Les protéines carnées apportent tous les acides aminés indispensables, en quantité équilibrée par rapport aux besoins de l'Homme. La viande étant également une bonne source de vitamine B12 et de fer, son potentiel nutritionnel est très élevé. Ce potentiel pourrait cependant être modulé 1) par une digestion des protéines plus ou moins complète dans l'intestin grêle, déterminant la quantité d'acides aminés absorbés, 2) par une vitesse de digestion plus ou moins élevée, influençant la capacité d'assimilation des acides aminés absorbés. Les procédés de transformation impliqués dans la préparation des viandes peuvent générer des modifications physicochimiques des protéines. Leurs conséquences sur la mise à disposition des acides aminés constitutifs ont été peu étudiées. Après avoir déterminé l'impact des opérations unitaires de transformation de la viande sur les caractéristiques biochimiques et structurales des protéines, les conséquences sur les paramètres de digestion ont été étudiées, in vitro, sur des extraits myofibrillaires, et in vivo en utilisant le miniporc comme modèle animal. L'approche protéomique est utilisée, en parallèle, pour comparer la composition de muscles de porcs issus de modes d'élevage différents et étudier les corrélations avec la digestion. Plusieurs marqueurs protéiques des paramètres de digestion in vitro sont trouvés sur la viande maturée et cuite, et sont liés au processus de détoxification et de contraction musculaire. La cuisson est le procédé qui a le plus d'impact sur les caractéristiques du produit prêt à consommer, l'application de températures croissantes se traduisant par une combinaison progressive de dénaturation, d'oxydation puis d'agrégation des protéines. Le développement d'un modèle de digestion in vitro, sur des protéines myofibrillaires, a permis d'étudier les différents paramètres de digestion pour les différents procédés. Maturation et hachage ont eu peu d'effets sur ces paramètres. Par contre, par rapport à la viande crue, la vitesse de digestion est supérieure pour une température de cuisson de 70°C, ce qui n'est plus le cas à partir de 100°C. Inversement le potentiel de dégradation maximale est plus élevé pour des températures supérieures à 100°C. La mise en relation des caractéristiques de la viande, avec les paramètres de digestion, suggère que pour des températures de cuisson de l'ordre de 70°C, la dénaturation des protéines favorise une dégradation rapide des protéines en accroissant l'accessibilité des sites de coupure pour les enzymes digestives, mais que pour des températures supérieures, l'oxydation conduit à des agrégats qui limitent cette accessibilité. L'étude in vivo, sur le miniporc, a confirmé cette hypothèse, la vitesse d'apparition des acides aminés dans le sang, suite à l'ingestion des viandes étant supérieure pour une température de cuisson à coeur de 75°C, par rapport à des cuissons à 60 ou 95°C. Par contre contrairement à ce qui était observé in vitro, l'utilisation de viande marquée avec un isotope stable (15N), nous a permis de montrer que la température de cuisson n'affecte pas la quantité totale de protéines digérées dans l'intestin grêle (environ 95% des protéines ingérées). En conclusion, parmi les opérations unitaires impliquées dans la préparation des viandes, la cuisson semble être celle qui influence le plus la digestion des protéines. L'équilibre entre les processus de dénaturation et d'oxydation des protéines en fonction de la température de cuisson semble être un point clé dans la détermination de la vitesse de digestion des protéines. Ce paramètre est important notamment dans le cadre de la nutrition des personnes âgées. Par contre, les compensations au cours des étapes de la digestion font que ces différences de vitesses ne se traduisent pas par des différences de digestibilité dans l'intestin grêle. / In France, meat consumption represents one third of the total protein intake. Meat proteins have a high content of well-balanced essential amino acids near to Human needs. Meat is also a good source of vitamins B12 and iron. Its nutritional potential is thus very higher, but it could be modulated 1) by a protein digestion in the small intestine more or less complete (digestibility), determining the amount of absorbed amino acids, 2) by a speed of digestion higher or lower, affecting the postprandial utilization of absorbed amino acids in protein metabolism. Technological treatments involved in the meat preparation can generate physical-chemical changes of protein. Their impacts on the availability of constitutive amino acids (quantity, kinetics) have been little studied. After determining the impact of unitary