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1
Collin, Olivier L. "Development of a Novel Tandem Mass Spectrometry Technique for Forensic and Biological Applications." View abstract, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3292877.
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COGHI, MARIA DONATA. "Samdi mass spectrometry for high yield protein modification reaction development." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/50887.
Texte intégralRésumé :
Efficient chemical strategies that attach synthetic molecules to desired positions on protein surfaces are useful tools in the field of chemical biology and represent one major prerequisite for the development of new drugs and materials. Protein modification with polyethylene glycol (PEG) groups is indeed routinely performed on therapeutic proteins to improve serum half-life, or even cytotoxins or imaging agents are efficiently conjugated to cancer-targeting elements. In a typical approach, a synthetic functional group of interest is attached to a uniquely reactive amino acid group introduced by recombinant methods. Most bioconjugation reactions, however, do not reach full conversion. Therefore the development of a straightforward and reliable method to increase the extent of conversion into bioconjugates would be very helpful. In this perspective, we developed a generalizable combinatorial peptide library screening platform suitable for the identification of sequences displaying high levels of reactivity toward a desired bioconjugation reaction. This was achieved by using SAMDI MS technique (Self-Assembled Monolayer and Desorption/Ionization Mass Spectrometry) as a new, efficient and simple method for the evaluation of highly reactive amino acid motifs. The bioconjugation reaction we selected is the oxidative modification of electron-rich tyrosine residues performed using cerium(IV) ammonium nitrate (CAN) as oxidant reagent. The peptides were identified on a 361-member hexapeptide array, wherein the two N- and C-terminal residues to the target residue were varied. The arrays were prepared by immobilizing the peptides to a self-assembled monolayer of alkanethiolates on gold and could therefore be analyzed by mass spectrometry. We found that the most reactive peptides had either a serine N-terminal to the tyrosine residue or another tyrosine in proximity of the reactive site. Conversely, peptides displaying the lowest conversion level contained a positive charged residue: histidine, lysine or arginine, where the lowest relative activity was reached with arginine and leucine as C- and N- terminal residues, respectively. This study provides an important example of how synthetic peptide libraries can accelerate the discovery and optimization of protein bioconjugation strategies.
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Sproch, Norman K. "Electrospray mass spectrometry : an investigation of non- covalent interactions of cytochrome c/crown ether complexes and applied methods of computational chemistry." Virtual Press, 1994. http://liblink.bsu.edu/uhtbin/catkey/917033.
Texte intégralRésumé :
This research is directed at developing the interplay of experimental and computational methods in the area of biochemical mass spectrometry. The experimental method is that of electrospray ionization mass spectrometry (ESI-MS). The computational methods employed are those of semi-empirical quantum mechanics and molecular modeling.The use of Electrospray Mass Spectrometry was developed to investigate whole proteins and the non-covalent complexes that may be formed with small molecules. This method provides the soft ionization needed to accurately determine a noncovalently bound complex's mass with an error of less than 0.1 %. An original design electrospray ionization source (ESI) and a syringe pump have been built to fulfill the goals of the research. The ESI source design has been published in The Journal of the American Society for Mass Spectrometry, (1993, 4, 964-967).In this work the protein selected was cytochrome c and its variants from different species. The small molecules chosen were a broad class of structures known as crown ethers. With the ESI technique the proteins are prepared in an acidic solution that fully protonates the solvent-exposed basic amino acid residues. This provides the protein with many positive charges which makes the analysis by ESI mass spectrometry possible with a single quadrupole instrument, an Extrel ELQ 400. The mass of the protein is divided by the number of positive charges. The small molecules, the crown ethers, were chosen due to their ability to bind ammonium ion and protonated amino groups. This binding is non-covalent, hydrogen bonds stabilize the complex formation. Because this complex is non-covalent in nature the charge of proteins does not change. To aid in the interpretation of our electrospray mass spectra we have originated a new kind of linear plot for use with ESI data. It was found that in using the ESI technique that ion currents representing non-covalent complexes of cytochrome c and crown ethers could be observed in the mass spectra. The measurements of the total ion counts of peaks in the mass spectra allowed binding constants to be calculated. This had not been reported before in the literature.The accurate weight determination and the characteristic charge distribution in the ESI mass spectrum provides data suitable for computer modeling. The nature of the protein's positive charges in ESI had not been well defined. The experimentally determined binding constants allowed comparison to results from computational chemistry and molecular modeling. This result shows that the binding occurs at specific, protonated amino acid residues. The calculations performed yielding the Heats of Formation (OH f) for protonated amino acids complexed with crown ethers indicates that the OH binding of crowns increases from histidine, to arginine, to lysine. The use of a 3D model of cytochrome c from crystallographic data provided in the Brookhaven Protein Database and the SYBYL molecular modeling program allows a structural correlation to be made between the 3D model of the protein and protein/crown ether complex. The stoichiometric ratios of bound crown ether to protein determined from experiment, along with the computational results, have been used to rationalize a protein molecular model that allows predictions to be made about the potential for binding of other small molecules.<br>Department of Chemistry
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Thiery, Gwendoline. "Imagerie par désorption laser/spectrométrie de masse de multiples marqueurs spécifiques : développement de la technique TAMSIM "Targeted Multiplex Mass Spectrometry Imaging"." Paris 6, 2008. http://www.theses.fr/2008PA066253.
Texte intégralRésumé :
La protéomique est devenue un domaine de recherche essentiel en biologie et en médecine. Afin, de répondre aux enjeux de cette discipline, il est nécessaire de pouvoir caractériser et localiser les protéines exprimées au niveau cellulaire. De nombreuses techniques d’analyses in situ des ces protéines considérées comme étant des marqueurs spécifiques d’une pathologie existent et sont utilisées en routine, notamment pour le suivi des cancers, dans de nombreux laboratoires d’anatomo pathologie. La plus répandue est l’immunohistochimie (IHC). Cette technique consiste à révéler spécifiquement in situ un complexe immun (antigène-anticorps). Dans l’optique d’accroître la capacité de détection multiple (multiplexage) d’une immunoréaction, nous avons développé une nouvelle technique d’imagerie in situ de multiples marqueurs spécifiques. Des traceurs chimiques photoclivables (Tag) sont fixés spécifiquement sur des anticorps. Les anticorps marqués sont complexés in situ aux protéines cibles présentent sur le tissu. Les Tag sont ensuite clivés de leurs anticorps respectifs par désorption laser. Apres une irradiation de la coupe par le laser à 355 nm une image est générée à partir des différents spectres de masse enregistrés pour chaque Tag utilisés. Contrairement au mode MALDI, l’utilisation de la matrice n’est pas nécessaire pour favoriser l’ionisation de ces composés chimiques. Ce qui simplifie grandement l’analyse par spectrométrie de masse. Cette technique appelée TAMSIM pour TArgeted multiplex Mass Spectrometry IMaging a pu être validée pour l’analyse de différents marqueurs spécifiques localisés au sein des tissus pancréatiques et sur des sections tissulaires de foie humain.
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Spencer, Matthew Todd. "New approaches for the chemical and physical characterization of aerosols using a single particle mass spectrometry based technique." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3264603.
Texte intégralRésumé :
Thesis (Ph. D.)--University of California, San Diego, 2007.<br>Title from first page of PDF file (viewed August 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Angelico, Vincent James. "The development of a mass spectrometry-based technique that uses low energy ion-surface collisions to characterize surfaces." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/280148.
