Rare Earth Elements (REEs: La–Lu, Y, and Sc) are critical components for technological innovations, therefore more effective methods for the domestic extraction and purification of REEs are in ever-increasing demand. Metal-chelating polymers have great potential in these applications due to their relatively low cost and high affinity for target elements. However, while much research has focused on specific ligands attached to polymers, little is known about the effect of polymer architecture itself on metal chelation. This dissertation reports recent progress in the design, synthesis, and application of polymers for the chelation of various REEs. In addition to synthesizing a series of metal-chelating polymers, we elucidated the thermodynamics of binding using isothermal titration calorimetry (ITC) to gain insight into the specific relationship between polymer structure and metal binding. ITC enables the direct measurement of the binding affinity (Ka), enthalpy changes (ΔH), and stoichiometry of the interactions between macromolecules and metal ions in solution. The thermodynamics of metal chelation underpins many technologies for REE extraction. Consequently, elucidating these parameters enables the rational design of future materials. / Doctor of Philosophy / Rare-Earth Elements (REEs) are critical metals used in many modern technologies, therefore more effective methods for the recovery and purification of REEs are in ever-increasing demand. Metal-chelating polymers—materials that can bind metals—have great potential in these applications due to their relatively low cost and high affinity for target elements. However, while much research has focused on the specific metal-binding group attached to the polymer, little is known about the effect of polymer architecture itself on metal chelation. This dissertation reports recent progress in the design, synthesis, and application of materials that bind to various REEs. In addition to synthesizing a series of metal-binding polymers, we measured the heat absorbed or produced during metal-binding interactions. These experiments produced fundamental insights into the interactions between the polymers, metals ions, and water molecules in solution. Overall, this work produces a depiction of the polymer–metal binding process, which enables insight into each polymer's properties as a metal-binding material. Future researchers can use these guidelines to develop the next generation of materials for the extraction of these critical metals.

No / Pterin-4a-carbinolamine dehydratase (PCD) is an essential component of the phenylalanine hydroxylase (PAH) system, catalyzing the regeneration of the essential cofactor 6(R)-L-erythro-5,6,7,8-tetrahydrobiopterin [6(R)BH4]. Mutations in PCD or its deactivation by hydrogen peroxide result in the generation of 7(R,S)BH4, which is a potent inhibitor of PAH that has been implicated in primapterinuria, a variant form of phenylketonuria, and in the skin depigmentation disorder vitiligo. We have synthesized and separated the 7(R) and 7(S) diastereomers confirming their structure by NMR. Both 7(R)- and 7(S)BH4 function as poor cofactors for PAH, whereas only 7(S)BH4 acts as a potent competitive inhibitor vs. 6(R)BH4 (Ki=2.3–4.9 μM). Kinetic and binding studies, as well as characterization of the pterin-enzyme complexes by fluorescence spectroscopy, revealed that the inhibitory effects of 7(R,S)BH4 on PAH are in fact specifically based on 7(S)BH4 binding. The molecular dynamics simulated structures of the pterin-PAH complexes indicate that 7(S)BH4 inhibition is due to its interaction with the polar region at the pterin binding site close to Ser-251, whereas its low efficiency as cofactor is related to a suboptimal positioning toward the catalytic iron. 7(S)BH4 is not an inhibitor for tyrosine hydroxylase (TH) in the physiological range, presumably due to the replacement of Ser-251 by the corresponding Ala297. Taken together, our results identified structural determinants for the specific regulation of PAH and TH by 7(S)BH4, which in turn aid in the understanding of primapterinuria and acute vitiligo. —Pey, A. L., Martinez, A., Charubala, R., Maitland, D. J., Teigen, K., Calvo, A., Pfleiderer, W., Wood, J. M., Schallreuter, K. U. Specific interaction of the diastereomers 7(R)- and 7(S)-tetrahydrobiopterin with phenylalanine hydroxylase: implications for understanding primapterinuria and vitiligo