operations on meat processing (aging, mincing, cooking) on the biochemical and structural characteristics of proteins, the effect on digestion parameters were studied in vitro on myofibrillar extracts, and in vivo using the minipig as an animal model. The proteomic approach is used in parallel to compare the composition of pig muscles from different rearing methods and study the correlations with digestion. Several protein markers of in vitro digestion are found for both aged and cooked meat, linked to detoxicant process and muscle contraction. The cooking is the process that has the greatest impact on characteristics of "ready-to-eat" product, the application of increasing temperatures (70, 100 and 140°C) resulting in a progressive combination of denaturation, oxidation and then of protein aggregation. Development of an in vitro digestion model (pepsin alone or coupled with trypsin/α-chymotrypsin), on myofibrillar proteins, was used to study the various parameters of digestion (initial slope, maximum rate, time to maximal rate, half-life time and maximal degradation) for the different processes. Aging and mincing have little impacts on these parameters. However, compared to raw meat, the rate of digestion is higher for a cooking temperature to 70°C, which is no longer the case for temperatures above 100°C. Conversely, the potential of maximal degradation is higher for temperatures above 100°C. Linking characteristics of meat with digestion parameters, suggests that for cooking temperatures of around 70°C, denaturation of proteins promotes rapid degradation of proteins by increasing the accessibility of digestive enzymes to their cutting sites, but for higher temperatures, oxidation leads to aggregates that limit accessibility. In vivo study on the minipig, confirms this hypothesis, the rate of appearance of amino acids in the blood following meat ingestion is higher with a core cooking temperature to 75°C, compared to cooking with 60 or 95°C. Furthermore, contrary to what observes in vitro, the use of meat labeled with a stable isotope (15N), we show that the cooking temperature are not affect the total amount of digested proteins in the small intestine (about 95% of ingested proteins). In conclusion, among the unitary operations involved in the preparation of meat, the cooking seems to be the one that most influence the digestion of proteins. The balance between the denaturation processes and protein oxidation according to the cooking temperature appears to be a key point in determining the speed of proteins digestion. This parameter is particularly important in the context of elderly nutrition. As it does not impact on the protein digestibility in the small intestine, the cooking temperature appears as an interesting lever to modulate the speed of meat protein digestion, according to the targeted consumer.

La Maladie de Huntington (MH) reste à ce jour une pathologie neurodégénérative dévastatrice pour laquelle aucun traitement n'est disponible. L'agrégation de la Huntingtine Mutante (Htt PolyQ) joue un rôle majeur dans les processus pathologiques. Dans ce contexte, des études récentes ont démontré que la partie N-terminale de la Huntingtine Humaine (Htt wt) ou de son Homologue drosophile (dHtt) sont toutes deux capables de réduire l'agrégation et la toxicité de Htt PolyQ. En se basant sur cette observation, le travail de thèse décrit dans ce manuscrit a mis au point un découpage du fragment N-terminal de Htt wt de manière à isoler en son sein, une courte séquence de 23 acides aminés (nommée P42), capable d'inhiber spécifiquement l'agrégation de Htt PolyQ en modèle cellulaire. L'effet protecteur de ce peptide a été confirmé in vivo, sur un modèle drosophile de la MH. Le potentiel thérapeutique que représente P42 a servi de point de départ à une étude menée sur le modèle murin R6/2 de la MH. L'effet de P42 a été potentialisé par l'ajout du peptide de transduction TAT de manière à faciliter son entrée dans les cellules cibles. Puis, la protéine fusion P42-TAT a été vectorisée sous forme de microémulsion de manière à assurer à la fois une administration simple de la molécule, et un accès au système nerveux central. Ce protocole original a permis d'observer des bénéfices sans précédent sur les phénotypes comportementaux, histologiques et moléculaires que présentent les souris R6/2.Au-delà de son aspect thérapeutique, P42 est avant tout une séquence méconnue située dans une région cruciale de la Huntingtine. L'étude du rôle physiologique de ce site, a mené à une meilleure compréhension de la fonction sauvage de la protéine toute entière. En outre, une analyse biochimique a montré la