Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The acrylamide monomer is used mainly for the production of polyacrylamides, flocculation aids used in water supply systems. While its polymeric form does not pose health risks, the World Health Organization warns of the presence of residual acrylamide in flocculants, which would be responsible for releasing this contaminant in tap water. Acrylamide is considered as probably carcinogenic to humans, and has its standard for drinking water set at 0.5 μg L -1 in Brazil and in the United States, and 0.1 μg L-1 in Europe. Given the concern of the possibility of drinking water intake with the presence of acrylamide and lack of constant monitoring of this parameter, the objective of this study was to evaluate the application of photolytic processes for degradation of acrylamide and develop analytical methodology to quantify the acrylamide levels in trait, based on the Brazilian benchmark. The study was conducted following up the following steps: (I) development of bench photolytic reactor in Engineering Laboratory of Environment - LEMA, the Federal University of Santa Maria - UFSM; (II) conducting initial tests of direct photolysis (UV) photolysis combined with hydrogen peroxide (UV / H2O2) and use of hydrogen peroxide in the built reactor; (III) acrylamide analysis of development in the range of 0.5 to 5 mg L-1 via liquid chromatography with ultraviolet detection for monitoring the degradation in Environmental Analytical Chemistry Laboratory - LQAA, from the Chemistry Institute of the Federal University of Rio Grande do Sul - IQ-UFRGS; (IV) adequacy of degradation parameters and carrying out final tests of photolysis with lamp cooled reactor and analysis of results and preparation of the degradation kinetics, the LQAA; (V) defining parameters for most appropriate method of solid phase extraction to acrylamide; and (VI) adequacy of liquid chromatography via acrylamide analysis methodology of high efficiency with ultraviolet detection for a lower concentration range and validation of the method. The results demonstrated that acrylamide is slowly degraded via direct photolysis (k = 0.0143 mg L-1 min-1) and almost instantaneously when adding hydrogen peroxide (UV/H2O2), although alone peroxide has no effect. As for the method SPE according to the literature, active carbon is the most efficient for solid concentration of acrylamide. Thus, activated carbon was used cartridge for this step to give a satisfactory recovery of 72% acrylamide. The method developed via HPLC-UV showed good results as to the validation parameters of standard solutions. Same quality was not obtained when evaluated SPE-HPLC-UV conjunction with real fortified sample, probably due to the large number of possible interferences present in drinking water, coupled with the high solubility of acrylamide and difficulty of retention. The improvement of these analytical conditions should be required to make feasible the use of this method for the analysis of drinking water. / A acrilamida é um monômero utilizado principalmente para produção de poliacrilamidas, auxiliares de floculação empregadas em sistemas de abastecimento de água. Embora sua forma polimérica não represente riscos à saúde, a Organização Mundial da Saúde alerta para a presença de residuais de acrilamida nos floculantes, o que seria responsável por liberar esse contaminante na água tratada. Acrilamida é considerada como provavelmente carcinogênica para humanos, e tem seu padrão para água potável estabelecido em 0,5 μg L-1 no Brasil e nos Estados Unidos da América, e de 0,1 μg L-1 na Europa. Diante da preocupação da possibilidade de ingestão de água potável com a presença de acrilamida e da falta de monitoramento constante desse parâmetro, o objetivo desse trabalho foi avaliar a aplicação de processos fotolíticos para degradação da acrilamida e desenvolver metodologia analítica capaz de quantificar a acrilamida em níveis traço, baseado no valor de referência brasileiro. O estudo foi realizado seguindo-se as seguintes etapas: (I) desenvolvimento de reator fotolítico de bancada no Laboratório de Engenharia do Meio Ambiente - LEMA, na Universidade Federal de Santa Maria UFSM; (II) realização de testes iniciais de fotólise direta (UV), fotólise conjugada com peróxido de hidrogênio (UV/H2O2) e uso de peróxido de hidrogênio no reator construído; (III) desenvolvimento de análise de acrilamida na faixa de 0,5 a 5 mg L-1 via cromatografia a líquido com detecção por ultravioleta para acompanhamento da degradação, no Laboratório de Química Analítica Ambiental LQAA, do Instituto de Química da Universidade Federal do Rio Grande do Sul IQ-UFRGS; (IV) adequação dos parâmetros de degradação e realização dos testes finais de fotólise com reator de lâmpada resfriada, bem como análise dos resultados e avaliação da cinética de degradação, no LQAA; (V) definição de parâmetros para escolha do método mais adequado de extração em fase sólida para acrilamida; e (VI) adequação da metodologia de análise de acrilamida via cromatografia líquida de alta eficiência com detecção por ultravioleta para uma menor faixa de concentração e validação do método. Os resultados demonstraram que a acrilamida é lentamente degradada via fotólise direta (k = 0,0143 mg L-1 min-1) e, praticamente, de forma instantânea quando se adiciona peróxido de hidrogênio (UV/H2O2), embora, isoladamente, o peróxido não tenha qualquer efeito. Quanto ao método de EFS, de acordo com a literatura, o carvão ativo é o mais eficiente sólido para concentração de acrilamida. Assim, foi utilizado cartucho de carvão ativo para essa etapa, obtendo-se uma recuperação satisfatória de 72 % de acrilamida. O método desenvolvido via CLAE-UV demonstrou bons resultados quanto aos parâmetros de validação em soluções padrão. No entanto, os resultados não foram tão bons quando esta metodologia (EFS-CLAE-UV) foi aplicada à amostra real fortificada, provavelmente pela presença de grande quantidade de interferentes na água potável, aliada à grande solubilidade da acrilamida e dificuldade da sua retenção. A melhoria dessas condições analíticas deve ser pretendida a fim de tornar viável a utilização do método para análise de acrilamida em água potável.