O estudo da variação da composição atmosférica contribui para a compreensão dos efeitos das emissões antrópicas sobre a troposfera. A análise química da água de chuva assume importância neste contexto, uma vez que a precipitação úmida constitui um excelente meio de remoção de muitos poluentes da atmosfera. O aumento de acidez das chuvas, em várias partes do planeta, tem sido associado, predominantemente, à presença de ácidos fortes como o sulfúrico e nítrico, e ácidos orgânicos como acético e fórmico, originados pela oxidação de compostos de enxofre, nitrogênio e carbono, respectivamente. Dando continuidade a pesquisas anteriores sobre deposição úmida realizadas no IQ-USP, no presente trabalho buscou-se extrair mais informações de titulações potenciométricas e condutométricas de água de chuva, mediante aperfeiçoamento dos métodos de cálculo, com recursos quimiométricos modernos, de modo a complementar as medidas de pH e condutividade convencionais. As concentrações de espécies ácidas ou básicas nas amostras de água de chuva são da ordem de 10-5 mol L-1, muito abaixo das concentrações empregadas na prática cotidiana das titulações potenciométricas (tipicamente, no intervalo de 10-1 a 10-3 mol L-1). Dessa forma, propôs-se o uso de um método de regressão não linear (RNL) multiparamétrica, baseado no método de Levenberg-Marquardt, para a análise de dados potenciométricos (TP-RNL) após procedimento de transposição de coordenadas das curvas de titulação. Ao lado das determinações das concentrações dos analitos, pôde-se estimar ou refinar as constantes de protonação das bases de Brönsted presentes. Para tanto, procedeu-se ao ajuste por RNL das concentrações e/ou das constantes de protonação das bases presentes, de modo a minimizar o quadrado dos desvios entre os valores experimentais e os calculados em função do titulante adicionado, recorrendo a uma equação geral baseada no número médio de protonação de cada uma das bases. Ficou demonstrada a possibilidade de se determinar a soma de ácidos fortes completamente dissociados, soma de ácidos fracos com pK próximo a 4 (principalmente ácidos acético e fórmico), HCO3-/H2CO3 e a soma de bases fracas com pK ao redor de 9 (essencialmente NH3/NH4+). Durante as titulações, a facilidade em se coletar medidas de condutância simultaneamente às de pH levou a elaboração de um método sofisticado de análise de curvas de titulação condutométrica. Para tanto, desenvolveu-se uma equação de RNL baseada na contribuição das espécies em cada valor de pH e na condutância iônica medida (TC-RNL). A equação de TC-RNL é alimentada por dados de pH em função do titulante adicionado, oriundos de titulações potenciométricas. Dessa forma, foi possível caracterizar diretamente amônio e bicarbonato, além do conteúdo iônico total que não participa dos equilíbrios ácidos/base existentes no sistema. Adicionalmente, foi possível separar a contribuição do ácido acético da do fórmico, tarefa impossível por TP-RNL, ao menos nas baixas concentrações encontradas na chuva. Nas mesmas amostras de chuva tituladas foi procedida a análise por eletroforese capilar de zona com detecção condutométrica sem contato (CZE-CCD), conforme procedimento descrito na literatura, estimando-se os cátions e ânions majoritários. Num aperfeiçoamento do método para ânions, viabilizou-se a determinação simultânea HCO3-. Para validar os resultados obtidos por CZE-CCD, recorreu-se à cromatografia de íons. As concentrações de vários analitos, dependendo das amostras de chuva, avizinham-se do limite de quantificação das técnicas TP-RNL, TC-RNL e CZE-CCD. Mesmo assim, para as amostras de chuva analisadas, em geral, houve concordância satisfatória entre os valores estimados pelas três técnicas para espécies agrupadas da seguinte forma: ácidos fortes, ácidos fracos, amônio e bicarbonato. / Ivestigation of the variability of atmospheric chemical composition is an important tool for the evaluation and comprehension of anthropic emissions effects.Rainwater analysis has great importance in this context because wet deposition represents an efficient removal route of many atmospheric pollutants. The acidification of rainwater over wide regions of the planet is associated with the increased presence of strong acids, like sulfuric and nitric ones, and organic acids, such as acetic and formic, mainly originated from oxidative reactions od sulfur, nitrogen and carbon compounds in the atmosphere. In the context of a broad research line at IQ-USP devoted to the study of wet deposition and associated atmospheric chemistry, this dissertation advances the subject of using moderm chemometric methods