capacité du fragment N-terminal de Htt wt à se lier aux microtubules. Cette interaction avec le cytosquelette dépend de plusieurs processus (clivages, dimérisation) et semble affilier la Huntingtine à la grande famille des MAP.L'identification de P42 ouvre donc une voie nouvelle vers la compréhension du rôle physiologique de la Huntingtine, mais représente surtout un espoir thérapeutique captivant. / Huntington's disease (HD) is a devastating and incurable neurodegenerative disorder. Aggregation processes of mutant Huntingtin (Htt PolyQ) play a central part in the pathology onset. In this context, recent studies pointed out the capacities of wild-type Huntingtin N-terminus to reduce both aggregation and toxicity associated with Htt PolyQ. The drosophila Homologue shares the sames properties. Basing on these observations, the present work realised a cut of human Huntingtin N-terminus in order to identify the region responsible for therapeutic benefits. This screen highlighted a 23 amino-acid sequence (noted P42), that inhibits Htt PolyQ aggregation in a HeLa cells model. Then, the protective effect of this peptide was confirmed in vivo, in a HD drosophila model.P42 therapeutic potential was explored in the R6/2 HD mouse model. The entry of the peptide into cells, was potentialised by grafting to P42, the transduction sequence of TAT. Then, the fusion protein P42-TAT was vectorised in microemulsion, in order to enhance the delivery of the peptide to the brain by resorting to a non-invasive administration way. This original protocol exhibited highly-significant rescues on behavioural, histological and molecular R6/2 phenotypes..Over the therapeutic aspect, P42 also represents an important region of Huntingtin. The study of this site led to a better understanding of Huntingtin physiological function. Biochemestrial experiments underlined the binding of Htt N-terminus on microtubules networks. This interaction depends on a range of complex processes (dimerization, cleavage) and suggests that the Huntingtin belongs to the family of Structual MAPs.In summary, the identification of P42 enhances the knowledge about Huntingtin function, and opens a new promising therapeutical avenue for HD.

La bêta lactoglobuline (βlg) est une protéine globulaire qui forme le constituant majoritaire du sérum du lait ou petit lait. Par chauffage la protéine se dénature irréversiblement, puis s’assemble pour former des agrégats ou gels présentant des structures très différentes selon les conditions environnementales, en particulier de pH et de force ionique. Des travaux récents ont montré la possibilité de créer des agrégats stables de βlg de forme sphérique, de 100 à 400 nm de diamètre dans une plage de pH bien spécifique. Ces particules sphériques que nous appelons microgels, sont potentiellement très intéressantes pour des applications dans l’agroalimentaire (blanchissement, stabilisation d’interfaces et encapsulation). L’objectif de la thèse est d’étudier le mécanisme de formation de ces microgels et leurs propriétés structurales dans différentes conditions environnementales afin de pouvoir créer de nouvelles fonctionnalités. La première partie de la thèse a consisté à étudier l’influence du pH sur la formation des microgels. Les suspensions stables de microgels sont formées par chauffage de la solution de βlg en absence de sel jusqu’à 50 g.L-1 de protéine si le pH est placé dans une gamme très étroite entre 5,75 et 6,1. La densité de ces particules sphériques est environ 150 g.L-1 et leur rayon hydrodynamique diminue de 200 nm à 75 nm en augmentant le pH. La formation de ces microgels entraine une augmentation de pH, qui est nécessaire pour obtenir une suspension stable. L’augmentation spontanée du pH pendant la formation des microgels entraine une augmentation de leur densité de charge à la surface qui a pour conséquence d'empêcher leur agrégation. Ce mécanisme d’auto-stabilisation n’est plus suffisant si le pH initial est inférieur à 5,75 et on observe alors la précipitation des microgels. Les microgels ne sont plus formés au-delà d’une valeur critique du pH initial. Dans ce cas, les agrégats fibrillaires sont formés avec un rayon hydrodynamique d’environ 15 à 20 nm. La seconde partie de ce travail traite de la formation des microgels induite par l’ajout des ions calcium. Nous avons montré que des suspensions stables de microgels peuvent être obtenues en chauffant les solutions de βlg en présence des ions calcium. Les conditions de formation des microgels ont été étudiées à différents pH entre 5.8 et 7.5 et différentes concentrations de protéine entre 5 et 100 g.L-1. Il existe un rapport molaire critique