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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Avaliação da aplicação de potencial elétrico em extração em fase sólida na determinação de sulfonamidas e fluoroquinolonas em ovos / Evaluation of the application of electric potential in solid phase extraction for the determination of sulfonamides and fluoroquinolones in eggs

Ribeiro, Cyntia Cabral, 1977- 26 August 2018 (has links)
Orientadores: Felix Guillermo Reyes Reyes, Susanne Rath / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-26T09:04:09Z (GMT). No. of bitstreams: 1 Ribeiro_CyntiaCabral_D.pdf: 2553496 bytes, checksum: c2200295b5cb6899de7fa33b75518899 (MD5) Previous issue date: 2014 / Resumo: Sulfonamidas e fluoroquinolonas são fármacos veterinários amplamente utilizados na produção aviária para prevenção e tratamento de doenças e, quando não respeitadas as boas práticas veterinárias, resíduos desses fármacos podem ser encontrados acima dos limites máximos de resíduos podendo representar risco à saúde dos consumidores. Sendo o ovo uma matriz biológica complexa, quantidades significativas de interferentes podem prejudicar a determinação dos analitos de interesse por cromatografia líquida, especialmente resíduos de fármacos veterinários, que se encontram em níveis na ordem de ng g-1. Entre as diversas técnicas de preparo de amostras capazes de eliminar interferentes e concentrar o analito de interesse, a extração em fase sólida (SPE) se destaca pela sua eficiência, robustez, seletividade e baixo consumo de solventes. Ainda assim, devido à complexidade da matriz e a baixa concentração dos analitos, o estabelecimento de métodos de preparo de amostras com seletividade na remoção de interferentes e eficiência de extração adequados ainda é um desafio na análise de resíduos. Desta forma, afim de se contornar as limitações da SPE convencional, esta tese teve como objetivo avaliar a aplicação de potencial elétrico em SPE (E-SPE) para a determinação de resíduos de sulfonamidas e fluoroquinolonas em ovos por cromatografia líquida de alta (HPLC) e ultra eficiência (UHPLC) associada à detectores por arranjo de fotodiodos (DAD), fluorescência (FLD) ou espectrômetro de massas sequencial (MS/MS). Os parâmetros de E-SPE foram avaliados de forma a obter a melhor condição no preparo de amostras e o método para a determinação de resíduos de sulfonamidas e fluoroquinolonas em ovos por E-SPE UHPLC-MS/MS foi avaliado em relação a linearidade, precisão, exatidão, além dos efeitos de supressão ou incremento de sinal analítico (efeito matriz) / Abstract: Sulfonamides and fluoroquinolones are veterinary drugs widely used in the poultry production for the prevention and treatment of diseases and, when good veterinary practices are not observed, residues of these drugs can be found above the maximum residue limit and may represent a risk to the consumers health. Since egg is a complex biological matrix, significant amounts of interferents can hinder the determination of analytes by liquid chromatography, particularly residues of veterinary drugs, which are at levels in the order of ng g-1. Among the various sample preparation techniques capable to eliminate interferences and concentrate the analyte of interest, the solid phase extraction (SPE) stands out for its efficiency, robustness, selectivity and low solvent consumption. Nevertheless, due to the complexity of the matrix and the low concentration of the analytes, the establishment of sample preparation methods with selectivity in removing interferents and appropriate extraction efficiency is still a challenge in residue analysis. Thus, in order to overcome the limitations of conventional SPE, this thesis aimed to evaluate the application of electrical potential in SPE (E-SPE) for the determination of sulfonamides and fluoroquinolones residues in eggs by high efficient (HPLC) and ultra efficient (UHPLC) performance liquid chromatography associated with a photodiode array (DAD), fluorescence (FLD) or sequential mass spectrometer (MS/MS) detectors. The E-SPE parameters were evaluated to obtain the best condition for sample preparation and the method for the determination of sulfonamides and fluoroquinolones residues in eggs by E-SPE UHPLC-MS/MS was evaluated for linearity, precision, accuracy, in addition to the effects of suppression or increase of the analytical signal (matrix effect) / Doutorado / Ciência de Alimentos / Doutora em Ciência de Alimentos
182

