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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.
41

A study of bibracchial lariat ether complexes and linked cyclodextrin dimer complexes / by Lee Charles West.

West, Lee Charles January 2000 (has links)
Includes errata attached to first leaf. / Includes bibliographical references. / vi, 158 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The complexation of a range of monovalent and divalent metal ions by the bibracchial lariat ethers has been investigated. Also investigates the complexation of metal ions and the anionic azo dye Brilliant Yellow by the diazacrown linked cyclodextrin dimers. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000
42

The chemistry of Osmium carbonyl clusters containing organomercurials and azo-compounds /

Kong, Fung-sze. January 1999 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references.
43

Azobenzenes: Make, Measure, and Roll

Stone, Ilana B. January 2021 (has links)
This dissertation describes the synthesis of novel, small molecule building blocks and the phenomena that are revealed when they are studied in unusual environments. Chapter 1 is divided into two sections, serving as introductions for chapters 2-3 and 4-5 respectively. The first section introduces the scanning tunneling microscope break junction (STM-BJ) as a new environment for reaction chemistry. Chapter 2 describes a truly single molecule reaction in which azobenzenes are formed in the STM-BJ one molecule at a time. Chapter 3 describes an electrostatically driven Ullmann coupling reaction of biphenyl iodides in the STM-BJ. In contrast to the reaction described in chapter 2, this reaction occurs throughout the solution in the presence of an electric field that surrounds the nanoelectrodes. The second half of chapter 1 provides a primer on the photoisomerization of azobenzenes, a class of small molecule dyes whose unique photochromic profile and switchable properties have been exploited across a wide range of fields. Chapter 4 introduces azobenzenes as photoswitchable ligands on superatomic clusters. Chapter 5 details the phenomenon and mechanism of white light driven rolling of Cu(I) isocyanoazobenzene crystals. Finally, chapter 6 is a self-contained research project. It details an organocatalytic O₂-coupled oxidation platform that capitalizes on the capacity of hydrazines to undergo rapid autoxidation to diazenes.
44

Identification of the products and mechanism of the disproportionation of DI(p-sulfonic acid)phenylthiocarbazide

Riggs, Ralph Lee 01 January 1961 (has links) (PDF)
It is the purpose of this paper to separate and identify the products resulting from treatment of this compound with strong base. This will be done using both column and paper chromatography, and through interpretation of infrared spectra. In addition, a discussion of the structure of the complexes of heavy metals with di(p-sulfonic acid) phenylthiocarbazide in basic solution will be presented.
45

Development and characterization of novel nitric oxide-releasing probes for magnetic resonance imaging

Czerniewski, Alexandre Adam. January 2007 (has links)
While providing non-invasive tissue detection, magnetic resonance imaging (MRI) presently possesses limited sensitivity for protein target recognition. This limitation was addressed for the target beta-galactosidase (beta-gal) by constructing three beta-gal-specific MRI probes. The probes are based on a bipartite design in which a vasoactive moiety known as a diazeniumdiolate (NONOate) is bound to a specifier, specifically galactose. Upon galactose' interaction with beta-gal, the NONOate is cleaved from galactose, and actively generates nitric oxide (NO). The released NO leads to microvascular permeability changes in surrounding tissues affecting localized T1 measurements. These changes serve as a quantitative index of beta-gal detection. The three beta-gal-specific NO-releasing probes constructed include GALPYRNONO, GALPIPNONO and a 'bi-functional' probe, which is similar to the first two but with glucose additionally incorporated so that the third probe may easily cross cellular membranes. Synthesis and characterization of this novel class of MRI probes are described in this work. / Keywords: non-invasive detection, magnetic resonance imaging (MRI), nitric oxide (NO), diazeniumdiolates (NONOates), NO-releasing compounds, novel MRI probes, molecular targets, protein targets, specifier, vasoactive, vasodilation, microvascular permeability, tissue localization, bipartite systems, bifunctional probes, blood-brain barrier, cell membrane trafficking, saccharide-bound NONOates, sugar diazeniumdiolates, glycosylated diazeniumdiolates, galactose, beta-galactosidase, glucose, glucose transporters, thermal & photolytic degradation, half-life optimization, Griess test, rat serum, stability.
46