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Low energy (tens of eV) ion-surface collisions carried out in a tandem mass spectrometer are investigated as a tool to characterize self-assembled monolayer (SAM) films. The target films are prepared by spontaneous chemisorption of thiol-based (HS-R) compounds onto Au (111) substrates. Most of the films used as targets contain alkane or fluoro-alkane backbones, some with unique groups in the terminal position (e.g., -CD₃, -OH, -OC(O)CF₃). Pyrazine is the most frequently used probe ion, however in certain cases other small organic molecules are also used. Common interactions between the impinging ion and the target film that vary as a function of film characteristics include, but are not limited to, reactive scattering, neutralization and T → V conversion. Pyrazine ion readily reacts when colliding with hydrocarbon films at 20-eV, forming product ions that incorporate a hydrogen atom or a methyl group. Several examples of the utility of these processes to characterize film properties are presented. For hydrocarbon films, ion-surface reactions of pyrazine ion resulting in addition of a hydrogen atom or a methyl group are shown to vary with the quality, chemical composition and orientation of the target film. Experiments with isotopically labeled films show that the ion beam interacts predominantly with the end groups of the film, however interactions with underlying groups increase as the film or substrate quality decreases. The orientation difference of odd and even chain length n-alkanethiols produces a measurably different degree of hydrogen addition with the higher free energy odd chain length orientation being more reactive. The composition of mixed component films (H, D or H, F) is tracked by measuring the abundance of unique reaction products, energy transfer (translational to vibrational conversion) and charge exchange properties. When mixed films containing deuterium labeled and unlabeled n-alkanethiols are subjected to collisions of 20-eV pyrazine ion, the D-addition ion abundance increases linearly with the surface concentration of D-containing alkane chains. When mixed films containing different ratios of H and F components are the target, several processes track with the changing population of surface species. As the target films become more fluorocarbon in nature H-addition decreases, total ion current reaching the detector increases, and dissociation increases. Several properties of electron transfer from the film to the ion are examined. When the probe ion and collision energy remain consant, charge exchange is shown to be primarily governed by the work function of the film and the thickness of the adsorbed layer. Fluorocarbon films, which have a higher work function than hydrocarbon films, consistently show less charge exchange. When comparing hydrocarbon films of varying chain lengths (ranging from 15 to 18 carbons), a increase of ∼1% in total ion current measured at the detector is observed for each additional methylene in the chain.
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Tang, Jianhua. "Development of a Novel Gradient Chromatofocusing Tandem Mass Spectrometry Technique for the Determination of Cationic Compounds in Biofluids; Identification of Caspase 3 Cleavage Sites of NHE-1 by High Performance Liquid Chromatography-Mass Spectrometry." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1247344073.
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Tang, Jianhua. "Development of a novel gradient chromatofocusing tandem mass spectometry technique for the determination of cationic compounds in biofluids identification of caspace 3 cleavage sites of nhe-1 by high performance liquid chromatography- mass spectrometry /." Cleveland, Ohio : Cleveland State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1247344073.
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Thesis (Ph. D.)--Cleveland State University, 2009.<br>Abstract. Title from PDF t.p. (viewed July 29, 2009). Includes bibliographical references (p. 105). Available online via the OhioLINK ETD Center and also available in print.
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Fedrizzi, Bruno. "Identification, quantitation and origin of sulfur compounds in grape products. An approach via hyphenated mass spectrometry techniques." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3426543.
Texte intégralRésumé :
The contribute of the Analytical Chemistry in the study of complex matrices, as for instance foodstuff, is crucial. In particular the development of chromatographic methods allows to quantify important technological, microbiological and physiological markers. The ensemble of all these information furthers a deeper and higher knowledge.
This Ph.D. project was designed to define the tools and evaluate the contribution of an important class of molecule on wine aroma.
Grape products are really important in the cultural and dietary Italian traditions; moreover Italy is both the first producer and the first consumer around the world. Oenological products have been largely studied since the early ’70, even if the lack of biochemical and microbiological knowledge and the poor sensitivity of the analytical techniques did not allow to carry an deep study on sulfur compounds.
This project, planned to bid analytical and oenological chemistry, focussed its attention on the study of sulfur compounds.
Dealing with complex matrices, the first problem we had to face was the matrix effects. The overcoming of such issue or the attempts in reducing it, costs to chemical laboratory, wasting of time and money to prepare suitable internal standards.
In this thesis we proposed a statistical approach based on the variance component model able to handle matrix effects. The benefits obtained by this approach definitely outweigh both the slightly worse sensitivity and uncertainty.
Another topic discussed in the thesis is the definition of analytical methods to quantify sulfur compounds. This subject has been studied distinguishing sulfur compounds into two sub-groups:
o fermentative sulfur compounds: molecules produced by yeast metabolisms from amino acidic precursors.
o varietal sulfur compounds: molecules present in specific variety, as conjugated with cysteine and glutathione. The free forms, which are sensorially active, are released during fermentation by means of a specific enzymatic activity.
This further classification was kept in the development of the analytical methods because the two classes required different sensitivity as well as metabolomics study were separated.
Concerning fermentative sulfur compounds a HS-SPME/GC-MS method was optimised and validated. With this method a wide range of sulfur compounds were quantified. Such tool was applied to metabolomic studies, concerning the influence of variety, ageing, yeast strain and other technological practice on the level of 13 fermentative sulfur compounds.
The results obtained from the development of the analytical method permitted to highlight the potentiality of the HS-SPME technique in sampling volatile compounds in complex matrices. This approach allows an easier and safer lab conditions, avoiding the use of organic solvents. The metabolomic studies furnished important suggestion on the influence of important oenological variables on the level of important sulfur compounds.
The last topic discussed in this thesis concerns the study of varietal sulfur compounds. The lack of suitable analytical technique, sufficiently rapid and avoiding the use of mercuro-organic compounds stimulated our research in verifying the performance of headspace technique in extracting these analytes.
We optimised and validated HS-SPME and purge and trap methods and finally we defined a non-parametric robust approach to compare performances from different analytical methods.
Owing to the recent interest of the scientific research in trying to understand the formation and evolution of varietal sulfur compounds, we focussed our attention on their precursors.
The first step was the synthesis of the putative precursors, followed by the optimisation of LC-MS/MS methods to quantify them. It was possible to identify a new precursor by LC-MS/MS experiments.
Finally, by the isolation of the enzyme potentially responsible of the biosynthesis of the varietal thiols precursors, we gave a preliminary explanation of the formation of these glutathionylated precursors during grape ripening.
By this project it has been possible to study and apply the newest analytical techniques available and it has been possible to define statistical procedures to overcome the most common issues in studying complex matrices. Furthermore it was clarified the contribution of an important class of molecules, such as sullfur compounds, on oenological matrices.<br>Il contributo della Chimica Analitica nello studio delle matrici complesse, quali ad esempio quelle alimentari, è cruciale. In particolare lo sviluppo di metodi cromatografici avanzati può permettere di dosare importanti marker tecnologici, microbiologici e fisiologici e quindi consentire un approfondimento delle attuali conoscenze.
Questo lavoro è stato concepito allo scopo di definire gli strumenti per valutare il contributo di un’importante classe di molecole all’aroma dei vini.
Il vino riveste un ruolo di primaria importanza nelle tradizioni culturali ed alimentari Italiane, inoltre l’Italia risulta primo produttore e primo consumatore mondiale di vino. I prodotti enologici sono stati largamente studiati fin dai primi anni ’70, anche se l’assenza di conoscenze biochimiche e microbiologiche e la mancanza di tecniche analitiche sufficientemente sensibili non ha consentito lo studio esaustivo della classe dei composti solforati.
Questa tesi, nata da esigenze legate alla chimica analitica e alla chimica enologica, ha avuto come punto centrale lo studio dei composti solforati nei vini.
Il primo problema che si è dovuto affrontare nello studio di matrici complesse come quelle enologiche è stato quello relativo agli effetti matrice. Il superamento o il contenimento di questo problema crea ogni giorno costi in termini di tempo e di preparazione di opportuni standard interni. In questa tesi si è proposto un metodo statistico basato sul modello a componente di varianza in grado di gestire questo problema. I vantaggi sono notevoli, a fronte di una incertezza leggermente maggiore e di una sensibilità di poco peggiorata.
Altro argomento trattato è stata la definizione dei metodi analitici in grado di quantificare e quindi di studiare i composti solforati. Questa materia è stata affrontata riconoscendo una prima distinzione all’interno del gruppo degli analiti indagati:
o composti solforati fermentativi: molecole derivanti dal metabolismo del lievito a partire da precursori amminoacidici
o composti solforati varietali: molecole presenti in specifiche varietà come coniugati della cisteina e del glutatione e rilasciati durante la fermentazione alcolica ad opera di specifiche attività enzimatiche.
Questa suddivisione è stata mantenuta anche nello sviluppo dei metodi analitici, in quanto sensibilità richieste e conseguenze metabolomiche erano anch’esse distinte.
