Thesis (M.Sc.)--York University, 2004. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 100-103). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ99372

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 162-163)

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 189-190)

Thesis (Ph. D.)--University of North Texas, May, 2007. / Title from title page display. Includes bibliographical references.

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The study of rapid cleavage of organophosphate esters by metal ions is of great interest as it is the most important reaction in both biological and environmental sciences. A good understanding of organophosphate hydrolysis by metal ions is important as it can be exploited in formulation of useful detoxifying agents for organophosphate contaminants in the environment. The knowledge can also help in developing effective artificial enzymes. The hydrolysis of 4-NPP in the presence of Ferrous and Ferric ions in o/w microemulsion media was investigated. The reaction was monitored by measuring the absorbance of the 4-nitrophenolate ion produced in the reaction aliquots with time. The order of effectiveness of the ME media towards the hydrolysis of 4-NPP was found to be CME > AME > aqueous in the presence of Fe(II), Fe(III) and Prussian blue at neutral pH. In comparison with individual metal ions used in the investigation, it was found that polymetallic Prussian blue showed enhanced rate of hydrolysis. The degree of effectiveness is as follows; Prussian blue (insoluble) > Prussian blue (soluble) > Fe(III) > Fe(II). The result of the present investigation enriches our understanding of the possible roles polymetallic ions play in hydrolysis reactions and the effect of different reaction media. The reactions mimic the roles of purple acid phosphatases in the hydrolysis of phosphate esters. The application of the above systems for environmental decontamination of organophosphates is also envisaged. / Chemistry / M.Sc.(Chemistry)

Made available in DSpace on 2016-03-07T19:20:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-12-01. Added 1 bitstream(s) on 2016-03-07T19:24:21Z : No. of bitstreams: 1 000859508.pdf: 1838240 bytes, checksum: 1fa5f7aa491aadaed645f3cddd5945bd (MD5) / No presente estudo, a nanoplataforma de oligosilsesquioxano foi organofuncionalizada com a molécula 5-Amino-1,3,4-Tiadiazol-2-Tiol, resultando no material denominado POSS-ATT. O POSS-ATT foi caracterizado através das técnicas de microscopia eletrônica de varredura-EDX, e espectroscopia de infravermelho com transformada de Fourier. Foram analisados os parâmetros que afetam o comportamento, no processo de adsorção, do POSS-ATT, tais como o pH e o tempo para o equilíbrio cinético. Os resultados evidenciaram que o POSS-ATT apresentou-se mais eficiente para pH maior que 5,32, e o tempo de contato necessário para o equilíbrio na adsorção dos íons em solução aquosa foi de 20 minutos para o Ni(II), Zn(II), e de 30 minutos para o Fe(III), Cu(II) e Pb(II). Os dados experimentais obtidos na cinética química foram descritos usando os modelos de cinética pseudo-segunda ordem e de difusão intrapartícula. O POSS-ATT foi aplicado na adsorção de íons metálicos Cu(II), Ni(II), Zn(II), Pb(II) e Fe(III) em solução aquosa através dos processos de batelada e em coluna de leito fixo. Os dados experimentais de adsorção em batelada foram melhor ajustados ao modelo de Langmuir quando comparados aos modelos de Freundlich e de Temkin. Adicionalmente, a capacidade do POSS-ATT foi avaliada na adsorção, dessorção e regeneração utilizando-se solução aquosa de alimentação contendo os referidos íons através do processo de coluna de coluna de leito fixo. A capacidade de adsorção pelo processo de coluna de leito fixo do POSS-ATT deu-se na seguinte sequência Fe > Cu > Ni > Zn > Pb. Testou-se a capacidade de adsorção do Fe(III) sobre o POSS-ATT variando-se a concentração da solução, o fluxo de alimentação e o tamanho médio das partículas. Os dados experimentais obtidos pelo processo de adsorção em leito fixo se ajustaram melhor ao modelo de Yoon-Nelson quando comparados aos modelos de... / In this study the oligosilsesquioxane nanoplatform was organofunctionalized with 5-amino- 1,3,4-thiadiazole-2-thiol molecule, resulting in a material so called POSS-ATT. POSS-ATT was characterized through techniques of electron microscopy EDX scan, infrared spectroscopy and Fourier transform. Parameters that affect behavior were analyzed, in the adsorption process, for POSS-ATT, such as pH and time to reach kinetic equilibrium. Results obtained showed that the POSS-ATT is more efficient for pH higher than 5.32 and the contact time needed to achieve equilibrium in adsorption of ions in aqueous solution was 20 minutes for Ni (II), Zn (II) and 30 minutes for Fe(III), Cu(II) and Pb(II). The experimental data obtained for chemical kinetics have been described using pseudo-second order and intraparticle diffusion kinetic models. The POSS-ATT was applied to adsorption of metallic ions Cu (II), Ni (II), Zn (II), Pb (II) and Fe (III) in aqueous solutions via batch processes and fixed bed column. The experimental data for adsorption in batch were better adjusted to the Langmuir model when compared to the models of Freundlich and Temkin. Additionally, the ability of POSS-ATT was evaluated in the adsorption, desorption and regeneration using aqueous feed solution containing mentioned ions through the packed bed column process. Adsorption capacity, by fixed bed column process, of POSS-ATT occurred in the following order Fe> Cu> Ni> Zn> Pb. It was tested the adsorption capacity of Fe (III) by POSS-ATT varying solution concentration, flow feed rate and average particle size. The experimental data obtained for the adsorption process in fixed bed fitted best to the model Yoon-Nelson when compared to models of Clark and Bohart-Admas

