Skin pigmentation is an important issue in most cultures. Until recently we have not understood the most important elements of pigmentation regarding detailed chemical structure. The synthesis of melanin is very complex, and although core enzymes, other important proteins, and parts of the melanin structure have been identified much information in this context awaits disclosure. The function of the melanocyte and the deposition of melanin pigments into the keratinocytes are very important in the protection against UV light. Melanin pigments consist of high-molecular structures often described as brown to black eumelanin and yellow to red pheomelanin. Eumelanin is photoprotective, whereas pheomelanin is believed to be carcinogenic after UV radiation. There is strong evidence that people of fair complexion with freckles who tan poorly are at higher risk of developing melanoma. These people have a higher pheomelanin to eumelanin ratio in their skin. Melanoma, one of the most widely spread cancers, is derived from melanocytes. There is accumulating evidence that pigment constitution is highly involved in the development of melanoma. We found that patients with advanced melanoma secrete substantial amounts of pigment structures into the urine, in particular those with diffuse melanosis. In subsequently performed experiments we purified these pigments and subjected the product to chemical degradation by either hydrogen peroxide oxidation or hydriodic hydrolysis. Several new chromatographic methods were developed for the structural analysis of these products. Structural analysis of new chromatographic peaks was performed. In conclusion, complex pheomelanin structures as well as low molecular weight pigments and free benzothiazoles have been identified in the urine of patients with melanoma and diffuse melanosis. The present thesis provides new insight into melanogenesis and melanoma progression. This opens the doorway to further approaches to the investigation of melanins and can help to understand fundamental problems about the structure and biosynthesis of natural melanins.

Hydrophilic interaction chromatography is well known as a powerful technique separation of polar and ionizable compound nowadays. However the retention mechanism of the technique is still under debate. Understanding retention mechanism would facilitate the method development using the technique and its future improvement. This was inspiring and became the goal of this thesis. This work involves the characterization of the water enriched layer regarding to water and buffer salt accumulation. Twelve HILIC stationary phase with a diverse surface chemistry regarding to function groups and modification type were studied. Effect of water and salt on regarding to the retention mechanism was investigated by correlating the adsorption data to the retention of selected solutes This also involved the characterization of interactions involve in the separation of 21 HILIC columns. Interactions was probe by retention ratio of pair solutes which are characteristic for each specific interaction. The data was evaluate using principle component analysis – a multivariable data analysis method. The model was comprehensive and its outcomes were confirmed by the studies on adsorptions of water and salts.

No description available.

The aim of this master thesis project was to develop methods for sample preparation and analysis by LC-MS suitable for global metabolomics of human plasma samples. In this thesis six different methods was tested, based on precipitation, solid phase extraction (SPE), and ultrafiltration. The methods differ in their mechanisms of action, but the end goal is the same, to remove the proteins and other high molecular weight compounds from the samples and to retain as many metabolites as possible in a reproducible manner. The LC-MS analysis were performed on a C18 and a HILIC type column using electrospray ionization (ESI) with both positive and negative ionization to cover as much of the metabolome as possible. The MarkerLynx software was then used to extract features from the chromatograms. The coefficient of variation (CV) was calculated and the features with CV > 30 % were removed. The features were then used to compare the methods with each other in order to see whether any of the methods yielded the same capture of features. The largest amount of features was detected for precipitation with MeOH when using a C18 type column. For HILIC type columns precipitation with MeOH with a small addition of H3PO4 resulted in most unique features detected. The ionization mode was found to be less important, compared whit the choice of column, but more features was detected using positive mode than negative mode.

