Neste trabalho, apresentamos a eletrossíntese de um novo polímero condutor derivado do polipirrol (PPI) funcionalizado com um grupo carboxílico, o polipirrol-2-ácido carboxílico (PPI-2-COOH), e o seu uso como transdutor amperométrico em biossensores pelo uso da polifenol oxidase (PFO). São apresentadas todas as etapas de síntese e de caracterização dos filmes poliméricos em microeletrodos e o preparo e a resposta dos biossensores montados para a detecção de um composto fenólico. Nossos estudos sobre eletrossíntese, respostas eletroquímicas dos filmes, juntamente com resultados de microgravimetria e modelagem molecular de dímeros e trímeros derivados de PI-2-COOH, permitiram com que pudéssemos sugerir pela primeira vez um mecanismo de eletropolimerização deste monômero em meio não aquoso. Na caracterização dos filmes por espectroscopia in situ no UV-visível e infravermelho próximo foram observadas duas bandas idênticas às transições pi-pi* características dos filmes de PPI no seu estado neutro e de maior dopagem, confirmando a possibilidade de haver duas conformações na cadeia do PPI-2-COOH. Com a modelagem molecular de um oligômero formado a partir da oxidação do PI-2-COOH, verificamos que para cada 4 anéis heterocíclicos acoplados entre si na posição 4-5, um par de anéis se encontrava em um plano diferente do segundo par de anéis, mantendo este padrão em toda a extensão da cadeia polimérica. A resposta redox dos filmes nos permitiu observar a preferência do polímero pela entrada de cátions em sua estrutura. Nos espectros de FTIR também comprovamos a presença do grupo carboxílico na estrutura do polímero, o que permitiu uma imobilização enzimática por ligação covalente. A confecção de microeletrodos destinados para a análise por injeção em fluxo (FIA) nos possibilitou uma economia de reagentes, praticidade e boa reprodutibilidade das medidas. Os biossensores amperométricos obtidos pela imobilização covalente da PFO sobre filmes de PPI-2-COOH apresentaram um pH ótimo de funcionamento em 9,4 e um potencial ótimo de trabalho em +70 mV vs Ag/QRE. Finalizamos nosso trabalho obtendo as respostas amperométricas dos biossensores para a detecção de um composto fenólico, pirocatecol, com uma linearidade entre as concentrações de 5x10-4 até 2,5x10-2 mol/L. / In this work, we present the electrochemical synthesis of a new conducting polymer derived of polypyrrole (PPI) functionalized by carboxylic group, the polypyrrole-2-carboxylic acid, and its application as amperometric transducer in biosensor by use of polyphenol oxidase (PFO). All the steps of syntheses and characterization of the polymer film in microelectrodes and response of the biosensor build for detection of phenolic compost. Our study about electrosyntheses, electrochemical response of the films (PPI-2-COOH) together with microgravimetry result and the molecular modeling of dimer and trimer derived from PI-2-COOH allowed one to suggest, for the first time, the mechanism of electropolymerization of this monomer in non-aqueous medium. When the technique of in-situ ultraviolet-visible spectroscopy (UV-VIS in-situ) was observed two bands, identical to the transition pi-pi* which are characteristics of the PPI films on their neutral state and of bigger doping, confirming the possibility that there may be two conformations in the PPI-2-COOH chain. With the molecular modeling of an oligomer formed by PI-2-COOH oxidation, we verified that for each four heterocyclic ring coupled together in the position 4-5, there´s a pair of rings, maintaining this pattern in all the extension of the polymeric chain. The redox response through the electrochemical measurement we could observe in FTIR the polymer preference for the cations adsorption. On the FTIR measurements, we could also observe the presence of the carboxylic group in the polymers structure, which is needed for the enzymatic immobilization by covalent binding. The fabrication of the microelectrode destined to flow injection analysis (FIA), made possible not only to save a lot of reagents, but also demonstrated praticity in the experimental set up and good reproducibility of results. Hence, the obtaining of amperometric biosensor by covalent binding of PFO on the PPI-2-COOH film, presented good pH in 9.4 and great work potential in +70 mV vs Ag/AgCl. We finish the work with the amperometric response of the biosensor in the detection of pyrocatechol, forming a straight line between the concentrations of 5x10-4 to 2.5x10-2 mol/L.