calcium/protéine (R) pour former des microgels qui est indépendant de la concentration de protéine. R diminue en diminuant le pH. Les microgels ont un rayon hydrodynamique qui varie entre 100 et 300 nm et leur densité est comprise entre 200 et 450 g.L-1. La détermination de quantité de calcium lié aux microgels indique que le paramètre crucial pour la formation des microgels est la densité des charges nettes des protéines natives. Les suspensions de microgels sont stables dans certaines gammes étroites de R mais s’agrègent et précipitent ou gélifient à des concentrations de calcium plus élevées. Dans la troisième partie, nous avons continué à étudier la formation des microgels dans les étapes initiales et observer leur croissance en présence des ions calcium. On a proposé un mécanisme de formation des microgels de βlg, qui commence par un processus de nucléation et croissance. Des nucléi de tailles bien définies sont formés à la première étape, puis ils continuent à grossir jusqu’à la taille finale des microgels. A des faibles concentrations de calcium les microgels sont stables. A des concentrations plus élevées, les microgels peuvent s’agréger pour former des agrégats plus grands et finalement un gel. La structure des gels de microgels est hétérogène à l’échelle de la microscopie confocale et similaire à celle formée en présence de NaCl 0.3M. Pourtant le processus de formation de ces gels n’est pas le même... / Beta lactoglobulin (βlg) is a major whey protein in the bovine milk. Upon heating above its denaturation temperature (which is pH-dependent), this globular protein undergoes molecular changes leading to the irreversible aggregation. Depending on the pH and ionic strength, either protein aggregates or gels exhibiting various structures and morphologies have been described. Very recently, it was found that in a narrow range of the pH close to iso-electric point, stable suspensions of rather monodisperse spherical particles with a radius of about a hundred nanometers were formed. These spherical particles which were called microgels might be of special interest for the production of liquid dispersions of β-lactoglobulin aggregates exhibiting various functionalities for food applications. The project on which I report here was a collaboration with the Nestlé Reseach Center (Lausanne, Switzerland) and its objective was to study the formation and structural properties of the microgels in different environmental conditions. The first part of the project is to study the influence of the pH on the formation of microgels. Stable suspensions of protein microgels are formed by heating salt free βlg solutions at concentrations up to about C = 50 g.L-1 if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g.L-1 and the average hydrodynamic radius decreases with increasing pH from 200 nm to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm. The second part of the work is about the formation of microgels driven by the addition of calcium ions. We found that stable suspensions of spherical protein particles (microgels) can be formed by heating βlg solutions in the presence of calcium ions. The conditions for the calcium induced microgel formation were studied at different pH between 5.8 and 7.5 and different protein concentrations between 5 – 100 g.L-1. The results showed that a critical molar ratio of calcium to proteins (R) is needed to form microgels independent of the protein concentration. R decreases with decreasing pH. The microgels have a hydrodynamic radius ranging from 100 to 300 nm and their internal protein concentration ranges from 0.2 to 0.45 g.mL-1. The determination of calcium bound to the microgels suggests that the crucial parameter for microgel formation is the net charge density of the native proteins. The microgel suspensions are stable in a narrow range of R but aggregate at higher Ca2+ concentrations. In the third part, we continued to investigate the formation of microgels at initial step and how it is growing in the presence of calcium ions. We have proposed a mechanism of formation of blg microgels which follows a nucleation and growing process. The nucleus with define size are formed at the initial state and that is growing in size to reach final size of aggregates. At low calcium concentration it stabilizes and then we obtain a stable suspension of microgels. But at high concentrations, the microgels here can jump to form big aggregates and finally a gel. The structure of gel from microgels is heterogenous at the scale of confocal microscopy and similar to those formed in the presence of NaCl 0.3 M. However the process of formation of these gels is not the same...

