Tracertests stellen heute einen integralen Bestandteil im Repertoire der hydro(geo)logischen Charakterisierungstechniken dar. Insbesondere konservative Stoffe werden zur Bestimmung von hydraulischen Reservoir- und Aquiferparametern eingesetzt. Diese Stoffe verhalten sich weitestgehend inert und unterliegen somit nur vernachlässigbaren physikochemischen Wechselwirkungen während ihrer Verweilzeit im untersuchten Geosystem. Im Gegensatz dazu stellt der Einsatz nicht-konservativer organischer Stoffe als Tracer einen relativ neuen Ansatz dar, welcher das Potential birgt, zusätzliche Informationen zu ablaufenden Untergrundprozessen zu gewinnen, sofern die Wechselwirkungsarten und somit das Tracerverhalten bekannt sind. Folglich ist die genaue Kenntnis potentieller Transportprozesse und deren Abhängigkeiten eine unabdingbare Voraussetzung für eine erfolgreiche Interpretation dieser Tracer. In diesem Zusammenhang ist die Sorption an Festphasen für zahlreiche gelöste organische Verbindungen der wohl bedeutendste physikochemische Transportprozess. Aus diesem Grund ist die systematische Untersuchung von Sorptionsprozessen und deren Abhängigkeiten von den Moleküleigenschaften bzw. Randbedingungen ein Hauptbestandteil der hier vorgestellten, kumulativen Dissertationsschrift. Die aus den Sorptions-untersuchungen abgeleiteten Schlussfolgerungen wurden in die Entwicklung eines neuen, reaktiven Reservoir-Tracers für die geologische Speicherung von CO2 mit einbezogen. Um einen Überblick über das Sorptionsverhalten organischer Verbindungen mit unterschiedlichen Funktionalitäten zu gewinnen, wurde zunächst der pH-abhängige Stofftransport mehrerer dissoziierbarer Arzneimittelwirkstoffe (Säuren, Basen, Zwitter) mit Hilfe von Sedimentsäulenexperimenten untersucht. Hierzu wurden die Sorptionskoeffizienten bestimmt und mit den vorausberechneten Ergebnissen zweier Korrelationsansätze verglichen. Eine starke pH-Abhängigkeit zeigte die Sorption für alle Moleküle mit einem pKS-Wert im oder nahe des untersuchten pH-Bereiches. Eine zufriedenstellende Vorhersage war nur für neutrale und anionsche (saure) Verbindungen möglich. Im Gegensatz dazu war die Sorption der kationischen (basischen) und zwitter-ionischen Verbindungen stärker als erwartet. Als Ursache dafür kann das Auftreten zusätzlicher, elektrostatischer Sorptionsmechanismen angesehen werden, welche in den konventionellen Korrelationsansätzen nicht berücksichtigt werden. Somit konnte unter anderem erwartet werden, dass auch Kationenaustausch einen signifikanten Prozess für die Retardation organischer Kationen im Untergrund darstellt. Mit zwei kationischen Beta-Blockern durchgeführte Säulenversuche belegen die dominierende Rolle von Kationenaustauschprozessen. Steigende Konzentrationen anorganischer Kationen führen aufgrund der verstärkten Konkurrenz um die Austauscherplätze des Sorbens zu einer geringeren Sorption der organischen Kationen. Der Beitrag nicht-hydrophober Wechselwirkungen zur Gesamtsorption konnte mit >99% abgeschätzt werden. Aufgrund der großen Bedeutung von Kationenaustauschprozessen sollten weitere Einflussfaktoren berücksichtigt werden, um den Transport organischer Kationen zuverlässig vorhersagen zu können. Daher wurde anschließend der Einfluss konkurrierender anorganischer Kationen auf die Sorption organischer Kationen in Wasser/Sediment-Batchtests systematisch untersucht. Die bei verschiedenen Hintergrundkonzentrationen an anorganischen Kationen aufgenommenen Sorptionsisothermen des kationischen Beta-Blockers Metoprolol zeigten eine deutlich stärkere Beeinflussung der Sorption durch Ca2+ als durch Na+. Durch die gefundene Korrelation zwischen dem Freundlich-Koeffizienten und der Konzentration anorganischer Kationen wird eine Vorhersage der Metoprolol-Sorption im Bereich der untersuchten Randbedingungen möglich. Zudem konnte der Beitrag sorptiver Wechselwirkungen zum organischen Kohlenstoff des Sediments als vernachlässigbar bestimmt werden. Insgesamt liefern die erzielten Ergebnisse einen weiteren wichtigen Beitrag zur Prozessbeschreibung der Sorption und helfen somit, die Vorhersage des Stofftransportes organischer Kationen im Untergrund zu verbessern. Im letzten Teil der Arbeit werden das Konzept und die Entwicklung eines neuen, reaktiven Tracers (KIS-Tracer) zur Charakterisierung von Grenzflächen während Injektionen von überkritischem CO2 in tiefe salinare Aquifere beschrieben. Durch eine Hydrolysereaktion an der CO2/Wasser-Grenzfläche mit bekannter Kinetik wird ein Zusammenhang zur zeitlichen Änderung der Grenzflächengröße geschaffen. Basierend auf den vorangegangenen Untersuchungen zur Sorption, wurde das konservative, organische Anion Naphthalinsulfonat als Basisstruktur für die Tracersynthese (Veresterung) und somit auch als gewünschtes Hydrolyseprodukt ausgewählt. Neben der Definition notwendiger Tracereigenschaften wurden bereits erste Verbindungen synthetisiert, im Labor getestet und mit einem neuentwickelten, makroskopischen Modell ausgewertet. Abschließend wurde das Tracerverhalten exemplarisch für verschiedene hypothetische Funktionen der zeitlichen Grenzflächenänderung numerisch modelliert. Die bisher erzielten Ergebnisse sind sehr vielversprechend und gewähren einen ersten Einblick in das Potential von KIS-Tracern.