Les pesticides sont un sujet d’actualité suscitant de nombreuses interrogations. Lors de leur épandage, une partie des pesticides sont émis dans l’atmosphère, important vecteur de dissémination. Ils se répartissent dans les différentes phases de l’atmosphère dont notamment la phase particulaire par la multiplication des usages de pesticides semi-volatils. Ils s’adsorbent à la surface des particules atmosphériques et sont soumis à des processus photochimiques régissant leur devenir. Actuellement, les estimations de la dégradation atmosphérique des pesticides ne prennent en compte que la phase gazeuse. Afin d’appréhender leur devenir et leurs impacts sur la santé et l’environnement, la réactivité hétérogène de 8 pesticides (cyprodinil, deltaméthrine, difénoconazole, fipronil, oxadiazon, pendiméthaline, perméthrine et tétraconazole) adsorbés à la surface de particules modèles a été étudiée. Ce travail s’est centré sur la détermination des temps de vie de ces 8 pesticides en présence d’humidité vis-à-vis du rayonnement solaire, de l’ozone (O3) et des radicaux hydroxyles (OH). Pour un ensoleillement moyen, les temps de vie en phase particulaire varient de 1 à 68 jours. Pour une concentration moyenne de 40 ppb d’O3 et de 10^6 molécule.cm^-3 en radicaux OH, les temps de vie sont respectivement compris entre 8 et plus de 35 jours et entre 24 à plus de 54 jours. La réactivité en phase particulaire est donc beaucoup plus lente qu’en phase gazeuse et confirme la nécessité de prendre en compte cette phase. Par l’identification des produits de dégradation, des mécanismes réactionnels mettent en évidence la formation de composés potentiellement plus toxiques que leurs précurseurs. / Pesticides represent a topic which raise an important number of questions. During their application, one fraction of the pesticides is emitted in the atmosphere, an important dissemination vector. In the atmosphere, pesticides are partitioned between different phases. However, due to increased use of semi-volatile pesticides, they are mostly enriched in the atmospheric particulate phase. They are adsorbed on the surface of atmospheric particles and undergo photochemical processes which govern the fate of pesticides in the atmosphere. Currently, the atmospheric fate of pesticides is based only on gas-phase reactivity. In order to properly understand the fate of pesticides and their impact on human health and on the environment, heterogeneous reactivity of 8 pesticides (cyprodinil, deltamethrin, difenoconazole, fipronil, oxadiazon, pendimethalin, permethrin and tetraconazole) adsorbed on the surface of silica particles, is evaluated. This work deals with the determination of lifetimes of these 8 pesticides under solar light irradiation, ozone (O3) and hydroxyl radicals (OH), in presence of humidity. With a daily average sunshine, the lifetimes of the pesticides in the particle phase are between ca. 1 day and 68 days. For an average mixing ratio of 40 ppb of O3 and 10^6 cm^-3 of OH radicals, the lifetimes span between 8 and more than 35 days and 24 and more than 54 days, respectively. This study shows that the reactivity in the particle phase is slower than in the gas phase and confirm the necessity to be taken into account. Degradation products are identified and reaction mechanism is proposed bringing to light the formation of compounds more toxic than their precursors.

Du fait de l’omniprésence de l’homme au sein du compartiment intérieur, y passant jusqu’à 90% de son temps au cours d’une journée, il est devenu essentiel de caractérisé correctement l’atmosphère et donc les polluants présent dans ce milieu. Ce travail de thèse prend la suite d’une étude menée au sein de notre laboratoire montrant une importante présence de radicaux hydroxyles dans cette atmosphère. Le polluant précurseur des radicaux supposé au cours de cette étude est l’acide nitreux (HONO), présent dans des quantités de l’ordre du ppb pour l’intérieur. Ce travail de thèse a donc eu pour but, dans un premier temps de caractériser la photolyse de l’acide nitreux conduisant à la formation de radicaux hydroxyles, et dans un second temps d’établir ses différentes voies de formation, directes et indirectes, afin de quantifier ses sources dans les atmosphères intérieures. / People in Western societies spend about 90% of their time indoors, predominantly within indoor places. The residence time of the airborne indoor pollutants is much longer due to the smaller volumes compared to the outdoor atmosphere and low air exchange rates. Therefore, a comprehensive understanding of indoor air quality is essential.Nitrous acid (HONO) is an emerging indoor pollutant because 1) it can lead to human respiratory tract irritation and formation of carcinogenic nitrosamines, and 2) it can be effectively photolyzed leading to a pulse of hydroxyl radicals (OH).The PhD work here presented is focused on understanding of the formation processes of oxidizing species such as HONO and, hence, OH radicals in the built environment.