Mammalian fertilization is a sequence of unique and fascinating events, during which seminal proteins are of crucial role. In case of bull (Bos taurus), proteins of seminal plasma (BSP), especially its major component PDC-109, are known to be in aggregated forms, but little is known about mechanism of forming aggregates and their biological function. In present thesis we discovered some interesting properties of PDC-109 and BSP proteins. We found that concentration of these proteins influences their aggregation state significantly, which can be of great biological importance. Separation of seminal proteins by size exclusion chromatography revealed three main fractions denoted I, II and III, with apparent molecular weights of Mr > 150 000, Mr = 30 000 and Mr = 13 000, respectively. In case of PDC-109, molecular weights of theese fractions were retained even after purification procedure, which implies very stable interactions in forming of aggregates. In addition, there was a difference in distribution of PDC-109 glycoforms among fractions, which can be related to the fact, that theese fractions have different sperm membrane binding patterns as we determined by fluorescence microscopy. However, further experiments are needed for better understanding this issue.

This diploma thesis is aimed at the evaluation of the efficiency of surface water treatment technology in water treatment plant U svaté Trojice (Kutná Hora, Vrchlice reservoir). The plant performs destabilisation of impurities by coagulant aluminium sulphate (Al2(SO4)3 . 18 H2O) followed by aggregation induced by mixing with perforated baffles. Suspension is removed by double-stage separation process by means of sedimentation and filtration. When increased concentrations of manganese occur in raw water, manganese is removed by means of oxidation by potassium permanganate. Firstly, the quality of raw water was analysed. Then, the reaction conditions for the effective destabilisation (pH, dose of coagulant) were set using the jar tests. Moreover, sedimentation analysis was used to evaluate the properties of formed suspension and the length of filter cycles was assessed. Measurements were conducted between September 2012 and February 2013. Average value of raw water pH was 7.3, alkalinity was 1.64 mmol/l. DOC concentrations during September and October 2012 were equal to 6.7 mg/l and during November 2012 - February 2013 were 7.6 mg/l. Very low concentrations of aluminium (< 0.02 mg/l) were ascertained throughout the whole period investigated. Results of the jar tests showed that the optimum pH for...

Doctor of Philosophy / Department of Biochemistry / Michal Zolkiewski / ClpB is a bacterial heat-shock protein that disaggregates and reactivates strongly aggregated proteins in cooperation with the DnaK chaperone system. ClpB contains two ATP-binding AAA+ modules, a linker coiled-coil domain, and a highly mobile N-terminal domain. It forms ring-shaped hexamers in a nucleotide-dependent manner. The unique aggregation reversing chaperone activity of ClpB involves ATP-dependent translocation of substrates through the central channel in the ClpB ring. The initial events of aggregate recognition and the events preceding the translocation step are poorly understood. In addition to the full-length ClpB95, a truncated isoform ClpB80, that is missing the whole N-terminal domain, is also produced in vivo. Various aspects of the structure and function of ClpB were addressed in this work. The thermodynamic stability of ClpB in its monomeric and oligomeric forms, as well as the nucleotide-induced conformational changes in ClpB were investigated by fluorescence spectroscopy. Equilibrium urea-induced unfolding showed that two structural domains-the small domain of the C-terminal AAA+ module and the coiled-coil domain-were destabilized in the oligomeric form of ClpB, which indicates that only those domains change their conformation or interactions during formation of the ClpB rings. Several locations of Trp-fluorescence probes were also found to respond to nucleotide binding. The biological role of the two naturally-occurring ClpB isoforms was also investigated. We discovered that ClpB achieves optimum chaperone activity by synergistic cooperation of the two isoforms that form hetero-oligomers. We found that ClpB95/ClpB80 hetero-oligomers form preferentially at low protein concentration with higher affinity than homo-oligomers of ClpB95. Moreover, hetero-oligomers bind to aggregated substrates with a similar efficiency as homo-oligomers of ClpB95, do not show enhanced ATPase activity over that of the homo-oligomers, but display a strongly stimulated chaperone activity during the reactivation of aggregated proteins. We propose that extraction of single polypeptides from aggregates and their delivery to the ClpB channel for translocation is the rate-limiting step in aggregate reactivation and that step is supported by the mobility of the N-terminal domain of ClpB. We conclude that the enhancement of the chaperone activity of the hetero-oligomers is linked to an enhancement of mobility of the N-terminal domains.