Preparação, caracterização e aplicação de sorvente C8 imobilizado termicamente sobre sílica zirconizada para extração em fase sólida / Preparation, characterization and application of thermally immobilized C8 onto zirconized silica as sorbent for solid-phase extraction

Magueta, Renata da Costa, 1984- 06 July 2013 (has links)
Orientador: Isabel Cristina Sales Fontes Jardim / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T21:45:28Z (GMT). No. of bitstreams: 1 Magueta_RenatadaCosta_M.pdf: 9269521 bytes, checksum: ce3c0368312fe2614e36d33195d8da7b (MD5) Previous issue date: 2013 / Resumo: Um novo sorvente para extração em fase sólida foi preparado utilizando a imobilização térmica do polímero poli(metiloctilsiloxano) sobre sílica zirconizada. Foram estudadas as etapas de preparo do sorvente, avaliando-se a quantidade de polímero, a temperatura e o tempo de imobilização e a extração do excesso de polímero não imobilizado. Também se determinou o volume de breakthrough e a eficiência de extração dos cartuchos preparados. Para avaliação da eficiência de extração dos sorventes, foram utilizadas amostras de água fortificadas com uma mistura dos agrotóxicos carbendazim, imidacloprido, acetamiprido, cimoxanil, carbofuram, carbaril, metiocarbe, tebuconazol, difenoconazol, pirimifós-metílico e piriproxifem. Os resultados de cada estudo realizado foram comparados com os obtidos para o sorvente preparado sobre sílica não modificada e foram consideradas adequadas as eficiências de extração entre 70 e 120%, com coeficiente de variação de até 20%. Com a sílica zirconizada, os melhores resultados foram obtidos com 50% de polímero sobre o suporte, imobilização a 120 °C por 4 horas e extração do excesso de polímero utilizando n-hexano, numa proporção de 36 mL de solvente para cada 1 g de material, a temperatura de 50 °C e vazão de 0,6 mL/min. A caracterização físico-química dos materiais mostrou que houve incorporação satisfatória do zircônio ao suporte de sílica no processo de metalização e o polímero encontra-se fisicamente sorvido e quimicamente ligado ao suporte. O estudo do volume de breakthrough dos cartuchos e a avaliação do desempenho do sorvente frente a variações de pH mostraram que a presença de átomos de zircônio na superfície do suporte aumenta a acidez dos grupos silanóis residuais, de modo que estes sítios interagem fortemente com os analitos básicos em pH elevado. Pôde-se observar que as eficiências de extração dos agrotóxicos também variam com a polaridade dos compostos, sendo que, o mecanismo de retenção é complexo, alternando entre interações hidrofóbicas e eletrostáticas. A aplicação do sorvente zirconizado na extração de agrotóxicos em amostras de suco de tomate mostrou que o mesmo apresenta potencial para ser empregado na extração em fase sólida de multirresíduos com características diversas de matrizes complexas / Abstract: A new sorbent for solid-phase extraction was prepared using thermal immobilization of the polymer poly(methyloctylsiloxane) onto a zirconized silica support. The steps of the preparation were studied evaluating the polymer loading, the temperature and time of immobilization and the extraction of the excess non-immobilized polymer as well as the cartridge¿s breakthrough volume and extraction efficiency. To evaluate the cartridge¿s extraction efficiency water samples fortified with a mixture of the pesticides carbendazin, imidacloprid, acetamiprid, cymoxanil, carbofuran, carbaryl, methiocarb, tebuconazole, difenoconazole, pirimiphos-methyl and pyriproxyfen were used. The results of each step were compared with those from the sorbent prepared with unmodified silica and adequate extraction efficiencies were considered as being between 70 and 120% with variation coefficients under 20%. With zirconized silica the best results were achieved with 50% polymer loading onto the support, immobilization at 120 °C for 4 hours and extraction of the excess non-immobilized polymer using n-hexane, in the proportion of 36 mL of solvent for 1 g of material, at 50 °C and at a 0.6 mL/min flow rate. The physical-chemical characterization of the materials showed that the incorporation of zirconium onto the silica support in the metalization process was satisfactory and the polymer is physically sorbed and chemically attached to the support. The studies concerning the breakthrough volume and the evaluation of the cartridge¿s performance over pH variations showed that the presence of the zirconium on the support¿s surface increases the acidity of the residual silanol so that these sites interact strongly with basic analytes at high pH. It was also possible to observe that the extraction efficiencies vary with the polarity of the compounds. The retention mechanism is complex, mixing hydrophobic and electrostatic interactions. The application of the zirconized sorbent in the extraction of pesticides from tomato juice samples showed that the sorbent has the potential to be used for multiresidue solid-phase extraction of complex matrices having a wide range of characteristics / Mestrado / Quimica Analitica / Mestra em Química
183