Made available in DSpace on 2016-06-02T20:37:48Z (GMT). No. of bitstreams: 1 5597.pdf: 3304343 bytes, checksum: 0c450aff960d822ff2236d773f596f7f (MD5) Previous issue date: 2013-10-17 / This work describes for the first time an isocratic method in a single analytical run to quantify deacetyl iodixanol (iodixanol related compound C), iopentol (iodixanol related compound D) and cyclized iodixanol (iodixanol related compound E), as impurities in iodixanol. Iodixanol is a drug substance, dimeric, nonionic, water-soluble, used as a radiographic contrast medium, which is administered by intravascular injection. The impurities A and B were not evaluated in this work, since they are not commercially available as standards. The method was also validated for the quantitative assay, since there is no chromatographic method described in the current USP compendium for the assay. The impurities can be formed during the synthesis process of iodixanol, and it is important to quantify them due to their related toxicity. In this work, the reverse and hydrophilic interaction (HILIC) modes of elution were evaluated. The hydrophilic elution mode was selected due to good efficiency and selectivity. In both modes of elution, columns having the technology fused-core were used, since they demonstrate high efficiency due to their better mass transfer in comparison to conventional HPLC columns. The chromatographic separation was carried out on a kinetex® HILIC column (150 x 4.6 mm; 2.6 μm) at 20 °C using acetonitrile-formic acid (pH 3.2; 1.0 mmol L-1) (92:08, v/v) at a flow rate of 0.8 mL/min. The compounds were monitored at 243 nm and the total time of analysis was 45 min. The method was validated in accordance with the current ICH guidelines for determination of impurities which include selectivity, linearity, accuracy, precision, limits of quantification and detection and robustness. The limits of quantification (LOQ) were 0.479; 0.0606 and 0.133 μg/mL for the impurities C, D and E, respectively. Furthermore, the validated methods were tested in iodixanol samples. The test results of the analyses of impurities and assay in those samples are presented and discussed accordingly. / Este trabalho descreve pela primeira vez um método isocrático em uma única corrida analítica para quantificação das impurezas deacetil iodixanol (iodixanol composto relacionado C), iopentol (iodixanol composto relacionado D) e iodixanol ciclizado (iodixanol composto relacionado E) na matéria-prima iodixanol. Iodixanol é um composto dímerico, não-iônico, solúvel em água, usado para contraste para raios X com administração intravascular. As impurezas A e B não foram avaliadas neste trabalho, uma vez que não existem padrões disponíveis comercialmente dos mesmos. O método também foi validado para a quantificação de teor, uma vez que não existe método cromatográfico descrito no compêndio atual da USP para o teor. Estas impurezas podem ser formadas durante a síntese do iodixanol, e a importância da quantificação destas está relacionada à toxicidade. Neste trabalho foram avaliados os modos de eluição reverso e por interação hidrofílica (HILIC). O modo HILIC foi o selecionado, pois ofereceu boa eficiência cromatográfica com boa seletividade. Em ambos os modos, o uso de colunas de tecnologia fused-core foi empregado, por apresentar alta eficiência devido à sua melhor transferência de massa em comparação com as colunas analíticas convencionais. A separação cromatográfica foi conduzida utilizando-se a coluna analítica kinetex® HILIC (150 x 4,6 mm; 2,6 μm) a 20 °C e acetonitrila ácido fórmico (pH 3,2; 1,0 mmol L-1) (92:08, v/v) com 0,8 mL/min de vazão. Os compostos foram monitorados a 243 nm e o tempo total de análise foi de 45 min. Os métodos foram validados em acordo com as recomendações atuais do ICH para a determinação de impurezas, nas quais incluem seletividade, linearidade, exatidão, precisão, limites de quantificação e de detecção, e robustez. Os limites de quantificação foram de 0,479; 0,0606 e 0,133 μg/mL para as impurezas C, D e E, respectivamente. Deste modo, os métodos validados foram aplicados em amostras de iodixanol. Os resultados para a análise de impurezas e teor nestas amostras são, portanto, apresentados e discutidos.

