-psychoactive cannabinoids in fiber-type Cannabis female inflorescences. The analytical method was developed and fully validated to show compliance with international requirements. This technique finds application in the monitoring of the plant material, to guarantee a better reproducibility for biological assays, and to ensure the efficacy and safety of Cannabis-derived products. As a continuation of this project, the potentialities and drawbacks of separation and non-separation methods for the analysis of cannabinoids were considered and compared. Finally, C. sativa non-psychoactive varieties were selected for the preparation of cannabinoids rich extracts to evaluate their antiproliferative activity, by using cellular models. In Chapter 2 the chemical composition of Italian mulberry was investigated, as a source of phytochemicals in the context of new therapeutic approaches for diabetes mellitus. The first aim was to assess the quality of the plant material in comparison to Far Eastern Asia cultivations, where mulberry has been considered as a medicine for the treatment of diabetes for decades. The antiglycative capacity and hypoglycaemic effect of leaf extracts were evaluated on different in vitro models, to understand the potentialities of mulberry for the therapy of hyperglycaemia. Finally, the development of novel strategies for delaying the release of mulberry active constituents and enhancing therapeutic results will be discussed and are intended as the conclusion of this research project. In Chapter 3 the chemical composition of S. campanulata was investigated by HPLC-ESI-MS2, to clarify which are the most active components responsible for the inhibition of H. pylori growth. The aim was also to disclose the mechanisms underlying the biological activity. In Chapter 4 the phenolic composition of A. polystachya was investigated by means of three different MS techniques coupled to HPLC. The analytical method was developed and validated for the identification of metabolites and some phenylpropanoids were detected in this plant for the first time.
19
Martel, Dimitri. "Spectroscopie 2D de corrélation quantitative : Méthode de quantification, études expérimentales et applications in vivo." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0004/document.
Full textAbstract:
En spectroscopie de résonance magnétique (SRM) in vivo, les principales méthodes utilisées permettent la quantification des concentrations de métabolites en utilisant des signaux à une dimension spectrale. Les travaux réalisés dans le cadre de cette thèse portent sur le développement de méthodes de SRM à deux dimensions spectrales (SRM 2D) de corrélation localisée afin d’accroître le pouvoir de résolution spectrale et la précision de la quantification de la SRM in vivo. Le premier axe de cette thèse concerne le développement d’une méthode fondée sur la spectroscopie 2D de corrélation localisée pour l’exploration des métabolites cérébraux. La séquence L-COSY (spectroscopie de corrélation localisée) est implantée sur imageur petit animal et étudiée. Une procédure de quantification dédiée aux signaux de corrélation acquis est développée. Cette dernière opère dans le domaine d’acquisition du signal, et s’appuie sur : 1) une connaissance a priori forte obtenue par simulation de l’effet quantique des séquences sur les spins des composés présents dans le spectre 2) un modèle de pondération lié aux effets de relaxation agissant sur le signal de SRM 2D. 3) une contrainte sur la relaxation liée aux effets d’inhomogénéités supposés toucher tous les spins de la même manière. Les résultats présentés s’attachent à étudier les performances quantitatives de la SRM 2D de corrélation, en comparaison à la SRM 2D dite J-résolue (avec la séquence JPRESS), de manière expérimentale, sur fantômes de métabolites mais aussi à travers la théorie des bornes de Cramér-Rao (CRBs). La quantification des signaux L-COSY, bien que défavorisée par une perte théorique du rapport signal sur bruit par unité de temps, présente des CRBs théoriques relatives du même ordre de grandeurs voire, pour certains métabolites couplés (e.g la glutamine, le GABA) plus petites que celles correspondantes à la spectroscopie J-résolue pour un même temps d’acquisition. Le second axe de cette thèse porte sur l’adaptation la SRM 2D de corrélation pour l’étude in vivo du métabolisme lipidique du foie et des tissus adipeux sous-cutanés sur un modèle de souris obèse à 7T. Cette application inédite montre la faisabilité de la SRM 2D de corrélation à être acquise sur un tel organe mouvant et sa capacité à être quantitative pour l’étude et la caractérisation des triglycérides hépatiques et sous-cutanéesIn in vivo Magnetic Resonance Spectroscopy (MRS), the main methods used allow metabolite concentration quantification using signals having one spectral dimension. This work focuses on the development of in vivo two dimensional correlated MRS in order to increase spectral resolution and quantification precision. The first axis is about the development of a method based on a 2D localized correlation MRS (L-COSY) for brain metabolite exploration. The L-COSY is implemented and studied on a small animal scanner. A dedicated quantification procedure operating in the acquisition domain is described. This latter is based on 1) a strong prior knowledge obtained by quantum mechanically simulate the effect of sequence on metabolite spin systems 2) a model function taking into account the relaxation weighting 3) constraints on the relaxation term linked to the field inhomogeneity effects which are assumed to act the same way on all the spins. Results are given experimentally using metabolites phantoms and through a comparison to other existing 2D MRS method, namely the J-resolved MRS (with the JPRESS sequence) using the Cramer Rao Lower Bounds (CRBs) theory. Although its inherent loss of signal to noise ratio is a disadvantage compared to J-PRESS, L-COSY quantification shows theoretically competitive relative CRBs, and even smaller CRBs for some coupled metabolites (e.g Glutamine or GABA), for an acquisition time similar to JPRESS. Second axis is about the adaptation of the 2D correlation MRS for the in vivo lipid metabolism study in the liver and subcutaneous adipose tissues of obese mice at 7T. This application shows the feasibility of 2D correlated MRS to be acquired on a moving organ and its quantitative relevance for triglyceride quantification and characterization in fatty liver and subcutaneous tissue
20
Dücker, Eibe Behrend. "Enhancement Strategies in NMR Spectroscopy." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E3E4-9.