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the upper and lower motor neurons causing muscle atrophy and paralysis followed by death. Aggregates containing superoxide dismutase (SOD1) are found as pathological hallmark in diseased ALS patients. Consequently ALS is regarded as a protein misfolding disorder like Alzheimer’s disease and Parkinson’s disease. So far, little is known about the cause and mechanism behind SOD1 aggregation but the inherent property of all polypeptide chains to form stable aggregated structures indicates that the protein misfolding diseases share a common mechanism. Our results show that SOD1 aggregation starts from the globally unfolded state, since fibrillation is fastest at full occupancy of denatured protein induced either by chemical denaturation or mutation. Even so, the fibrillation rate shows a surprisingly weak dependence on the concentration of globally unfolded SOD1 indicating fibril fragmentation as the dominant mechanism for aggregate formation. This is further supported by the observation that the SOD1 sample has to be mechanically agitated for fibrillation to occur.  Interestingly, we observe a similar SOD1 aggregation behaviour in vivo, where the survival times of ALS transgenic mice correlates with mutant stability, and aggregate growth depends weekly on the concentration of unfolded monomer. Additionally, in-cell NMR measurements reveal that in live cells the thermodynamic equilibrium is shifted towards the unfolded state of SOD1, which is also more fully extended than in vitro. This suggests that the globally unfolded aggregation competent protein is more abundant in the crowded environment in vivo than dilute in vitro conditions. Finally, antibody analysis of aggregates from ALS transgenic mice reveals the existence of aggregate strains involving different parts of the protein depending on mutation, which may offer an explanation for the various disease phenotypes observed in ALS. Altogether these findings provide important clues for understanding SOD1 aggregation with implications for ALS, as well as other protein misfolding diseases.

Adequate access to affordable, healthy food has long been a public health concern and has become a more pressing societal issue following the Great Recession and rising incidents of diet-related diseases. In response, research and government efforts have largely focused on identifying disadvantaged areas with poor food access and formulating policies to improve accessibility. However, the approaches that have been widely relied upon by researchers and practitioners for food access assessment are severely flawed, which may lead to inconsistent research findings or neglect of the needs of under-served/un-served neighborhoods. This dissertation identifies three important aspects of food access for improvement: the appropriate scale/neighborhoods for analysis, the use of food outlets as a proxy for affordable, healthy food; and the assessment method. In particular, three studies are conducted to: (1) examine how varying spatial scales and aggregation methods affect accessibility assessments; (2) explore the role of independent grocers, which have been neglected in previous food access studies as elements of the food landscape that may change the perception of food deserts; and (3) investigate how individual-level food access patterns compare to the widely used, area-based neighborhood measures of expected accessibility. While the dissertation discusses and addresses theoretical challenges in food access, the empirical studies conducted in the Tucson, Arizona metropolitan area contribute to a better understanding of the real-world complexity of food access. The results shed light on some predicaments identified in recent studies and have important policy implications for how best to efficiently and effectively design strategies and initiatives to enhance food-provision access.