[ES] La luz solar puede producir daños en el ADN por absorción directa de luz UVB, o por fotosensibilización tras la absorción de luz UVA por parte de fármacos, que pueden actuar como fotosensibilizadores (PS). La benzofenona (BP), presente en la estructura química de una amplia variedad de fármacos, tiene el potencial de fotosensibilizar daño al ADN, especialmente hacia la base de timina (Thy). Este daño puede dar lugar a dímeros de pirimidina de tipo ciclobutano (CPD) y a fotoproductos (6-4) pirimidina-pirimidona ((6-4)PPs), los cuales pueden causar mutaciones graves, melanomas o incluso la muerte celular. En algunos organismos, los (6-4)PPs pueden repararse de manera eficiente por las fotoliasas, en lo que se podría entender como una reacción Paternò-Büchi (PB) inversa a través de un intermedio de oxetano altamente inestable. Con el fin de profundizar en la fotorreactividad de los derivados BP-Thy y en la ruptura fotoinducida de oxetanos, se sintetizaron por primera vez una variedad de diadas en las que Thy y BP están covalentemente unidas por un espaciador lineal de diferente longitud y naturaleza. La fotorreactividad de los diferentes derivados se investigó por fotólisis de destello láser (LFP) y espectroscopía de absorción transitoria a escala de femtosegundo; además, se aislaron y caracterizaron los principales fotoproductos (PPs) derivados de la irradiación en estado estacionario. Los resultados mostraron un alto grado de quimioselectividad en la longitud y conformación del espaciador. En cuanto a la reactividad fotoquímica, se formaron PPs derivados de la PB y de la abstracción formal de hidrógeno; así, las diadas con el espaciador más largo dieron lugar a la formación de oxetanos y de PPs de abstracción de hidrógeno. Por el contrario, las diadas con espaciadores más cortos formaron un fotoproducto de abstracción formal de hidrógeno y/o polimerización. Por tanto, la fotorreactividad se vio influida por la longitud del espaciador, correlacionándose bien con los tiempos de 3BP*, observándose los tiempos más cortos para las diadas de espaciadores largos. En relación con la fotoapertura de oxetanos, la irradiación de los diferentes regio- y estereoisoméros condujo a la formación de la típica banda de absorción triplete-triplete de BP; por tanto, dicho proceso opera de forma adiabática. La fotólisis del oxetano que resulta de la irradiación de la diada con el espaciador más largo mostró una banda de absorción transitoria sobre 400 nm, atribuida a la formación del exciplejo triplete entre BP y Thy covalentemente unidos. Por otro lado, se investigó la reacción PB y la cicloreversión de oxetanos que surgen de la interacción entre Thy o derivados de uracilo (Ura) y BP. Así, se sintetizó una amplia gama de oxetanos Thy-BP y Ura-BP con diferentes sustituyentes en las posiciones 1 y 5 de la nucleobase, incluyéndose los regioisómeros cabeza-cabeza (HH) y cabeza-cola (HT). Los estudios espectroscópicos (absorción transitoria ultrarrápida y LFP), junto con el análisis teórico, coinciden en que la cicloreversión fotoinducida para los isómeros HH y HT implica la formación de un exciplejo en el estado excitado triplete antes de la ruptura. Generalmente, se observó que la reacción fue completamente adiabática para los regioisómeros HH. En el caso del oxetano HH que surge de la interacción entre 1,3-dimetiltimina (DMT) y BP, se observó la formación de una banda ~400 nm, que se atribuyó al exciplejo triplete 3[DMT···BP]*. Su formación fue altamente regioselectiva, siendo más rápida y eficiente para el isómero HH que para HT. Estos resultados fueron confirmados por análisis computacional. En general, se observó adiabaticidad en el proceso de fotorreversión para todos los oxetanos investigados, con un alto grado de regioselectividad y con la participación de exciplejos triplete. / [CA] La llum solar pot produir danys a l'ADN per absorció directa de llum UVB, o per fotosensibilització després de l'absorció de llum UVA per part de fàrmacs, que poden actuar com fotosensibilitzadors (PS). La benzofenona (BP), present en l'estructura química d'una àmplia varietat de fàrmacs, té el potencial de fotosensibilitzar dany a l'ADN, especialment a la base de timina (Thy). Aquest dany pot donar lloc a dímers de pirimidina de tipus ciclobutà (CPD) i a fotoproductes (6-4) pirimidina-pirimidona ((6-4)PPs), els quals poden causar mutacions greus, melanomes o fins i tot la mort cel·lular. En alguns organismes, els (6-4)PPs poden reparar-se de manera eficient per les fotoliases, en el que es podria entendre com una reacció Paternò-Büchi (PB) inversa a través d'un intermedi d'oxetà altament inestable. Amb la finalitat d'aprofundir en la fotoreactivitat dels derivats BP-Thy i en la ruptura fotoinduïda d'oxetans, es van sintetitzar per primera vegada una varietat de diades en les quals Thy i BP estan covalentment unides per un espaiador lineal de diferent longitud i naturalesa. La fotoreactivitat dels diferents derivats es va investigar per fotòlisi de centelleig làser (LFP) i espectroscopía d'absorció transitòria a escala de femtosegons; a més, es van aïllar i caracteritzar els principals fotoproductes (PPs) derivats de la irradiació en estat estacionari. Els resultats van mostrar un alt grau de quimioselectivitat en la longitud i conformació de l'espaiador. Quant a la reactivitat fotoquímica, es van formar PPs derivats de la PB i de l'abstracció formal d'hidrogen; així, les diades amb l'espaiador més llarg van donar lloc a la formació d'oxetans i de PPs d'abstracció d'hidrogen. Per contra, les diades amb espaiadors més curts van formar un fotoproducte d'abstracció formal d'hidrogen i/o polimerització. Per tant, la fotoreactivitat es va veure influïda per la longitud de l'espaiador, correlacionant-se bé amb els temps de 3BP*, observant-se els temps més curts per a les diades amb espaiadors llargs. En relació amb la fotoapertura d'oxetans, la irradiació dels diferents regi- i estereoisòmers va conduir a la formació de la típica banda d'absorció triplet-triplet de BP; per tant, aquest procés opera de manera adiabàtica. La fotòlisi de l'oxetà que resulta de la irradiació de la diada amb l'espaiador més llarg va mostrar una banda d'absorció transitòria