Full text
21
Stonehouse, Jonathan. "New techniques in NMR spectroscopy." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360628.
Full text
22
Hughes, Colan Evan. "New techniques in NMR spectroscopy." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297524.
Full text
23
Fulwood, Russell. "Chiral analysis by NMR spectroscopy." Thesis, Durham University, 1992. http://etheses.dur.ac.uk/5979/.
Full textAbstract:
The analysis of the enantiomeric purity of chiral carboxylic acids requires a reagent to give acceptable NMR chemical shift non-equivalence with a wide range of substrate acids. Extensive studies of the behaviour of N-mono- methyl, N,N-dimethyl and cyclic amines as chiral solvating agents led to the finding that 1,2 diphenyl-1,2-diaminoethane can induce substantial non- equivalence in the diastereomeric salts of chiral a-phenyl and a-halo carboxylic acids. The diastereoisomeric complexes of the diamine with primary carboxylic acids (RCH(_2)CO(_2)H) presents an unusual case in which the internally enantiotopic methylene protons are rendered internally diasteretopic by an external non-covalently bonded reagent. Investigations of the physical parameters determining non-equivalence (stoichiometry, concentration, temperature and substrate enantiomeric purity), combined with NOE observations of the diastereomeric pairs and the crystal structure of the mono- hydrobromide salt were used to suggest the structure for the conformation responsible for shift non-equivalence. The zero valent platinum complex, 3-0-isopropylidene-2,3-dihydroxy-1,4- bis(diphenyl-phosphino)butane-platinum(0)-ethene (DlOP-Pt-ethene) was shown to be a versatile chiral derivatising agent for electron poor and strained η(^2)-donors. This was demonstrated by the enantiomeric purity determinations for alkynes, enones and norbornene derivatives. The crystal structure of DIOP-Pt-ethene was determined and found to be similar to the palladium analogue. If the achiral rhodium complex rhodium(I)-acetylacetone-diethene undergoes a reaction with 2 equivalents of a suitable chiral η(^2)-donor, it will result in the formation of 4 stereoisomers, two meso forms and a pair of enantiomers. The diasteroisomers should display chemical shift non-equivalence in the NMR spectrum of the product, reflecting the enantiomeric purity of the η(^2)-donor (self recognition). The derivatisation of rhodium(l)-acetylacetone-diethene with chiral η(^2)-donors was attempted.
24
Edden, Richard Anthony Edward. "New methods in NMR spectroscopy." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613719.
Full text
25
Zhu, Jian-Ming. "Spatially localized proton NMR correlation spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23681.pdf.
Full text
26
Nordstierna, Lars. "Molecular Association Studied by NMR Spectroscopy." Doctoral thesis, Stockholm : Physical Chemistry, Department of Chemistry, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3947.
Full text
27
Kenwright, A. "Applications of NMR spectroscopy to solids." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482971.
Full text
28
Ha, Dongwan. "Scalable NMR Spectroscopy with Semiconductor Chips." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11635.