Development and characterization of novel nitric oxide-releasing probes for magnetic resonance imaging

Czerniewski, Alexandre Adam. January 2007 (has links)
No description available.
47

Estudos de biopolímeros a base de quitina e quitosana quimicamente transformados para quelação de metais e para a captura e fixação de dióxido de carbono / Study of chitin and chitosan biopolymers chemically modified for metal chelation and for capture and fixation of carbon dioxide

Pereira, Fernanda Stuani [UNESP] 09 June 2016 (has links)
Submitted by Fernanda Stuani Pereira null (ferstuani@hotmail.com) on 2016-06-22T22:22:49Z No. of bitstreams: 1 Tese-FERNANDA STUANI PEREIRA.pdf: 6105856 bytes, checksum: 653cf59956934017da496664aa74e886 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-24T17:11:14Z (GMT) No. of bitstreams: 1 pereira_fs_dr_prud.pdf: 6105856 bytes, checksum: 653cf59956934017da496664aa74e886 (MD5) / Made available in DSpace on 2016-06-24T17:11:14Z (GMT). No. of bitstreams: 1 pereira_fs_dr_prud.pdf: 6105856 bytes, checksum: 653cf59956934017da496664aa74e886 (MD5) Previous issue date: 2016-06-09 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho descreve modificações estruturais feitas na cadeia lateral do polímero quitosana mediante a N-alquilação com diferentes aldeídos aromáticos, a qual originam bases de Schiff como produtos intermediários, seguido de uma redução com cianoborohidreto de sódio (NaBH3CN). Subsequentemente, reações de acoplamento entre o produto sintetizado N-benzil quitosana e diferentes sais de diazônio foram realizadas para produzir uma nova classe de compostos poli-azóicos a partir deste polímero. Diferentes materiais foram sintetizados para investigar a influencia de diferentes substituintes na complexação de metais e futuros estudos de eficiência biológica. Pela técnica de ressonância magnética nuclear de próton em solução, o grau de substituição dos poli-azo-compostos foi de 46 a 66%. Os compostos foram caracterizados por FT-IR e RMN de 13C no estado sólido e RMN de 15N em solução, que confirmaram a síntese dos derivados poliméricos. Também foi realizado um estudo da interação destes materiais sintetizados com os íons metálicos Cu(II) e Zn(II). Para a caracterização dos complexos, utilizou-se as técnicas de titulação complexométrica, FAAS, MEV, EDS, difratometria de raios X, EPR e TG/DTG. Por titulação complexométrica e FAAS, a quitosana pura mostrou maior capacidade em complexar/adsorver os metais do que seus derivados. A capacidade de adsorver íons Cu(II) foi maior do que íons Zn(II) para todos os compostos. Por MEV e EDS, observou-se que além do cobre coordenado pelos sítios reativos dos materiais, o sal sulfato de cobre foi adsorvido pela superfície polimérica dos mesmos. Assim, foram realizadas reações de complexação utilizando o sal CuCl2.2H2O e os resultados mostraram que esse comportamento não ocorre para este sal. Para os complexos utilizando o sal sulfato de zinco, praticamente não se observa o sal adsorvido na superfície polimérica, devido à baixa capacidade de complexação por esse metal. A difratometria de raios X mostrou uma redução da cristalinidade dos complexos de cobre e zinco formados pela quitosana e o derivado Q1Benzil devido a maior capacidade desses materiais em quelar íons metálicos. Para os complexos de Cu(II) e Zn(II) formados a partir do composto Azo-Anisidina, o índice de cristalinidade aumenta, o que pode estar associado a formação de diferentes ligações de coordenação nesse composto. A formação dos complexos também foi confirmada por espectroscopia Raman. Os espectros de EPR dos complexos de Cu(II) formados a partir do sal CuCl2.2H2O mostram a presença de uma estrutura hiperfina bem resolvida, da