Microextração em fase sólida e cromatografia gasosa convencional e bidimensional para classificação de méis / Solid phase microextraction and conventional and comprehensive gas chromatography for the classification of honeys

Marques, Sandra Regina Rivellino, 1975- 19 August 2018 (has links)
Orientador: Fabio Augusto / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T18:08:24Z (GMT). No. of bitstreams: 1 Marques_SandraReginaRivellino_D.pdf: 2317302 bytes, checksum: fe68941a7328088e8aaba96b46928a24 (MD5) Previous issue date: 2011 / Resumo: A técnica de microextração em fase sólida através do headspace (HS-SPME) combinada com a cromatografia gasosa bidimensional abrangente e detecção por ionização em chama (GCxGCxFID) foi empregada para detectar artefatos formados durante o preparo da amostra de méis, que poderiam ser prejudiciais ao processo de identificação de sua origem floral. O método foi otimizado utilizando-se planejamento multivariado. Para isso, uma mistura de diferentes tipos de méis brasileiros foi usada como modelo. Os artefatos de extração identificados foram classificados como resultantes da manipulação através do HS. A influência da temperatura e do tempo de exposição ao tratamento térmico também foi avaliada. A identificação da fração volátil da mistura de mel foi realizada por GCxGCxFID e cromatografia gasosa acoplada à espectrometria de massas com analisador quadrupolar (GC-QMS) comparando-se o índice de retenção linear com programação de temperatura obtido na primeira dimensão (D-LTPRI), calculado a partir dos cromatogramas obtidos por GCxGCxFID, e os índices obtidos por GC-QMS para as mesmas amostras. Esta identificação foi confirmada por cromatografia gasosa bidimensional abrangente combinada a um espectrômetro de massas por tempo de vôo (GCxGCxTOFMS). Portanto, a identificação e detecção de artefatos de extração previamente desconhecidos é atribuída às vantagens da GCxGC. A GCxGCxFID combinada com ferramentas quimiométricas foi empregada para classificar algumas amostras de méis de diferentes origens do Piauí-Brasil. A GCxGCxQMS foi empregada para identificação dos voláteis de algumas destas amostras. A combinação de HS-SPME - (GCxGC ou GC) com o poder de identificação do detector MS, juntamente com índices de retenção e de métodos quimiométricos forneceram informações valiosas sobre a classificação química dos méis / Abstract: Solid phase microextraction through headspace (HS-SPME) was otimizated by a multivariate design. This technique combined with comprehensive two-dimensional gas chromatography with flame ionization detection (GCxGC-FID) was employed to detect potential artifacts formed during preparation of honey samples, that could possibly be relevant to the identification of its floral origin. A mixture of different types of brazilian honeys was used as the model sample. The extraction artifacts identified were classified as resulting from HS manipulation. The influence of temperature and time exposure of the thermal treatment was also evaluated. The identification of the volatile fraction of the honey blend was performed through combination of GCxGC-FID and GC coupled to quadrupole mass spectrometry (GC-QMS) by comparing the one dimensional linear temperature programmed retention index (D-LTPRI) calculated from GCxGCxFID chromatograms to that of chromatograms of the same samples obtained on GC-QMS. This identification was confirmed by GCxGC combined with a time-of-flight mass analyzer (GCxGC-TOFMS). Therefore, the identification and detection of previously unknown extraction artifacts is attributed to advantages of GCxGC. GCxGCxFID in combination with chemometric tools was employed to classify some honey samples from different origins from Piauí-Brazil. GCxGCxQMS was employed for the identification of the volatiles from some one of these samples. The combination of HS-SPME - (GCxGC or GC) and the qualitative information of MS, retention index and chemometric methods may be able to provide valuable information on the chemical classification of honeys / Doutorado / Quimica Analitica / Doutor em Ciências
184

