Specific ion effects on protein interfaces have been observed for many years, but yet comprehensive explanations regarding the mechanism by which ions interact with proteins and more general aqueous interfaces are still under investigation. Realistically, ion specificity on protein stability is due to numerous contributions and interactions between the solution and protein. However, the most important contribution is arguably the hydrophobic effect, specifically the change in free energy when water molecules are liberated from the interfacial region upon protein folding. In the work presented here, the effects of different ions on the critical micelle concentration (CMC) of 1, 2 –Hexanediol were examined to study salt effects on hydrophobicity by the means of fluorescence spectroscopy. Our results show that anions and cations do exhibit the specific effects on hydrophobic interactions. However, the origin of these specific ion effects different for cations and anions. Cation specific effects are caused by their ability to form cavities in solution, while anion specific effects arise from their ability to interact with the interface. These results are of interest to the researchers in the protein folding field, providing significant experimental hydrophobicity data necessary for theoretical biologists that are attempting to predict protein structures. / February 2015

The presented thesis is a continuation of the bachelor work, in which the effects of monovalent ions on neutral model lipid membranes were characterized. Herein physical properties of physiologically relevant anionic membranes in the presence of monovalent cations and oxidized lipids were studied. Hydration and mobility of the lipid bilayer at glycerol level were investigated using fluorescent solvent relaxation technique. In the first part of this work the interactions of cations (Na+ , K+ , Cs+ ) with negatively charged POPC/POPS lipid mixture, which is a good model of inner leaflet of cellular membrane, were studied. The presence of cations resulted in dehydration and substantial hinderence of mobility of hydrated lipids at the glycerol level probed by Laurdan. Clear specificity of those effects, which correlated with Hofmeister series have been observed. In the second part of the work truncated oxidized phospholipids, oxPLs (PazePC, PoxnoPC, PGPC, POVPC), which are known to be important in pathophysiology of numerous diseases, were investigated. 10 mol% of each oxPL was incorporated into neutral and anionic lipid bilayers, the hydration and mobility of which were measured in water or in KCl solution. The results reveal complex interactions between oxPLs, negatively charged lipids, and K+ . In...

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Specific ion effects, identified for more than hundred years, play an important role in a wide range of phenomena and applications. Several mechanisms such as direct ion interaction with molecules have been suggested to explain these effects, but quantitative experimental evidence remains scarce. Electrophoretic NMR (eNMR) has been emerging as a very powerful tool for studying molecular association and ionic transport in a variety of systems. Yet its potential in studying specific ion effect has been unexplored. In this thesis, eNMR was in part developed further as an analytical method and was in part used as one of the main techniques to study ions interacting with macromolecules in aqueous and non-aqueous solutions. The complexation of a large group of cations with poly ethylene oxide (PEO) in methanol was studied with eNMR. The binding of monovalent ions was demonstrated not to follow the Hofmeister order; multivalent cations except barium all showed negligible complexation. As a unifying feature, only cations with surface charge density below a threshold value were able to bind suggesting that ion solvation is critical. The binding mechanism was examined in greater detail for K+ and Ba2+ with oligomeric PEO of different chain lengths. Those two cations exhibited different binding mechanisms. K+ was found to bind to PEO by having at least 6 repeating units wrap around it while retaining the polymer flexibility. On the other hand, Ba2+ (and, to some extent, (BaAnion)+) needs a slightly shorter section to bind, but the molecular dynamics at the binding site slow considerably. The binding of anions with poly (N-isopropylacrylamide) in water was quantified at low salt concentration with eNMR and the binding affinity, though very weak, followed the Hofmeister order. This result indicates the non-electrostatic nature of this specific ion effects. The increase of binding strength with salt concentration is well described by a Langmuir isotherm. The specific ion binding to a protein, bovine serum albumin (BSA), was also studied at pH values where BSA has either net positive and negative charges. Our results show that anions have the same binding affinity irrespective of the surface charge while the binding strength of cations is reversed with the change in net surface charge. This indicates different binding mechanisms for cations and anions. The ionization of cellobiose in alkaline solutions was measured quantitatively by eNMR. The results show a two-step deprotonation process with increasing alkaline strength. Supported by results from 1H-13C HSQC NMR and MD simulation, ionization was proposed to be responsible for the improved solubility of cellulose in alkaline solution. eNMR was also used to characterize the effective charge of tetramethylammonium ions in a variety of solvents. In solvents of high polarity, the results agree well with predictions based on Onsager’s limiting law but for nonpolar solvents deviations were found that were attributed to ion pair formation. / <p>QC 20170216</p>