mesma forma que foi observado para o complexo Quitosana-CuSO4, na qual a grande maioria dos centros de cobre são monoméricos e provavelmente ligados aos polímeros. As curvas de TG/DTG mostraram que os derivados poliméricos degradam a temperaturas menores que o polímero não modificado, e os complexos com sulfato de cobre apresentaram perfis TG/DTG diferentes dos complexos sintetizados a partir do sal cloreto de cobre. Por fim, tanto a quitosana quanto seus derivados Q1Benzil, Q2Benzil e Q2Benzil utilizando a quitosana de baixo peso molecular se mostraram efetivos na síntese de carbonatos através da captura e fixação de CO2 por estes materiais poliméricos. / The present work describes structural modifications in the side chain of the polymer chitosan by N-alkylation with different aromatic aldehydes, which originates Schiff base as an intermediate, followed by reduction with sodium cyanoborohydride (NaBH3CN). Subsequently, coupling reactions between the synthesized product N-benzyl chitosan and various diazonium salts were carried out to produce a new class of poly-azo compounds from this polymer. Different materials were synthesized to investigate the influence of different substituents on metal chelation and future studies of their biological efficience. From nuclear magnetic resonance technique, the degree of substitution of the poly-azo compounds was between 46 and 66%. The compounds were characterized by FT-IR, 13C NMR in solid state and 15N NMR in solution, which confirmed the synthesis of the polymeric derivatives. The interaction of the synthesized materials with the metal ions Cu(II) and Zn(II) was also studied. For the characterization of such metal complexes, the techniques complexometric titration, FAAS, SEM, EDS, X-ray diffraction, EPR and TG/DTG were employed in this work. By complexometric titration and FAAS, pure chitosan showed greater capacity for complex/adsorb metals than its derivatives. The capacity of adsorbing Cu(II) ions was greater than Zn(II) ions for all compounds. The synthesized complexes were studied by various spectroscopic techniques. By SEM and EDS, it was observed that in addition of copper coordination, copper sulphate salt was adsorbed by the polymer surface. Thus, complexation reactions were carried out using the salt CuCl2.2H2O and the results showed that this behavior does not occur for this salt. For complexes using zinc sulfate salt, hardly observes this salt adsorbed on the polymeric surface due to the low capacity for complexing this metal. The X-ray diffraction showed a reduction of the crystallinity of copper and zinc complexes formed by chitosan and Q1Benzil derivative due to the greater ability of these materials to chelate metal ions. For the complexes of Cu(II) and Zn(II) formed from Azo-Anisidine compound, the crystallinity index increases, which can be associated with formation of different coordination bonds with the compound. The formation of the complex was also confirmed by Raman spectroscopy. EPR spectra of Cu(II) formed from the CuCl2.2H2O salt showed the presence of well resolved hyperfine structure in the same way as it was observed for chitosan-CuSO4, in which the majority of copper centers are monomeric and probably bound to the polymer. The TG/DTG curves showed that polymeric derivatives are less stable than the unmodified polymer, and complexes with copper sulfate had TG/DTG curves different from the complexes synthesized from copper chloride salt. Finally, chitosan and the derivatives Q1Benzil , Q2Benzil and Q2Benzil from low molecular weight chitosan were effective in the synthesis of carbonates through the capture and sequestration of CO2 by these polymeric materials. / FAPESP: 2012/13901-3
48