G-quadruplexes represent a versatile sensing platform for the construction of label-free molecular detection assays due to their diverse structures that can be selectively recognized by G-quadruplex-specific luminescent probes. In this thesis, we have explored the applications of the label-free G-quadruplex-based luminescent detection platforms for the detection of biomolecules and metal ions. Chapter 1 provides an overview of the principles and recent developments of the field of luminescent oligonucleotide-based probes, and highlighting in particular the use of the “label-free” strategy for the construction of simple and inexpensive sensing platforms. Chapter 2 introduces the basic experiments performed during the course of this thesis, including UV/Vis absorption spectroscopy, luminescence spectroscopy, nuclear magnetic resonance, mass spectrometry circular dichroism spectroscopy and G-quadruplex fluorescent intercalator displacement assay. Chapter 3 describes a G-quadruplex-based switch-on luminescence assay for the detection of gene deletion using iridium(III) complex 1 as a G-quadruplex-selective probe. Our method is based on the formation of a split G-quadruplex upon hybridization of two critically designed quadruplex-forming sequences with the mutant DNA sequence, resulting in a “switch-on” luminescence response. Chapter 4 describes a label-free, oligonucleotide-based, switch-on luminescence detection method for T4 polynucleotide kinase activity using a G-quadruplex-selective luminescent iridium(III) complex 2. The application of the assay for screening potential T4 PNK inhibitors is also demonstrated. To our knowledge, this is the first metal-based assay for PNK activity that has been reported in the literature. Chapter 5 describes a label-free oligonucleotide-based luminescence switch-on assay for the selective detection of sub-nanomolar Pb2+ ions in aqueous solution and real water samples. Iridium(III) complex 1 was employed as a G-quadruplex-specific luminescent probe and a guanine-rich DNA sequence (PS2.M, 5.-GTG3TAG3CG3T2G2-3.) was employed as recognition unit for Pb2+ ions. The assay could detect Pb2+ ions in aqueous media with a limit of detection of 600 pM, and also exhibited good selectivity for Pb2+ ions over other heavy metal ions. Furthermore, the application of the assay for the detection of Pb2+ ions in spiked river water samples was demonstrated. Chapter 6 describes a label-free G-quadruplex-based luminescent switch-on assay for the selective detection of micromolar histidine in aqueous solution. Iridium(III) complex 8 was employed as a G-quadruplex-specific luminescent probe while a guanine-rich oligonucleotide (Pu27, 5.-TG4AG3TG4AG3TG4A2G2-3.)/cupric ion (Cu2+) ensemble was employed as a recognition unit for histidine. The assay could detect down to 1 µM of histidine in aqueous media, and also exhibited good selectivity for histidine over other amino acids with the use of the cysteine-masking agent N-ethylmaleimide. Furthermore, the application of the assay for the detection of histidine in diluted urine samples was demonstrated. Chapter 7 summarizes the work that was conducted in this thesis, and the future outlook of G-quadruplex-based sensing is presented.

Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2003Bitstream added on 2014-06-13T20:18:56Z : No. of bitstreams: 1 castro_gr_me_araiq.pdf: 1557562 bytes, checksum: 702b45f9cf5642eae90a11d6eab0b0a4 (MD5) / Este trabalho descreve a síntese, a caracterização da celulose modificada com grupos p-aminobenzóico (Cel-PAB) e os resultados do estudo da capacidade de adsorção de Cd(II), Cu(II), Ni(II), Zn(II) e Pb(II) pelo novo adsorvente, em diferentes valores de pH e tempos de contato dinâmico. A caracterização da Cel-PAB foi feita por espectroscopia de absorção na região do infravermelho com transformada de Fourrie (FT-IR), análise elementar de nitrogênio e determinação da área superficial específica. A capacidade máxima de sorção de íons metálicos pela Cel-PAB, determinada pelo método de sorção em batelada, foi da ordem de 2,00 mmol g-1 para os íons metálicos estudados. A pré-concentração de soluções analíticas dos metais com posterior eluição e leitura dos eluatos por espectrometria de absorção atômica por chama (FAAS), possibilitou a diminuição do limite de detecção (L. D.), o que permitiu a determinação dos metais presentes em baixas concentrações. O sistema desenvolvido para pré-concentração de íons metálicos foi aplicado em amostras de águas naturais, mineralizadas e não mineralizadas, da represa de Barra Bonita/Rio Tietê-SP e as determinações foram feitas por FAAS. Esses resultados foram comparados com aqueles obtidos por espectrometria de absorção atômica em forno de grafite (FGAAS) nas mesmas amostras de água. Diferenças significativas não foram encontradas, o que demonstrou a aplicabilidade do sistema proposto. / This work describes the synthesis, characterization of the modified cellulose with p-amino benzoic groups (Cel-PAB) and the results of the study of adsorption capacity from ions Cd (II), Cu (II), Ni (II), Zn (II) and Pb (II) by new adsorbent, in different pH values and dynamic contact times. The characterization of Cel-PAB was performed by FT-IR, elemental analysis of N2 and determination of the specific surface area. The maximum adsorption capacity of all metal ions by the Cel-PAB, determined by batch adsorption procedure, was approximately 2.00 mmol g-1 for studied metal ions. The pre-concentration in analytical metal ions solutions with further elution and read-out of elutes by flame atomic absorption spectrometry (FAAS), improve the detection limit (D.L.) allowing the detection of small amount of cations. The metal ions preconcentration system developed was applied in natural mineralized and non mineralized waters samples from Barra Bonita weir/Tietê River-SP and the analysis was carried out by FAAS technique. These results were compared with those obtained by atomic absorption spectrometry in graphite furnace (FGAAS) in the same sample waters. Small differences were not observed showing the applicability of the proposed system.