Dusty plasmas are plasmas that contain solid particles of nano- or micrometer size. They are widespread in the cosmic environment and act as precursors in the formation of planets and stars. Such plasmas are also used in laboratories for the synthesis of nanocomposites, which have wide technological and medical applications. While a large scientific effort has been invested in the study and control of such plasmas, the initial growth mechanism of powders (i.e. before they reach several tens of nanometers) remains poorly known. This work contributes primarily to expand the fundamental knowledge in the field of dusty plasmas. Our goal is to understand the physical chemistry of high-frequency plasmas magnetically confined in chemically reactive gases. In addition, we aim by examining the kinetics of the precursors in the plasma to understand the mechanisms of nanoparticle formation in the volume and to control their characteristics in a magnetically confined low pressure Ar/C2H2 plasma. This contribution has a direct impact on science and plasma applications. Among the applications related directly to this research, we mention the synthesis of carbon-based nanocomposites for their integration in solar cells and biomaterials. By examining the plasma characteristics (plasma temperature and density, cation and anion density) and correlating them to those of the dust particles, we found that the magnetic field changes the process of the formation of these particles in the discharge at very low pressure. Specifically, it stimulates the nucleation of carbon nanoparticles through several channels, i.e. through the anions and cations. These nanoparticles include two different phases, an amorphous carbon layer and a porous core formed of grains aggregate. These grains are formed of graphite nanocrystals coated with an amorphous layer. Moreover, the radius of the dust particles increases with the magnetic field, which is related to the enhancement of their residence time in the plasma volume. / Les plasmas poudreux sont des plasmas qui contiennent des particules solides de taille nano- ou même micrométrique. Ils sont répandus dans l'environnement cosmique et jouent le rôle de précurseurs dans la formation des planètes et des étoiles. Ce type de plasma est également utilisé dans les laboratoires pour la synthèse des nanocomposites possédant de vastes applications dans le monde technologique et médical. Tandis qu’un grand effort scientifique a été investi dans l’étude et le contrôle de ce type de plasmas, les mécanismes initiaux de formation des poudres (i.e. avant qu’elles atteignent quelques dizaines de nanomètres) demeurent très peu connus. On sait toutefois que des réactions physico-chimiques sont à l’origine de précurseurs des poudres qui déclenchent la nucléation. Ce travail contribue en premier lieu à accroître les connaissances fondamentales dans le domaine des plasmas poudreux en général. Il s’agit en particulier de comprendre la physico-chimie des plasmas de haute fréquence de très basse pression soumis à un confinement magnétique dans des gaz chimiquement réactifs. Plus spécifiquement, l’objectif de ce travail est d’examiner la cinétique des précurseurs produits dans le plasma afin de comprendre les mécanismes de formation de nanoparticules en volume et le contrôle de leurs caractéristiques dans des mélanges d’Ar/C2H2 de très basse pression confinés magnétiquement. Cet apport a des retombées directes en science et applications des plasmas. Parmi les applications directement visées par cette recherche, notons la synthèse de nanomatériaux composites à base de carbone pour leur intégration dans les cellules solaires et les biomatériaux. En examinant les caractéristiques du plasma (température et densité du plasma, densité des cations et des anions) et en les corrélant à celles des particules de poudre, on constate que le champ magnétique modifie le processus de la formation des particules poudreuses dans la décharge à très basse pression. Plus précisément, il favorise la nucléation des nanoparticules de carbone à travers plusieurs voies impliquant les anions et les cations. Ces nanoparticules comprennent deux phases différentes, une couche de carbone amorphe et un noyau poreux formé d'un agrégat de grains eux-mêmes constitués de nanocristaux de graphite revêtus d'une couche amorphe. On constate que le rayon moyen des particules de poudre augmente avec le champ magnétique, ce qui est lié à l’amélioration de leur temps de résidence dans le volume du plasma.