to extract reliable analytical information from potentiometric and conductometric titrations of rainwater. The concentrations of acidic and alkaline species in rainwater are typically below 5 x 10-5 mol L-1, out of the reach of conventional potentiometric titrations (widely applied in the range of 10-1 and 10-3 mol L-1). Thus, multiparametric non-linear regression based on Levenberg-Marquardt method combined with coordinates transposition to reduce iterative calculation is proposed for the analysis of potentiometric data (PT-NLR). General equations based on the average protonation number of each base are used to describe the system. Bases concentrations and/or protonation constants are adjusted by NLR in order to minimize the sum-of-squares of the residuals between experimental and calculated values of the titration curves. The data analysis was tuned to provide four parameters as output: the sum of strong acids, the sum of weak acids with pK around 4.2 (mainly acetic and formic acids), the sum of HCO3-/H2co3 and the sum of weak bases with pK near 9 (essentially NH3/NH4+). To extract more analytical information from the acid/base titrations, conductance meassurements were made simultaneously with the pH readings, and a sophisticated data analysis method was envisioned. The pH data and available protonation constants for bases included in the model are used to compute the distribution of the species. The available conductivity of each species of the model is introduced in a general equation where the only unknowns are the total concentrations of the bases and of electrolyte not involved in acid/base equilibria. All these concentrations are adjusted by NLR on the conductance data, resulting in the first successful conductometric titration method with non-linear regression analysis, CT-NLR. The great advantage over PT-NLR was the capability to distinguish the contributions of acetic and formic acids in rainwater (an impossible task in PT-NLR method), but total strong acids, ammonium and bicarbonate are determined as well, beside the total ionic content of species not involved acid-base equilibria. Rainwater samples were also analysed by capillary zone electriphoresis equipment with contactless conductometric detection (CZE-CCD), as decribed in literature, regarding the major cations and anions. An improved CE method for anions was developed to afford the simultaneous determination of HCO3-. Validation of results was made with the reference method of ion chromatography. Although in many samples some analytes are low and close to the quantification limits od CZE-CCD, PT-NLR and CT-NLR, satisfactory agreement was achieved between values obtained by the three techniques for strong acids, weak acids, ammonium and bicarbonate.

O estudo da variação da composição atmosférica contribui para a compreensão dos efeitos das emissões antrópicas sobre a troposfera. A análise química da água de chuva assume importância neste contexto, uma vez que a precipitação úmida constitui um excelente meio de remoção de muitos poluentes da atmosfera. O aumento de acidez das chuvas, em várias partes do planeta, tem sido associado, predominantemente, à presença de ácidos fortes como o sulfúrico e nítrico, e ácidos orgânicos como acético e fórmico, originados pela oxidação de compostos de enxofre, nitrogênio e carbono, respectivamente. Dando continuidade a pesquisas anteriores sobre deposição úmida realizadas no IQ-USP, no presente trabalho buscou-se extrair mais informações de titulações potenciométricas e condutométricas de água de chuva, mediante aperfeiçoamento dos métodos de cálculo, com recursos quimiométricos modernos, de modo a complementar as medidas de pH e condutividade convencionais. As concentrações de espécies ácidas ou básicas nas amostras de água de chuva são da ordem de 10-5 mol L-1, muito abaixo das concentrações empregadas na prática cotidiana das titulações potenciométricas (tipicamente, no intervalo de 10-1 a 10-3 mol L-1). Dessa forma, propôs-se o uso de um método de regressão não linear (RNL) multiparamétrica, baseado no método de Levenberg-Marquardt, para a análise de dados potenciométricos (TP-RNL) após procedimento de transposição de coordenadas das curvas de titulação. Ao lado das determinações das concentrações dos analitos, pôde-se estimar ou refinar as constantes de protonação das bases de Brönsted presentes. Para tanto, procedeu-se ao ajuste por RNL das concentrações e/ou das constantes de protonação das bases presentes, de modo a minimizar o quadrado dos