L’objet de cette thèse a été la réalisation de sondes moléculaires fluorescentes pour de la détection de césium et de potassium en milieu aqueux. Deux problématiques ont été abordées : la détection de traces de césium en vue d’applications environnementales, et la mesure de variations de potassium en milieu biologique en vue d’applications biologiques. La première partie de cette thèse concerne la détection du césium. Dans un premier temps, différentes entités complexantes du césium ont été étudiées dans le but de mesurer des concentrations de césium comprises entre 1.10-3 et 5 ppm. Certaines de ces sondes ont ensuite été utilisées au sein d’un système de mesures basé sur un circuit micro-fluidique destiné à mesurer le césium de façon continue. La seconde partie de cette thèse s’intéresse à la détection du potassium. Dont le but a été de mettre au point des sondes pour mesurer le potassium extracellulaire par imagerie de fluorescence. Une cage complexante sélective du potassium a tout d’abord été identifiée. Différentes stratégies ont ensuite été développées pour remplacer la coumarine par un fluorophore excitable à de plus hautes longueurs d’ondes. Parmi les sondes étudiées, le Calix-COU-Alcyne-Sulf a permis d’effectuer des mesures in vitro préliminaires qui ont montré que ce type de sondes ne perturbe pas l’activité neuronale et permet de détecter le potassium dans la gamme de concentration visée. / The aim of this PhD was to study fluorescent molecular sensors in order to detect cesium and potassium in aqueous media. Two different issues have been addressed: the detection of cesium traces for environmental applications, and the measure of potassium fluctuations for biological applications. The first part concerns the detection of cesium. Several complexing units were first studied, to measure cesium concentration between 1.10-3 and 5 ppm. Some of the molecules made were then used in a measuring system based on a micro-fluidic chip to measure cesium in a continuous way. The second part concerns the detection of potassium. The aim was to design sensors to measure extracellular potassium fluctuations by fluorescence imaging. A selective complexing unit was first found. Several strategies were then explored to replace a coumarin by a fluorophore excitable at higher wavelengths. Among the molecules made, the Calix-COU-Alcyne-Sulf enabled preliminary in vitro measurements and showed that this type of molecules does not affect the neuronal activity and enables to measure potassium in the range of concentration targeted.

The problem with which this research is concerned is the determination of inorganic anions and cations with single injection ion chromatography. Direct detection of the separated analyte ions occurs after the analyte ions have passed through ion-exchange resins where they are separated according to their affinity for the ion-exchange resin active sites. The techniques involve the use of essentially a non-suppressed ion chromatographic system followed by a suppressed ion chromatographic system. With this system it is possible to accomplish both qualitative and quantitative determinations.

No description available.

These studies indicate that tetraethylammonium (TEA) is transported by saturable processes from bath to lumen and lumen to bath in isolated, perfused snake (Thamnophis spp.) proximal renal tubules and that the unidirectional flux from bath to lumen (Jᵇ¹(TEA)) exceeds the unidirectional flux from lumen to bath (J¹ᵇ (TEA)) at all TEA concentrations studied. In order to examine the transport process further, the effects of N¹-methylnicotinamide (NMN), temperature, sodium cyanide, and the removal of Na⁺ on TEA transport were studied. Steady-state Jᵇ¹(TEA) (103.2 ± 1.1 fmoles min⁻¹ mm⁻¹ at {TEA}(b) = 8.1 μM) was inhibited by 50% at {NMN}(b) = 4.0 mM. When TEA and NMN were present in the lumen, J¹ᵇ (TEA) was depressed initially (T < 8 min). However, at steady-state, the presence of NMN in the lumen appeared to stimulate J¹ᵇ (TEA). This suggests a trans-stimulation effect of NMN on J¹ᵇ (TEA). During some flux experiments tubules were perfused at room temperature (24°C) and then cooled to 2.8°C. Jᵇ¹(TEA) decreased approximately 25% when compared to control values. This effect was reversible. Other tubules were perfused in the presence of 2.5 mM sodium cyanide in the perfusate and bath. Cellular concentrations of TEA dropped from 67 to 27 times the bath concentration during Jᵇ¹(TEA) measurements and from 21 to 6 times the mean luminal concentration during J¹ᵇ (TEA) measurements. This indicates that little if any intracellular binding of TEA occurs, as passive accumulation should be 16.1 times the bath or lumen TEA concentration (assuming a -70 mV PD). To determine if TEA transport was dependent on the presence of Na⁺, Na⁺ in the bath and perfusate solutions was replaced isosmotically by sucrose. Jᵇ¹(TEA) was not significantly changed in the absence of Na⁺. J¹ᵇ (TEA) decreased to 56% of control in the absence of Na⁺. This effect was reversible. Thus, J¹ᵇ (TEA) is Na⁺-dependent and Jᵇ¹(TEA) is not. These data suggest that the transport characteristics of the carrier for TEA at the luminal and peritubular membranes of the distal-proximal tubules of garter snakes are dissimilar.