Eletrogeração de peróxido de hidrogênio (H2O2) em eletrodos de difusão gasosa (EDG) modificados com quinonas (metil-p-benzoquinona, antraquinona-2-ácido carboxílico e ácido antraflávico) e azocomposto (Sudan Red 7B) / Electrogeneration of hydrogen peroxide (H2O2) in gas diffusion electrodes (GDE) modified with quinones (methyl-p-benzoquinone, anthraquinone-2-carboxylic acid and anthraflavic acid) and azo compound (Sudan Red 7B)

Juliana Moreira 13 November 2018 (has links)
Os processos oxidativos avançados (POA) são uma alternativa para complementar os processos clássicos de tratamento de efluentes que podem não ser eficientes para remoção de alguns tipos de poluentes como, por exemplo, os poluentes emergentes. Os POA se baseiam na geração de espécies altamente reativas (radicais hidroxila), a partir de peróxido de hidrogênio (H2O2), que oxidam os poluentes. O H2O2 pode ser eletrogerado in situ pela reação de redução de oxigênio (RRO) no meio reacional. O uso de eletrodos de difusão gasosa (EDG) altamente porosos proporciona o suprimento de oxigênio na interface eletrodo/solução podendo aumentar a velocidade da RRO. O uso de modificadores como quinonas e azocompostos imobilizados à matriz de carbono dos EDG podem aumentar a geração de H2O2. Portanto, os modificadores orgânicos Sudan Red 7B (SR7B), metil-p-benzoquinona (MPB), ácido antraflávico (AA) e antraquinona-2-ácido carboxílico (A2CA) foram adicionados em diferentes teores ao carbono Printex L6 (CP) e microcamadas porosas destes materiais foram estudados por voltametria cíclica e de varredura linear em eletrodo de disco-anel rotatório (RRDE). Os materiais contendo 0,5% de SR7B e 5,0% de MPB levaram a aumento na eficiência de geração de H2O2 para 86,2 e 85,5%, respectivamente, em relação ao CP puro que levou a 82,8%. EDG de CP modificados com 0,5% de SR7B foram construídos com telas metálicas em sua faces externas e a aplicação de densidades de corrente de 75, 100 e 150 mA cm-2 levou a uma maior eletrogeração de H2O2. Em densidades de corrente de 75 mA cm-2, o EDG modificado gerou 1020,1 mg L-1 de H2O2 com consumo energético de 118,0 kWh kg-1 de H2O2, constante cinética aparente de 37,3 mg L-1 min-1 e eficiência de corrente de 17,9%, enquanto o EDG de CP puro gerou menor concentração de H2O2; 717, 3 mg L-1, com maior consumo energético; 168,5 kWh kg-1, menor constante cinética aparente; 21,4 mg L-1 min-1, e menor eficiência de corrente; 12,6%. Portanto, o EDG modificado poderia ser empregado em sistemas que precisem de altas gerações de H2O2. / The advanced oxidation processes (AOP) are an alternative to the classical processes of treatment of effluents that may not be effective for the removal of some types of pollutants such as emerging pollutants. The AOP are based on the highly reactive species (hydroxyl radicals) from hydrogen peroxide (H2O2), which oxidize pollutants. H2O2 can be electrogenerated in situ by the oxygen reduction reaction (ORR) in the reaction medium. The use of highly porous gas diffusion electrodes (GDE) provides the supply of oxygen at the electrode/solution interface, which can increase the RRO speed. The use of modifiers such as quinones and azocompounds immobilized on the carbon matrix of GDE may increase H2O2 generation. Therefore, the organic modifiers Sudan Red 7B (SR7B), methyl-p-benzoquinone (MPB), anthraflavic acid (AA) and anthraquinone-2-carboxylic acid (A2CA) were added in different contents to carbon Printex L6 (CP) and microporous layers of these materials were studied by cyclic voltammetry and linear sweep voltammetry on a rotating ring- disc electrode (RRDE). Materials with 0.5% of SR7B and 5.0% of MPB increased the current efficiency for electrogeneration of H2O2 to 86.2 and 85.5%, respectively, in relation to pure CP that leaded to 82.8%. GDE of CP modified with 0.5% of SR7B were constructed with metallic screens on their outer faces and an application of current densities of 75, 100 and 150 mA cm-2 led to a greater electrogeneration of H2O2. At current densities of 75 mA cm-2, the modified GDE generated 1020.1 mg L-1 of H2O2 with energy consumption of 118.0 kWh kg-1 of H2O2, apparent kinetic constant of 37.3 mg L-1 min-1 and current efficiency of 17.9%, while GDE of pure CP generated lower H2O2 concentration; 717, 3 mg L-1, with higher energy consumption; 168.5 kWh kg-1, lower apparent kinetic constant; 21.4 mg L-1 min-1, and lower current efficiency; 12.6%. Therefore, the modified GDE could be applied in systems that require high generations of H2O2.
49