Per quanto riguarda i composti solforati fermentativi, durante il dottorato di ricerca è stato ottimizzato e validato un metodo HS-SPME/GC-MS per l’analisi di un’ampia gamma di molecole tipicamente derivanti dal metabolismo del lievito. Tale approccio è poi stato la base per studi di natura più squisitamente metabolomica in cui è stato verificato come il cultivar (i.e. la varietà), l’invecchiamento, il ceppo di lievito e altre pratiche tecnologiche potessero influenze il livello e l’evoluzione degli analiti indagati.
I risultati ottenuti per quanto attiene lo sviluppo del metodo in spettrometria di massa hanno potuto confermare con la tecnica SPME con campionamento in spazio di testa sia una tecnica di elezione per l’analisi di molecole volatili. Inoltre questo approccio consente una gestione semplice ed enviromental friendly in confronto con i più obsoleti metodi di estrazione con solvente. Gli studi metabolomici hanno consentito di trarre importanti considerazioni su aspetti molto importanti nella definizione della qualità del prodotto finale. Tali risultati consentono anche una trasferibilità nei settori della ricerca applicata e dell’enologia.
Come ultima classe di analiti indagati si sono studiati i composti solforati varietali. L’assenza di metodi sensibili e sufficientemente rapidi da essere applicati per studi su un numero significativo di campioni ha spinto la nostra attenzione alla verifica delle potenzialità delle tecniche in spazio di testa nel dosare queste molecole. Si sono ottimizzati e validati metodi HS-SPME e purge and trap ed è stata definita una procedura non parametrica robusta per il confronto delle performance delle diverse procedure.
Visto il recente interesse della ricerca scientifica operante nel settore al controllo della formazione ed evoluzione di queste molecole, abbiamo focalizzato la nostra attenzione sui precursori dei composti solforati varietali.
Il primo stadio è stata la sintesi di queste molecole, seguito poi dall’ottimizzazione di metodi LC-MS/MS per il dosaggio di queste molecole. In questo contesto è stato possibile identificare per la prima volta un nuovo potenziale precursore di aroma, tramite esperimenti LC-MS/MS.
Da ultimo, attraverso l’isolamento dell’enzima responsabile della biosintesi dei precursori d’aroma è stato possibile proporre una preliminare spiegazione alla formazione di tali molecole durante la maturazione della materia prima.
In conclusione, grazie a questa tesi di dottorato, è stato possibile approfondire ed applicare alcune delle più moderne tecniche analitiche a disposizione, è stato possibile definire procedure statistiche per superare i più comuni ostacoli nello studio di matrici complesse, ed è stato possibile chiarire il contributo di una classe importante di molecole come i composti solforati nelle matrici enologiche.
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Shewmaker, Patricia Lynn Wallace. "Enhanced biodegradation of phenolic compounds and cellular fatty acid analysis of bacteria using infrared pyrolysis/gas chromatography-mass spectrometry." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/25732.
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Sergeyeva, Viktoriya. "Développement d'une technique innovante de dosimétrie en réacteur pour la caractérisation du spectre neutronique dans le domaine d'énergie 1 keV - 1 MeV." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4069/document.
Texte intégralRésumé :
La dosimétrie neutronique en réacteur se base sur l'analyse de l'activité de dosimètres irradiés, dont certains isotopes-cibles sont l'objet de réactions d'activation ou de fission sous l'effet des neutrons. Les différentes cibles sont sensibles aux neutrons d’énergie particulière. La caractérisation des spectres neutroniques est bien établie dans les domaines thermique, epithermique (Eneutron <1 keV) et rapide (Eneutron >1 MeV), mais il y a une absence de détecteur dans le domaine énergétique entre 1 keV et 1 MeV. Le travail de thèse a abouti sur un choix final: la capture (n, γ) sur les isotopes 92Zr et 94Zr, présents dans le zirconium naturel, pour former les isotopes 93Zr (stable) et 95Zr (radioactif). L'expérience ZIMA a été réalisée sur le réacteur OSIRIS pour démontrer la faisabilité de la méthode de détection proposée. Les analyses post-irradiation sont la spectrométrie γ et la spectrométrie de masse par accélérateur. Pour analyser les résultats expérimentaux, ZIMA a été simulée avec le code neutronique TRIPOLI-4 basé sur la méthode de Monte Carlo. Les rapports Calcul/Expérience présentés dans la thèse permettent de conclure que la détection neutronique (1 keV – 1 MeV) par capture de 94Zr et 92Zr donne des résultats probants. Les mesures obtenues sont exploitables<br>Reactor dosimetry goal is to reconstruct neutron spectrum in a particular reactor location. Today we can reconstruct with precision thermal (MeV) parts of neutron spectrum by using dosimeters with an adequate sensitivity. Nowadays there is no dosimeter for the intermediate energy region 1 keV - 1 MeV. Thus, the PhD goal is to select the 1 keV - 1 MeV sensible target-isotope and nuclear reaction and verify our solution by experimental irradiation. PhD final choice is for neutron capture reaction (n, γ) on 92Zr and 94Zr. Neutron irradiation produces 2 isotopes: 93Zr and 95Zr, stable and radioactive. Irradiation experiment was performed in OSIRIS reactor. Post-irradiation analyses of irradiated Zr samples are γ spectrometry and Accelerator Mass Spectrometry. In order to simulate irradiation experiment we performed calculation with neutron transport code TRIPOLI-4, based on Monte Carlo method. The goal of ZIMA (Zirconium Irradiation for Mass and Activity analysis) experiment was to prove the feasibility of 1 keV - 1 MeV neutron detection by (n,γ) capture on 92Zr and 94Zr under boron nitride filter. C/E ratios presented in this PhD allow us to conclude that activation of 94Zr and 92Zr gives us acceptable results
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Wang, Tongwen. "Hyphenated HPLC-MS technique for analysis of compositional monosaccharides of transgenic corn glycoprotein and characterization of degradation products of diazinon, fonofos and aldicarb in various oxidation systems." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/WangTongwen_09007dcc804e975c.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--University of Missouri--Rolla, 2007.<br>Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 23, 2008) Includes bibliographical references.
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Reid, Joy Emily. "The development and geological application of a whole rock-LA-ICP-MS technique for the determination of high field strength elements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ42434.pdf.
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Wirtz, Tom. "Optimisation de l'analyse quantitative des matériaux en utilisant des agrégats MCs[indice]x[exposant]+ : application au développement de la technique Cation Mass Spectrometry (CMS)." Vandoeuvre-les-Nancy, INPL, 2002. http://www.theses.fr/2002INPL073N.
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La spectrométrie de masse d'ions secondaires (SIMS), technique extrêmement sensible pour l'analyse de surfaces, souffre de sérieux problèmes de quantificàtion causés par la forte variation de la probabilité d'ionisation des ions secondaires avec la composition de l'échantillon (" effet de matrice "). Pour y remédier, on a souvent recours à la technique MCs[indice]x[exposant]+ consistant à incorporer du Cs dans le matériau et à détecter les espèces intéressantes sous forme de clusters. Dans ce travail, nous avons tenté d'optimiser cette technique analytique avantageuse. Dans un premier temps, nous avons étudié l'influence de la concentration en Cs présente dans l'échantillon sur la sensibilité des analyses. En nous basant sur ces résultats, nous avons ensuite mis au point trois procédures expérimentales ainsi que les développements instrumentaux rendus nécessaires permettant de varier la concentration en Cs sur une gamme importante afin de pouv6ir ajuster ce paramètre crucial à sa valeur optimale pour n'importe quel type d'échantillon: la méthode de la variation de l'angle d'incidence du faisceau primaire, le mode cobombardement Cs[exposant]+ / Ga[exposant]+ et l'analyse sous bombardement Ga[exposant]+ accompagnée d'un dépôt de Cs[exposant]o à la surface de l'échantillon. L'instrument CMS (Cation Mass Spectrometer), qui est un prototype SIMS développé dans le cadre de ce travail, permet ainsi un gain en sensibilité jusqu'à un facteur 100 par rapport aux instruments SIMS classiques actuellement commercialisés grâce notamment à des conditions de travail de sortie menant à des probabilités d'ionisation de Cs[exposant]+ élevées. D'autre part, l'évaporateur de Cs installé sur là machine CMS permet pour la première fois un découplage entre la concentration en Cs incorporée dans l'échantillon et les conditions de bombardement primaires; de cette façon des analyses peuvent être réalisées avec une très bonne sensibilité en mode MCs[indice]x[exposant]+ tout en maintenant une résolution en profondeur optimale.