No description available.

The generation and isolation of two novel borenium cations has been described. The observation that the reaction of the Lewis acid B(C6F5)3 and the Lewis base diazabicyclo[2.2.2]octane (DABCO) with pinacol borane (HBpin) resulted in the activation of the B–H bond of HBpin and formation of a stable borenium cation/borohydride salt. This stable salt was used as a catalyst in the hydroboration reaction. It was shown to catalytically reduce a wide array of substrates including imines, N-heterocycles, nitriles, and ketones using pinacol borane as the source of hydride. Another borenium ion, synthesized from trityl tetrakis-pentafluorophenyl borate, DABCO, and HBpin did not contain a nucleophilic borohydride counterion and it was isolated in the solid state. This salt was also found to reduce the same substrates with similar yields and reaction times. The mechanisms of both of these catalysts were investigated and were found to be proceeding by a similar borenium catalyzed process. Quantitative analysis of the initial rates of each catalyst under identical conditions yielded rate constants on the same order of magnitude which strongly suggested that both catalysts operated via similar mechanisms. Stoichiometric experiments and isotope labelling using deuterated pinacol borane demonstrated that the nucleophilic counterion was not a kinetically relevant reducing agent under the reaction conditions. Furthermore, these reactions and the use of an isolable iminium ion as a hydride acceptor indicated that the hydride delivery agent was a DABCO•HBpin adduct. The DABCO•HBpin adduct was observed spectroscopically at ambient and subzero temperatures. Lastly, the rate of reduction using pinacol borane and [d1]-pinacol borane were significantly different and produced a high kinetic isotope effect (KIE = kH/kD = 6.6 ± 0.2). This high KIE strongly indicates that hydride delivery is the rate limiting step in the catalytic cycle. With this knowledge an asymmetric model is discussed and the beginnings of the development of an asymmetric borenium cation catalyzed process are described. / Thesis (Master, Chemistry) -- Queen's University, 2012-10-13 08:48:37.506

The role that aquatic actinomycetes play, in the production of tastes and odors in water supplies has been investigated since 1948. The ability of these organisms to produce by-products in lakes and streams, which renders the water unpalatable, is of considerable public health importance. It is desirable that the waterworks industry has as much information as possible concerning the factors that contribute to the growth of these organisms. Since it appears that the aquatic actinomycetes may be isolated from most fresh-water sources, the problem of diversified environments and nutritional requirements offers an excellent field of investigation. The fresh-waters of the world contain variable quantities of electrolytes that may determine in part the biological activity of these organisms. The unsolved questions in this instance are concerned with the electrolytes present and their quantitative effects on the growth and development of these forms.

Thèse de doctorat : Chimie et Physico-Chimie Moléculaires : Nancy 1 : 2008. / Titre provenant de l'écran-titre.

The increased worldwide interest in nuclear power and the politically charged threat of nuclear weapons release has made understanding the components, as well as the waste, of nuclear energy an important area of research. More specifically, the identification and selective extraction of the dioxoactinide cations uranyl (UO₂²⁺) and plutonyl (PuO₂⁺), low valent actinides scuh as Am³⁺ or Cm³⁺ and various anions, such as pertechnetate (TcO₄⁻), is essential in the event of a weapons release or the spill of nuclear waste. It has been previously demonstrated that the expanded porphyrin [24]hexaphyrin(1.0.1.0.0.0), commonly referred to as isoamethyrin, displays a dramatic color change, from golden yellow to red, upon coordination of uranyl, neptunyl and plutonyl cations. Chapter 2 details quantitative investigations of isoamethyrin with the uranyl cation as well as the interactions of isoamethyrin with other, potentially competing, cations. This work was carried out in order to assess the ability of isoamethyrin to serve as a colorimetric sensor for the actinide cations. Chapter 3 describes the synthesis and properties of periphery-modified isoamethyrin analogues. The addition of functional groups to this expanded porphyrin allows for immobilization onto a solid support and may enhance its utility as a sensor. Chapter 4 presents the preliminary investigations into the metalation and anion binding properties of a new series of macrocycles, the cyclo[n]pyrroles. Chapter 5 provides experimental methods and characterization data. / text

No description available.