Ces travaux de thèse concernent les développements d'une méthode de séparation chromatographique couplée simultanément à l'ESI-MS et l'ICP-MS afin de réaliser l'analyse de spéciation exhaustive des lanthanides en phase aqueuse représentative des phases de désextraction des procédés de traitement du combustible usé. Cette méthode analytique permet de séparer, caractériser et quantifier des complexes de lanthanides à ligands polyaminocarboxyliques comme le DTPA et l'EDTA, utilisés comme agents complexants dans ces procédés. La méthode de séparation par chromatographie HILIC des complexes de lanthanides a été mise au point avec la phase stationnaire à fonctions amide. Un criblage d'une large gamme de compositions de phase mobile a permis de déterminer que le mécanisme d'adsorption est prédominant lors l'élution des complexes de lanthanides et d'obtenir des conditions de séparation optimisées. Des conditions d'analyse plus rapides obtenues avec une colonne à fonctions amide de granulométrie sub-2 µm et de longueur plus faible ont permis de réduire le temps d'analyse d'un facteur 2,5 et la consommation de solvant de 25 %. La caractérisation structurale et isotopique par HILIC ESI-MS a été réalisée ainsi que la mise au point d'une méthode d'étalonnage externe. Les performances analytiques de la méthode de quantification ont été déterminées. Enfin, le développement d'un système de couplage de l'HILIC à l'ESI-MS et l'ICP-MS a été réalisé. Une méthode de quantification simultanée par ESI-MS et par ICP-MS a permis de déterminer la distribution quantitative des espèces en solution ainsi que les performances analytiques associées. / This work focuses on the development of a chromatographic separation method coupled to both ESI-MS and ICP-MS in order to achieve the comprehensive speciation analysis of lanthanides in aqueous phase representative of back-extraction phases of advanced spent nuclear fuel treatment processes. This analytical method allowed the separation, the characterization and the quantitation of lanthanides complexes holding polyaminocarboxylic ligands, such as DTPA and ETDA, used as complexing agents in these processes. A HILIC separation method of lanthanides complexes has been developed with an amide bonded stationary phase. A screening of a wide range of mobile phase compositions demonstrated that the adsorption mechanism was predominant. This screening allowed also obtaining optimized separation conditions. Faster analysis conditions with shorter amide column packed with sub 2 µm particles reduced analysis time by 2.5 and 25% solvent consumption. Isotopic and structural characterization by HILIC ESI-MS was performed as well as the development of external calibration quantitation method. Analytical performances of quantitation method were determined. Finally, the development of the HILIC coupling to ESI-MS and ICP-MS was achieved. A simultaneous quantitation method by ESI-MS and ICP-MS was performed to determine the species quantitative distribution in solution. Analytical performances of quantitation method were also determined.

Gd-Kontrastmittel werden in der Medizin für die Magnetresonanztomographie (MRT) benötigt, um einen besseren Bildkontrast zu erzielen. Nach der Anwendung gelangen diese Arzneimittel über das Abwasser in die Klärwerke und von dort in die jeweiligen anliegenden Oberflächengewässer. Somit wird es notwendig, den Verbleib der Gd-MRT-Kontrastmittel in der Umwelt zu verfolgen und aufzuklären. In dieser Arbeit werden für die Analyse von Umweltproben Methoden zur Speziesanalytik von Gd-Kontrastmitteln entwickelt und optimiert. Hierbei wird u.a. die Zwitterionische Hydrophile Interaktionschromatographie (HILIC) verwendet, die mit einer Induktiv- gekoppelten Plasma – Massenspektrometrie (ICP-MS) gekoppelt ist. / Gd based contrast agents are used for medical magnetic resonance imaging (MRI) to enhance the contrast of the image. After application and excretion, the drugs pass through the wastewater treatment plant (WWTP) and make their way into the surrounding surface water bodies. This makes it necessary to monitor the fate of the Gd based contrast agents in the environment. In this work, methods for speciation analysis of Gd based contrast agents in environmental samples were developed and optimised. For this purpose i.a. zwitterionic hydrophilic interaction chromatography (HILIC) is used, which is hyphenated with inductively coupled plasma mass spectrometry (ICP-MS).