Full textAbstract:
Conventional nuclear magnetic resonance (NMR) spectrometers—the electronic brain that orchestrates and monitors nuclear spin motions—are bulky, expensive, thus, not scalable. In this thesis, we report on scalable 4-mm2 silicon spectrometer chips that perform a broad range of two-dimensional NMR spectroscopy—e.g., correlation spectroscopy, J-resolved spectroscopy, and heteronuclear quantum coherence spectroscopy—as well as one-dimensional spectroscopy and relaxometry. In this way, they examine a wealth of nuclear spin behaviors and interactions in biological, organic, and pharmaceutical compound molecules, elucidating their structures and dynamics. This semiconductor-based NMR spectroscopy opens up new exciting vistas with two prime advantages. First, with size/cost economy and scalability, the spectrometer chips can be parallelized sharing the same bore of a magnet—whether a large superconducting or small permanent magnet—to greatly simplify multi-channel spectroscopy and vastly increase the spectroscopy throughput, overcoming the intrinsic slowness of NMR spectroscopy; such parallelism may enable the much-desired high-throughput NMR paradigm for drug discovery, metabolomics/metabonomics, and structural biology. We demonstrate the concept of this parallelism by 2-channel heteronuclear quantum coherence NMR experiments, where 2 chips run synchronously in an ultra-compact configuration. Second, the chip spectrometers can complement the recent advance in magnet miniaturization to realize bona fide portable NMR spectroscopy systems. To demonstrate this miniaturization benefit (in addition to the orthogonal benefit of parallelism), we perform all our spectroscopy experiments in a platform combining the spectrometer chips with a compact permanent NdFeB magnet. These demonstrations suggest new dimensions to the technology and applications of NMR spectroscopy enabled by the integrated spectrometers.Engineering and Applied Sciences
29
Warne, Mark Anthony. "Theoretical studies in proton NMR spectroscopy." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321165.
Full text
30
Smith, Timothy Andrew David. "Conformational analysis studies in NMR spectroscopy." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243220.
Full text
31
Stott, Katherine Mary. "Pulsed field gradients in NMR spectroscopy." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627246.
Full text
32
Amero, Carlos D. "Protein Function Study by NMR Spectroscopy." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1205431343.
Full text
33
Fauré, De la Barra Nicole Eloísa. "Understanding immobilised enzymes by NMR spectroscopy." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7319/.
Full textAbstract:
Enzyme immobilisation is the conversion of a soluble enzyme molecule into a solid particle form. This allows the recovery of the enzyme catalyst for its re-use and avoids protein contamination of the product streams. A better understanding of immobilised enzymes is necessary for their rational development. A more rational design can help enormously in the applicability of these systems in different areas, from biosensors to chemical industry. Immobilised enzymes are challenging systems to study and very little information is given by conventional biochemical analysis such as catalytic activity and amount of protein. Here, solid-state NMR has been applied as the main technique to study these systems and evaluate them more precisely. Various approaches are presented for a better understanding of immobilised enzymes, which is the aim of this thesis. Firstly, the requirements of a model system of study will be discussed. The selected systems will be comprehensibly characterised by a variety of techniques but mainly by solid-state NMR. The chosen system will essentially be the enzyme α-chymotrypsin covalently immobilised on two functionalised inorganic supports – epoxide silica and epoxide alumina – and an organic support – Eupergit®. The study of interactions of immobilised enzymes with other species is vital for understanding the macromolecular function and for predicting and engineering protein behaviour. The study of water, ions and inhibitors interacting with various immobilised enzyme systems is covered here. The interactions of water and sodium ions were studied by 17O and 23Na multiple-quantum techniques, respectively. Various pore sizes of the supports were studied for the immobilised enzyme in the presence of labelled water and sodium cations. Finally, interactions between two fluorinated inhibitors and the active site of the enzyme will be explored using 19F NMR, offering a unique approach to evaluate catalytic behaviour. These interactions will be explored by solution-state NMR firstly, then by solid-state NMR. NMR has the potential to give information about the state of the protein in the solid support, but the precise molecular interpretation is a difficult task.
34
Kok, Trina. "Detection of brain metabolites in magnetic resonance spectroscopy." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/46602.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Includes bibliographical references (p. 59-61).
While magnetic resonance imaging (MRI) derives its signal from protons in water, additional and potentially important biochemical compounds are detectable in vivo within the proton spectrum. The detection and mapping of these much weaker signals is known as magnetic resonance spectroscopy or spectroscopic imaging. Among the complicating factors for this modality applied for human clinical imaging are limited chemical-shift dispersion and J-coupling that cause spectral overlap and complicated spectral shapes that limit detection and separation of several brain metabolites using MR spectroscopic imaging. Existing techniques for improved detection include so-called 2D spectroscopy, where additional encoding steps aid in the separation of compounds with overlapping chemical shift. This is achieved by collecting spectral data over a range of timing parameters and introducing an additional frequency axis, fl. Spectral editing techniques attempt to enhance metabolite signal detection along fl in order to resolve specific metabolite signals. While these techniques have been shown to improve signal separation, they carry a penalty in scan time and more complicated reconstruction compared to conventional spectroscopy, and are often prohibitive when combined with spectroscopic imaging. The task of this thesis is to characterize and optimize existing 2D spectroscopy techniques for improved metabolite resolution with reduced number of timing steps through numerical simulation and experimental validation in phantoms.
Trina Kok.
S.M.
35
Khajeh, Maryam. "Kinetic measurements using time-resolved NMR spectroscopy." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/kinetic-measurements-using-timeresolved-nmr-spectroscopy(aae85bb3-de19-450a-96ab-50e2dfd89da7).html.