Das Diffusions- und Aktivierungsverhalten von Arsen und Phosphor in Germanium

Wündisch, Clemens 18 February 2016 (has links) (PDF)
Seit 2002 kam ein neues Interesse an Germanium als Material für CMOS-Bauelemente auf, angetrieben durch die höhere Beweglichkeit der Ladungsträger im Vergleich zu Silizium. Für die Herstellung von Germanium MOSFETs bestehen allerdings noch einige Herausforderungen. Speziell die Problematik der hohen n-Dotierung für die Source- und Draingebiete der PMOS-Transistoren hat sich dabei als potentieller Roadblocker herauskristallisiert. Die geringe Aktivierung und die hohe Diffusivität der Donatoren in Germanium stellen ein Problem für die Herstellung von CMOS-Schaltkreisen aus Germanium dar. Als ursächlich dafür wurden Vakanzen identifiziert (Bracht et.al.). Um das Diffusions- und das Aktivierungsverhalten von Arsen und Phosphor in Germanium zu untersuchen, wurden p-Typ Germaniumwafer durch Ionenimplantation mit beiden Spezies dotiert und anschließend durch Rapid-Thermal-Annealing und/ oder Flash-Lamp-Annealing ausgeheilt. Zusätzlich wurden Experimente mit kodotierten und P-dotierten Proben mit verringerter Schichtkonzentration durchgeführt. Untersuchungen mit Rutherford-Backscattering-Spektroskopie und Transmissions-Elektronen-Mikroskopie werden durchgeführt, um die strukturellen Eigenschaften der Proben infolge der Implantation und der Ausheilung festzustellen. Mittels Sekundärionen-Massen-Spektroskopie wird die Dotandenkonzentration bestimmt. Es folgen elektrische Messungen des Schichtwiderstandes bei Raumtemperatur und in geeigneten Fällen bei Temperaturen unterhalb 10K. An ausgewählten Proben werden Hallmessungen durchgeführt. Die Gesamtheit der Analyseverfahren ermöglicht eine Analyse des Rückwachsverhaltens, der Diffusion und der elektrischen Aktivierung der Dotanden unter den verschiedenen Implantations- und Ausheilbedingungen. Die nach verschiedenen Methoden bestimmten Größen wie die Ladungsträgerkonzentration und -mobilität werden betrachtet und im Hinblick auf die Parameter der Probenpräparation analysiert und mit der Literatur verglichen. Abschließend werden mögliche Mechanismen zur Deaktivierung von Donatoren in Germanium erörtert.
185

Comparison of Medical and Forensic Profiling Potential of Volatile Biomarkers from Different Biological Specimens from Individuals and Across Populations