sobre 400 nm, atribuïda a la formació de l'exciplex triplet entre BP i Thy covalentment units. D'altra banda, es va investigar la reacció PB i la cicloreversió d'oxetans que sorgeixen de la interacció entre Thy o derivats d'uracil (Ura) i BP. Així, es va sintetitzar una àmplia gamma d'oxetans Thy-BP i Ura-BP amb diferents substituents en les posicions 1 i 5 de la nucleobase, incloent-se els regioisòmers cap-cap (HH) i cap-cua (HT). Els estudis espectroscòpics (absorció transitòria ultraràpida i LFP), juntament amb l'anàlisi teòric, coincideixen en que la cicloreversió fotoinduïda per als isòmers HH i HT implica la formació d'un exciplex en l'estat excitat triplet abans de la ruptura. Generalment, es va observar que la reacció va ser completament adiabàtica per als regioisòmers HH. En el cas de l'oxetà HH que sorgeix de la interacció entre 1,3-dimetiltimina (DMT) i BP, es va observar la formació d'una banda ~400 nm, que es va atribuir a l'exciplex triplet 3[DMT···BP]*. La seua formació va ser altament regioselectiva, sent més ràpida i eficient per a l'isòmer HH que per a HT. Aquests resultats van ser confirmats per anàlisi computacional. En general, es va observar adiabaticitat en el procés de fotoreversió per a tots els oxetans investigats, amb un alt grau de regioselectivitat i amb la participació d'exciplexes triplet. / [EN] Sunlight light can produce damage to DNA through direct absorption of UVB or, more commonly, by photosensitization upon absorption of UVA light by drugs, that act as a photosensitizer (PS). Benzophenone (BP) as a building-block is present in a wide variety of drugs, and have the potential to photosensitize damage to DNA, specially towards the thymine (Thy) nucleobase. The resulting DNA damage can give rise to bulky dimers, i.e. cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4) photoproducts ((6-4)PPs), which can cause severe mutations, melanomas, or even be fatal for the cell. In some organisms, (6-4)PP can be efficiently repaired by photolyase enzymes, in what could be a reverse Paternò-Büchi (PB) reaction through an unstable oxetane intermediate. With the aim of getting deeper insight into the photoreactivity of BP-Thy derivatives and in the photoinduced cleavage of oxetanes, a variety of dyads where Thy and BP are covalently linked by a linear spacer of different lengths and nature were first synthesized. The photochemical reactivity and the photophysical properties of the different derivatives were investigated by means of laser flash photolysis (LFP) and femtosecond transient absorption spectroscopy; besides, the main photoproducts (PPs) arising from steady-state irradiation were also isolated and characterized. The results showed a high degree of chemoselectivity on the linking bridge length and conformation. Concerning the photochemical reactivity, PPs arising from the PB and from formal hydrogen abstraction were formed. In this context, the PB reaction took place for the dyads with the longest spacer with complete regio- and stereoselectivity, along with a hydrogen abstraction process. Finally, the dyads with shorter spacers gave rise to a formal hydrogen abstraction photoproduct and/or polymerization. Accordingly, the overall photoreactivity was proportional to the spacer length and was well correlated with the 3BP* lifetimes, the longer spacers giving rise to shorter lifetimes. In connection to the oxetane photocleavage, irradiation of the different regio- and stereoisomeric oxetanes led to the formation of the typical triplet-triplet absorption band of BP. Accordingly, the photoinduced cycloreversion also operates as an adiabatic process. Photolysis of the oxetane that results from irradiation of the dyad with the longest spacer showed a transient absorption at ~400 nm, which is ascribed to formation of the purported triplet exciplex between BP and Thy covalently linked. Additionally, the PB reaction and the cycloreversion of oxetanes arising from the interaction between Thy or uracil (Ura) derivatives and BP were also investigated. Thus, a wide range of Thy-BP and Ura-BP oxetanes with varying substituents at positions 1 and 5 of the nucleobase were synthesized, including both the head-to-head (HH) and head-to-tail (HT) regioisomers. Spectroscopic studies, including femtosecond transient absorption and LFP results, as well as theoretical multiconfigurational quantum chemistry analysis, agree that the photoinduced cycloreversion for the HH and HT isomers involved the formation of a triplet excited exciplex before the cleavage takes place. Generally, the photochemical reaction was fully adiabatic for the HH regioisomers. In the case of the HH-oxetane arising from the interaction between 1,3-dimethylthymine (DMT) and BP, an absorption band at ca. 400 nm was formed, and was attributed to the triplet exciplex 3[DMT···BP]*. Its formation was highly regioselective towards the HH regioisomer, being faster and more efficient than for the HT isomer. These results were confirmed by computational analysis. In general, adiabaticity was observed in the photoreversion process for all oxetanes, with a high degree of regioselectivity, which falls in line with the theory of the involvement of a triplet exciplex in the process. / Thanks to the Generalitat Valenciana for the finantial support through the Santiago Grisolía grant. / Blasco Brusola, A. (2021). Mechanistic Studies on the Photochemical Formation and Cleavage of Oxetanes Derived from Pyrimidine Bases [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165256