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Torabi-Pour, Nosrollah. "Use of immunobead-purification technique in combination with high performance liquid chromatography and mass spectrometry for isolation and identification of HLA class1 antigen bound peptides." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246922.
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Homazava, Nadzeya. "Development of a novel microflow-capillary technique online hyphenated to the inductively coupled plasma mass spectrometry for the spatial- and time-resolved investigation of local corrosion /." [S.l.] : [s.n.], 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000288126.
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Trefjord, Terese. "Investigations on the Applicability of Membrane Introduction as a Sampling Technique for Oil in Air and Water with Flame Ionization Detector (FID) and Mass Spectrometry (MS) Detection." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16363.
Texte intégralRésumé :
During a membrane introduction (MI) analysis the analytes are separated from the bulk matrix (e.g. air or water) by a semi-permeable membrane and transported to the detector by a carrier gas (usually helium). The most commonly used detector for MI-analyses is the mass spectrometer, resulting in membrane introduction mass spectrometry (MIMS). The main advantages of MIMS are short response times, high sensitivity, simplicity and elimination of sample preparation and pre-separation. Membrane introduction analyses are suitable for detection of volatile organic compounds (VOCs) and semi volatile organic compounds (SVOCs). In this project the applicability of MIMS and membrane introduction flame ionization detector (MIFID) for oil analyses were tested. Investigations of 12 different oil samples from light crude oils to heavy oils were performed by MIFID and MIMS for both water and air (only two oil samples were analyzed by water MIMS). For the oil in air analyses good response were achieved, and information about response times and half-times could be obtained within a reasonable period of time. The water analyses however showed some limitations. Even after long analysis times (up to 1200 minutes) useful information on response time were rarely obtained, and no half-times for depletion could be measured. Pre-equilibration of the oil samples seems to be necessary to enable reasonably fast MI analyses of water samples (approximately) equilibrated with the oil, allowing an estimation of oil concentrations in water. For the MIMS analyses spectral information are obtained, providing an indication of the content of the oil samples, as well as information about how the abundance of different ions change throughout the analyses due to weathering.Best results were obtained by the lighter oil samples, due to higher amounts of compounds favorable for MI-detection. Analysis times obtained were slightly shorter for MIFID analyses, as compared to MIMS analyses.
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Stoytschew, Valentin [Verfasser], Birgit [Akademischer Betreuer] Kanngießer, Birgit [Gutachter] Kanngießer, and Milko [Gutachter] Jakšić. "Megaelectron volt secondary-ion mass spectrometry – yield dependence on experimental parameters and new capabilities of the technique / Valentin Stoytschew ; Gutachter: Birgit Kanngießer, Milko Jakšić ; Betreuer: Birgit Kanngießer." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1187333298/34.
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Diegor, Wilfredo G. "Development of a high pressure digestion technique and a data acquisition/reduction procedure and their application to the ICP-MS analysis of urban sediments and soils from Cebu, Philippines." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ42368.pdf.
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Fox, ramos Alexander. "Exploration de la diversité chimique des Apocynaceae par la technique des réseaux moléculaires : de la création d’une base de données vers l’annotation in silico." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS543/document.
Texte intégralRésumé :
Les alcaloïdes indolo-monoterpéniques (AIMs) constituent une classe de molécules naturelles très étudiée en raison d’un fort potentiel pharmacologique et thérapeutique et d’une grande diversité structurale. D’autre part, les techniques de déréplication par chromatographie liquide couplée à la spectrométrie de masse tandem ont évolué récemment, avec l’émergence de l’approche par réseaux moléculaires (molecular networking). Dans ce contexte, nous avons créé une base de données de spectres de masse tandem moyennés de 172 AIMs témoins, en collaboration avec plusieurs équipes de pharmacognosie dans le monde. Cette base de données, nommée MIADB (Monoterpene Indole Alkaloids DataBase), rendue publique, peut être utilisée comme référence dans des stratégies de déréplication fondées sur l’utilisation des réseaux moléculaires. Nous avons ensuite exploité la MIADB pour l’étude phytochimique de deux Apocynaceae : Geissospermum laeve (Vell.) Miers et Alstonia balansae Guillaumin. Dans un premier temps, l’annotation par la MIADB d’un extrait alcaloïdique des écorces de G. laeve a permis l’isolement et l’élucidation structurale de 3 nouveaux AIMs, dont deux à motif butyrolactone. Par la suite, notre approche a été améliorée par l’emploi du nouvel outil d’annotation in silico MetWork, fondé sur une prédiction métabolique et la modélisation de spectres de masse tandem. C’est ainsi que l’exploration de l’espace chimique d’un extrait alcaloïdique des feuilles d’A. balansae a permis l’identification, puis l’isolement, de 5 nouveaux AIMs du type N-oxyde-sarpagane. La stéréochimie des nouveaux composés a pu être déterminée par l’exploitation de spectres prédits et expérimentaux de dichroïsme circulaire éléctronique.Ce manuscrit décrit, après une introduction consacrée notamment aux emplois du molecular networking pour le ciblage et la découverte de petites molécules naturelles puis aux interconnections biosynthétiques en série AIM, la création puis l’évolution de la MIADB, puis son utilisation dans un workflow de déréplication efficace et de ciblage de nouveaux composés dans des mélanges complexes issus d’Apocynaceae<br>Monoterpene indole alkaloids (MIAs) constitute a class of natural products that has been extensively studied due to its important pharmacological and therapeutic potentials, and to its large structural diversity. Dereplication techniques based on liquid chromatography coupled to tandem mass spectrometry have recently evolved, with the implementation of molecular networking-based approaches.In this context, we have created a spectral database that encompasses the averaged tandem mass spectra of 172 reference MIAs, in collaboration with several pharmacognosy research teams around the world. This database, named MIADB (standing for Monoterpene Indole Alkaloids DataBase), was made publicly available and can be used as a reference in the application of molecular networking as a dereplication strategy. Thereafter, we used the MIADB to carry out the phytochemical investigation of two Apocynaceae species: Geissospermum laeve (Vell.) Miers and Alstonia balansae Guillaumin. As a first application, the MIADB-based annotation of an alkaloid extract of the barks of G. laeve led to the isolation and the structural elucidation of three new MIAs, two having a butyrolactone moiety. Afterwards, this approach was improved by the application of a new tool for in silico annotation called MetWork, which is based on metabolic prediction and on the generation of predicted tandem mass spectra. Following this approach, the exploration of the chemical space of an alkaloid extract of the leaves of A. balansae allowed the anticipation and further isolation of five novel MIAs of the N-oxide-sarpagine type. The stereochemistry of all the new molecules could be determined on the basis of experimental and predicted electronic circular dichroism spectra.In the introduction of this manuscript the multiple uses of molecular networking for the identification of small natural molecules are described, as well as the biosynthetic interconnections in the MIAs group. The creation and evolution of the MIADB are then presented, followed by its utilization in efficient dereplication workflows for the targeting of new natural products within complex mixtures from Apocynaceae species
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Jeanne, dit Fouque Dany. "Analyses structurale et quantitative de composés iso-mères/bares en mélange par spectrométrie de masse tandem et multi-étapes." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0116.