This thesis focuses on the development of new stationary phases for use in hydrophilic interaction liquid chromatography using TRIS-based and phosphorylcholine typed monomers and porous silica particles as starting substrates. In this thesis, several ways of polymerizing highly hydrophilic mono­mers onto pore surfaces of silica supports are described, based on several “grafting from” schemes. “Controlled/living” radical polymerizations including atom transfer radical polymerization (ATRP) and iniferter-mediated polymerization in conjunction with conventional free radical polymerization are demonstrated to be successful tools for grafting different hydrophilic monomers (polyhydroxyl and phosphorylcholine [meth]acrylamide/acrylates) onto the silica surfaces. Reaction solvents are proven to play an essential role to achieve efficient graft polymerization of activated silica surfaces with these amphiphilic vinylic monomers, which is difficult because of their restricted access to the activated surface in solvents that can be used because of solubility constraints. Two tentacle TRIS-based polymer grafted silica, namely TRIS-WAX – TRIS functionality bonded to silica via a C–N–C imine bond and TRIS-Amide – TRIS bonded to silica via an amide bond, prove to be useful as stationary phases for hydrophilic interaction chromatography (HILIC).The TRIS-WAX exhibits a mixed mode hydrophilic partitioning and weak anion exchange (HILIC/WAX) retention mechanism while retention by hydrophilic partitioning is the dominant mechanism on the neutral TRIS-Amide phase which lacks weak anion exchange (WAX) properties. Interestingly, both these phases have selectivities that are radically different from most commercial HILIC stationary phases. Finally, a method is demonstrated for synthesizing a stratified (graft-copolymerized) silica material based on N,N′-methylenebisacrylamide and 2-methacryloyloxyethyl phosphorylcholine (MPC) using a “controlled/living” photoiniferter-mediated polymerization from the N,N-diethyldithiocarbamate iniferter moiety immobilized silica surfaces. This polymerization method proves to be successful for graft-blockcopolymerization of different highly hydrophilic monomers onto the activated surfaces of porous silica. In this way, silica surfaces are grafted with a cross-linked amide-based hydrogel, on top of which a tentacle zwitterionic phosphorylcholine-typed layer is synthesized. The resulted material proves to be useful for HILIC separations and possesses different selectivity for the tested organic acids compared to that of commercial ZIC-cHILIC stationary phase.

Ce manuscrit expose le développement de méthodes bidimensionnelles en ligne pour l'analyse de composés chargés en couplage avec la spectrométrie de masse. Le contexte de l'étude et les principes théoriques de la chromatographie en phase liquide unidimensionnelle et bidimensionnelle sont tout d'abord présentés. Les conditions expérimentales telles que l'instrumentation, les colonnes, les composés étudiés sont détaillés. Des études unidimensionnelles ont été effectuées afin de connaître le comportement cinétique des petites molécules ionisables et des peptides selon la phase mobile et la température. L'orthogonalité de systèmes chromatographiques et les capacités de pics générées ont ensuite été étudiés afin de connaître les conditions expérimentales les plus intéressantes pour l'analyse des composés chargés. Les comparaisons de systèmes ont été effectuées avec de nouveaux descripteurs d'orthogonalité et de capacité de pic effective qui ont été établit. Les systèmes bidimensionnels LCxLC ont ensuite été mis en place. L'utilité d'un split pour réduire le volume injecté en seconde dimension est envisagée. Des limites en termes de volume injecté dans la seconde dimension ont été définies en RPLC et en HILIC. Des mélanges de peptides ont été séparés par RPLCxRPLC(-MS), RPLCxHILIC(-MS) et HILICxRPLC. Le couplage avec la spectrométrie de masse est optimisé. L'intérêt des séparations bidimensionnelles est mis en évidence par rapport à des séparations LC-MS classiques

In this thesis, an analytical platform was designed and applied to various in vitro bacterial and eukaryotic cell cultures. An extraction and an analytical protocol were developed for comprehensive and simultaneous analysis of both lipid and polar metabolites for intra- and extracellular metabolomics using HILIC-LC-TOF-MS. This analytical platform was applied to four diverse research questions such as the effect of oxygen environment on growth, the interplay between gene expression and metabolism, metabolic changes that occur with age, and PAH toxicity. Specifically: (i) the effect of oxygen on the growth, physiology and metabolism of the Gram positive Streptococcus intermedius were investigated by comprehensive intra- and extracellular metabolomes and transcriptome. (ii) Metabolic insights into the role of the multipartite genome of the Gram negative bacteria Sinorhizobium meliloti and its metabolic preferences in a nutritionally complex environment. (iii) Age-associated metabolic dysregulation in murine bone marrow-derived macrophages during bacterial lipopolysaccharide-induced inflammation. (iv) Comprehensive intracellular metabolomic profiles of Sinorhizobium meliloti to sub-lethal exposure of individual or mixtures of polycyclic aromatic hydrocarbon revealed additive and dose-dependent effects. This thesis has demonstrated the versatility of the designed analytical platform and its use for diverse research in cell biology. / Thesis / Doctor of Philosophy (PhD)