Ces dernières années, la notion de Développement Durable a bouleversé la recherche académique etindustrielle dans le domaine de la chimie. L’utilisation de matières premières issues des ressources renouvelables en constitue l’un des aspects les plus marquants. De même, le développement de procédés originaux, qui s’appuient sur des systèmes catalytiques recyclables, des transformations chimiques innovantes et de nouveaux solvants plus respectueux de l’environnement font l’objet d’un intérêt croissant, en raison des gains environnementaux et économiques. Les travaux de recherche décrits dans cette thèse s’inscrivent dans ce contexte et présentent la mise au point de nouvelles voies d’accès aux éthers de glycérol, des molécules à haute valeur ajoutée. Plusieurs procédés originaux ont été développés en utilisant le glycérol comme substrat biosourcé issu de l’industrie oléo-chimique. Ainsi, l’alkylation réductrice d’acides carboxyliques avec le glycérol en présence de palladium sur charbon et d’une résine acide a permis de préparer une variété de 1-Oalkyléthersde glycérol. Une procédure alternative a été développée à partir des huiles végétales et des esters méthyliques, par transestérification puis réduction de l’ester intermédiaire sous hydrogénation catalytique. Ensuite, un procédé d’alkylation déshydrogénante de dérivés de la cyclohexanone avec le glycérol a donné un nouvel accès aux 1-O-aryléthers de glycérol et a été étendu aux éthers et aux amines aromatiques. Enfin, de nouveaux solvants aprotiques dérivés du glycérol ont été synthétisés par une catalyse de transfert de phase. En particulier, la toxicité du 1,2,3-triméthoxypropane ainsi que son utilisation dans des transformations chimiques comme nouveau solvant ont été évaluées. / In recent years, sustainable development brought unprecedented changes in industrial and academic researches. The use of raw materials from renewable resources is one of the most outstanding aspects of these changes. The development of original processes, with recyclable catalytic systems, new chemical transformations as well as new solvents with a lower environmental impact are of growing interest, because of environmental and economical profits. The research work described in this thesisis focused on the development of new accesses to glyceryl ethers as high value added coumpounds.Thus, several processes were developed by using glycerol as accessible and bio-based starting material from the oleochemical industry. First, we found a benign and eco-friendly process for the synthesis of1-O-alkyl glyceryl ethers by catalytic reductive alkylation of carboxylic acids with a recyclable catalytic system associating palladium on carbon and an acid ion exchange resin. A second two steps procedure was also developed when starting from a vegetable oil or a methyl ester, which was transesterified to the corresponding monoglyceride followed by its reduction by catalytic hydrogenation. We report also a straight forward and palladium catalyzed dehydrogenative alkylation of cyclohexanone derivatives with alcohols, including glycerol, and amines in order to prepare avariety or aryl ethers and aryl amines. Finally, we prepared new aprotic and glycerol-based solvents bya solvent-free phase-transfer catalysis. In particular, the toxicity of 1,2,3-trimethoxypropane and its utilization as alternative solvent in chemical transformations was evaluated.

No description available.