Orientador: Newton Luiz Dias Filho / Banca: Tsunao Matsumoto / Banca: Enes Furlani Junior / Banca: Cláudio Teodoro de Carvalho / Banca: Claudia Andrea Lima Cardoso / Resumo: No presente estudo, a nanoplataforma de oligosilsesquioxano foi organofuncionalizada com a molécula 5-Amino-1,3,4-Tiadiazol-2-Tiol, resultando no material denominado POSS-ATT. O POSS-ATT foi caracterizado através das técnicas de microscopia eletrônica de varredura-EDX, e espectroscopia de infravermelho com transformada de Fourier. Foram analisados os parâmetros que afetam o comportamento, no processo de adsorção, do POSS-ATT, tais como o pH e o tempo para o equilíbrio cinético. Os resultados evidenciaram que o POSS-ATT apresentou-se mais eficiente para pH maior que 5,32, e o tempo de contato necessário para o equilíbrio na adsorção dos íons em solução aquosa foi de 20 minutos para o Ni(II), Zn(II), e de 30 minutos para o Fe(III), Cu(II) e Pb(II). Os dados experimentais obtidos na cinética química foram descritos usando os modelos de cinética pseudo-segunda ordem e de difusão intrapartícula. O POSS-ATT foi aplicado na adsorção de íons metálicos Cu(II), Ni(II), Zn(II), Pb(II) e Fe(III) em solução aquosa através dos processos de batelada e em coluna de leito fixo. Os dados experimentais de adsorção em batelada foram melhor ajustados ao modelo de Langmuir quando comparados aos modelos de Freundlich e de Temkin. Adicionalmente, a capacidade do POSS-ATT foi avaliada na adsorção, dessorção e regeneração utilizando-se solução aquosa de alimentação contendo os referidos íons através do processo de coluna de coluna de leito fixo. A capacidade de adsorção pelo processo de coluna de leito fixo do POSS-ATT deu-se na seguinte sequência Fe > Cu > Ni > Zn > Pb. Testou-se a capacidade de adsorção do Fe(III) sobre o POSS-ATT variando-se a concentração da solução, o fluxo de alimentação e o tamanho médio das partículas. Os dados experimentais obtidos pelo processo de adsorção em leito fixo se ajustaram melhor ao modelo de Yoon-Nelson quando comparados aos modelos de... / Abstract: In this study the oligosilsesquioxane nanoplatform was organofunctionalized with 5-amino- 1,3,4-thiadiazole-2-thiol molecule, resulting in a material so called POSS-ATT. POSS-ATT was characterized through techniques of electron microscopy EDX scan, infrared spectroscopy and Fourier transform. Parameters that affect behavior were analyzed, in the adsorption process, for POSS-ATT, such as pH and time to reach kinetic equilibrium. Results obtained showed that the POSS-ATT is more efficient for pH higher than 5.32 and the contact time needed to achieve equilibrium in adsorption of ions in aqueous solution was 20 minutes for Ni (II), Zn (II) and 30 minutes for Fe(III), Cu(II) and Pb(II). The experimental data obtained for chemical kinetics have been described using pseudo-second order and intraparticle diffusion kinetic models. The POSS-ATT was applied to adsorption of metallic ions Cu (II), Ni (II), Zn (II), Pb (II) and Fe (III) in aqueous solutions via batch processes and fixed bed column. The experimental data for adsorption in batch were better adjusted to the Langmuir model when compared to the models of Freundlich and Temkin. Additionally, the ability of POSS-ATT was evaluated in the adsorption, desorption and regeneration using aqueous feed solution containing mentioned ions through the packed bed column process. Adsorption capacity, by fixed bed column process, of POSS-ATT occurred in the following order Fe> Cu> Ni> Zn> Pb. It was tested the adsorption capacity of Fe (III) by POSS-ATT varying solution concentration, flow feed rate and average particle size. The experimental data obtained for the adsorption process in fixed bed fitted best to the model Yoon-Nelson when compared to models of Clark and Bohart-Admas / Doutor