Les cryptophanes sont des récepteurs moléculaires qui présentent des propriétés de complexation intéressantes vis-à-vis de nombreux substrats. Ces quinze dernières années, les cryptophanes ont fait l’objet de beaucoup d’études portant sur leur utilisation pour l’obtention de biosondes pour l’IRM du xénon hyperpolarisé. De très nombreux progrès ont été réalisés, et des études in vivo semblent à présent envisageables, à condition de parvenir à synthétiser les biosondes en larges quantités. Plus récemment, un champ d’application parallèle s’est développé. Celui-ci porte sur la complexation des cations métalliques monovalents en solution aqueuse au sein de cryptophanes polyphénoliques. Ceci laisse envisager des applications pour la dépollution des eaux contaminées par des cations Cs+ ou Tl+. Cependant, ici encore, l’un des enjeux majeurs est la synthèse de larges quantités de cryptophanes présentant les caractéristiques recherchées. Les travaux réalisés au cours de cette thèse traitent de la conception et de la synthèse de nouvelles plateformes moléculaires pour l’obtention de biosondes au xénon hyperpolarisé et pour la complexation des cations métalliques monovalents Cs+ et Tl+. Les voies de synthèse mises au point permettent l’obtention de quantités appréciables d’un ensemble de nouvelles plateformes hydrosolubles pour chacune de ces applications. Les propriétés d’encapsulation de ces molécules hôtes envers leur substrat de prédilection ont été étudiées par RMN des noyaux encapsulés, par dichroïsme circulaire ou encore par titrage calorimétrique. Dans chaque cas, les nouvelles plateformes remplissent les caractéristiques recherchées et ouvrent la voie aux applications visées. / Cryptophanes are molecular receptors known for their complexation properties of various substrates. Over the last fifteen years, cryptophanes were the subject of numerous studies for they can be used to obtain biosensors for xenon MRI. This field has experienced significant growth and advances to the point were in vivo applications are now envisioned, provided that large amounts of biosensors can be synthesized. More recently, polyphenolic cryptophanes have been studied for their ability to encapsulate monovalent metallic cations like Cs+ and Tl+ in aqueous solution. This could lead to applications for depollution of contaminated water sources but would require, once again, the synthesis of large amounts of cryptophanes.The work carried out during this thesis focus on the conception and the synthesis of new molecular platforms that could either be used to obtain new hyperpolarized xenon biosensors or to encapsulate monovalent metallic cations as Cs+ and Tl+. Synthetic routes have been developed to produce good amounts of a variety of new hydrosoluble molecular platforms designed for each application. The encapsulation properties of these new host molecules were studied through NMR of the encapsulated nucleus, circular dichroism or isothermal calorimetry. In each case, the new platforms meet the expected requirements thus opening the door for the envisioned applications.