Vibrational sum frequency spectroscopy har använts för att studera interaktionerna mellan monovalenta joner och laddade fettsyramonolager. Subfasen bestod av utvalda alkalihydroxidsaltlösningar med pH12, med huvudfokus på cesiumjonen. Molekylär information erhölls genom att rikta in sig på vibrationerna hos karboxylsyragruppen, alkylkedjor, och vattenmolekyler i kontakt med monolagret, samt i det diffusa dubbellagret. Ytans laddning uppskattades genom att observera sträckningsvibrationerna hos hydratiserade karboxylat och protonerade karboxylsyror. Ytans potential beräknades utifrån signalresponsen hos vattenmolekylerna i det diffusa dubbellagret. Beteendet hos ytans laddning och potential överensstämmer väl med Gouy-Chapman-teorin för stora områden per molekyl, men avviker avsevärt vid kompression av monolagret. Vid små områden per molekyl, eller hög laddningsdensitet, stämmer resultaten bättre överens med en storleksmodifierad version av Poisson-Boltzmann-teorin. Resultaten från experiment med en cesiumhydroxidsubfas jämfördes med motsvarande experiment med natrium och litium, vilket beskriver cesiumjonen i relation till de andra alkalijonerna vad gäller jonspecifika effekter. Resultaten som har samlats in här ger insikt i hur effektiv jonstorlek kan användas för att modellera och förutsäga jonspecifika effekter med karboxylsyragruppen i ett Langmuir-monolager. / Vibrational sum frequency spectroscopy has been used to study the interactions of monovalent ions with highly charged fatty acid monolayers. The subphase consisted of selected alkali hydroxide salt solutions of pH 12, primarily focusing on the cesium ion. Molecular information was obtained by targeting the vibrational modes of the carboxylic acid headgroups, alkyl chains, and water molecules in the immediate surface and diffuse double layers. The surface charge was estimated by monitoring the stretching modes of the hydrated carboxylate and protonated carboxylic acid. The surface potential was estimated from the signal response of the water molecules in the diffuse double layer. The behaviour of the surface charge and surface potential agrees well with Gouy-Chapman theory for large areas per molecule, but deviates significantly upon monolayer compression. At small areas per molecule or high surface charge density, the results better align with a size-modified version of the Poisson-Boltzmann theory. The results obtained with a cesium hydroxide subphase were compared to equivalent experiments with sodium and lithium, which puts the cesium ion into context with the other alkali ions in terms ion specific effects. The results collected here provide insight into how effective ion size can be used in modelling and predicting ion specific effects with the carboxylic acid moiety in a Langmuir monolayer.

No description available.

Magnetic nanoparticles that display high saturation magnetization and high magnetic susceptibility are of great interest for medical applications. Nanomagnetite is particularly desirable because it displays strong ferrimagnetic behavior, and is less sensitive to oxidation than magnetic transition metals such as cobalt, iron, and nickel. Magnetite nanoparticles can be prepared by co-precipitating iron (II) and iron (III) chloride salts in the presence of ammonium hydroxide at pH 9-10. One goal of this work has been to develop a generalized methodology for stabilizing nanomagnetite dispersions using well-defined, non-toxic, block copolymers, so that the resultant magnetite-polymer complexes can be used in a range of biomedical materials. Hydrophilic triblock copolymers with controlled concentrations of pendent carboxylic acids were prepared. The triblock copolymers contain carboxylic acids in the central urethane segments and controlled molecular weight poly(ethylene oxide) tail blocks. They were utilized to prepare hydrophilic-coated iron oxide nanoparticles with biocompatible materials for utility in magnetic field guidable drug delivery vehicles. The triblock copolymers synthesized contain 3, 5, or 10 carboxylic acids in the central segments with Mn values of 2000, 5000 or 15000 g/mol poly(ethylene oxide) tail blocks. A method was developed for preparing ~10 nm diameter magnetite surfaces stabilized with the triblock polymers. The carboxylic acid is proposed to covalently bind to the surface of the magnetite and form stable dispersions at neutral pH. The polymer-nanomagnetite conjugates described in this thesis have a maximum of 35 wt. % magnetite and the nano-magnetite particles have an excellent saturation magnetization of ~66 - 78 emu/g Fe3O4. Powder X-ray diffraction (XRD) confirms the magnetite crystal structure, which appears to be approximately single crystalline structures via electron diffraction spectroscopy analysis (EDS). These materials form stable magnetic dispersions in both water and organic solvents. / Ph. D.