Full textAbstract:
Many thousands of pounds are spent every year by pharmaceutical companies on understanding the mechanisms and kinetics of chemical reactions involved in drug discovery and production. NMR spectroscopy is often at the core of these studies as it is a powerful, non-destructive method for structure elucidation. As such investigations can be time-consuming and cost-inefficient, AstraZeneca, the project sponsor, is interested in more efficient methods for studying the kinetics of pharmaceutical reactions. In this work a number of different techniques have been devised, studied, and implemented to study the kinetics of chemical reactions by time-resolved NMR spectroscopy, in which every species in a reaction can be monitored simultaneously. These novel techniques allow the study of reactions which are difficult or impossible to study by conventional NMR methods (such as heterogeneous reactions), or which are complicated by having overlapping signals. It is possible to monitor the kinetics of a reaction very simply by acquiring a series of 1H spectra, and obtaining the integrals of the signals by least squares fitting. This technique has been used for kinetic studies of static and on-flow reactions. In the static systems the reaction mixture was placed in the normal NMR tube in the magnet, while in the flow system the reaction mixture was placed outside of the magnet, and the solution flowed through an NMR tube placed in the magnet. The novel flow system designed, constructed and tested here has been used for kinetic studies of illustrative homogeneous and heterogeneous reactions, and is suitable for use in a wide range of NMR instrumentation. Kinetic studies have also been carried out by acquiring a series of DOSY datasets, analysing the results using the multi-way method PARAFAC (PARAllel FACtor analysis). A series of DOSY datasets contains multivariate information on spectrum, time evolution and diffusion. Without providing any predetermined model, the data can be decomposed by PARAFAC to yield the spectrum, kinetics, and diffusion profiles for each of the components. It has also been shown that PARAFAC is remarkably robust to low signal-to-noise ratio data, significantly below the level at which conventional methods would fail.
36
Säwén, Elin. "NMR spectroscopy and MD simulations of carbohydrates." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-61569.
Full textAbstract:
Knowledge about the structure, conformation and dynamics of carbohydrates is important in our understanding of the way carbohydrates function in biological systems, for example in intermolecular signaling and recognition. This thesis is a summary of five papers studying these properties in carbohydrate-containing molecules with NMR spectroscopy and molecular dynamics simulations. In paper I, the ring-conformations of the six-membered rings of two carbaiduronic analogs were investigated. These carbasugars could potentially be used as hydrolytically stable mimics of iduronic acid in drugs. The study showed that the equilibrium is entirely shifted towards the 4C1 conformation. Paper II is an investigation of the conformational flexibility and dynamics of two (1→6)-linked disaccharides related to an oligosaccharide epitope expressed on malignant tumor cells. In paper III, the conformational space of the glycosidic linkage of an alfa-(1→2) linked mannose disaccharide present in N- and O-linked glycoproteins, was studied. A maximum entropy analysis using different priors as background information was used and four new Karplus equations for 3JC,C and 3JC,H coupling constants, related to the glycosidic linkage, were presented. Paper IV describes a structural elucidation of the exopolysaccharide (EPS) produced by Streptococcus thermophilus ST1, a major dairy starter used in yoghurt and cheese production. The EPS contains a hexasaccharide repeating unit of d-galactose and d-glucose residues, which is a new EPS structure of the S. thermophilus species. In paper V, the dynamics of three generations of glycodendrimers were investigated by NMR diffusion and 13C NMR relaxation studies. Three different correlations times were identified, one global correlation time describing the rotation of the dendrimer as a whole, one local correlation time describing the reorientation of the C-H vectors, and one correlation time describing the pulsation of a dendrimer branch.
37
Bergin, Paul Gerald. "Applications of tritium and tritium NMR spectroscopy." Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/842709/.
Full textAbstract:
Tritium labelled compounds are widely used in the physical and life sciences. The preparation of such compounds is a very important area of chemistry. Although the methods are, on the whole, fairly simple and straightforward, there is still a need for improvement. The same applies as far as the analysis of the tritium distribution is concerned. High resolution 3H NMR spectroscopy of solutions is now a well established technique. However many compounds exist as solids which are either insoluble or sparingly soluble in organic solvents, consequently there is a need to develop high resolution 3H NMR spectroscopy of solids. The thesis therefore consists of four chapters. The first is a review dealing with the properties of tritium, the various labelling methods and tritium nuclear magnetic resonance spectroscopy. In the second chapter an account is given of the way in which complex metal tritides and tritiated methyl iodide, an important reagent which enables one to introduce three tritium atoms in a single step and therefore obtain products of very high specific activity, are prepared. In the third chapter an account is given of the synthesis and attempted tritiation of two potential 5-HT re-uptake inhibitors, prior to their use in biological studies. Whilst the synthesis of the two compounds N-[[[l-[(l-bromo-2-naphthalenyl)methyl]-4-piperidinyl]amino]carbonyl]-3-pyridinecarboxamide, and N-[[[l-[(l-bromo-6-fluoro-2-naphthalenyl)methyl] -4-piperidinyl]amino]carbonyl]-3-pyridinecarboxamide, was successful the tritiation procedure led to unforseen difficulties. Finally in the fourth chapter solid state tritium NMR spectroscopy, using a magic angle accessory, was developed and used in the analysis of several tritiated compounds.