Eletrogeração de peróxido de hidrogênio (H2O2) em eletrodos de difusão gasosa (EDG) modificados com quinonas (metil-p-benzoquinona, antraquinona-2-ácido carboxílico e ácido antraflávico) e azocomposto (Sudan Red 7B) / Electrogeneration of hydrogen peroxide (H2O2) in gas diffusion electrodes (GDE) modified with quinones (methyl-p-benzoquinone, anthraquinone-2-carboxylic acid and anthraflavic acid) and azo compound (Sudan Red 7B)

Moreira, Juliana 13 November 2018 (has links)
Os processos oxidativos avançados (POA) são uma alternativa para complementar os processos clássicos de tratamento de efluentes que podem não ser eficientes para remoção de alguns tipos de poluentes como, por exemplo, os poluentes emergentes. Os POA se baseiam na geração de espécies altamente reativas (radicais hidroxila), a partir de peróxido de hidrogênio (H2O2), que oxidam os poluentes. O H2O2 pode ser eletrogerado in situ pela reação de redução de oxigênio (RRO) no meio reacional. O uso de eletrodos de difusão gasosa (EDG) altamente porosos proporciona o suprimento de oxigênio na interface eletrodo/solução podendo aumentar a velocidade da RRO. O uso de modificadores como quinonas e azocompostos imobilizados à matriz de carbono dos EDG podem aumentar a geração de H2O2. Portanto, os modificadores orgânicos Sudan Red 7B (SR7B), metil-p-benzoquinona (MPB), ácido antraflávico (AA) e antraquinona-2-ácido carboxílico (A2CA) foram adicionados em diferentes teores ao carbono Printex L6 (CP) e microcamadas porosas destes materiais foram estudados por voltametria cíclica e de varredura linear em eletrodo de disco-anel rotatório (RRDE). Os materiais contendo 0,5% de SR7B e 5,0% de MPB levaram a aumento na eficiência de geração de H2O2 para 86,2 e 85,5%, respectivamente, em relação ao CP puro que levou a 82,8%. EDG de CP modificados com 0,5% de SR7B foram construídos com telas metálicas em sua faces externas e a aplicação de densidades de corrente de 75, 100 e 150 mA cm-2 levou a uma maior eletrogeração de H2O2. Em densidades de corrente de 75 mA cm-2, o EDG modificado gerou 1020,1 mg L-1 de H2O2 com consumo energético de 118,0 kWh kg-1 de H2O2, constante cinética aparente de 37,3 mg L-1 min-1 e eficiência de corrente de 17,9%, enquanto o EDG de CP puro gerou menor concentração de H2O2; 717, 3 mg L-1, com maior consumo energético; 168,5 kWh kg-1, menor constante cinética aparente; 21,4 mg L-1 min-1, e menor eficiência de corrente; 12,6%. Portanto, o EDG modificado poderia ser empregado em sistemas que precisem de altas gerações de H2O2. / The advanced oxidation processes (AOP) are an alternative to the classical processes of treatment of effluents that may not be effective for the removal of some types of pollutants such as emerging pollutants. The AOP are based on the highly reactive species (hydroxyl radicals) from hydrogen peroxide (H2O2), which oxidize pollutants. H2O2 can be electrogenerated in situ by the oxygen reduction reaction (ORR) in the reaction medium. The use of highly porous gas diffusion electrodes (GDE) provides the supply of oxygen at the electrode/solution interface, which can increase the RRO speed. The use of modifiers such as quinones and azocompounds immobilized on the carbon matrix of GDE may increase H2O2 generation. Therefore, the organic modifiers Sudan Red 7B (SR7B), methyl-p-benzoquinone (MPB), anthraflavic acid (AA) and anthraquinone-2-carboxylic acid (A2CA) were added in different contents to carbon Printex L6 (CP) and microporous layers of these materials were studied by cyclic voltammetry and linear sweep voltammetry on a rotating ring- disc electrode (RRDE). Materials with 0.5% of SR7B and 5.0% of MPB increased the current efficiency for electrogeneration of H2O2 to 86.2 and 85.5%, respectively, in relation to pure CP that leaded to 82.8%. GDE of CP modified with 0.5% of SR7B were constructed with metallic screens on their outer faces and an application of current densities of 75, 100 and 150 mA cm-2 led to a greater electrogeneration of H2O2. At current densities of 75 mA cm-2, the modified GDE generated 1020.1 mg L-1 of H2O2 with energy consumption of 118.0 kWh kg-1 of H2O2, apparent kinetic constant of 37.3 mg L-1 min-1 and current efficiency of 17.9%, while GDE of pure CP generated lower H2O2 concentration; 717, 3 mg L-1, with higher energy consumption; 168.5 kWh kg-1, lower apparent kinetic constant; 21.4 mg L-1 min-1, and lower current efficiency; 12.6%. Therefore, the modified GDE could be applied in systems that require high generations of H2O2.
50