Recent synthetic approaches to a series of [P₉]X salts (X = [F{Al(ORꜰ)₃}₂], [Al(ORꜰ)₄], and (Rꜰ = C(CF₃)₃); Ga₂Cl₇) overcome limitations in classical synthesis methods that proved unsuitable for phosphorus cations. These salts contain the homopolyatomic cation [P₉]⁺ via (I) oxidation of P₄ with NO[F{Al(ORꜰ)₃}₂], (II) the arene-stabilized Co(I) sandwich complex [Co(arene)₂][Al(ORꜰ)₄] [arene = ortho-difluorobenzene (o-DFB) and fluorobenzene (FB)], or (III) the reduction of [P₅Cl₂][Ga₂Cl₇] with Ga[Ga₂Cl₇] as Ga(I) source in the presence of P₄. Quantum chemical CCSD(T) calculations suggest that [P₉]⁺ formation from [Co(arene)2]⁺ occurs via the nido-type cluster [(o-DFB)CoP₄]⁺, which resembles the isoelectronic, elusive [P₅]⁺. Apparently, the nido-cation [P₅]⁺ forms intermediately in all reactions, particularly during the Ga(I)-induced reduction of [P₅Cl₂]⁺ and the subsequent pick up of P₄ to yield the final salt [P₉][Ga₂Cl₇]. The solid-state structure of [P₉][Ga₂Cl₇] reveals the anticipated D₂d-symmetric Zintl-type cage for the [P₉]⁺ cation. Our approaches show great potential to bring other [Pn]⁺ cations from the gas to the condensed phase.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Plant defensin peptides have become promising and attractive candidates to be used as antifungal agents in agricultural biotechnology. These peptides have a broad spectrum antifungal activity and play a vital role in the innate immune system of plants. Plant diseases caused by fungi are a major contributor to the decrease in the quality and safety of agricultural products. Due to the dangerous effects and negative environmental impact of pesticides, an effective, safe, natural and durable method to control crop pathogens has therefore become one of the major concerns in modern agriculture. Although these peptides are promising and attractive candidates, their precise mechanism of action is to date still unknown. Several common observations have been made. These include the antagonistic effect of cations on the activity of plant defensins. It is of vital importance to understand the underlying mechanism of the cation-antagonistic effect on the antifungal potency of defensin peptides in order to evaluate the possible contribution to defence reactions against microorganisms in planta. To this end we set out to characterize the effect of cations in the form of biological salts, NaCl, KCl, MgCl2 and CaCl2 on the structural stability and activity in terms of growth inhibition, morphological effects and permeabilization. In order to perform these characterization experiments, a production method resulting in a greater yield and involving simple and rapid purification methods was required. Heliophila coronopifolia peptides have previously been produced in a bacterial system, however the purification methods were tedious resulting in poor yields. Pichia pastoris was selected as production system as several other plant defensins have been successfully produced in this eukaryotic system. Hc-AFP1 and Hc-AFP3 was successfully produced using the Pichia production system and rendered active peptides. Hc-AFP2 and Hc- AFP4 was, however, not produced correctly, due to a post-translational modification event leading to the cyclization of the N-terminal glutamine to generate pyroglutamic acid. This modification negatively influenced the activity of these peptides. An active Hc-AFP2 could be produced by replacing the production buffer with a reduced ionic buffer. The effect of divalent and monovalent cations on the secondary structure of Hc-AFP1 was evaluated by circular dichroism spectroscopy. These cations induced a conformational change in the secondary structure of Hc-AFP1, with NaCl and MgCl2 inducing a more defined secondary structure and KCl and CaCl2 inducing a less defined secondary structure. Monovalent cations caused a slight reduction in the growth inhibition activity of Hc-AFP1 on Botrytis cinerea, however, characteristic hyperbranching and other morphogentic effects were still visible. Divalent cations had a greater antagonistic effect on the activity of Hc-AFP1, completely abolishing the growth inhibitory activity of the peptide, but the induced morphological effects on hyphae remained present. The activity of Hc-AFP1 to permeabilize B. cinerea hyphae was not influenced by the addition of cations, however it was in fact increased to up to 10-fold. However, since the growth inhibition activity of Hc-AFP1 was reduced in the presence of the biological salts indicates that permeabilization is not the sole activity responsible for growth inhibition caused by Hc-AFP1. This peptide probably has an alternative/primary target and more complex MOA. This is the first known report of the