38
Hu, Song 1969. "Thrombin exosite interactions studied by NMR spectroscopy." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23897.
Full textAbstract:
Fibrinogen, thrombin receptor and heparin cofactor II are three major thrombin substrates recognized specifically through its exosite, a regulatory binding site. Based on the native protein sequences, four peptides were selected to study the specificity of exosite interactions on structural basis using transferred NOE methods. The binding sequences of all the peptides are identified and possible thrombin binding sites of thrombin receptor and heparin cofactor II peptides are speculated by comparing with known hirudin-thrombin complex structures. A new binding mode may exist in thrombin-fibrinogen contacts according to its exosite binding sequence and interaction patterns. In terms of the binding sequence, it suggested that the most important factor in thrombin exosite specific binding is the hydrophobic residues position rather than the analogous sequence.
39
Varma, S. C. "Polymer end-group studies using NMR spectroscopy." Thesis, Lancaster University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374665.
Full text
40
Zagdoun, Alexandre. "Dynamic Nuclear Polarisation Surface Enhanced NMR Spectroscopy." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2014. http://tel.archives-ouvertes.fr/tel-01065554.
Full textAbstract:
Since its discovery in the 1950's, DNP has been a topic of significant interest in magnetic resonance. DNP is the transfer of polarization between single electrons and nuclei, driven by micro-wave irradiation. Since its renaissance at high field in the 90's, due to the introduction of gyrotrons as high-power, high-frequency microwave sources most application of this technique have been samples of biological interest in frozen solution. The long standing interest of our group in the characterization of surface species such as supported catalysts on silica lead us to apply this technique to the study of surfaces. The goal of this thesis is the development of this method, dubbed DNP Surface Enhanced NMR Spectroscopy. To that end, we first introduce new polarizing agents, soluble in organic solvents. The influence of the electron relaxation times on the DNP enhancements is demonstrated and efficient tailored polarizing agents are introduced. The optimization of the sample preparation to obtain optimal sensitivity is also discussed, as well as the interaction between the radical and the surface. These developments made it possible to apply the technique to many functionalized materials, with some examples developed in this manuscript. Finally, the issue of DNP on polarization conductors is discussed, and we show how microcrystals can be efficiently polarized using DNP.
41
Eyles, Stephen J. "Studies of protein folding by NMR spectroscopy." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:06b8fb16-790c-4b72-80d0-8317920655fe.
Full textAbstract:
This thesis describes an investigation of the folding and stability of a series of derivatives of the proteins lysozyme and α-lactalbumin which lack one or more of their four native disulphide bridges. Removal of the disulphide bridge which links the N- and C-termini from hen lysozyme results in a three-disulphide derivative (CM6,127-lysozyme). This has a profound effect on its stability against thermal denaturation, the Tm for unfolding being reduced by 25°C at pH 3.8. Calorimetric measurements performed on this three-disulphide derivative indicate that this reduction in stability may be attributed entirely to an increase in the entropy difference between the native and denatured states. Kinetic refolding studies of CM6,127-lysozyme using stopped flow optical methods and hydrogen exchange pulse labelling in conjunction with NMR and electrospray ionisation mass spectrometry (ESI-MS) suggest that this reduced stability manifests itself primarily in the α-domain of the protein. A transient intermediate populated during refolding of the unmodified protein can no longer be detected during folding of the derivative resulting in highly cooperative folding under the conditions investigated. The structure and stability of a three- and two-disulphide derivative of the homologous protein, α-lactalbumin have been investigated by NMR spectroscopy. The three-disulphide species, like its lysozyme counterpart, can adopt native structure but this is much more unstable than the intact protein. Removal of a second disulphide bridge, however, destabilises α-lactalbumin to the extent that the native state is no longer formed. Instead, in the presence of Ca2+ and high concentrations of salt, a partially structured state is induced which has some elements of tertiary structure present. Novel techniques of ESI-MS have been developed to study protein folding and stability using hydrogen exchange techniques. Applications to the investigation of cooperativity in protein folding, stability in native, partially folded and unfolded states, and the interactions of a partially folded protein with the chaperone GroEL are described.
42
Grieves, R. A. "Multinuclear NMR spectroscopy of transition metal complexes." Thesis, University of Bradford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372167.
Full text
43
Edgar, Mark. "Studies in proton and flourine NMR spectroscopy." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240501.