desvios entre os valores experimentais e os calculados em função do titulante adicionado, recorrendo a uma equação geral baseada no número médio de protonação de cada uma das bases. Ficou demonstrada a possibilidade de se determinar a soma de ácidos fortes completamente dissociados, soma de ácidos fracos com pK próximo a 4 (principalmente ácidos acético e fórmico), HCO3-/H2CO3 e a soma de bases fracas com pK ao redor de 9 (essencialmente NH3/NH4+). Durante as titulações, a facilidade em se coletar medidas de condutância simultaneamente às de pH levou a elaboração de um método sofisticado de análise de curvas de titulação condutométrica. Para tanto, desenvolveu-se uma equação de RNL baseada na contribuição das espécies em cada valor de pH e na condutância iônica medida (TC-RNL). A equação de TC-RNL é alimentada por dados de pH em função do titulante adicionado, oriundos de titulações potenciométricas. Dessa forma, foi possível caracterizar diretamente amônio e bicarbonato, além do conteúdo iônico total que não participa dos equilíbrios ácidos/base existentes no sistema. Adicionalmente, foi possível separar a contribuição do ácido acético da do fórmico, tarefa impossível por TP-RNL, ao menos nas baixas concentrações encontradas na chuva. Nas mesmas amostras de chuva tituladas foi procedida a análise por eletroforese capilar de zona com detecção condutométrica sem contato (CZE-CCD), conforme procedimento descrito na literatura, estimando-se os cátions e ânions majoritários. Num aperfeiçoamento do método para ânions, viabilizou-se a determinação simultânea HCO3-. Para validar os resultados obtidos por CZE-CCD, recorreu-se à cromatografia de íons. As concentrações de vários analitos, dependendo das amostras de chuva, avizinham-se do limite de quantificação das técnicas TP-RNL, TC-RNL e CZE-CCD. Mesmo assim, para as amostras de chuva analisadas, em geral, houve concordância satisfatória entre os valores estimados pelas três técnicas para espécies agrupadas da seguinte forma: ácidos fortes, ácidos fracos, amônio e bicarbonato. / Ivestigation of the variability of atmospheric chemical composition is an important tool for the evaluation and comprehension of anthropic emissions effects.Rainwater analysis has great importance in this context because wet deposition represents an efficient removal route of many atmospheric pollutants. The acidification of rainwater over wide regions of the planet is associated with the increased presence of strong acids, like sulfuric and nitric ones, and organic acids, such as acetic and formic, mainly originated from oxidative reactions od sulfur, nitrogen and carbon compounds in the atmosphere. In the context of a broad research line at IQ-USP devoted to the study of wet deposition and associated atmospheric chemistry, this dissertation advances the subject of using moderm chemometric methods to extract reliable analytical information from potentiometric and conductometric titrations of rainwater. The concentrations of acidic and alkaline species in rainwater are typically below 5 x 10-5 mol L-1, out of the reach of conventional potentiometric titrations (widely applied in the range of 10-1 and 10-3 mol L-1). Thus, multiparametric non-linear regression based on Levenberg-Marquardt method combined with coordinates transposition to reduce iterative calculation is proposed for the analysis of potentiometric data (PT-NLR). General equations based on the average protonation number of each base are used to describe the system. Bases concentrations and/or protonation constants are adjusted by NLR in order to minimize the sum-of-squares of the residuals between experimental and calculated values of the titration curves. The data analysis was tuned to provide four parameters as output: the sum of strong acids, the sum of weak acids with pK around 4.2 (mainly acetic and formic acids), the sum of HCO3-/H2co3 and the sum of weak bases with pK near 9 (essentially NH3/NH4+). To extract more analytical information from the acid/base titrations, conductance meassurements were made simultaneously with the pH readings, and a sophisticated data analysis method was envisioned. The pH data and available protonation constants for bases included in the model are used to compute the distribution of the species. The available conductivity of each species of the model is introduced in a general equation where the only unknowns are the total concentrations of the bases and of electrolyte not involved in acid/base equilibria. All these concentrations are