Kusano, Maiko 28 October 2010 (has links)
There is limited scientific knowledge on the composition of human odor from different biological specimens and the effect that physiological and psychological health conditions could have on them. There is currently no direct comparison of the volatile organic compounds (VOCs) emanating from different biological specimens collected from healthy individuals as well as individuals with certain diagnosed medical conditions. Therefore the question of matching VOCs present in human odor across various biological samples and across health statuses remains unanswered. The main purpose of this study was to use analytical instrumental methods to compare the VOCs from different biological specimens from the same individual and to compare the populations evaluated in this project. The goals of this study were to utilize headspace solid-phase microextraction gas chromatography mass spectrometry (HS-SPME-GC/MS) to evaluate its potential for profiling VOCs from specimens collected using standard forensic and medical methods over three different populations: healthy group with no diagnosed medical or psychological condition, one group with diagnosed type 2 diabetes, and one group with diagnosed major depressive disorder. The pre-treatment methods of collection materials developed for the study allowed for the removal of targeted VOCs from the sampling kits prior to sampling, extraction and analysis. Optimized SPME-GC/MS conditions has been demonstrated to be capable of sampling, identifying and differentiating the VOCs present in the five biological specimens collected from different subjects and yielded excellent detection limits for the VOCs from buccal swab, breath, blood, and urine with average limits of detection of 8.3 ng. Visual, Spearman rank correlation, and PCA comparisons of the most abundant and frequent VOCs from each specimen demonstrated that each specimen has characteristic VOCs that allow them to be differentiated for both healthy and diseased individuals. Preliminary comparisons of VOC profiles of healthy individuals, patients with type 2 diabetes, and patients with major depressive disorder revealed compounds that could be used as potential biomarkers to differentiate between healthy and diseased individuals. Finally, a human biological specimen compound database has been created compiling the volatile compounds present in the emanations of human hand odor, oral fluids, breath, blood, and urine.
186

Identification of the Active Odors From Illicit Substances for the Development of Optimal Canine Training Aids

Huertas-Rivera, Adhly M 04 November 2016 (has links)
The exploitation of illicit substances, such as drugs and explosives, is on the rise. Special attention must therefore be considered to reduce the transportation and storage of these illicit substances by improving the capability of detection, even when hidden from view. Although analytical methods of detection for both drugs and explosives have improved over time, biological detectors, such as canines, are still commonly used. In comparison to humans, these canines have a larger number of olfactory receptors and a greater olfactory epithelium surface area, providing them with a more enhanced olfaction than that of humans. The premise for the detection of illicit drugs and explosives is based on the premise that these substances though hidden, will emit volatile organic compounds (VOCs). These VOCs are not often the parent drug or explosive, they are essentially a chemical associated with the source and provide a reliable indication of the illicit substance. Previous successful research has been conducted on the identification of the active odors present in the headspace of cocaine, methamphetamine, and MDMA but instead for marijuana and heroin there have been minimum success. Thus, in the present research a method using headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) was optimized to identify the VOCs makeup of heroin and marijuana to further identify the active odor compound(s) responsible for the alert response of biological detectors (canines). A mixture of acetic acid and acetylsalicylic acid was identified as target odor mimic for heroin by certified detector canines, while a mixture of limonene and caryophyllene was recognized as odor mimic for marijuana by conducting ORTs. The training aids developed successfully mimic the scent of the actual illicit substance and can be used to improve the capabilities of both drug and explosive detection canines. Additionally, as growing threat of improvised explosives has created a worldwide concern and emphasized the requirement of a greater spectra of canine training aids that covers the complete range of explosives available, a new approach for the creation of training aids for IEDs have been evaluated. The use of a dynamic collection system have proved to be an option to develop fast and reliable canine training aids for IEDs.
187

Potential prebiotic roles of (amino-)acylation in the synthesis and function of RNA