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Dans le domaine de la séparation sélective pour le traitement et la valorisation des combustibles nucléaires usés, l'extraction liquide-liquide est largement utilisée au niveau industriel. Cependant dans le cadre des technologies nucléaires du futur, des procédés alternatifs de séparation sont recherchés. Notamment la précipitation sélective d'actinides par des tensioactifs cationiques en milieu aqueux (l'extraction liquide-solide étudié par Heckmann et al dans les années 80) apparaît comme une approche intéressante. Le principal avantage de cette technique, comparée à l'extraction liquide-liquide, est lié à la diminution du nombre d'étapes dans le processus comme le lavage du solvant ou la désextraction des métaux. De plus, c'est une technique sans solvant organique ce qui réduit considérablement la quantité de déchets contaminés. Pour ces travaux de thèse, nous avons utilisé des méthodes physico-chimiques pour mieux comprendre l'interaction spécifique entre le cation métallique et le tensioactif cationique. Nous avons tout d'abord analysé l'effet spécifique des contre-ions anioniques (Cl-, NO3-, C2O42-) provenant des acides utilisés; puis nous avons étudié finement l'introduction de cations alcalins monovalents et quelques cations multivalents sélectionnés (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) sur l'auto-assemblage et les propriétés structurels du tensioactif en variant les conditions thermodynamiques. Nous en avons conclu que l'adsorption d'un complexe anionique stable du métal, à l'interface des agrégats micellaires, influence fortement les paramètres d'agrégation du tensioactif et détermine ainsi les limites d'utilisation de cette technique de séparation. / In the field of selective separation for recycling of spent nuclear fuel, liquid-liquid extraction processes are widely used (PUREX, DIAMEX …) in industrial scale. In order to guarantee a sustainable nuclear energy for the forthcoming generations, alternative reprocessing techniques are under development. One of them bases on the studies from Heckmann et al in the 80's and consists in selectively precipitating actinides from aqueous waste solutions by cationic surfactants (liquid-solid extraction). This technique has some interesting advantages over liquid-liquid extraction techniques, because several steps are omitted like stripping or solvent washing. Moreover, the amount of waste is decreased considerably, since no contaminated organic solvent is produced. In this thesis, we have carried out a physico-chemical study to understand the specific interactions between the metallic cations with the cationic surfactant. First, we have analysed the specific effect of the different counter-ions (Cl-, NO3-, C2O42-) and then the effect of alkaline cations on the structural properties of the surfactant aggregation in varying thermodynamical conditions. Finally, different multivalent cations (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) were considered; we have concluded that depending on the anionic complex of these metals formed in acidic media, we can observe either an adsorption at the micellar interface or not. This adsorption has a large influence of the surfactant aggregation properties and determines the limits of the application in term of ionic strength, temperature and surfactant concentration.

Micelas são agregados coloidais formados por moléculas anfifílicas i.e., moléculas com uma região hidrofóbica e uma porção hidrofílica (surfactantes). Efeitos específicos de íons (EEIs) são observados em micelas iônicas, uma vez que as propriedades físico-químicas de agregado micelares, como tamanho e geometria, dependem da natureza do contra-íon. Diferentes ânions inorgânicos produzem alterações modestas nas propriedades de agregados micelares catiônicos, mas ânions orgânicos podem induzir efeitos mais pronunciados, como transições de forma do agregado ou separações de fase. Em sistemas micelares, os EEIs podem estar relacionados a: (a) diferenças na localização dos ânions nas micelas; (b) diferenças na hidratação micellar e de íons; e (c) possível formação de pares iônicos entre surfactantes e contra-íons na interface micelar. Diversos modelos foram desenvolvidos para descrever a formação e estabilidade de agregados micelares, considerando diferentes termos energéticos que possivelmente contribuem para a formação/estabilidade de micelas. Contudo, os termos descritos acima (a - c) geralmente não são incluídos nos modelos micelares. Assim, não deve ser possível predizer as propriedades de micelas catiônicas, usando os modelos atuais, caso o contra-íon seja pequeno, desidratado e capaz de formar pares iônicos, como o ânion trifluorometilsulfonato (triflato, Tf). Tendo isso em vista, determinamos as propriedades micelares de triflato de dodeciltrimetilamônio (DTATf) e comparamos com micelas análogas formadas por brometo, cloreto e metanosulfonato, visando identificar diferenças estruturais das micelas e suas origens. Para determinação de propriedades micelares, utilizamos uma série de técnicas experimentais: fluorescência resolvida no tempo, espalhamento de raio-X de baixo ângulo, condutometria, cinética química, ressonâncias paramagnética eletrônica e magnética nuclear e espectroscopia de relaxação dielétrica, entre outras. Observamos que o agregado de DTATf possui uma estrutura discoidal altamente empacotada, ordenada e desidratada e estas propriedades foram reproduzidos em simulações de dinâmica molecular. A