Development of new strategies for the synthesis of radiotracers labeled with short-lived isotopes: application to 11C and 13N

Gómez Vallejo, Vanessa 09 July 2010 (has links)
S'ha desenvolupat una nova estratègia per la síntesi ràpida i eficient de L-[metil-11C]metionina basada en el captive solvent method. La reacció de L-homocisteína (dissolució bàsica en aigua/etanol 1:1) amb [11C]CH3I en un loop de HPLC va permetre la formació del radiotraçador desitjat amb elevat rendiment radioquímic (38.4 ± 4.1%) en un temps curt (< 12 min). Tots el paràmetres analítics compleixen les especificacions requerides per la versió actual de la Farmacopea Espanyola, tot i que els valors d'activitat específica obtinguts van ser relativament baixos. Degut a això, es van estudiar i quantificar les principals fonts que contribueixen a la contaminació de carboni-12 durant les síntesis de [11C]CH3I efectuades segons el "wet" method. Es va observar que la principal font de contaminació de CO2 no radioactiu (contribució>90%) és el propi procés de bombardeig, probablement degut a la combustió (causada per les altes temperatures i pressions assolides durant la irradiació) dels compostos que contenen carboni i que es troben al gas irradiat (o a l'interior del blanc). Es van establir procediments generals per realitzar abans, durant i després de la radiosíntesi per prevenir la contaminació exterior i, d'aquesta manera, augmentar l'activitat específica dels radiotraçadors sintetitzats.En quant al marcatge amb nitrogen-13, s'ha desenvolupat un procés totalment automàtic per a la producció de [13N]NO2- a partir de [13N]NO3- generat en el ciclotró. El precursor radioactiu [13N]NO2- s'ha utilitzat per la radiosíntesi de compostos amb interès biològic com ara S-nitrosotiols (donadors de NO.), N-nitrosamines (molècules amb potencials efectes carcinogènics) i azo compostos (amb possible aplicació com a radiotraçadors per a la detecció in vivo de plaques de &#946;-amiloide). En tots els casos es van obtenir excel·lents conversions radioquímiques (48.7% - 74.5% per S-[13N]nitrosotiols, 45.6% - 53.4% per N-[13N]nitrosamines i 40.0% - 58.3% per 13N-azo compostos) i bons rendiments radioquímics (33.8% - 60.6% per S-[13N]nitrosotiols, 34.0% - 37.8% per N-[13N]nitrosamines i 20.4% - 47.2% per 13N-azo compostos). A més a més, s'ha dissenyat i implementat un mòdul automàtic amb control remot pel marcatge de molècules amb 13N. / Se ha desarrollado una nueva estrategia para la síntesis rápida y eficiente de L-[metil-11C]metionina basada en el captive solvent method. La reacción de L-homocisteína (disolución básica en agua/etanol 1:1) con [11C]CH3I en un loop de HPLC permitió la formación del radiotrazador deseado con elevado rendimiento radioquímico (38.4 ± 4.1%) en un tiempo corto (< 12 min). Todos los parámetros analíticos cumplían las especificaciones requeridas por la versión actual de la Farmacopea Española, aunque los valores de actividad específica obtenidos fueron relativamente bajos. Por ello, se estudiaron y cuantificaron las principales fuentes que contribuyen a la contaminación de carbono-12 durante las síntesis de [11C]CH3I efectuadas según el "wet" method. Se observó que la principal fuente de contaminación de CO2 no radiactivo (contribución>90%) es el propio proceso de bombardeo, probablemente debido a la combustión (causada por las altas temperaturas y presiones alcanzadas durante la irradiación) de los compuestos que contienen carbono y que se encuentran presentes en el gas irradiado (o en