Chan, Christopher K. W. January 2013 (has links)
The Sutherland group recently demonstrated that from a mixture of oligoribonucleotide-2'- or 3'-phosphates the latter is chemoselectively acetylated. This is shown to mediate a template-directed ligation to give predominantly 3',5'-linked RNA that is acetylated at the ligation junction (acetyl-RNA). It was suggested that RNA emerged prebiotically via acetyl-RNA and also is proposed to have favourable genotypic properties due to greater propensity to form duplex structure. To study the properties of acetyl-RNA, their synthesis by solid-phase chemistry was required and described is the design of a 2'/3'-O-acetyl orthogonal protecting group strategy. Key to the orthogonal protecting group strategy is the use of (2-cyanoethoxy)carbonyl for the protection of the nucleobase exocyclic amines and a photolabile solid-phase linker group that allowed partial on-column deprotection. The synthesis of the 2'/3'-O-acetyl and 2'/3'-O-TBDMS phosphoramidites, in addition to preparation of a photolabile solid-phase support, are described. With the materials to hand the procedures for an automated synthesis of acetyl-RNA were optimised and several acetyl-RNA oligonucleotides were synthesised. The duplex stability of acetyl-RNA with up to four sites of 2'-O-acetylation were assessed by UV melting curve analysis. Remarkably, the acetyl groups caused a consistent decrease in Tm of between 3.0-3.2 °C. Thermodynamic parameters indicated a decrease in duplex stability that was consistent with a decrease in hydration of the minor groove resulting in a reduction of the stabilising hydrogen bonding network. The stability of a tetraloop was also found to decrease on acetylation. The acetylated- tetraloop it is able to form duplex at lower concentrations than the natural tetraloop. Additionally, it is more stable at high concentrations, indicating that acetyl-RNA favours duplex over other secondary structure. These properties are considered to give acetyl-RNA competitive advantage for their non-enzymatic replication. Aminoacylation of RNA is an important process in modern biology but the intermediacy of aminoacyl-adenylates is considered to be prebiotically implausible. A potentially prebiotic aminoacylation of nucleoside-3'-phosphates, selective for the 2'-hydroxyl, is presented. However, it was thought the aminoacylation yields could be improved and so a search for an alternative activator was conducted. Oligoribonucleotide-3'-phosphates were exposed to the aminoacylation conditions and selective aminoacylation at only the 2'-hydroxyl of the 3'-end was observed. In particular, the aminoacylation of a trimer lends support to Sutherland’s theory of a linked origin of RNA and coded peptide synthesis.
188

Méthodologie spécifique globale de caractérisation des écoulements gaz/solides pour l'optimisation d'enceintes thermiques / Global specific methodology of characterization of the flows gas/solids for the thermal optimization of surrounding walls

Bellil, Ahmed 02 December 2014 (has links)
Les dysfonctionnements observés dans les enceintes de conversion thermochimique tels que les zones mortes et les courts-Circuits conduisent en général à une mauvaise valorisation de la ressource énergétique et à une pollution atmosphérique. Ils trouvent leur origine dans les conditions aérauliques au sein de ces enceintes. Ils pourront alors être évités par une meilleure maîtrise de ces écoulements. Nous proposons dans ce travail d’une part, le développement d’un nouvel outil pour la détermination de la distribution des temps de séjour de la phase solide, basé sur la luminescence de particules préalablement enrobées de pigments phosphorescents. Cette méthode systémique, optique, non intrusive et souple d’emploi a été mise en place à l’échelle laboratoire sur un banc d’essais aéraulique. D’autre part, nous avons développé un modèle numérique permettant de déterminer la distribution des temps de séjour afin de maîtriser les écoulements à la sortie des enceintes en vue de les optimiser et les extrapoler à l’échelle industrielle. Cette approche analytique est basée sur une modélisation par couplage MFN de type volumes finis du comportement d’un fluide à l’aide du Code Saturne et DEM de type éléments discrets du comportement du solide à l’aide du code SIGRAME. Enfin une confrontation de la DTS du modèle numérique avec laDTS expérimentale a été réalisée. / Dysfunctions observed in thermochemical conversion reactors like dead zones and short circuits generally lead to inaccurate pricing of energy resources and air pollution. They originate in the air flow conditions in these aeraulic reactor. They can then be avoided by a better control of these flows. We propose in this work to develop a new tool for determining the distribution of residence time of the solid phase, based on the luminescence of particles previously coated with phosphorescent pigments. This optical method, non-Intrusive and flexible, has been implemented at a laboratory scale, on an aeraulic test bench.On the other hand, we have developed a numerical model allowing to determine the distribution of the residence time to master the flows at the exit of surrounding walls to optimize them and extrapolate them at the industrial scale. This analytical approach is based on a modelling by coupling MFN by finite volume types via the Code Saturn and DEM by discrete elements of the solid behavior by means of the code SIGRAME. Finally a confrontation of the DTS of the digital model with the experimental DTS has been done.
189