Texte intégralRésumé :
Ces travaux de thèse sont consacrés au développement de nouvelles méthodologies pour l’analyse structurale et quantitative de composés isomères ou isobares en mélange par spectrométrie de masse en tandem (MS/MS) ainsi que par la technique des ions survivants (SY). À l’aide de cette technique, nous avons développé une méthode de « purification collisionnelle en phase gaz » consistant à purifier un composé par fragmentation sélective du contaminant isomère ou isobare afin de permettre l’analyse structurale et quantitative du composé d’intérêt. Nous avons montré que cette approche peut être utilisée avec succès à la fois lors de l’étape d’excitation collisionnelle (CID) d’une expérience MS/MS, mais également lors du processus d’ionisation (in-source CID). Utilisant cette approche MS/MS sur une fenêtre de 15 m/z, nous avons ainsi pu quantifier, par la méthode de l’étalon interne, un peptide trypsique malgré la présence d’un contaminant isobare. L’optimisation des performances de quantification pour la technique SY a ensuite été étudiée sur des peptides isomères topologiques en mélange et comparée à l’analyse par microscopie infrarouge. Parmi les alcalins, alcalino-terreux et métaux de transition testés, nous avons obtenu les meilleurs résultats avec les adduits au césium. Des résultats comparables à la technique infrarouge ont confirmé la pertinence de notre approche avec de surcroît de meilleures performances analytiques, en particulier en terme de rapidité d’exécution, de sensibilité, d’erreur de prédiction et de limite de quantification<br>This PhD work focused to the development of new methodologies for the structural and quantitative analysis of isomers or isobars compounds in mixture using tandem mass spectrometry (MS/MS) and the Survival Yield technique (SY).Using this technique, we have developed a method of « gas phase collisional purification » of purifying a compound by selective fragmentation of the isomeric or isobaric contaminant to allow the structural and quantitative analysis of the compound of interest. We have shown that this approach can be used successfully both during the collisional excitation step (CID) of a MS/MS experiment, but also during the ionization process (in-source CID). Using this MS/MS approach on an isolation window of 15 m/z, we were able to quantify, by the internal standard method, a tryptic peptide despite the presence of an isobaric contaminant.Optimization of quantification performances for the SY technique was then studied on topological isomeric peptides in mixture and compared with infrared microscopy analysis. Among the alkali, alkaline earth and transition metals tested, we obtained the best results with cesium adducts.Results comparable to the infrared technique confirmed the relevance of our approach with, moreover, better analytical performances, in particular in terms of speed of execution, sensitivity, prediction error and limit of quantification
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LAZZATI, ZELDA. "Speciation of particulate matter's organic fraction and its mechanis of action on human health." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7466.
Texte intégralRésumé :
Three main researches have been employed for the implementation of a protocol analysis for the characterization and quantification of the lignin fraction in the particulate matter at the concentration matrix level; the implementation of different methods of analysis of the toxic interesting pollutants, Oxy-PAHs; Nitro-PAHs and the Bisphenol A, that together with the large set of performed analysis, allowed the characterization of some PM fractions in relation with Indoor and Outdoor concentrations, human exposure and Urban – Rural – Remote sites composition. At last an in silica method was developed for the research of the proteins involved in the interaction with the pollutants of interest, optimized on Bisphenol A because of its history and recent interaction study with the Nuclear Receptors. From the involved pathway the Blood Serine Proteases are used to test the accuracy and reproducibility of obtained Autodock4.0 and Dock4.0 data. The method results useful for research on the biological mechanism of action in relation with both matrix concentrations and in vivo and in vitro studies. The data predicted will be confirmed by NMR analysis. The newest docking program gives more and more reproducible data, accurate and empirically shaped on the domain problem, at last the experimental data had to confirm or not confirm the predictions.
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Sakata, Shuhei. "Development of analytical technique for precise age determination of Quaternary zircons with the correction of the initial disequilibrium on U-Th-Pb decay series using a laser ablation-ICP-mass spectrometry." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199112.
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Lorenzetti, Raquel. "Metodo de quantificação de nucleotideos por HPLC-MS/MS e avaliação da atividade de analogos de sildenafil sobre fosfodiesterase." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/309493.
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Orientador: Gilberto de Nucci<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas<br>Made available in DSpace on 2018-08-10T06:11:56Z (GMT). No. of bitstreams: 1
Lorenzetti_Raquel_D.pdf: 2089930 bytes, checksum: f6ed8b98e678ffdfc6051c645efc8b4b (MD5)
Previous issue date: 2007<br>Resumo: No presente trabalho foi padronizado um novo método para a dosagem da atividade de fosfodiesterase in vitro, por HPLC-MS/MS. Este novo método conseguiu apresentar exatidão, precisão, sensibilidade e rapidez nas análises; monitorando os nucleotídeos (AMP, GMP, AMPc e GMPc). O desenvolvimento de novos fármacos derivados de um protótipo aponta para a obtenção de moléculas com um melhor perfil farmacocinético ou uma melhor relação estrutura-atividade. Atualmente o sildenafil é considerado o principal fármaco para o tratamento de disfunção erétil. Neste trabalho, avaliaram-se novos compostos denominados análogos de sildenafil (carbonato de lodenafil, dímero uréia e dímero uretana). Os análogos foram analisados quanto à atividade em PDE5 e agregação plaquetária humana, in vitro. Foi determinada a estabilidade destes compostos, em meio ácido e plasma humano, in vitro, além de seus possíveis metabólitos em microssomas e hepatócitos de rato in vitro, e os seus parâmetros farmacocinéticos via intravenosa e oral, em cão, in vivo. Os resultados mostraram que os análogos de sildenafil inibem a atividade de PDE e não inibem a agregação plaquetária do mesmo modo que o sildenafil in vitro, no entanto potencializam a ação do doador de NO (SNP). Os análogos de sildenafil foram estáveis em meio ácido e em plasma humano. No ensaio de metabolização, os dímeros uréia e uretana não foram metabolizados, entretanto o carbonato de lodenafil foi metabolizado principalmente em lodenafil, in vitro. O carbonato de lodenafil é rapidamente biotransformado em lodenafil, após administração v.i. e v.o. em cão. Concluiu-se que este trabalho apresenta um novo método de dosagem de PDEs e uma nova perspectiva terapêutica para a disfunção erétil, representada pelo carbonato de lodenafil, o qual inibe concentração-dependente a atividade de PDE5<br>Abstract: In the present work a new method for the dosage of the activity of phosphodiesterase was standardized in vitro, for HPLC-MS/MS. This new method obtained to present exactness, precision, sensitivity, and rapidity in the analyses; monitoring the nucleotides (AMP, GMP, cAMP and cGMP). The development of new drug derived from an archetype points with respect to the molecule attainment with one better pharmacokinetic profile or one better relation structure-activity. Currently the sildenafil is considered the main drug for the treatment of erectile dysfunction. In this work, we evaluate new analogous called composites of sildenafil (carbonate of lodenafil, dimer urea and dimer uretana). The analogous ones had been analyzed how much the activity in PDE5 and platelet aggregation human being, in vitro. The stability of these composites was determined, in human acid way and plasma, in vitro, beyond its possible metabolites in microsomes and hepatocytes of rat in vitro, and its pharmacokinetic profile after intravenous and oral, in dog, in vivo. The results had shown that the analogous of sildenafil inhibit the activity of PDE and they do not inhibit the platelet aggregation in a similar way that the sildenafil in vitro, however potencializam the action of the giver of NO (SNP). The analogous ones of sildenafil are presented steady in human acid way and plasma. In the metabolization assay, metabolization of dimer urea and dimer uretana was not observed, however the lodenafil carbonate was metabolizado mainly in lodenafil, in vitro. The lodenafil carbonate quickly is biotransformation in lodenafil, after administration v.i. and v.o. in dog. We conclude that this work presents a new method for analyze activity of PDEs and a new therapeutically perspective for the erectile dysfunction, represented for lodenafil carbonate, which inhibits concentration-dependent the activity of PDE5<br>Doutorado<br>Doutor em Farmacologia
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Stubberud, Karin. "Studies of Micellar Electrokinetic Chromatography as an Analytical Technique in Pharmaceutical Analysis - an Industrial Perspective." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2002. http://publications.uu.se/theses/91-554-5281-7/.
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Mitchell-Roberts, Alisha C. "Advanced techniques in mass spectrometry for forensic applications." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012146.
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Müller, Lukas Niklaus. "Novel computational techniques for quantitative mass spectrometry based proteomics /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17802.
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Wooding, Madelien. "Identification of micropollutants by combined chromatography and mass spectrometry techniques." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/63364.
Texte intégralRésumé :
The presence of micropollutants in South African aquatic systems has emerged as an
issue of public health concern. Micropollutants, such as endocrine disrupting
chemicals (EDCs) and antiretroviral compounds, have previously been detected in
surface water of South Africa. Micropollutants are often present in complex
environmental matrices at ultra-trace levels, complicating their detection.
In order to address shortcomings with traditional sample preparation methods, an inhouse
developed cheap, disposable polydimethylsiloxane (PDMS) sorptive sampler
was developed. The validity of the PDMS sampler was established by comparison with
a commercial stir bar sorptive sampler (SBSE). The sample introduction process into
a gas chromatograph (GC) was also simplified by using thermal desorption of a PDMS
sampler directly in the inlet liner of a GC. Direct thermal desorption was validated by
comparison to time-consuming thermal desorption using an expensive commercial
thermal desorption system (TDS).