Full text
44
Cantalapiedra, Nuria Aboitiz. "Intramolecular hydrogen-bonding studies by NMR spectroscopy." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366715.
Full text
45
Kraft, Robert A. (Robert Arthur) 1970. "In vivo two-dimensional NMR correlation spectroscopy." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85271.
Full text
46
Le, Guennec Adrien. "Fast 2D NMR spectroscopy for complex mixtures." Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01191697/document.
Full textAbstract:
La métabolomique est un domaine récent dont le but est d’analyser l'ensemble des molécules participant aux réactions chimiques d'un organisme. L'utilisation de la Résonance Magnétique Nucléaire (RMN) pour la métabolomique est en plein essor grâce à une méthodologie basée sur des spectres à une dimension (1D) du proton. Cependant, les spectres 1D de mélanges complexes, comme les extraits ou fluides biologiques, présentent un recouvrement important des signaux RMN, ce qui peut poser problème pour l'identification et la quantification des molécules d’intérêt. L'utilisation d’expériences RMN à deux dimensions (2D) permet en principe de limiter les risques de recouvrement. Cependant, la durée des expériences 2D est souvent prohibitive pour la métabolomique. Plusieurs approches existent afin de réduire la durée des expériences RMN 2D, mais elles n'ont pas à ce jour été évaluées dans le cadre de la métabolomique. Au cours de cette thèse, nous avons démontré le potentiel de la RMN 2D rapide pour la métabolomique et optimisé ses performances. Deux approches RMN 2D rapides ont été testées : la RMN ultrarapide et l'échantillonnage non-uniforme. Par une étude avec des échantillons synthétiques, nous avons pu démontrer, dans un premier temps, l'intérêt de la RMN 2D par rapport à la RMN 1D pour la métabolomique, puis l'utilisation des approches 2D rapides pour obtenir la même information que la RMN 2D conventionnelle avec un temps d'acquisition réduit. Nous avons ensuite cherché à optimiser l'utilisation des approches 2D rapides pour l'analyse des mélanges complexes. Dans un premier temps, une nouvelle séquence a été développée en RMN 2D ultrarapide du proton, afin de supprimer les pics diagonaux, qui peuvent recouvrir des pics de corrélations et donc réduire l'information disponible sur les spectres. Ensuite, l'échantillonnage non-uniforme a été utilisé afin d'augmenter jusqu'à 32 fois la résolution dans la dimension indirecte sans perte de sensibilité ou de répétabilité ou d'augmentation de la durée d'expérience. Enfin, des essais ont été effectués afin d’automatiser la détermination des constantes de relaxation directement dans les mélanges complexes. Ces différents outils ouvrent des perspectives d’application prometteuses pour l’analyse métabolomique à haut débit d’échantillons biologiquesMetabolomics is a recent area of research, which aims at analyzing the entirety of molecules involved in chemical reactions in an organism. Nuclear Magnetic Resonance (NMR) is widely used in metabolomics nowadays thanks to a methodology based on one-dimensional (1D) NMR. However, 1D spectra of complex mixtures, like biological extracts or fluids, are characterized by important overlap between peaks, which can be detrimental to the identification and quantification of molecules of interest. Two-dimensional (2D) NMR can be used to reduce the risk of overlap. However, the duration of 2D experiments is often prohibitive for metabolomics studies. Several approaches exist to reduce the duration of 2D experiments, but they have not been evaluated so far for metabolomics. In this thesis, we have shown the usefulness of fast 2D NMR for metabolomics and optimized its performances. Two fast 2D NMR approaches have been evaluated, ultrafast 2D NMR and non-uniform sampling. In a study with synthetic samples, we first demonstrated the usefulness of 2D NMR compared to 1D NMR, then we showed that the experimental time of 2D spectra could be reduced with fast 2D NMR approaches without loss of information. Then we optimized the use of fast 2D NMR for complex mixture analysis. First, we developed a new pulse sequence with ultrafast 2D NMR of proton, in order to suppress the diagonal peaks, which can overlap with correlation peaks and therefore reduce the information content of 2D spectra. Then non-uniform sampling was used to increase up to 32 times the resolution in the indirect dimension without increasing the experimental time and without loss of sensitivity or repeatability. Finally, we worked on automating the determination of relaxation constants in complex mixture. These tools open promising perspectives for high-throughput metabolomics of complex biological samples
47
Gao, Chun. "19F DOSY Diffusion NMR Spectroscopy of Fluoropolymers." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1447069266.
Full text
48
Rogerson, Alexandria. "New techniques in diffusion-ordered NMR spectroscopy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/new-techniques-in-diffusionordered-nmr-spectroscopy(aa3eaee0-984b-4434-b460-8c3118a7c3b2).html.