[ES] Los inhibidores de la tirosina quinasa (TKIs) son fármacos anticancerígenos que actúan atacando selectivamente a las células cancerosas, inhibiendo su crecimiento descontrolado y, por tanto, la consiguiente aparición de tumores. Sin embargo, muchos TKIs presentan un cromóforo en su estructura que les permite interaccionar con luz solar y, consecuentemente, pueden generar reacciones de fotosensibilización. A pesar de ello, existen pocos estudios sobre el mecanismo de reacción asociado a estos eventos. En este sentido, conocer la fotorreactividad de un fármaco en medio biológico es clave para entender dichos mecanismos y correlacionar el comportamiento fotofísico del fármaco con el daño fotobiológico que genera. La espectroscopía de fluorescencia y de absorción transitoria son técnicas altamente sensibles que permiten estudiar las especies transitorias generadas tras la absorción de luz por parte de un fármaco, las cuales podrían ser las responsables de las reacciones de fotosensibilización inducidas por éste. Habiendo estudiado recientemente la foto(geno)toxicidad asociada al TKI gefitinib (GFT) y a sus principales metabolitos fenólicos (GFT-M1 y GFT-M2), se ha llevado a cabo un estudio completo de la fotorreactividad de éstos tanto en disolución orgánica, utilizando disolventes de distintas polaridades, como en medio biológico, utilizando las proteínas transportadoras de origen humano albúmina sérica (HSA) y ¿1-glicoproteína ácida (HAG). Para ello, se han utilizado las técnicas espectroscópicas de absorción, fluorescencia y absorción transitoria, entre otras. Adicionalmente, se han llevado a cabo estudios teóricos de modelización molecular para investigar la unión ligando@proteína, así como las interacciones que tienen lugar en el complejo supramolecular tras la absorción de luz UV-A. Con este trabajo, se ha conseguido establecer una buena correlación entre el comportamiento fotofísico observado para gefitinib y sus dos metabolitos fenólicos con su potencial fototóxico. / [CA] Els inhibidors de la tirosina quinasa (TKIs) són fàrmacs anticancerígens que actuen atacant selectivament a les cèl·lules canceroses, inhibint el seu creixement descontrolat i, per tant, la consegüent aparició de tumors. No obstant això, molts TKIs presenten un cromòfor en la seua estructura que els permet interaccionar amb llum solar i, conseqüentment, poden generar reaccions de fotosensibilització. Malgrat això, existixen pocs estudis sobre el mecanisme de reacció associat a estos esdeveniments. En este sentit, conéixer la fotorreactivitat d'un fàrmac al mig biològic és clau per a entendre estos mecanismes i correlacionar el comportament fotofísic del fàrmac amb el dany fotobiològic que genera. La espectroscopia de fluorescència i d'absorció transitòria són tècniques altament sensibles que permeten estudiar les espècies transitòries generades després de l'absorció de llum per part d'un fàrmac, les quals podrien ser les responsables de les reaccions de fotosensibilització induïdes per aquest. Havent estudiat recentment la foto(geno)toxicitat associada al TKI gefitinib (GFT) i d'els seus principals metabòlits fenòlics (GFT-M1 i GFT-M2), s'ha dut a terme un estudi complet de la fotorreactivitat d'estos tant en dissolució orgànica, utilitzant dissolvents de diferents polaritats, com al mig biològic, utilitzant les proteïnes transportadores d'origen humà albúmina sèrica (HSA) i ¿1-glicoproteïna àcida (HAG). Per a això, s'han utilitzat les tècniques espectroscòpiques d'absorció, fluorescència i absorció transitòria, entre altres. Addicionalment, s'han dut a terme estudis teòrics de modelització molecular per a investigar la unió lligant@proteína, així com les interaccions que tenen lloc en el complex supramolecular després de l'absorció de llum UV-A. Amb este treball, s'ha aconseguit establir una bona correlació entre el comportament fotofísic observat per a gefitinib i els seu dos metabòlits fenòlics amb el seu potencial fototòxic. / [EN] Tyrosine kinase inhibitors (TKIs) are anticancer drugs that target cancer cells, inhibiting their uncontrolled growth and thus the subsequent development of tumours. However, many TKIs contain a chromophore in their structure that allows them to interact with sunlight and, consequently, to induce photosensitivity reactions. Despite this, there are few studies on the reaction mechanism associated with these events. In this regard, a better understanding on the photoreactivity of a drug in a biological environment is key to correlate the photophysical behaviour of the drug with the photoinduced damage it can induce to biomolecules. Fluorescence and transient absorption spectroscopies are very sensitive techniques that allow the study of the transient species generated after drug excitation, which could be responsible for drug-induced photosensitivity reactions. Having recently studied the photo(geno)toxicity associated with the TKI gefitinib (GFT) and its main phenolic metabolites (GFT-M1 and GFT-M2), a complete study of their photoreactivity has been carried out both in organic medium, using solvents of different polarities, and in a biological environment, using transport proteins such as human serum albumin (HSA) and human ¿1-acid glycoprotein (HAG). For this purpose, absorption, fluorescence and transient absorption techniques, among others, have been used. In addition, molecular dynamics simulation studies have been carried out to investigate the ligand@protein binding, as well as the interactions arising in the supramolecular complex after absorption of UV-A light. Therefore, a good correlation between the photophysical behaviour of gefitinib and its two phenolic metabolites and their phototoxic potential has been established in this research work. / Tamarit Mayo, L. (2024). Fotorreactividad de gefitinib y sus metabolitos fenólicos en disolución y en proteínas transportadoras [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/204145

Cette étude a pour but d’explorer le comportement de radicaux centrés sur des atomes de soufre dans des silices nanostructurées de type hexagonales 2D. Une large variété de silices a été synthétisée en jouant sur la nature et la charge en précurseurs organiques. La synthèse de silices de type SBA-15 fonctionnalisées avec des précurseurs de radicaux sulfanyle, sulfinyle et sulfonyle a été réalisée grâce au procédé sol-gel. Ces matériaux nanostructurés ont permis de fortement exalter la persistance des radicaux formés en leur sein.Des radicaux alkyl- et arylsulfanyle ont été formés par photolyse de thiols greffés dans des silices. Ces radicaux ont été piégés par la tert-butylphénylnitrone et les adduits de spin ainsi formés ont vu leur temps de vie grandement augmenter par rapport aux mêmes expériences conduites à partir de précurseurs non greffés. L’observation directe du radical arylsulfanyle à température ambiante a pu être réalisée, le temps de