With the aim of identifying a vast range of micropollutants in aquatic systems
comprehensive gas chromatography coupled to time-of-flight mass spectrometry
(GC×GC-TOFMS) was employed. The increased selectivity, sensitivity and larger
peak capacity of GC×GC-TOFMS allows the identification of more compounds in
complex matrices when compared to conventional GC-MS. An initial screening using
sorptive extraction techniques and GC×GC-TOFMS tentatively identified various
micropollutants, including EDCs, in surface water samples from the Rietvlei Nature
Reserve, Gauteng, South Africa.
Ultra-high pressure liquid chromatography coupled to mass spectrometry (UHPLCQTOFMS)
was used as a complementary analytical technique in conjunction with
GC×GC-TOFMS. Solid phase extraction (SPE) and large volume injection (LVI)
sample preparation steps preceded analysis by UHPLC-QTOFMS. SPE is more time
consuming and uses expensive solvents, however, adds selectivity to the sample
preparation step, by reducing possible matrix interferences which can be problematic
with LVI.
Matrix matched calibration curves were constructed to identify and quantify target
analytes in surface water samples. After validation of the analytical methods using chemometric approaches, these methods were employed to detect micropollutants in
surface water from a metropolitan area (Rietvlei Nature Reserve, Gauteng) and a rural
area (Albasini and Nandoni Dams, Limpopo Province) in South Africa. Limits of
detection (LOD) for the GC methods ranged from 1 to 98 pg/L for the PDMS loop and
1 to 190 pg/L for SBSE. The LODs for the LC methods ranged from 1.97 to 135 ng/L
for LVI and 73 pg/L to 57.3 ng/L for SPE.
The two simplified methods, the in-house developed PDMS loop with GC×GCTOFMS,
and LVI with UHPLC-QTOFMS, were used as complementary methods to
detect micropollutants, such as EDCs, in surface water. EDCs such as
pharmaceuticals, personal care products and pesticides, as well as the antiretroviral
compounds, efavirenz and nevirapine, were detected in surface water from South
Africa at concentration levels ranging from 0.16 ng/L to 227 ng/L.
As they have not been reported in literature before, experimental linear retention
indices are provided for the target analytes on the proprietary phase Rtx®-
CLPesticides II column. Lastly, the variance between different sampling sites was
investigated using principal component analysis (PCA). PCA revealed a difference in
micropollutant profile between sampling sites in the metropolitan and the rural area.<br>Dissertation (MSc)--University of Pretoria, 2017.<br>National Research Foundation (NRF)<br>Chemistry<br>MSc<br>Unrestricted
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Kapoore, Rahul Vijay. "Mass spectrometry based hyphenated techniques for microalgal and mammalian metabolomics." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/8234/.
Texte intégralRésumé :
In metabolomics, the analytical challenge is to capture the chemical diversity of the metabolome. With the current technologies only a portion of the metabolome can be analysed. As a result there is a drive to direct significant analytical efforts towards capturing the metabolome or changes in the metabolome reliably and reproducibly in biological systems. Apart from analytical challenges, the challenges also include development of appropriate methodologies to quench and extract metabolites which is a crucial parameter in sample preparation and is required to achieve an accurate representation of phenotype. This thesis focuses on addressing both the challenges in mammalian and microalgal metabolomics. Metabolomics in cancer research is gaining momentum as a tool to understand the molecular mechanism of disease progression and for the identification of specific biomarkers which may assist distinguishing between normal, benign and metastatic cancer states. In our first investigation we developed GC-MS based modified direct cell scraping, bead harvesting and LN2 methods for harvesting three adherently grown mammalian cell lines (two breast cancer cell lines MDA-MB 436, MCF7 and an endothelial cell line HMEC1) which provided rapid and reliable route with three fold improved metabolome coverage and reduced the artifacts due to metabolome leakage compared to conventional methods. Later optimized treatments were employed and the influence of various washing and quenching solvents (buffered/unbuffered) on metabolite leakage was investigated for metastatic cancer cell line MDA-MB-231. This identified one washing step with PBS followed by quenching with 60% methanol (buffered with HEPES) as the best washing and quenching solvents. Further validation and comparison of proposed workflows for metabolomic study of two metastatic TNBC cell lines (MDA-MB-231 and MDA-MB-436) resulted in recovery of 154 unique metabolites and demonstrated the robustness and reliability of these methods in pathway based analysis in cancer. In case of GC-MS based microalgal metabolomics, with comprehensive evaluation of selected quenching and extraction methods in model microalga C. reinhardtii, we have successfully demonstrated that the choice of quenching and extraction solvents have significant impact on recovery of different classes of metabolites. Our results clearly indicate that 60% methanol (buffered with HEPES) and 25 % aqueous methanol are the best suited quenching and extraction solvent respectively for untargeted metabolomic analysis of C. reinhardtii, as the highest number of metabolites belonging to various chemical classes were recovered with good intensities and reproducibilities with this miniaturized proposed method compared to other evaluated methods. Later impact of various stages involved in biodiesel production workflow from microalga on recovery of biodiesel was assessed in three microalgal species namely C. reinhardtii, D. salina and N. salina. Within which we have developed an optimized GC-FID method and miniaturized direct TE method for quantification of fatty acids, which can be applied to a small amount of biomass and saves tremendous amounts of time, solvents and reagents required, is less expensive and uses environment friendly solvents making it more suitable for sustainable large scale production. In our final investigation, we directed our efforts towards preliminary optimization and comparative analysis of HILIC and IP-RP-HPLC based separation for the retention and separation of specific metabolites classes. This identified HILIC as the best available column till date for untargeted metabolomic studies. The descriptive understanding gained from each of these investigations provides greater insight into biology of mammalian and algal systems by improving the metabolome coverage for various metabolite classes. These insights illustrating the underlying molecular pathways involved in respective biology's, will help scientific communities in identifying as-of-yet-missing reactions in the metabolic network. In addition these insights will surely help in generating many hypothesis based investigations in microalgal and cancer community.
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Nielsen, Michael Lund. "Characterization of Polypeptides by Tandem Mass Spectrometry Using Complementary Fragmentation Techniques." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7409.
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Ford, Michael James. "Modern mass spectrometric techniques applied to occupational hygiene analysis." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268553.
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Alvarez, David A. "The development of time-of-flight mass spectrometry techniques for studying the surface of Europa for astrobiology." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009m/alvarez.pdf.
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Chainet, Fabien. "Spéciation du Silicium dans les charges d'hydrotraitement." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3022/document.
Texte intégralRésumé :
Le silicium est connu pour être un poison sévère des catalyseurs d'hydrotraitement (HDT). L’objectif de la thèse a donc été de mettre en place des outils analytiques pour la spéciation du silicium afin d'identifier toutes les molécules silicées réellement formées dans les charges d'HDT. Différents outils analytiques de pointe basés sur des couplages entre la chromatographie en phase gazeuse et la spectrométrie de masse (MS et ICP/MS) ont été développés. Étant donnée la réactivité de certaines espèces silicées, des échantillons représentatifs de la dégradation du PDMS ont été produits dans des conditions de craquage thermique d'un mélange heptane/xylène. L'application à ces échantillons de la stratégie analytique, développée initialement, a démontré la présence du silicium sous différentes formes chimiques. Plus d’une centaine de molécules réparties en 10 familles comprenant un nombre d’atomes de silicium entre 1 et 1500 a été caractérisée. Ces composés silicés vont donc pouvoir être présents dans toutes les coupes pétrolières, des fractions gaz aux fractions les plus lourdes, couvrant ainsi un domaine de coupes pétrolières beaucoup plus vaste que celui des essences. Les siloxanes cycliques (Dn) ont été confirmés comme produits majoritaires de dégradation du PDMS. Les autres composés silicés, jamais caractérisés pour la plupart, sont présents à l’état de traces mais possèdent des groupements réactifs de type hydroxy, métoxy, hydropéroxy susceptibles d’interagir fortement avec le support du catalyseur (Al2O3) et donc de conduire à sa désactivation<br>Silicon is known to be a severe poison for hydrotreatment (HDT) catalysts especially in naphtha and gasoline samples. The objective of the PhD was to develop analytical methods for silicon speciation in order to characterize silicon molecules formed during refining steps which potentially affects HDT catalysts. For the analytical strategy, different high-technology analytical tools based on gas chromatography coupled to mass spectrometry (MS and ICP/MS) were developed. Due to the high reactivities of several silicon species, representative samples of PDMS degradation were produced under thermal cracking of a mixture of heptane/xylene (500°C) using a pilot plant. The previously developed analytical strategy was applied to these samples and demonstrated the occurrence of silicon under a wide array of chemical forms. More than a hundred of silicon species belonging to 10 chemical families with a number of silicon atoms ranging from 1 to 1,500 were characterized. These silicon compounds could be present in all petroleum cuts, from the gas fractions to the heavier fractions. Therefore, the investigated range of boiling points was inevitably more important than for naptha and gasoline cuts. Cyclic siloxanes (Dn) were confirmed as the major PDMS degradation products. The other silicon compounds, almost never characterized before, were recovered at trace levels but consisted of reactive groups such as hydroxy, methoxy and hydroperoxy. These silicon species were able to strongly react with the catalytic support (Al2O3) and led to its deactivation
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Goolsby, Brian James. "Techniques for improved mass spectrometric analysis of biologically relevant molecules produced by MALDI and ESI in the quadrupole ion trap /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004273.