Full textAbstract:
The analysis of mixtures is a subject that spans several different analytical techniques. In NMR, a powerful technique for this analysis is Diffusion-Ordered NMR Spectroscopy (DOSY), in which signals from different chemical species can be distinguished by their different diffusion coefficients. DOSY NMR allows an analysis of mixture components and their interactions in a non-invasive way and is proving to be an accurate and time effective method for looking at mixtures.An in-depth analysis of DOSY NMR is presented using the commercial mixture “monoacetin”. The chemically cognate species in this mixture produce complex and overlapping multiplet signals in 1H NMR that are difficult to assign and interpret. A previous analysis of this mixture used 1H NMR together with Liquid Chromatography (LC) and Gas Chromatography (GC) to identify the components present, but failed to provide complete assignments of all the signals. Here, the possibility of using DOSY as an alternative to hyphenated techniques is examined, and it is shown that a full analysis of the spectrum of “monoacetin” is possible with careful selection of experimental parameters and processing techniques, without recourse to chromatography. DOSY NMR can be ineffective when signals overlap and/or diffusion coefficients are similar. Many methods have been proposed to overcome these problems, and some of these are presented here. In order to increase resolving power, it is possible to gather further information about a mixture and incorporate this into diffusion experiments as another dimension. This creates a 3D dataset that can be analysed using a multiway method, such as PARAFAC, to extract the component spectra. This method is explored for the mixture “monoacetin” that has been partially separated by high-performance liquid chromatography. Resolution of two out of four components was achieved from poor HPLC separation; the decomposition obtained the component spectra, diffusional decay and HPLC elution profile for these components. Improved HPLC separation should result in further resolution.Diffusion coefficients of different mixture species can be manipulated by changing the matrix in which they diffuse: Matrix-Assisted DOSY (MAD). Previous techniques have involved either improving resolution in the diffusion domain or aiming to improve resolution in chemical shift. A method is presented here that simultaneously addresses both problems in a chemically-selective way, using lanthanide shift reagents. The chemically-selective binding of the LSR to mixture components can both enhance chemical shift dispersion and increase diffusion resolution in DOSY. This neatly deals with the two main drawbacks of the DOSY experiment, and is demonstrated using a mixture of an alkane, alcohol and aldehyde. The manipulation of a molecule’s electrostatic charge through pH control has been investigated, where small ions with a high charge density would be highly solvated, resulting in a change in D. The effect, however, was not measurable and so the indirect effect of pH on the interaction of charged species with the cationic micelle CTAB is presented, where an increase in resolution between of mixture of aspirin and salicylic acid is achieved.Although DOSY NMR is a powerful tool for mixture analysis, in recent years it has been used for studying molecular interactions. An example of this is presented here where species aggregate under specific conditions, a process identified by DOSY NMR.
49
Inglis, Benjamin Alastair. "In vivo NMR spectroscopy of the brain." Thesis, Queen Mary, University of London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.644797.
Full text
50
Miletti, Teresa. "Enzyme flexibility studied by solution NMR spectroscopy." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119414.
Full textAbstract:
The important connection between dynamics, structure and function of enzymes still remains unclear and is, hence, an interesting relationship to investigate. In this thesis, the enzymes NADH oxidase (NOX) from Thermus thermophilus and mycobacterium tuberculosis (Mtb) protein tyrosine phosphatase B (PtpB) were chosen as systems to study the influence of solution conditions on protein structure and flexibility in relation to their catalytic activity. Nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC) techniques were used in the study of NOX. NMR and differential scanning fluorimetry (DSF) were utilized to assess the sample stability of PtpB under various buffer conditions.NOX is a 54 kDa homodimeric enzyme with many potential biotechnology applications. It accepts cofactors flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD). It has high thermal stability and its activity increases with the addition of low concentrations of urea. Using enzymes in vitro provides us a lot of freedom to control its environment, which is useful to look at changes occurring under different conditions. Thus, NMR allowed us to investigate these interesting characteristics on NOX dynamics and structure. When Mtb infects host cells it secrets among others, PtpB, to disrupt signalling pathways and blunts immune responses. PtpB contains a two-helix lid that completely buries the active site and it is proposed that it has evolved as a novel mean of protection against host chemical defences and affords substrate access. An investigation of conformational dynamics of the lid domain of PtpB using NMR would elucidate a relation between conformation and function of Ptpb, which to date, is still unknown and would contribute to the development of inhibitors as potential drugs. In order to do this, it is essential to obtain a stable