investigation of the influence of cations on the structure of plant defensin peptides. It is clear that cations induce a secondary structural conformational change in Hc-AFP1. This may be linked to the antagonism on the activity of this peptide. This study provides significant progress towards the structure-function analysis of plant defensins. / AFRIKAANSE OPSOMMING: Plantdefensinpeptiede word beskou as belowende en aantreklike kandidate vir gebruik as swammiddles in agribiotegnologie. Hierdie peptiede beskik oor breë spektrum antifungiese aktiwiteit en speel ‘n essensiële rol in die ingebore immuunsisteem van plante. Plant siektes wat deur swamme veroorsaak word dra betekenisvol by tot die afname in die kwaliteit en veiligheid van landbouprodukte. As gevolg van die skadelike effekte en negatiewe omgewingsimpak van plaagdoders, het effektiewe, veilige, natuurlike en duursame metodes om gewaspatogene te beheer, van die belangrikste vraagstukke van moderne landbou geword. Alhoewel hierdie peptiede belowende en aantreklike kandidate is vir die toepassing, is hulle presiese meganisme van aksie tot vandag toe steeds onbekend. Verskeie algemene waarnemings is egter al gemaak. Dit sluit die antagonistiese effek van katione op die aktiwiteit van plantdefensinpeptiede in. Dit is kernbelangrik om die onderliggende meganisme van die katioon-antagonistiese effek op die antifungiese effektiwiteit te verstaan om die moontlike bydrae van die peptiede tot die verdedigingsreaksies teen mikro-organismes in planta te evalueer. Met die doel voor oë het ons gemik om die effek van katione, spesifiek in die vorm van die biologiese soute NaCl, KCl, MgCl2 en CaCl2, op die strukturele stabiliteit en aktiwiteit in terme van groei inhibisie, morfologiese effekte en permeabilisasie te karakteriseer. Om uiteindelik hierdie karakterisasie eksperimente uit te voer was dit nodig om ‘n metode met ‘n groter opbrengs en wat vinnige suiwering van die peptied ondersteun, te optimiseer. Heliophila coronopifolia peptiede was voorheen in ‘n bakteriese sisteem geproduseer, maar die suiweringsmetodes was tydsaam en het gelei tot ‘n swak opbrengs. Pichia pastoris is dus geselekteer as die produksie sisteem aangesien verskeie ander plantdefensinpeptiede al suksesvol geproduseer is in hierdie eukariotiese sisteem. Hc-AFP1 and Hc-AFP3 is suksesvol vervaardig in die Pichia sisteem en het aktiewiteit getoon. Hc-AFP2 and Hc-AFP4 kon egter nie korrek vervaardig word nie as gevolg van ‘n na-vertalingsverandering wat gelei het tot die siklisering van die N-terminale glutamien, om piroglutamiensuur te lewer. Hierdie verandering het die aktiwiteit van die peptied negatief beinvloed. ‘n Aktiewe Hc-AFP2 kon wel vervaardig word deur die produksiebuffer te vervang met ‘n lae-ionise buffer. Die effek van divalente en monovalente katione op die sekondêre struktuur van Hc-AFP1 is ge-evalueer deur van sirkulêre dikroisme spektroskopie gebruik te maak. Hierdie katione het ‘n vouingsverandering in die sekondêre struktuur van Hc-AFP1 geïnduseer, NaCl and MgCl2 het ‘n meer gedefinieërde sekondêre struktuur induseer, terwyl KCl and CaCl2 ‘n minder gedefinieërde sekondêre struktuur geinduseer het. Monovalente katione het ‘n effense vermindering in die groei-inhibisie aktiwiteit van Hc-AFP1 op Botrytis cinerea veroorsaak, alhoewel kenmerkende hife-oorvertakking en ander morfologiese effekte nogsteeds sigbaar was. Divalente katione het ‘n sterker antagonistiese effek gehad op die aktiwiteit van Hc-AFP1, waar dit totaal en al die groei-inhibisie aktiwiteit van die peptied vernietig het, alhoewel die geïnduseerde morfologiese effekte op die hiffes steeds sigbaar was . Die aktiwiteit van Hc-AFP1 om B. cinerea hyphae te permeabiliseer is nie negatief beinvloed deur die byvoeging van katione nie, tewens dit het die aktiwiteit tot 10-voudig verhoog. Aangesien die groei-inhibisie aktiwiteit van Hc-AFP1 nie verminder is in die teenwoordigheid van die biologiese soute nie, dui dit aan dat permeabilisasie nie die enigste aktiwiteit is wat die groei inhibisie veroorsaak het nie. Die peptied het dus moontlik ‘n alternatiewe of primêre teiken en ‘n meer komplekse meganisme van aksie. Dit is die eerste verslag wat die invloed van katione op die struktuur van plantdefensinpeptiede ondersoek het. Dit is duidelik dat katione ‘n sekondêre strukturele vouingsverandering in Hc-AFP1 induseer. Hierdie verandering mag dalk bydra tot die antagonistiese uitwerking op die aktiwiteit van hierdie peptied. Hierdie studie het betekensisvolle vordering gemaak met die analise van die struktuur-funksie interaksie van plantdefensinpeptiede. / The National Research Foundation (NRF), Institute of Wine Biotechnology (IWBT), THRIP and Winetech for financial assistance.