adjusted by NLR on the conductance data, resulting in the first successful conductometric titration method with non-linear regression analysis, CT-NLR. The great advantage over PT-NLR was the capability to distinguish the contributions of acetic and formic acids in rainwater (an impossible task in PT-NLR method), but total strong acids, ammonium and bicarbonate are determined as well, beside the total ionic content of species not involved acid-base equilibria. Rainwater samples were also analysed by capillary zone electriphoresis equipment with contactless conductometric detection (CZE-CCD), as decribed in literature, regarding the major cations and anions. An improved CE method for anions was developed to afford the simultaneous determination of HCO3-. Validation of results was made with the reference method of ion chromatography. Although in many samples some analytes are low and close to the quantification limits od CZE-CCD, PT-NLR and CT-NLR, satisfactory agreement was achieved between values obtained by the three techniques for strong acids, weak acids, ammonium and bicarbonate.

La digestion anaérobie est un des piliers de l'économie circulaire européenne, produisant du méthane et des engrais organiques à partir de déchets. Le développement de ce secteur passe par la co-digestion et l’optimisation de l'alimentation des procédés. Cela nécessite l'estimation de l'état biologique du digesteur, la caractérisation du substrat ainsi que l’utilisation de modèles prédictifs simulant les performances du digesteur, pour lesquels les solutions actuelles ne sont pas adaptées. Dans cette thèse, un capteur titrimétrique couplant pH et conductivité électrique pour l'estimation des concentrations en acides gras volatils, carbone inorganique et azote ammoniacale a été conçu, améliorant la précision d'estimation des acides gras volatils de 14,5 par rapport aux capteurs actuels. Couplé à l’analyse du biogaz, il permet d'estimer l'état biologique du procédé. En parallèle, une analyse spectroscopique proche-infrarouge, estimant les teneurs en glucides, protéines, lipides, demande chimique en oxygène, rendement et cinétique de production de méthane a été développée réduisant le temps de caractérisation des substrats à quelques minutes. La caractérisation rapide des substrats est utilisée pour implémenter le modèle de digestion anaérobie ADM1 de l’IWA qui prédit les performances d'un digesteur dans des conditions de digestion optimales. Le couplage de l’estimation de l'état biologique à cette approche permet de corriger la prédiction en prenant en compte l'état actuel du digesteur. Cette approche fournit un outil prédictif puissant pour le contrôle avancé des unités de digestion anaérobie ainsi que l'optimisation de la recette d'alimentation. / Anaerobic digestion is an important pillar of the European circular economy, producing methane and organic fertilizers from waste. The development of the anaerobic digestion sector goes through co-digestion and feeding strategy optimization. Its development requires the biological state estimation of the plant, substrate characterization and predictive models simulating the plant performances, for which current solutions are not suitable. In this thesis, a titration sensor coupling pH and electrical conductivity for the estimation of volatile fatty acids, inorganic carbon and ammonia has been designed, improving the accuracy on volatile fatty acids estimation by 14.5 compared to current sensors. Along with biogas analyses, it allows estimating the biological state of the unit. Besides, fast near infrared spectroscopic analysis, estimating in a matter of minute carbohydrate, protein and lipid contents, chemical oxygen demand, methane production yield and kinetics, has been developed. Thus fast substrate characterization is then used to implement a modified Anaerobic Digestion Model n°1 which predicts the performances of a plant under optimal condition. Coupling biological state estimation to this approach enables to correct the prediction with the current state of the plant. This approach provides a powerful predictive tool for advanced control of anaerobic digestion plants and feeding strategy optimization.