sample that will give optimal quality NMR spectra. NMR and DSF were used to optimize PtpB NMR sample conditions and spectral quality. We employed a suite of novel 15N NMR relaxation experiments to estimate the extent of broadening due to microsecond-timescale motions and to measure exchange-free transverse relaxation rates on a per-residue basis of NOX. These measurements allowed us to identify several residues involved in dynamical processes. Moreover, order parameters, S2, determined from standard 15N T1, T2 and {1H}-15N steady NOE experiments, allowed the identification of additional residues characterized by motions on nanosecond-picosecond time scales. We then investigated the effects of temperature, urea addition, cofactor and NAD+ product binding to NOX using NMR and ITC. For each condition studied, chemical shift displacement of NMR peaks is significant relative to all other peaks only for a reoccurring small subset of residues. This cluster of residues is located around the active site of the enzyme and thus, suggests evidence of a relationship between concerted conformational rearrangement of NOX structure and NOX catalytic activity. An increase in NMR spectral quality and a NMR sample of PtpB with increased thermal stability, higher yields and reduced aggregation was obtained for further NMR dynamic experiments. This was achieved by optimizing the sample conditions by performing several NMR titrations and DSF experiments. Assessing the thermal stability of enzymes with different additives using DSF could be easily introduced during the elaboration of protein purification protocols as a routine method to optimize NMR sample conditions for NMR studies.Le lien important entre la dynamique, la structure et la fonction des enzymes n'est pas encore bien défini et est donc une relation intéressante à étudier. Dans cette thèse, les enzymes NADH oxydase (NOX) de Thermus thermophilus et mycobacterium tuberculosis protéine tyrosine phosphatase B (PtpB) sont les systèmes choisis pour étudier l'influence des conditions de solution sur la structure et la flexibilité des protéines par rapport à leur activité catalytique. Les techniques de résonance magnétique nucléaire (RMN) et de calorimétrie de titration isothermique (ITC) ont été utilisées dans l'étude de NOX. La RMN et la fluorimétrie différentielle à balayage (DSF) ont été utilisées pour évaluer la stabilité de l'échantillon de PtpB dans diverses conditions de tampons. NOX est une enzyme homodimérique avec de nombreuses applications biotechnologiques potentielles. NOX accepte les cofacteurs flavine mononucléotide (FMN) ou flavine adénine dinucléotide (FAD). L'enzyme a une stabilité thermique élevée et son activité augmente avec l'addition de faibles concentrations d'urée. Utiliser des enzymes in vitro donne beaucoup de liberté pour contrôler leur environnement, utile pour examiner les changements qui se produisent dans différentes conditions. Ainsi, RMN nous a permis d'étudier ces caractéristiques intéressantes sur la dynamique et la structure de NOX. Lorsque Mtb infecte les cellules, il secrète PtpB qui perturbe les voies de signalisation et affaibli les réponses immunitaires. PtpB contient un couvercle de deux hélices qui enterre complètement le site actif et il est proposé qu'il ait évolué ainsi en protection contre les défenses chimiques et permet un accès au substrat. Une étude de la dynamique du domaine du couvercle de PtpB utilisant la RMN éluciderait la relation entre la conformation et la fonction de PTPB et contribuerait au développement d'inhibiteurs en tant que médicaments potentiels. Pour ceci, il est essentiel d'obtenir un échantillon stable qui donnera des spectres RMN de qualité optimale. RMN et DSF ont été utilisés pour optimiser les conditions d'échantillonnage de PtpB pour la RMN et la qualité spectrale. Nous avons utilisé une suite de nouvelles expériences de relaxation de 15N par RMN pour estimer l'ampleur de l'élargissement des signaux en raison de mouvements à l'échelle de temps des microsecondes et de mesurer les taux de relaxation transversale sans échange pour chaque résidu de NOX. Ces mesures nous ont permis d'identifier plusieurs résidus impliqués dans les processus dynamiques. De plus, les paramètres d'ordre, S2, déterminées à partir des expériences standards de T1, T2 et NOE, ont permis d'identifier des résidus additionnels caractérisés par des mouvements sur des échelles de temps de nanosecondes à picosecondes. Nous avons ensuite étudié les effets de la température, urée, la liaison de cofacteur et du produit à NOX en utilisant la RMN et le ITC. Pour chaque condition étudiée, la variation de déplacement chimique des signaux RMN n'est significative par rapport à tous les autres signaux que pour un petit sous-ensemble récurrent de résidus. Cet amas de résidus est situé autour du site actif de l'enzyme et ainsi, suggère preuve d'une relation entre un réarrangement conformationnel concertée de la structure de NOX et de son activité catalytique. Une augmentation de la qualité spectrale de RMN et un échantillon de PtpB pour la RMN avec une meilleure stabilité thermique, des rendements plus élevés et une agrégation réduite ont été obtenus pour de futures expériences dynamiques par RMN. Ceci a été réalisé en optimisant les conditions de l'échantillon en effectuant plusieurs titrages par RMN et des expériences de DSF. L'évaluation de la stabilité thermique des enzymes avec différents additifs à l'aide de DSF pourrait facilement être introduit lors de l'élaboration de protocoles de purification de protéines comme une méthode routinière pour optimiser les conditions d'échantillons pour les études par RMN.