demi-vie pouvant aller jusqu’à plusieurs jours, même en présence de dioxygène.Des précurseurs contenant un motif diazène greffés dans une silice ont permis la formation et l’observation directe de radicaux arylsulfanyle, arylsulfinyle et arylsulfonyle par photolyse à température ambiante et par thermolyse à 200 °C. Selon les conditions, des temps de demi-vie de plusieurs heures ont été enregistrés. / The aim of this study is to explore the behavior of sulfur-centered radicals in 2D-hexagonal nanostructured silicas. A large variety of silicas was synthesized by varying the nature and the loading of organic precursors. Synthesis of SBA-15 silicas functionalized with sulfanyl, sulfinyl and sulfonyl radicals precursors was achieved according to the sol-gel process. These nanostructured materials led to a dramatic enhancement in the lifetime of generated confined radicals.Alkyl- and arylsulfanyl radicals were formed by photolysis of thiols grafted in silicas. These radicals were trapped by tert-butylphenylnitrone and the resulting spin-adducts got their lifetime strongly enhanced as compared to the same experiment conducted with non-grafted precursors. Direct observation of arylsulfanyl radicals at room temperature was also achieved, the half-lifetime of which was recorded to be several days, even in the presence of dioxygen.Precursors containing a diazene framework grafted onto silica enabled the formation and direct observation of arylsulfanyl, arylsulfinyl and arylsulfonyl radicals by both photolysis at room temperature and thermolysis at 200 °C. Depending on the conditions, half-lifetimes of several hours were recorded for these radicals.

É grande a preocupação quanto à presença de poluentes persistentes (POP) no ambiente aquático, devido ao potencial destes micropoluentes em afetar organismos aquáticos e a saúde humana. Dentre os POP estão os herbicidas atrazina (ATZ) e amicarbazona (AMZ), empregados no controle de ervas daninhas no cultivo de cana-de-açúcar, responsável por grande parte do consumo de herbicidas no país. O conhecimento do destino desses compostos no meio ambiente é essencial para avaliar seus potenciais impactos, embora não haja na literatura estudos detalhados relacionados a esse tema. No presente trabalho, através da combinação de resultados de experimentos realizados em simulador solar empregando matéria orgânica natural isolada, dados da literatura e simulações matemáticas, foi investigado o destino ambiental fotoquímico da AMZ, considerando as características de corpos d\'águas brasileiros. Analogamente e para fins de comparação, simulou-se o destino ambiental fotoquímico da ATZ com base em informações da literatura. Os resultados das simulações indicaram que a matéria orgânica dissolvida e a profundidade da coluna d\'água são as variáveis que mais influenciam na persistência dos dois herbicidas. O tempo de meiavida pode chegar a aproximadamente 2 meses e 1 ano, para AMZ e ATZ, respectivamente. Assim como é importante o entendimento do destino ambiental dos POP, também é essencial a investigação de processos avançados de oxidação desses poluentes, muitos dos quais são fotoirradiados. Procurando contribuir nesse sentido, neste trabalho estudou-se a fotólise da ATZ sob radiação UV em 254 nm, considerando os efeitos da taxa específica de emissão de fótons e da concentração inicial do herbicida. Procurou-se investigar detalhadamente o papel de espécies reativas de oxigênio (ROS) neste processo, resultados até então não discutidos na literatura. Além disso, os resultados obtidos para ATZ foram comparados aos disponíveis na literatura para AMZ. A degradação dos dois herbicidas diminui com o aumento da concentração inicial dos herbicidas, seguindo decaimento de pseudo primeira-ordem e aumentando com a taxa de emissão de fótons. Os resultados sugerem a formação de produtos persistentes e as ROS foram apontadas como atores importantes durante a degradação fotolítica dos herbicidas. / The presence of Persistent Organic Pollutants (POP) in aquatic environment is a subject of great concern, especially due to their capacity to affect not only aquatic organisms but also the human health. Herbicides as atrazine (ATZ) and amicarbazone (AMZ) are also classified as POP and are widely applied to control weeds on sugarcane cultivations, which are responsible for the increased consumption of herbicides in Brazil. The knowledge regarding the fate of these compounds once released into the environment represents an important issue and is also a type of information usually lacking in the available literature. Through the use of results obtained in experiments performed with a solar simulator, literature data, and mathematical simulations, the photochemical destination of AMZ in the environment was studied considering the characteristics of Brazilian surface water bodies. For purposes of comparison, the environmental destination of ATZ was also simulated. The results indicate that the dissolved organic matter and the depth of the water column are the most influential variables in the environmental persistence of these pesticides. Their half-life may extend up to 2 months to a year, for AMZ and ATZ, respectively. Besides the environmental fate, this investigation also aims to shine a light on the degradation of these contaminants in irradiated advanced oxidation processes. Accordingly, ATZ photolysis through the use of UV radiation (254 nm) was studied, whilst taking into consideration both the herbicide initial concentration and the specific photon emission rate. Another important contribution of this study is the investigation of the role of reactive oxygen species (ROS) in photolytic processes, a subject not usually discussed in the literature. In addition, a crossed-reference analysis between the results obtained for ATZ and those available in the literature for AMZ is presented. The degradation of both herbicides diminishes with the increase in their initial concentration and follows a pseudo first-order decay, increasing with the photon emission rate. Moreover, the results indicate that the formation of persistent degradation products does occur and that ROS play a crucial role in photolytic herbicide degradation.