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Une étude récente sur le transfert peptidique pH dépendant effectuée avec divers ARNt aminoacyles a révélé la dépendance au pH du transfert peptidique. L’instabilité hydrolytique rend impossible l’obtention de la valeur expérimentale du pKa de l’eau donné pour le groupement α-amino des esters 3'-aminoacyladenosine. Comme les analogues de la puromycine sont les analogues les plus proches du 3’-terminal des ARNt aminoacyles et qu’ils contiennent une liaison amide stable en position 3’, il est intéressant de déterminer la valeur du pKa du groupement α-amino de différents analogues de la puromycine mais aussi de corréler ces valeurs de pKa aux valeurs de pKa des groupements ARNt aminoacyles correspondants obtenues par le transfert peptidique pH dépendant. Le premier chapitre de la thèse se concentre sur la synthèse de différents analogues de la puromycine et sur la détermination de leur basicité par une analyse RMN pH dépendante. Ce chapitre discutera aussi la conformation intrinsèque des analogues de la puromycine mesurée par la pH dépendance de leur constante de couplage J1’-2’. Les synthèses d’analogues dinucléotidiques, d’un analogue xylo-puromycine et d’un analogue de désoxyxylopuromycine seront aussi décrites. Les conjugués peptidyl-ARN miment des fragments importants d’intermédiaires de la transduction. Ces analogues peuvent être utilisés comme outils expérimentaux pour comprendre l’évolution de la synthèse codée des peptides. L’innovation dans le concept de ‘négoce moleculaire’ entre les peptides, les oligonucléotides et les bicouches lipidiques, qui pourrait être à la base de l’évolution de la synthèse peptidique contrôlée par l’ARN, nous a poussé à synthétiser des conjugués peptidyl-ARN amphiphiliques et à étudier leurs interactions avec les bicouches lipidiques. Dans le deuxième chapitre les stratégies de synthèse sur support solide utilisant des analogues de puromycine comme élément constitutif seront discutées / A recent pH dependent peptidyl transfer assay in the ribosome with various aminoacyl tRNAs revealed the pH dependence of the peptidyl transfer. Hydrolytic instability makes impossible to obtain the experimental bulk water pKa data for the α-amino groups of 3'-aminoacyladenosine esters. Since puromycin analogues are the most similar analogues of the 3’-end of the aminoacyl tRNAs and they contain a stable amide bond in 3’-position, the determination of the pKa value of the α-amino groups of different puromycin analogues and correlation of these pKa values with those of α-amino groups of the corresponding aminoacyl tRNAs obtained by pH dependent peptidyl transfer deserves attention. Chapter 1 of the thesis focuses on the synthesis of different puromycin analogues and on the determination of their basicities by a pH dependent NMR analysis. This chapter also analyses the intrinsic conformations accessed by the puromycin analogues, as measured by the pH dependence of their J1’-2’ coupling constants. The synthesis of dinucleotide analogues, a xylo-puromycin analogue and a deoxyxylopuromycin analogue will also be described. Peptidyl-RNA conjugates mimic important fragments of natural intermediates of translation. These analogues can be used as an experimental tool to understand the evolution of the coded synthesis of peptides. The novelty in the concept of a ‘molecular deal’ between peptides, oligonucleotides and lipidic bilayers, which may be the basis for the evolution of RNA controlled peptide synthesis, prompted us to synthesize amphiphilic peptidyl-RNA conjugates and to study their interactions with lipidic bilayers. In chapter 2 the solid support synthetic strategies using puromycin analogues as the building blocks will be discussed

Gegenstand der vorliegenden Arbeit ist die Synthese und Strukturaufklärung von neuartigen, chromophoren Barbituraten, welche als selektive Chemosensoren verwendet werden können. Als Schlüsselverbindungen dienten 5-(4-Nitrophenyl)-barbiturate, deren Enolisierungsfähigkeit systematisch untersucht wurden. Des Weiteren konnten SCHIFFschen Basen, Pyridinium-Barbiturat-Betain-Farbstoffe sowie ein fluoreszenzaktive Naphthalimid synthetisiert werden, in welchen der Barbitursäure-Substituent ebenfalls elektronenschiebende Eigenschaften aufweist. Die individuelle Interaktion der Barbiturate mit der Solvensumgebung wurde mittels Lineare-Solvatations-Energie (LSE)- Beziehungen unter Verwendung der empirischen Lösungsmittelparameter nach KAMLET-TAFT und CATALÁN untersucht. Besonderes Augenmerk lag auf dem Studium der molekularen Erkennung von ausgewählten Chromophoren mit Nukleinbasen und strukturell verwandten Verbindungen. Hierzu gelang es die supramolekularen Bindungsphänomene über Wasserstoffbrücken und die Beeinflussung des chromophoren Systems sowohl im Festkörper als auch in Lösung zu verfolgen.

Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

L’objectif de cette thèse est d’étudier les interactions entre polyélectrolytes (PE) de charges opposées par analyse frontale continue en électrophorèse capillaire (FACCE) et par titration calorimétrique isotherme (ITC), en fonction de la force ionique du milieu et des paramètres physico-chimiques relatifs aux deux partenaires (taux de charge chimique, masse molaire, ramification). Un copolymère statistique d’acrylamide et de 2-acrylamido-2-méthyl-propane sulfonate (PAMAMPS) de taux de charge variant entre 15% et 100% a été synthétisé et caractérisé pour cette étude. En tant que polycation modèle, la poly(L-lysine) a été retenue, sous sa forme linéaire (PLL) ou ramifiée / hyperbranchée (DGL). Des mesures par turbidimétrie ont permis d’étudier la stabilité des complexes de polyélectrolytes (PEC) en fonction de la force ionique du milieu. La détermination de la stœchiométrie des PEC par 1H-RMN a permis d’établir une règle générale pour prédire les stœchiométries de charge des PEC. Les paramètres thermodynamiques d’interactions (constantes et stœchiométries d’interaction, contribution entropique et enthalpique) ont été déterminés, par le tracé systématique des isothermes d’adsorption, en considérant le modèle d’interactions des sites indépendants de même énergie. Une dépendance linéaire entre le logarithme des constantes d’interactions et le logarithme de la force ionique a été observée. Cette dépendance en force ionique confirme le caractère entropique des interactions entre PE de charges opposées. Elle permet aussi de quantifier le nombre de contre-ions relargués lors de la formation du PEC. Cette quantité de contre-ions libérés a pu être comparée à la quantité totale de contre-ions condensés. Cette modélisation permet, en outre, de prédire les constantes d’interaction pour des taux de charge intermédiaires et à différentes forces ioniques. / The aim of this thesis is to study the interactions between oppositely charged polyelectrolytes (PE) by frontal analysis continuous capillary electrophoresis (FACCE) and isothermal titration calorimetry (ITC) as a function of the ionic strength of the medium and the physico-chemical properties related to the two partners (chemical charge density, molar mass, ramification). Statistical copolymers of acrylamide and 2-acrylamido-2-methyl-propane sulfonate (PAMAMPS) with chemical charge densities varying between 15% and 100% were synthesized and characterized for this study. Poly(L-lysine) under their linear (PLL) or ramified/hyperbranched (DGL) forms were used as model polycations. Turbidity measurements allowed the study of the stability of the polyelectrolyte complexes (PEC) as a function of the ionic strength of the medium. PEC charge stoichiometries were measured by 1H-NMR, and a general predictive rule that estimates the PEC charge stoichiometry was enounced. The thermodynamic binding parameters (binding constant, stoichiometry, enthalpic and entropic contributions) were determined, by systematically plotting the isotherms of adsorption, and using the model of independent and identical interacting sites. A linear dependence between the logarithm of the binding constants and the logarithm of the ionic strength was observed. This linear dependence confirmed the entropic character of the interactions between oppositely charged PE and allowed quantifying the number of released counter-ions that were compared to the total number of condensed counter-ions. Furthermore, this modelling allowed predicting the binding constants for intermediate chemical charge densities and at different ionic strengths.