Les travaux rapportés dans ce manuscrit ont porté sur la synthèse et l’étude structurale d’oligopeptides contenant l’acide N-aminoazétidine-2-carboxylique AAzC, dans le but de caractériser un nouveau foldamère.Nous avons dans un premier temps préparé les quatre stéréoisomères de l’acide 2 aminocyclobutane carboxylique ACBC et les deux stéréoisomères de l’AAzC. Ces synthèses ont été réalisées en employant deux méthodes similaires, rapportées par notre laboratoire, comportant une étape-clé de photocycloaddition [2 + 2] entre l’éthylène et l’uracile ou l’aza-uracile. L’étude de l’AAzC dans des couplages peptidiques a ensuite révélé une réactivité difficile à maîtriser à cause d’une forte propension à l’ouverture du cycle azétidine, ce qui nous a conduit à ne pouvoir synthétiser que des oligopeptides contenant un unique résidu AAzC, qui plus est en position N terminale. Trois cyclobutylamides du cis-ACBC, du trans-ACBC et de l’AAzC ainsi qu’un cyclobutylester de l’AAzC ont alors été préparés avec de bons rendements. Le couplage du (S) AAzC avec chacun des stéréoisomères de l’ACBC a fourni quatre dipeptides mixtes Boc−AAzC−ACBC−OMe avec de bons rendements également. Enfin, nous avons synthétisé des tétrapeptides, hexapeptides et octapeptides homochiraux du cis-ACBC ou du trans ACBC comportant un unique résidu (S)-AAzC en position N-terminale. Les composés de la série cis ont présenté une forte tendance à la gélification, entraînant une chute du rendement et augmentant la difficulté pour la caractérisation et l’analyse structurale.Enfin, nous avons analysé la structuration de ces différents composés par spectroscopie IR en solution, RMN, dichroïsme circulaire, modélisation moléculaire et diffraction des rayons X. Deux techniques de RMN plus poussées, l’IMPACT HMBC 1H-15N et la SOFAST HMBC 1H-13C ont été utilisées afin de détecter des liaisons H intramoléculaires. Nous avons ainsi pu mettre en évidence la formation d’un hydrazino turn en solution et à l’état solide pour le cyclobutylamide du (S)-AAzC. Cette structuration en hydrazino turn a également été observée pour les quatre dipeptides Boc−AAzC−ACBC−OMe, cependant en présence d'un second conformère pour les dérivés du cis ACBC. Les différentes analyses nous ont permis de conclure que le tétrapeptide Boc−AAzC−[t ACBC]3−OMe et l’hexapeptide Boc−AAzC−[t ACBC]5−OMe adoptent une structuration en hélice 8 dans le chloroforme, avec la formation d’un hydrazino turn dans la partie N-terminale. L’octapeptide Boc−AAzC−[t ACBC]7−OMe adopte quant à lui une structure chimère dans la pyridine, comportant un hydrazino turn dans la partie N-terminale puis se poursuivant en hélice 12 dans la partie C-terminale comme l’hexamère et l’octamère du trans ACBC.Nous avons ainsi montré que l’AAzC possède une préférence forte pour une structuration locale en cycle à 8 chaînons, mais également une forte tendance à induire une hélice 8, jusqu'à une certaine distance dans un oligopeptide. / This thesis is devoted to the synthesis and structural study of oligopeptides containing N aminoazetidine-2-carboxylic acid (AAzC), to find a new foldamer.First, we prepared each of the four stereoisomers of 2-aminocyclobutane carboxylic acid (ACBC), and the two stereoisomers of AAzC. This has been done using two similar techniques from our lab, based on a [2 + 2] photocycloaddition key-step between ethylene and uracile or aza-uracile. Peptide coupling using AAzC revealed a tricky reactivity of this new building block, due to an easy ring-opening. We were thus able to synthesize only oligopeptides containing a single AAzC residue, blocked in the N-terminal position. Three model cyclobutylamide derivatives containing ACBC or AAzC and one model AAzC cyclobutylester were prepared. Synthesis of four dipeptides each incorporating AAzC in the N terminal position and a single stereoisomer of ACBC in the C terminal position was performed within good yields. Finally, oligopeptides comprising a sequence of trans or cis-ACBC residues bearing a single AAzC unit at the N terminal position were obtained. Cis-oligopeptides were difficult to analyze due to gelation phenomenon.The folding behaviour of these peptides was examined on the basis of IR spectroscopy, NMR studies, circular dichroism, molecular modelling studies and X-ray diffraction. Two new NMR techniques, IMPACT HMBC 1H-15N and SOFAST HMBC 1H-13C were used to detect intramolecular hydrogen bonds. We proved the existence of a hydrazino turn for the AAzC cyclobutylamide and the four Boc−AAzC−ACBC−OMe dipeptides. For longer oligopeptides, analyzes revealed an 8-helix structuration in chloroform for both the tetrapeptide Boc−AAzC−[t ACBC]3−OMe and hexapeptide Boc−AAzC−[t ACBC]5−OMe, helped by a hydrazino turn in the N-terminal position. Finally, octapeptide Boc−AAzC−[t ACBC]7−OMe shows in pyridine a chimeric structure, starting with a hydrazino turn in the N-terminal position but going on with a 12-helix in the C-terminal position as in trans-ACBC hexamer or octamer.We demonstrated here that AAzC has a strong preference for an 8-membered ring local structuration, and a strong tendency to induce an 8-helix in a peptide.