Rhodopsin ist der Photorezeptor der Stäbchenzellen in der Retina von Vertebraten und wird als Prototyp für die gesamte Gruppe der GPCRs beforscht. Trifft ein Photon auf das Protein, so wird der über eine Schiffbase kovalent gebundene Chromophor von seiner 11-cis- in die All-trans-Konfiguration isomerisiert und setzt infolgedessen den Aktivierungsprozess in Gang. Dieser mündet in der aktiven Rezeptorkonformation, die das G-Protein Transducin aktivieren kann und dadurch eine Kaskade weiterer Aktivierungsschritten einleitet, die letztlich ein Nervensignal verursachen. Das Ziel dieser Arbeit war die Aufklärung der späten Aktivierungsschritte und ihrer Ursache-Wirkungs-Beziehungen. Zu diesem Zweck wurden Blitzlichtphotolyse, Elektronenspinresonanz (EPR) mit Spinlabeling (SDSL), UV/vis-Spektroskopie, FTIR-Spektroskopie und Fluoreszenzspektroskopie angewandt. Kinetische Messungen wurden unter identischen Bedingungen durchgeführt, um die Abfolge der mit den unterschiedlichen Techniken zugänglichen Aktivierungsschritte aufzuklären. Nach der Bildung des absorptionsspektroskopisch definierten Meta-II-Zustands bewegt sich die Helix TM6 in einem späteren Schritt als ganzes nach außen und markiert damit den Übergang von Meta-IIa zu Meta-IIb. Dadurch wird die bis dahin in der Membran verborgene D(E)RY-Region für das Umgebungsmedium zugänglich und nimmt ohne Zeitverzögerung ein Proton auf, wodurch der Meta-IIb*H+-Zustand gebildet wird. Die verfügbaren Daten sprechen dafür, dass das D(E)RY-Motiv bei der Aktivierung des Transducins sowohl die Alpha- als auch die Gamma-Untereinheit desselben bindet. Die Bindung von zu Transducin-Abschnitten analogen Peptiden kann dann erfolgen, wenn die Helix TM6 im nach außen bewegten Zustand ist, und führt zur Abgabe von bis zu zwei Protonen vom aktivierten Rhodopsin. Sowohl das D(E)RY- und das NPxxY(x)5,6F-Motiv als auch die beiden Zustände Meta-IIb und Meta-IIb*H+ könnten relevant für den sequenziellen Transducin-Aktivierungsmechanismus sein. / Rhodopsin is the photoreceptor in the rod cells of the vertebrate retina. It is considered as a prototype of the whole group of GPCRs. Upon absorption of a photon the chromophore, which is covalently bound through a Schiff base, is isomerized from its 11-cis into the all-trans configuration. This initiates the activation process and finally results in the active receptor conformation which is capable of activating the G protein transducin and thereby triggers a cascade of further activation steps which finally cause a nerve signal. The aim of this work was the clarification of the late activation steps and their cause-and-effect chain. For this purpose flash photolysis, electron paramagnetic resonance (EPR) with spin labeling (SDSL), UV/vis spectroscopy, FTIR spectroscopy and fluorescence spectroscopy were applied. Kinetic measurements were executed under identical conditions in order to elucidate the sequence of activation steps, which are accessible with the different techniques. After formation of the spectroscopically defined Meta-II state helix TM6 moves outward as a rigid body, thereby marking the transition from Meta-IIa to Meta-IIb. Therefore the D(E)RY region, which is until then buried in the membrane, gets accessible to the surrounding solution. It consequently takes up a proton without delay, thus forming the Meta-IIb*H+ state. Available data argue for the D(E)RY motif binding both the Alpha and the Gamma subunit of transducin during activation of the latter. The binding of peptides which are analogous to sections of transducin is possible when helix TM6 is in the outward position. It causes the release of up to two protons from the activated rhodopsin. Both the D(E)RY motif and the NPxxY(x)5,6F motif as well as both the states Meta-IIb and Meta-IIb*H+ are potentially relevant for the sequential transducin activation mechanism.