análise do conjunto de resultados obtidos para DTATf demonstrou que a formação de pares iônicos na interface micelar induz severas alterações nas propriedades micelares, como a desidratação dos agregados. Os dados obtidos com DTATf demonstram claramente que, para um modelo teórico de sistemas micelares ser capaz de predizer propriedades micelares de diferentes agregados, a possibilidade de formação de pares iônicos na interface micelar e as interações específicas entre contra-íons e surfactantes devem ser modeladas. Adicionalmente, devido aos resultados aqui reportados e analisando outros sistemas interfaciais, propomos um papel mais fundamental para a água (interfacial ou de hidratação) nas propriedades micelares / Micelles are colloidal aggregates formed by amphiphilic monomers i.e., molecules with a hydrophobic and a hydrophilic moiety (surfactants). Specific ion effects (SIEs) are observed in cationic micelles, because the physicochemical properties of the micellar aggregates, such as size and shape, depend on the nature of the counterion. Different inorganic counterions lead to small changes in micellar properties of cationic aggregates, but organic counterions can induce more pronounced effects, such as shape transitions of the aggregates or phase separation. In micellar systems, the SIEs can be related with: (a) differences in the location of anions in micelles; (b) differences in the hydration of micelles and ions; and (c) possible ion-pair formation between surfactants and counterions at the micellar interface. Several models have been developed to describe the formation and stability of micellar aggregates, considering different energy terms that possibly contribute to the formation/stability of micelles. However, the terms described above (a - c) are generally not included in micellar models. Thus, it should not be possible to predict the properties of cationic micelles, using the current models, if the counterion is small, dehydrated and capable of forming ion-pairs, such as the trifluoromethylsulfonate anion (triflate, Tf). In this context, we have determined the micellar properties of dodecyltrimethylammonium triflate (DTATf) micelles and we have compared the results with similar micelles formed by bromide, chloride and methanesulfonate, aiming to identify their structural differences and its origins. To determine the micellar properties, we have used several techniques: time resolved fluorescence, small angle X-ray scattering, conductometry, kinetic assays, electron paramagnetic and nuclear magnetic resonances and dielectric relaxation spectroscopy, among others. We have observed that the DTATf aggregate presents a highly packed, ordered and dehydrated disk-like geometry and these properties were reproduced in molecular dynamics simulations. The analysis of the DTATf properties showed that the formation of ion-pairs at the micellar interface induces severe changes in micellar properties, such as micellar dehydration. The DTATf properties clearly demonstrate that for a theoretical model of micellar system to be accurate and general, the possibility of ion-pair formation at the micellar interface and the counterions-surfactant specific interactions must be modeled. Additionally, due to the results reported herein and by analyzing other systems, we suggest a more fundamental role of water (interfacial or hydrating water) in the micellar properties.

Micelas são agregados coloidais formados por moléculas anfifílicas i.e., moléculas com uma região hidrofóbica e uma porção hidrofílica (surfactantes). Efeitos específicos de íons (EEIs) são observados em micelas iônicas, uma vez que as propriedades físico-químicas de agregado micelares, como tamanho e geometria, dependem da natureza do contra-íon. Diferentes ânions inorgânicos produzem alterações modestas nas propriedades de agregados micelares catiônicos, mas ânions orgânicos podem induzir efeitos mais pronunciados, como transições de forma do agregado ou separações de fase. Em sistemas micelares, os EEIs podem estar relacionados a: (a) diferenças na localização dos ânions nas micelas; (b) diferenças na hidratação micellar e de íons; e (c) possível formação de pares iônicos entre surfactantes e contra-íons na interface micelar. Diversos modelos foram desenvolvidos para descrever a formação e estabilidade de agregados micelares, considerando diferentes termos energéticos que possivelmente contribuem para a formação/estabilidade de micelas. Contudo, os termos descritos acima (a - c) geralmente não são incluídos nos modelos micelares. Assim, não deve ser possível predizer as propriedades de micelas catiônicas, usando os modelos atuais, caso o contra-íon seja pequeno, desidratado e capaz de formar pares iônicos, como o ânion trifluorometilsulfonato (triflato, Tf). Tendo isso em vista, determinamos as propriedades micelares de triflato de dodeciltrimetilamônio (DTATf) e comparamos com micelas análogas formadas por brometo, cloreto e metanosulfonato, visando identificar diferenças estruturais das micelas e suas origens. Para determinação de propriedades micelares, utilizamos uma série de técnicas experimentais: fluorescência resolvida no tempo, espalhamento de raio-X de baixo ângulo, condutometria, cinética química, ressonâncias paramagnética eletrônica e magnética nuclear e espectroscopia de relaxação dielétrica, entre outras. Observamos que o agregado de DTATf possui uma estrutura discoidal altamente empacotada, ordenada e desidratada e estas propriedades foram reproduzidos em simulações de dinâmica molecular. A análise do conjunto de resultados obtidos para DTATf demonstrou que a formação de pares iônicos na