La maladie d'Alzheimer (MA) est une maladie neurodégénérative qui est la cause la plus fréquente de démence chez les personnes âgées. Il est proposé que celle-ci ait pour origine l'agrégation du peptide l'amyloïde-ß (Aß) qui, produit à l'état monomérique, est retrouvé sous formes de plaques séniles dans le cerveau des patients. Lors de l'agrégation, le peptide se retrouve sous plusieurs formes, dont les formes oligomériques qui présentent la plus grande toxicité envers les neurones. Bien qu'il existe une grande diversité de structures chimiques utilisées comme sondes des plaques séniles, le développement d'outils de détection des formes précoces du processus d'agrégation reste un défi scientifique majeur. Pour cela, il est nécessaire de connaitre à l'échelle moléculaire la nature du(des) site(s) d'interaction entre la sonde et le peptide. Ceci permettrait l'élaboration rationnelle de ligands plus spécifiques pour chaque forme du peptide Aß (monomère, oligomère,...). Dans le cadre de ces travaux de thèse, la mise au point de synthèses modulaires de différents dérivés du motif 2-aryl-benzothiazole connu pour son interaction avec les agrégats a été effectuée. Ces dérivés permettent l'étude de l'agrégation et de l'identification du(des) site(s) d'interaction par différentes techniques. Au cours de ces travaux, la synthèse et l'étude de quatre principaux dérivés du 2-aryl-benzothiazole ont été réalisées ; (i) un dérivé comportant une amine secondaire présentant des propriétés photophysiques intéressantes, obtenu en 11 étapes avec un rendement global de 23 % ; (ii) un dérivé avec un motif ferrocène pour des études en électrochimie, obtenu avec 13 % de rendement en 11 étapes ; (iii) un dérivé comportant un motif TEMPO radicalaire pour des études par RPE et RMN, obtenu avec un rendement 16 % en 10 étapes ; et (iv) un dérivé comportant un motif diazirine obtenu avec un rendement global de 8 % en 19 étapes pour une étude de marquage par photo-affinité (création d'un lien covalent après irradiation) suivi d'une étude par spectrométrie de masse. Outre les synthèses de ces sondes, des résultats préliminaires des études menées par études photophysiques, électrochimie, RPE, RMN et spectrométrie de masse seront présentées dans ce manuscrit. / Alzheimer's disease (AD) is a neurodegenerative disease which is the most common cause of dementia in elderly people. It is proposed that it originates from the aggregation of amyloid-ß peptide (Aß), produced in the monomeric state, which is found as senile plaques in the brain of patients. During aggregation, the peptide is found in several forms, including oligomeric forms that are the most toxic to neurons. Although there is a wide variety of chemical structures used as probes for senile plaques, the development of tools to detect early forms of the aggregation process remains a major scientific challenge. To accomplish this, it is necessary to know, at the molecular level, the nature of the interaction site(s) between the probe and the peptide. This would allow the rational design of more specific ligands for each form of the Aß peptide (monomer, oligomer,...). As part of this thesis work, the development of modular syntheses of various derivatives of the 2-aryl-benzothiazole scaffold, known for its interaction with aggregates, was carried out. These derivatives allow the study of the aggregation and identification of the interaction site(s) by different techniques. During this work, the synthesis and study of four main 2-aryl-benzothiazole derivatives were carried out; (i) a derivative containing a secondary amine with interesting photophysical properties, obtained in 11 steps with an overall yield of 23%; (ii) a derivative with a ferrocene unit for electrochemistry studies, obtained with 13% yield in 11 steps; (iii) a derivative with a radical TEMPO moiety for EPR and NMR studies, obtained with a 16% yield in 10 steps; and (iv) a derivative with a diazirine unit obtained with an overall yield of 8% in 19 steps for photoaffinity labelling study (creation of a covalent bond after irradiation) followed by mass spectrometry analysis. In addition to the syntheses of these probes, preliminary results of studies conducted by fluorescence, electrochemistry, EPR, NMR and mass spectrometry will be presented in this manuscript.

This thesis is focused on mixed systems of various copolymers (double hydrophilic block and gradient polyelectrolytes, hydrophobic graft copolymers) and low-molar-mass compounds (sodium dodecyl sulfate as a representative of a ionic surfactant or superparamagnetic iron oxides in the form of nanocrystals). The electrostatic and hydrophobic interactions in the studied systems in aqueous solutions leading to aggregation behavior and to the formation of co-assembled nanoparticles were investigated by combination of scattering and microscopy techniques, including light, X-ray and neutron scattering, electron microscopy and atomic force microscopy. Powered by TCPDF (www.tcpdf.org)