Engineering cytochrome P450-reductase fusion enzymes for biocatalysis

Kelly, Paul January 2014 (has links)
Cytochromes P450 (P450s) are a superfamily of heme-thiolate monooxygenases. They catalyse a wide variety of reactions on a vast number of substrates and are of particular interest for biocatalyst development due to their ability to oxidise non-activated C-H bonds. Fusion of a P450 to a suitable redox partner protein produces a catalytically self-sufficient enzyme and removes the need to produce electron transfer proteins separately. The well-studied bacterial protein P450cam (Pseudomonas putida) has been fused to the reductase (RhFRed) from the natural fusion protein P450-RhF (Rhodococcus sp.). The P450cam-RhFRed system catalyses the oxidation of camphor and several non-natural substrates and served as the basis for P450cam re-engineering in this current project, with the aim of expanding the substrate scope towards a more mammalian-like activity. The P450cam active site was partitioned into seven paired amino acids and each pair randomised in turn to generate seven sub-libraries of P450cam variants. These were screened for activity using a specially developed colony screen for detection of the blue pigment indigo. In total 94 new variants were identified and then pooled for secondary screening on a number of new substrates, identifying potentially novel activities within the ‘indigo positive’ population. In a separate ‘chimeragenesis’ approach substrate recognition sites (SRSs) within P450cam were targeted for exchange with equivalent portions from a number of human P450s. The B’ helix and F-G loop regions from CYPs 1A2, 2C8, 2D6 and 3A4 were grafted onto the P450cam structure and several of the B’ helix swaps were produced as soluble proteins. The P450cam-2C8-B’-RhFRed chimera gave a Soret peak at 420 nm in the Fe(II)-CO state although an additional substitution next to the proximal cysteine appeared to restore a P450-like state. SRS-exchange therefore offered some insight into structural modularity in P450s, providing a basis for further biocatalyst development.
190

Critical Comparison of Total Vaporization-Solid Phase Microextraction vs Headspace-Solid Phase Microextraction

Alexandra Michelle Train (10873377) 05 August 2021 (has links)
<p>Solid Phase Microextraction (SPME) is a popular sampling technique that can be paired with Gas Chromatography/Mass Spectrometry (GC-MS). SPME-GC-MS is used in forensic chemistry due to its simplification of the sample preparation process. Headspace-Solid Phase Microextraction (HS-SPME) is a technique where the sample is heated to generate volatiles in the headspace of the vial. A SPME fiber is then inserted into the vial and the compounds in the headspace will bind to the fiber. Total Vaporization- Solid Phase Microextraction (TV-SPME) is a technique that is derived from the HS-SPME technique. </p><p>In Chapter 1, the critical comparison of HS-SPME and TV-SPME is discussed. Samples including marijuana, essential oils, and CBD oil were utilized to compare the two techniques. The compounds of interest in marijuana are the three main cannabinoids: cannabinol (CBN), cannabidiol (CBD), and tetrahydrocannabinol (THC). The sample preparation and GC-MS parameters were kept the same for all samples to determine which SPME technique works best for these sample types and yielded the greatest sensitivity. It was found that HS-SPME shows greater sensitivity with CBN and equivalent sensitivity with essential oils, THC and CBD. </p><p>In Chapter 2, the detection of synthetic cannabinoids utilizing liquid-liquid injection as well as HS-SPME and TV-SPME is discussed. The detection of these compounds is important because this type of drug has become more prevalent in the United States because they can be chemically altered slightly so they still have the effects of a drug but can evade drug legislation. The detection of synthetic cannabinoids using liquid injection was found to be successful but detection using HS-SPME and TV-SPME was found to be unsuccessful. </p>In Chapter 3, the analyses of real and artificial saliva utilizing HS-SPME and TV-SPME is discussed. Determining the compounds present in real saliva and artificial saliva will be of importance for future research into determining if the presence of drugs in saliva can be analyzed with these techniques. The analyses of real and artificial saliva were found to be successful using HS-SPME, without derivatization, and TV-SPME, with and without derivatization. Many of the compounds present in the real saliva were detected and were confirmed to be compounds regularly found in saliva by other scientific literature.

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