Palladium complexes have the ability to catalyse cross-coupling of two organic moieties through the formation of transient metal-carbon bonds, thus bringing them closer to each other to facilitate the formation of a new bond. Palladium-catalysed coupling reactions are one of the most important carbon-carbon forming reactions available to organic chemists and many of these reactions rely on the reactivity of aryl-palladium complexes. The investigation of new aryl-palladium precursors is thus of great interest, especially as more sustainable and economic methods can be developed. This thesis describes the use of carboxylic acids and sodium arylsulfinates as such new arylating agents. Protocols for microwave-assisted palladium(II)-catalysed decarboxylative synthesis of electron-rich styrenes and 1,1-diarylethenes were developed. However, these transformations had very limited substrate scopes which prompted the investigation of sodium arylsulfinates as alternative arylating agents. These substrates were employed in the microwave-assisted palladium(II)-catalysed desulfitative addition to nitriles, and the substrate scope was demonstrated by combining a wide array of sodium arylsulfinates and nitriles to yield the corresponding aryl ketones. The application of the desulfitative reaction in a continuous flow setup was demonstrated, and aluminium oxide was identified as safe alternative to borosilicate glass as a reactor material. The mechanisms of the decarboxylative and desulfitative transformations were investigated by density functional theory (DFT) calculations. The desulfitative reaction was also investigated by direct electrospray ionization mass spectrometry (ESI-MS), providing further mechanistic insight. Finally, a protocol for the safe and convenient synthesis of a wide range of sodium arylsulfinates was developed.

Este trabalho apresenta o estudo de um sistema polimérico bi-componente formado por Poli(Ácido carboxílico)-Poli(Eter-poliol), constituído primariamente de um polímero acrílico polimerizado pelo processo de polimerização em solução aquosa por mecanismo de radicais livres ao qual foi adicionado seqüencialmente, um Poli(Eter-poliol), ambos de baixo peso molecular médio. Tal sistema tem por finalidade atuar como dispersante-ligante em sistema cerâmico à base de caulim CADAM, uma vez que este sistema apresenta propriedades termoplásticas e termorrígidas a diferentes temperaturas. Foram sintetizados 03 protótipos de um sistema polimérico e o critério para escolha teve como base o pH do sistema em sentido generalizado, isto é, compreendendo as diversas fases de preparação dos polímeros e sua aplicação final. É do conhecimento comum que a reação de esterificação entre grupos COOHOH requer catálise ácida para ocorrer, o qual usualmente é realizada em pH abaixo de 4 e, neste ensaio, este pH ácido é devido à presença de ácido para-toluenosulfônico, que atua como catalisador de esterificação. Em tal intervalo de pH, em virtude do ponto isoelétrico do caulim ser comumentemente abaixo de 4, a estabilização da dispersão de caulim por repulsão eletrostática utilizando polímeros sintéticos é improvável de ocorrer, razão pela qual buscou-se mecanismos alternativos para obtenção de uma tal estabilização, entre os quais o mecanismo estérico surge como opção. O sistema polimérico do presente estudo apresenta-se na forma de uma solução aquosa sendo, de fato, uma mistura homogênea de um copolímero de ácido acrílico, N- metiloacrilamida e metacrilato de metoxipolietileno glicol e um poli(eter-poliol). O poli(eter-poliol) e N-metilolacrilamida presentes no sistema polimérico são principais fontes de grupo hidroxila para reação de poliesterificação e formação de ligações cruzadas à temperatura de 150 a 200 °C. No estado termoplástico o sistema polimérico produzido pela mistura poli(ácido carboxílico)-poli(eter-poliol) pode ser utilizado como dispersante de argilas com especial fóco sobre caulim como tratado neste trabalho. A propriedade dispersante pode ser atribuida à presença de grupos carboxílicos e metoxipolietilenoglicol aleatoriamente distribuídos ao longo da cadeia polimérica e, também, ao baixo peso molecular médio. A temperaturas entre 150 a 200 °C, o polímero é reticulado (crosslinked) por reação de poliesterificação, catalisada por ácido, entre grupos carboxila e grupos hidroxila, sendo as hidroxilas provenientes tanto de poliol como de N-metilolacrilamida (NMAM). Assim, do ponto de vista