Die vorliegende Arbeit beschäftigt sich mit der Untersuchung von a-Azidoalkoholen, welche über die Reaktion von aliphatischen sowie aromatischen Aldehyden mit HN3 leicht zugänglich sind und die im Gleichgewicht mit den jeweiligen Ausgangsstoffen vorliegen. Bei Raumtemperatur stellt sich dieses Gleichgewicht sehr schnell ein und man erhält spezifische Konzentrationen an Eduktaldehyd, Stickstoffwasserstoffsäure und a-Azidoalkohol. Die Reaktion von Aldehyden mit HN3 generiert dabei ein neues Chriralitätszentrum, wodurch die Umsetzung chiraler Aldehyde, wie z. B. von Zuckerderivaten, zwei anomere Produkte hervorbringt. Die erstmalig erfolgreichen Synthesen zur Erzeugung von 4-Brom-4-methylpentanal sowie 4-Azido-4-methylpentanal werden ebenfalls beschrieben. Letztere Verbindung reagiert dabei ebenso wenig via einer intramolekularen 1,3-dipolaren Cycloaddition zum entsprechenden 4,5-Dihydro-1,2,3,4-oxatriazol-Derivat wie das analoge-Azidobutanal, was im Gegensatz zu Literaturangaben steht. Des Weiteren werden einige interessante Reaktionen der a-Azidoalkohole untersucht. Die Oxidation mit Pyridiniumchlorochromat (PCC) bei –60°C führt zu Carbonylaziden. Die Photolyse bei –50°C generiert unter Stickstofffreisetzung Nitrene, welche mittels Wasserstoffwanderung und anschließender Tautomerisierung des resultierenden Intermediats zu Säureamiden umlagern. Die ebenfalls mögliche 1,2-Wanderung einer Gruppe R in a-Position führt dabei zu einem Intermediat, aus welchem sofort das entsprechende Formamid-Derivat entsteht. a-Azidoalkohole reagieren mit PBr3 in einer sauberen Reaktion durch die Substitution der Hydroxylfunktion unter Bildung der jeweiligen 1-Azido-1-brom-Verbindung. / In this work, α-azido alcohols which exist in equilibrium with the starting materials have been studied by the reactions of aliphatic and aromatic aldehydes with HN3. In some cases the title compounds can be isolated from the mixture at low temperature. At room temperature, however, the equilibrium is fast and there are again specific concentrations of the aldehyde, hydrazoic acid, and the α-azido alcohol. The reaction of aldehydes with HN3 creates a new chiral center and a chiral aldehyde, e.g. sugar derivatives, produces two anomeric products. The first procedures to prepare 4-bromo-4-methylpentanal and 4-azido-4-methylpentanal are also reported. The latter compound and also the parent 4-azidobutanal do not lead to 4,5-dihydro-1,2,3,4-oxatriazoles by intramolecular 1,3-dipolar cycloaddition, although it was claimed in the literature. Furthermore, some interesting reactions of the α-azido alcohols have been investigated. The oxidation of α-azido alcohols with pyridinium chlorochromate (PCC) at −60 °C leads to formation of carbonyl azides. The photolysis of α-azido alcohols at −50 °C generates nitrenes with liberation of dinitrogen, which lead to the formation of acid amides after the migration of hydrogen and subsequent tautomerism of the intermediate. 1,2-Migration of a group R in the α-position can produce an intermediate stage which is rapidly converted into formamide derivative. α-Azido alcohols react with PBr3 to give 1-azido-1-bromo derivatives in a clean reaction by substitution of hydroxyl group at the α-position.

Artificial photosynthesis is often considered to have great potential to provide alternative, renewable fuels by harvesting, conversion and storage of solar energy. One promising approach is the development of modular molecular photocatalysts inspired by natural photosynthetic enzymes. The first part of this thesis deals with artificial mimics of the water oxidizing photosystem II composed of a chromophore and an electron relay as synthetic counterpart of the P680-TyrZ/His190 ensemble of photosystem II. Three ruthenium polypyridyl - imidazole - phenol complexes with varying position of a methyl group on the phenol ring (Ru-xMe) were synthesized and characterized by electrochemical and photophysical methods. As an improvement compared to earlier complexes the increased redox potential (~0.9 V vs. Ferrocene) of the phenol groups makes their function as an electron relay in a photocatalytic system for water oxidation thermodynamically possible. Time-resolved absorption studies revealed fast intramolecular electron transfer (<5-10 µs in aprotic solvent and <100 ns in water) despite the low driving force and the importance of the hydrogen bond between the phenol and the imidazole group was put in evidence. Slight differences between the three Ru-xMe complexes and investigation of the effect of external bases allowed to derive a mechanistic picture in which the imidazole is involved in a "proton domino" reaction. Accepting the phenolic proton upon ligand oxidation (within the H-bond) renders its second nitrogen site more acidic and only deprotonation of this site pulls the overall equilibrium completely towards oxidation of the ligand. Another part of this thesis comprises a chromophore-tryptophan construct synthesized using a click chemistry approach. Light-induced oxidation of Trp in this Ru-tryptophan complex was shown to follow ETPT mechanism. Depending on the pH conditions tryptophan radicals, either Trp* or TrpH*⁺ were detected and spectral measurement at different time showed the transition between the two forms. Deprotonation of the radical was dependent on the concentration of water as proton acceptor. Later part of the thesis deals with efforts to covalently bind a catalytic unit to the previously characterized chromophore-electron relay module. The click chemistry approach was not successful to obtain the final photocatalytic assembly. Therefore bimolecular activation of a Mn salen catalyst was performed and formation of Mn(IV) species was observed. As a step towards utilization of these types of photocatalysts in a photoelectrochemical cell a [Ru(bpy)₃]²⁺ chromophore with phosphonate anchoring groups (Ru-Phosphonate) was synthesized and grafted on the surface of a TiO₂ mesoporous semiconductor surface anode to perform photocurrent measurements.