el mismo cuerpo del blanco). Se establecieron procedimientos generales para realizar antes, durante y con posterioridad a la radiosíntesis para prevenir la contaminación exterior y, de esta manera, aumentar la actividad específica de los radiotrazadores sintetizados.Respecto al marcaje con nitrógeno-13, se ha desarrollado un proceso totalmente automático para la producción de [13N]NO2- a partir del [13N]NO3- generado en el ciclotrón. El precursor radiactivo [13N]NO2- se ha utilizado para la radiosíntesis de compuestos con interés biológico tales como S-nitrosotioles (donadores de NO.), N-nitrosaminas (moléculas con potenciales efectos carcinogénicos) y azo compuestos (con posible aplicación como radiotrazadores para la detección in vivo de placas de &#946;-amiloide). En todos los casos se obtuvieron excelentes conversiones radioquímicas (48.7% - 74.5% para S-[13N]nitrosotioles, 45.6% - 53.4% para N-[13N]nitrosaminas y 40.0% - 58.3% para 13N-azo compuestos) y buenos rendimientos radioquímicos (33.8% - 60.6% para S-[13N]nitrosotioles, 34.0% - 37.8% para N-[13N]nitrosaminas y 20.4% - 47.2% para 13N-azo compuestos). Además, se ha diseñado e implementado un módulo automático con control remoto para el marcaje de moléculas con 13N. / A new strategy for the fast and efficient synthesis of L-[methyl-11C]methionine based on the captive solvent method has been developed. The in loop reaction of a basic water/ethanol 1:1 solution of L-homocysteine with [11C]CH3I led to the formation of the desired radiotracer with high radiochemical yield (38.4 ± 4.1%) in short production time (< 12 min). All analytical parameters were within the specifications of the current version of the Spanish Pharmacopoeia, although specific radioactivity values were relatively low. Thus, the main sources of carbon-12 during the synthesis of [11C]CH3I by the "wet" method were studied and the contribution attributable to each individual source was quantified. The most relevant contamination of non-radioactive CO2 (contribution>90%) was shown to be generated during the bombardment process, probably due to the combustion (caused by high temperature and pressure during irradiation) of carbon carrier compounds present in the irradiated gas (or target body). General procedures to be performed before, during and after the radiosynthesis were established to prevent external contamination and to improve the specific radioactivity of 11C-labeled radiotracers synthesized from [11C]CH3I produced via the "wet" method. Concerning 13N-labeling, a fully automatic process for the production of [13N]NO2- from cyclotron generated [13N]NO3- has been developed. The radioactive precursor [13N]NO2- has been used for the synthesis of biologically interesting 13N-labeled compounds such as S-nitrosothiols (well-known NO. donors), N-nitrosamines (molecules with potent carcinogenic effects) and azo compounds (with putative application as imaging probes for in vivo detection of &#946;-amyloid plaques). In all cases, excellent radiochemical conversion (48.7% - 74.5% for S-[13N]nitrosothiols, 45.6% - 53.4% for N-[13N]nitrosamines and 40.0% - 58.3% for 13N-labeled azo compounds) and good radiochemical yields (33.8% - 60.6% for S-[13N]nitrosothiols, 34.0% - 37.8% for N-[13N]nitrosamines and 20.4% - 47.2% for 13N-labeled azo compounds) were achieved. An automatic remote controlled synthesis module for the preparation of 13N-labeled structures has been designed and implemented.

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