térmico comporta-se como termorrígido, sendo nesta condição insolúvel em água e adequado atuar como ligante na manufatura de materiais cerâmicos. Medidas de mobilidade eletroforética e viscosidade são aplicadas à caracterização de caulim e do sistema polimérico a fim de avaliar a potencialidade de aplicação como dispersante desta argila. Também, as transições dos estados termoplásticos para termorrigidos foram determinadas por análise termogravimétrica (TG) e análise dinâmico mecânica (DMA) nos polímeros isoladamente e depois com medidas de resistência mecânica do sistema caulim/polímero. O sistema apresentou comportamento dispersante em água e ligante após cura. Um sistema polimérico assim sintetizado foi propriamente curado por calor tornando- se, na forma termorrígida, um ligante para peças cerâmicas com propriedades mecânicas de alto desempenho, como resistência a flexão no estado cru (green strenght). / This work presents the study of a polymeric bi-component system made from Poly(carboxylic acid)-Poly(ether-polyol) primarily constituted of an acrylic acid polymerized through the process of aqueous solution polymerization by free radical mechanism, to which a poly(ether-polyol) has been sequentially added, both of them of low average molecular weight. Such a system has the aim to act as dispersing-binding balance on CADAM kaolin targeting to evaluate the applicability potential or the preparation of ceramic bodies as this polymeric system presents thermoplastic and thermosetting properties at different temperatures. Were made the synthesis of 03 polymeric system prototypes which criteria for choice was based on pH of the system at whole sense, that is, regarding the several steps for polymers preparation and its final application. It is knowledge that esterification reaction between COOH-OH groups requires acid catalyst to occur, which usually is done at pH below 4 and, in this work this pH is due to p-toluene sulfonic acid that act as esterification catalyst. In this range of pH, due to the isoeletric point of kaolin to be below 4 the electrostatic stabilization of dispersion is unlikely to occur, from which reason was looked for an alternative mechanism to achieve the dispersion stabilization, among them the steric mechanism arises an option. The polymeric system of this study is the form of an aqueous solution, which actually is a homogeneous blend of a copolymer of acrylic acid, N-Methylolacrylamide Methoxypolyethyleneglycol Methacrylate (MPEGMA) and Poly(ether-polyol). The Poly(etherpolyol) and the N-Methylolacrylamide presents at the polymeric system are the main sources of hydroxyl groups to enhance the polyesterification reaction for further crosslinking at temperatures from 160 to 200 °C. At the thermoplastic state the polymeric system made by Poly(carboxilic acid)poly(ether-polyol) macromolecules may be used as clay dispersant focusing on kaolin for this work. The dispersant property may be attributed to the carboxylic and methoxypolyethyleneglycol group randomly distributed along the polymeric chain backbone and, also to the low average molecular weight. At temperatures between 150 to 200 °C, the polymer is crosslinked by polyesterification reaction catalized by acid between carboxyl groups and hydroxyl groups, in such way that hydroxyls groups comes both from the polyol base polymer and NMethylolacrylamide (NMAM) present at first polymer backbone. Thus, through a thermal standpoint it behaves as thermoset being that, under this condition, water insoluble and adequate to act as binder for manufacturing of ceramic materials. Electrophoretic mobility and viscosity measurements were applied for the characterization of kaolin and the polymeric system targeting to the evaluation its potential application as a dispersant for this clay. Also, the transitions from the thermoplastic to the thermoset state have been determined by thermo-gravimetric analysis (TG) and dynamicmechanical analysis (DMA) for the Poly(carboxylc acid)poly(ether-polyol) polymers alone and further by mechanical resistance measurements for a clay-polymer system. The system has presented both dispersant behavior on aqueous media and binder just afterward cure. A polymeric system thus synthesized was properly cured by heat turning and then, at the thermoset state, become suitable for act as a binder for ceramic bodies with high performance mechanical properties measured as flexural resistance at green strength.