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Ketola, Raimo. "Method development in membrane inlet mass spectrometry : air analysis and desorption techniques /." Espoo : Technical Research Centre of Finland, 1998. http://www.vtt.fi/inf/pdf/publications/1998/P364.pdf.
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Corbin, Inge. "Analysis of Improvised Explosives by Electrospray Ionization - Mass Spectrometry and Microfluidic Techniques." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2551.
Texte intégralRésumé :
Improvised explosives may be based on smokeless gunpowder, fertilizers, or inorganic oxidizers such as nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-) salts.
Identification is a priority for the military and law enforcement but due to their varying physical properties and complexity, identification can be challenging. Consequently, three methods have been developed to aid in presumptive and confirmatory detection.
Smokeless powder contains plasticizers, stabilizers, dyes, opacifiers, flash suppressants, and other compounds. Identification of these additives can narrow down or identify the brands of smokeless powder used in a device. Fourteen organic smokeless powder components were identified by capillary electrochromatography (CEC) using a hexyl acrylate monolithic stationary phase coupled to UV detection and time-of-flight mass spectrometry (TOF-MS). The CEC-UV method efficiently detects all 14 organic components, while TOF-MS provides sensitivity and selectivity. A mixed smokeless powder component standard was analyzed and the composition of the additive package in commercial smokeless powders determined. Detection limits ranged from 1.0 – 3.2 μg/ml and analysis time was 18 minutes.
Second, a procedure for the detection of urea nitrate (UN) and ammonium nitrate (AN) by infusion electrospray ionization - mass spectrometry (ESI-MS/MS) was developed. Solubility tests were performed to find a solvent for both UN and AN that did not cause UN to dissociate. Two adduct ions were detected for each explosive: for AN, m/z 178 [2AN+NH4]+ and m/z 258 [3AN+NH4]+ ions, and for UN m/z 185 [UN+NO3]− and m/z 248 [UN+HNO3+NO3]−. Specificity of the analysis was examined by mixing the explosives with various salts and interferents. Gas-phase adduct ions were useful in distinguishing between ion pairs and mixed salts.
Finally, a paper microfluidic device (PMD) was developed as a presumptive test using colorimetric reagents for the detection of ions associated with improvised explosives. The device was configured to test for nitrate (NO3-), nitrite (NO2-), chlorate (ClO3-), perchlorate (ClO4-), and urea nitrate (UN). Proof of concept was performed using extracts of soil containing inorganic oxidizers.
The development of these analytical methods allows the detection of smokeless powder components, fertilizers, and oxidizers and expands the suite of analytical methods available for the analysis of improvised explosives.
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Rutter, Abigail Victoria. "Improving the management of lung cancer using mass spectrometry and spectroscopy techniques." Thesis, Keele University, 2016. http://eprints.keele.ac.uk/2388/.
Texte intégralRésumé :
Lung cancer is a worldwide health problem associated with poor prognosis. The survival at 5 years remains between 5% and 15% in spite of the development of new drugs. One of the main reasons for this is the disease being diagnosed in late stages when curative treatments might not be available. Therefore, some of the most important factors within improving prognosis are both refining diagnostic techniques for early detection, and better assessing tumour response to treatment. Here lies a need for novel diagnostic tools for lung cancer. Spectroscopic and spectrometric analysis of the molecular underpinnings of the disease may provide biochemical signatures for use in diagnostics. Selected Ion Flow Tube – Mass Spectrometry (SIFT-MS) and Fourier Transform Infrared (FTIR) Spectroscopy may provide the gold standard of diagnostic assessment that is needed. Given both techniques previous contributions and technological advancements, their clinical requirements are being increasingly met. This is leading towards the opportunity for the study of lung cancer to benefit from the rapid, non-destructive and sensitive qualities they have to offer. In this thesis, both techniques have been used with the aim of improving the diagnosis and management of lung cancer.
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Jewett, Brent Nicholas. "Analysis of anionic and nonionic surfactants by liquid introduction mass spectrometry techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24859.pdf.
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Fuller, Daniel Raymond. "Probing Structure and Stability of Biomolecules with Ion Mobility-mass Spectrometry Techniques." Thesis, Indiana University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10844168.
Texte intégralRésumé :
<p> Ion mobility spectrometry – mass spectrometry (IMS-MS) based techniques have significantly advanced the study of both the structure and stability of biomolecules. Solution phase, biologically relevant peptide/protein conformations have been analyzed utilizing electrospray ionization (ESI) coupled to IMS-MS. The work presented here focuses on the development and application of IMS-MS for the study of the structure and stability of peptides and proteins. Structures originating in solution can be related to the biological activity of the system. Specifically, we examine the influence of both proline isomerization and metal binding on the conformational preferences and stabilities of a series of peptides and proteins. </p><p> The first study uses IMS-MS to examine the conformation specific binding of Zn<sup>2+</sup> to oxytocin (OT). When bound to Zn, OT has an increased affinity for its receptor. We observe two conformations which are the result of the <i>cis-trans</i> orientation of the Cys<sup>6</sup>-Pro<sup> 7</sup> bond. We find that Zn<sup>2+</sup> binds preferentially to the trans configuration demonstrating that <i>cis-trans</i> isomerization regulates the binding of Zn<sup>2+</sup> to OT, therefore linking the orientation of the Cys<sup>6</sup>-Pro<sup>7</sup> bond to the biological activity of the molecule. In another series of experiments, we look at the role of penultimate proline on the stability of bradykinin along with a library of penultimate proline containing peptides. For BK, we find that the Pro<sup>2</sup>-Pro<sup>3</sup> bond, which is enzymatically resistant, is cleaved with 100% specificity when incubated at high temperatures. With IMS-MS, we are able to monitor the mass spectral and conformational changes as a function of time, and find that <i>cis-trans</i> isomerization of a single bond regulates the rate of dissociation, and hence the stability of the system. Finally, we look at the thermal stability of the insulin-zinc hexamer complex. Utilizing temperature-controlled nano-ESI IMS-MS, we capture the dissociation of the insulin hexamer and the unfolding of insulin dimer and monomer, occurring simultaneously with increasing solution temperature. We show the ability of IMS-MS to observe the conformation specific melting temperatures of a protein complex, demonstrating a fast and sensitive assay for stability characterization.</p><p>
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Avula, Satya Girish Chandra. "Lipidomics of Algae and Human Plasma by Chromatography and Mass Spectrometry Techniques." Cleveland State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=csu1470822409.
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Leader, Ian Philip. "The study of personal care products using mass spectrometric techniques." Thesis, Royal Holloway, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420376.
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Nagaraj, Nagarjuna [Verfasser], and Matthias [Akademischer Betreuer] Mann. "Developing mass spectrometry towards applications in clinical proteomics : improved sample preparation techniques and mass spectrometric methods for unbiased identification of proteome from clinical samples / Nagarjuna Nagaraj. Betreuer: Matthias Mann." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2010. http://d-nb.info/1015203140/34.