interface micelar induz severas alterações nas propriedades micelares, como a desidratação dos agregados. Os dados obtidos com DTATf demonstram claramente que, para um modelo teórico de sistemas micelares ser capaz de predizer propriedades micelares de diferentes agregados, a possibilidade de formação de pares iônicos na interface micelar e as interações específicas entre contra-íons e surfactantes devem ser modeladas. Adicionalmente, devido aos resultados aqui reportados e analisando outros sistemas interfaciais, propomos um papel mais fundamental para a água (interfacial ou de hidratação) nas propriedades micelares / Micelles are colloidal aggregates formed by amphiphilic monomers i.e., molecules with a hydrophobic and a hydrophilic moiety (surfactants). Specific ion effects (SIEs) are observed in cationic micelles, because the physicochemical properties of the micellar aggregates, such as size and shape, depend on the nature of the counterion. Different inorganic counterions lead to small changes in micellar properties of cationic aggregates, but organic counterions can induce more pronounced effects, such as shape transitions of the aggregates or phase separation. In micellar systems, the SIEs can be related with: (a) differences in the location of anions in micelles; (b) differences in the hydration of micelles and ions; and (c) possible ion-pair formation between surfactants and counterions at the micellar interface. Several models have been developed to describe the formation and stability of micellar aggregates, considering different energy terms that possibly contribute to the formation/stability of micelles. However, the terms described above (a - c) are generally not included in micellar models. Thus, it should not be possible to predict the properties of cationic micelles, using the current models, if the counterion is small, dehydrated and capable of forming ion-pairs, such as the trifluoromethylsulfonate anion (triflate, Tf). In this context, we have determined the micellar properties of dodecyltrimethylammonium triflate (DTATf) micelles and we have compared the results with similar micelles formed by bromide, chloride and methanesulfonate, aiming to identify their structural differences and its origins. To determine the micellar properties, we have used several techniques: time resolved fluorescence, small angle X-ray scattering, conductometry, kinetic assays, electron paramagnetic and nuclear magnetic resonances and dielectric relaxation spectroscopy, among others. We have observed that the DTATf aggregate presents a highly packed, ordered and dehydrated disk-like geometry and these properties were reproduced in molecular dynamics simulations. The analysis of the DTATf properties showed that the formation of ion-pairs at the micellar interface induces severe changes in micellar properties, such as micellar dehydration. The DTATf properties clearly demonstrate that for a theoretical model of micellar system to be accurate and general, the possibility of ion-pair formation at the micellar interface and the counterions-surfactant specific interactions must be modeled. Additionally, due to the results reported herein and by analyzing other systems, we suggest a more fundamental role of water (interfacial or hydrating water) in the micellar properties.

Among ornamental plants, roses (Rosa L.) are considered the most economically important, being among the most popular garden shrubs, as well as the favorite cut flowers sold by florists. In the past roses have been classified as fairly salt-sensitive, however, recent nutrition studies suggest that they may actually tolerate moderate to relatively high salinities. The general objective of this research was to reassess the limits of tolerance to salinity of roses and the influence of the rootstock used, to determine the ameliorative properties of supplemental Ca2+ on the response to salt stress, and to establish the influence of Na+- and Cl--counter ions on the detrimental effects caused by these salinizing elements. The NaCl or NaCl-CaCl2-salinity tolerance limit for greenhouse roses, although greatly influenced by the rootstock, was between 12 and 15 mmol.L-1. Plants grafted on ?Manetti? sustained their productivity/quality characteristics for longer time periods, tolerated greater salinity concentrations, and accumulated less Cl- and Na+ in leaves of flowering shoots than those grafted on ?Natal Briar?, confirming the greater ability of the former rootstock to tolerate salt stress. Supplementing the saline solution with 0-10 mmol.L-1 Ca2+ (as CaSO4) did not alleviate the harmful effects caused by NaCl-salt stress (12 mmol.L-1) on the productivity and quality responses of roses. The detrimental effects caused by Na- and Cl-based salinity were greatly influenced by the composition of the salt mixtures (i.e. their counter ions). Sodium sulfate and CaCl2 were the least harmful salts; NaCl had intermediate effects, while NaNO3 and KCl were the most deleterious. Among the most distinguishable effects caused by the more toxic Na+ and Cl- counter ions were lower osmotic potential (piSS) and greater electrical conductivity (ECSS) of the salinized solutions, markedly increased uptake and/or transport of either Na+ or Cl- to the flowering shoot leaves, and altered uptake and/or transport of other mineral nutrients. Computations of the saline solutions? chemical speciation revealed that salts containing divalent ions had lower ionization and exhibited greater ion associations compared to monovalent ion salts, rendering a lower number in free ions/molecules in solution which caused greater SS and lower ECSS in those solutions.