L’oxydase de l’acide 1-AminoCyclopropane Carboxylique (ACC Oxydase, ACCO) catalyse la formation de l’éthylène, hormone essentielle à la vie des plantes. L’ACCO catalyse l’oxydation de l’ACC en éthylène en présence de dioxygène et de deux électrons (fournis in vitro par l’ascorbate). L'activité de l'enzyme requière également, pour des raisons encore incomprises, la présence de CO2 sous la forme d'ions bicarbonates. Il s’agit d’une enzyme qui contient un ion fer(II) dans un environnement non-hémique au site actif. Etant donné l’importance de l’éthylène chez les plantes, l’ACCO, ainsi que les autres enzymes impliquées dans sa biosynthèse, ont été très étudiées durant les vingt dernières années. Cependant, peu d’études ont porté sur le rôle de l’ion métallique et le mécanisme d’action ou sur les surprenants processus d’inactivation subis par l’enzyme. L’ACCO est en effet une enzyme connue pour son instabilité. Nous avons tout d’abord entrepris une caractérisation physicochimique et biochimique de l’enzyme. Le matériel protéique utilisé a tout d’abord été analysé une coupure entre les résidus Ala 290 et Gly 291 a été observée au cours de la purification de l'enzyme. Puis, grâce à l'utilisation de techniques spectroscopiques, nous avons cherché à obtenir plus d'informations sur la fixation des substrats/cofacteurs au site actif. Enfin l’étude des mutants et des complexes modèles de l’ACCO a été réalisée afin de mieux comprendre le mécanisme catalytique et de rechercher de nouvelles activités. Nous nous sommes aussi intéressés aux mécanismes d’inactivation de l’ACCO. En présence des effecteurs en excès, cette inactivation se traduit par une fragmentation et une modification de charge. Lorsque la concentration en fer est limitée, aucune modification physique de l’enzyme inactive n’est observée et l'enzyme garde un contenu global en aminoacide et une conformation tridimensionnelle intègres. Des processus oxydatifs se déroulant directement au site actif de l’enzyme sont susceptibles d’engendrer une telle perte d’activité par l'oxydation d'un nombre limité d'acides aminés. Des études en spectrométrie de masse ont été entreprises et sont toujours en cours afin d'identifier les modifications responsables de la perte d'activité de l'enzyme.Enfin nous avons recherché d’éventuelles partenaires protéiques qui pourraient conférer à l’ACCO une meilleure stabilité. Des études préliminaires ont été entreprises et des données de microscopie suggèrent que l'ACCO est localisée près des membranes de la vacuole. / The 1-AminoCyclopropane Carboxylic acid oxidase (ACC Oxidase, ACCO) catalyzes the last step of the biosynthesis of the plant hormone, ethylene. ACCO catalyzes the oxidation of ACC into ethylene in the presence of dioxygen and two electrons (provided in vitro by ascorbate). Carbon dioxide (or bicarbonate ions) are also required for optimum activity. ACCO is an non-heme iron(II) containing enzyme. Given the importance of ethylene in plants, studies on ACCO, as well as on the other enzymes involved in its biosynthesis, have attracted much attention in the past two decades. However, few studies focus on the role of the metal ion and on the catalytic mechanism or the intriguing inactivation processes. ACCO is indeed known for its instability. We first purified and characterised the enzyme. During the purification, a cleavage between residues Ala 290 and Gly 291 was observed. Then, using spectroscopic techniques, we intended to get more information on cofactor's binding in the active site. Finally studies of mutants and model complexes of ACCO were performed in order to get a better understanding of the catalytic mechanism and to look for new activities.We were also interested in the inactivation processes of ACCO. In the presence of an excess of effectors, this inactivation resulted in fragmentation and in pI modification. When the concentration of iron is limited, no modifications of the inactive enzyme were observed. The inactive enzyme maintained its amino acid content and three-dimensional conformation. The loss of activity is therefore likely to derive from oxidative processes directly at the active site. Mass spectrometry experiments were initiated and are still under progress. Finally we were interested in identifying possible protein partners of ACCO that could provide a better stability. Preliminary studies were thus initiated and from microscopy results, ACCO was found located close to the vacuole membrane.