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Spikmans, Valerie. "Sensitivity and selectivity enhancement by hyphenation of nanosample separation techniques to mass spectrometry." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271038.
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Benesch, Justin Luer Paul. "Novel mass spectrometry techniques for the study of the small heat shock proteins." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614981.
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Pacholarz, Kamila Jolanta. "Investigation of large protein and multimeric protein complex structures with mass spectrometry techniques." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/21084.
Texte intégralRésumé :
The biophysical properties, biological activity and function of macromolecular systems are highly dependent on their structure. Structure-activity relationships of proteins and their binding partners are critical for drug discovery, biochemical and medical research. While the gas-phase environment might present as an unusual venue from which to explore protein structure, for over the past two decades, nano-electrospray ionization (nESI) coupled to mass spectrometry (MS) has been recognized as having great potential for analysis of protein structure and protein non-covalent complexes. In conjunction with related technique of ion mobility (IM), mass spectrometry (IM-MS) provides insights into protein native-like conformations and any structural changes in may undergo upon ligand binding or alternations induced via physical parameters such as temperature, pressure or solution conditions. As most proteins tend to exist as multiple domains; from the distribution of oligomeric states in the Protein Data Base (PDB) 86% of proteins exist as oligomers; the work presented in this thesis focuses on application of MS techniques to probe the tertiary and quaternary structure of various large and multimeric protein complexes, their dynamics and/or conformational changes. Wherever relevant, the gas-phase studies reported here are complemented by other techniques, such as hydrogen deuterium exchange MS (HDX), molecular modelling (MD) and analytical ultracentrifugation (AUC). Firstly, the dynamics of intact monoclonal antibodies (mAbs) and their fragments are explored with IM-MS. Variations observed in conformational landscapes occupied by two mAb isotypes are rationalized by differences in disulfide linkages and non-covalent interactions between the antibody peptide chains. Moreover, mAb intrinsic flexibility is compared to other multimeric protein complexes in terms of collision cross section distribution span. Secondly, variable temperature MS (VT-MS) and variable temperature IM-MS (IM-MS) are used to probe unfolding and dissociation of four standard multimeric protein complexes (TTR, avidin, conA and SAP) as a function of the of analysis environment temperature. VT-MS is found to allow for decoupling of their melting temperature (Tm) from the protein complex dissociation temperature (TGPD). Whereas, VT-IM-MS is used to investigate structural changes of these protein complexes at elevated temperatures and provide insights into the thermally induced dissociation (TID) mechanism, as well as strength of the non-covalent interactions between subunits. Thirdly, VT-(IM)-MS methodology is applied to study behaviour of three mAbs: IgG1, IgG4 and an engineered IgG4 of increased thermal stability. Such analysis shows to be promising for comparative thermal stability studies for proteins of therapeutic interest. Lastly, the structure of ATP-phosphoribosyltransferase (MtATPPRT), an enzyme catalysing the first step of the biosynthesis of L-histidine in Mycobacterium tuberculosis, is explored. Conformational changes occurring upon feedback allosteric inhibition by L-histidine are probed with MS, IM-MS, HDX-MS and AUC. Reported results serve as the basis for IM-MS/HDX-MS based screening method to be used for screening of a library of novel and promising anti-tuberculosis agents.
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McBride, Ethan. "Utilizing Rapid Mass Spectrometry Techniques to Profile Illicit Drugs from Start to Finish." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248455/.
Texte intégralRésumé :
The increasingly complex world of illicit chemistry has created a need for rapid, selective means of determining the threat posed by new drugs as they are encountered by law enforcement personnel. To streamline this process, the entirety of the problem, from the production of illicit drugs all the way to the final analysis have been investigated. A series of N-alkylated phenethylamine analogues were synthesized in a shotgun method and subjected to direct-infusion analysis. A range of products were detected without the need for time-consuming purification steps, which was extended to novel pharmacological and receptor-binding assays where mass spectrometry is used as a detector. This direct-infusion technique was also applied to studies of methamphetamine and fentanyl production to preemptively determine improvements to common reaction conditions and explore the origins of common impurities. The ability to utilize these rapid techniques directly from the fume hood has also been critically reviewed to highlight gaps in current research and opportunities for improvement. When combined, these studies seek to provide a means for rapid, simplified analysis of illicit drugs to improve the quality of data and dramatically increase throughput.
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Shomo, Ronald Edward II. "Soft ionization techniques for Fourier transform ion cyclotron resonance and quadrupole mass spectrometry /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487597424138083.
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Pearce, Evan William. "The development of techniques to expand the capabilities of electrospray ionization-mass spectrometry /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Feely, Stephen Joseph. "Multidimensional chromatographic/mass spectrometric techniques for the trace determination of steroids." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388946.
Texte intégralRésumé :
Research has centred on multidimensional chromatographic techniques which utilise the high specificity of immunoaffinity chromatography for extraction of analytes from complex biological matrices. On-line immunoaffinity chromatography-high performance liquid chromatography-mass spectrometry (IAC-HPLC-MS) systems (IAC and HPLC coupled via a loop interface) were developed for the confirmatory analysis of the corticosteroids dexamethasone and flumethasone with MS detection. Utilising an atmospheric pressure chemical ionisation (APCI) LC-MS interface, dexamethasone was confirmed in both spiked and post administration equine urine samples, with a detection limit of 0.1 ug 1-l. Detection by quadrupole ion trap mass spectrometry (ITMS) using a particle beam (PB) interface was performed for dexamethasone and flumethasone in post administration equine urine samples with high precision (6.9-7.4 %) with limits of detection in the range 3-4 ug 1-l. Studies were also conducted in this work into the antibody crossreactivity and non-specific binding of corticosteroids on a HEMA bound anti-dexamethasone lAC column. On-line IAC-HPLC and IAC-HPLC-GC have been developed and assessed for the determination of testosterone in equine urine. A novel approach to interfacing lAC with HPLC being achieved using a porous graphitic carbon (PGC) column. The IAC-HPLC system developed was used for sample pre-treatment for combustion isotope ratio mass spectrometry analysis. The IAC-HPLC and IAC-HPLC-GC systems finally being coupled with mass spectrometry to enable confirmation of the endogenous steroid at 0.5 ug 1-l and 1 ug 1-l respectively in stripped equine urine.
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Cole, Harriet Lucy. "Elucidating the early events of protein aggregation using biophysical techniques." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7974.
Texte intégralRésumé :
Proteins and peptides can convert from their native form into insoluble highly ordered fibrillar aggregates, known as amyloid fibrils. The process of fibrillogenesis is implicated in the pathogenic mechanisms of many diseases and, although mature fibrils are well characterised by a plethora of biophysical techniques, the initiation and early steps remain, to date, ambiguous. Mass spectrometry can provide invaluable insights into these early events as it can identify the low populated and transient oligomeric species present in the lag phase by their mass to charge ratio. Recent evidence has shown that oligomers formed early in the aggregation process are cytotoxic and may additionally be central to the progression of diseases associated with amyloid fibril presence. The hybrid technique of ion mobility mass spectrometry can be employed to provide conformational details of monomeric and multimeric species present and elucidate the presence of oligomers which possess coincident mass to charge ratios. Molecular modelling, in conjunction with experimental results, can suggest probable monomeric and oligomeric structural arrangements. In this thesis three aggregating systems are investigated: amyloidogenic transthyretin fragment (105-115), insulin and two Aβ peptides. Initially amyloidogenic endecapeptide transthyretin (105-115) is studied as it has been widely utilised as a model system for investigating amyloid formation due to its small size. Secondly insulin, a key hormone in metabolic processes, is investigated as extensive research has been carried out into its aggregation into amyloid fibrils. The formation of insulin amyloid fibrils rarely occurs in vivo; however localised amyloidosis at the site of injection and the aggregation of pharmaceutical insulin stocks present problems. Thirdly the aggregation of A β peptides Aβ (1-40) and Aβ (1-42) and their interactions with an aggregation inhibitor, RI-OR2, are characterised. A (1-42), although less commonly produced in vivo, is more cytotoxic and has a faster aggregation mechanism than Aβ (1-40). Both Aβ peptides are implicated in the aetiology of Alzheimer’s disease whilst RI-OR2 has been reported to prevent the production of high molecular weight oligomers, with particular suppression of Aβ (1-42) aggregation.