This study is divided into three parts. Part I deals with the mechanism of the self-initiated polymerization (or thermal polymerization) of styrene in the gas phase. In this work, we present the first direct evidence for the thermally self-initiated polymerization of styrene in the gas phase. Our approach is based on on-line analysis of the gas phase Oligomers by mass-selected ion mobility. The mobility measurements provide structural information on the ionized oligomers based on their collision cross-sections (Ω) which depend on the geometric shapes of the ions. Theoretical calculations of possible structural candidates of the Oligomers ions are then used to compute angle averaged Ω for comparison with the measured ones. The agreement between the measured and calculated Ω of the candidate structures provides reliable assignments to the structures of the oligomers. Furthermore, collisional-induced dissociations of the mass-selected oligomer ions provide further support for the structures obtained from the mobility measurements. Our results indicate that the gas phase polymerization of styrene proceeds via essentially the same initiation mechanism (the Mayo mechanism) as in condensed phase polymerization. The structural evidence, the mechanism of formation and the observed fragmentation pathway of the growing dimers and trimers in the gas phase are presentedIn Part II the solvation of a variety of metal cations by benzene clusters have been studied using laser vaporization, cluster beam and time-of-flight mass spectrometry techniques. In this work strong magic numbers were observed for clusters containing 10, 13 and 14 benzene molecules depending on the nature of the metal cation involved. The metal cations exhibiting preference solvation by 14 benzene molecules show a strong tendency to form sandwich structures with two benzene molecules. The interpretation of these results in view of the proposed structures and the growth patterns of the clusters are presented. In Part III, the work is focused on the investigation of the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile).

Les anthracyclines tels que la doxorubicin et la daunorubicin sont une famille de médicaments anticancéreux hydrophiles qui doivent être transportés dans les cellules afin d’exercer leur action par intercalation à l’ADN dans le noyau cellulaire. Ceci mène à la perturbation du métabolisme de l’ADN et entraine la mort cellulaire. Les anthracyclines sont utilisés pour le traitement d’une variété de cancers incluant la leucémie, les lymphomes, le cancer du sein, le cancer des poumons et le cancer des ovaires. Étant donné que le transport actif des anthracyclines dans les cellules a partiellement été démontré, le transporteur spécifique impliqué dans ce processus n’est pas encore connu. En utilisant un modèle de cancer des ovaires, la lignée cellulaire TOV2223G, nous avons démontré que des substrats spécifiques au transporteur de cations organiques 1 (OCT1), notamment la ergothionéine, la thiamine et la phenformin, ont partiellement inhibé l’absorption de la daunorubicin en différence de la carnitine qui est un substrat de haute affinité des transporteurs CT2 et OCTN2. Ces résultats suggèrent que les transporteurs organiques spécifiques au transport de la carnitine ne sont pas impliqués dans le transport des anthracyclines. Ainsi, nos résultats ont démontré que l’absorption de la daunorubicin est orchestrée par le transporteur OCT1 dans les cellules TOV2223G (Km ~ 5 μM) et des concentrations micromolaires de choline ont complètement abolies l’absorption de la drogue. De plus, un ARN sh dirigé contre OCT1 a réprimé son expression protéique, ce qui a été confirmé par la technique d’immuno-buvardage en utilisant un anti-OCT1 anticorps. Les cellules déficientes en OCT1 n’ont pas été capables d’absorber la daunorubicin et ont été plus résistantes à l’action de la drogue par rapport aux cellules contrôle. La transfection des cellules HEK293T avec un plasmide construit de façon à faire exprimer OCT1 comme protéine de fusion avec la protéine fluorescente EYFP a montré que celle-ci est localisée dans la membrane plasmique. Les cellules transfectées ont été capables d’absorber cinq fois plus de daunorubicin comparé aux cellules contrôles. Cette étude est, selon nous, la première à démontrer que OCT1 est un transporteur de haute affinité des anthracyclines. Ainsi, nous avons émis l’hypothèse que des défauts de OCT1 peuvent contribuer à l’efficacité de la réponse des cellules cancéreuses à la chimiothérapie avec les anthracyclines. / Anthracyclines such as doxorubicin and daunorubicin are hydrophilic anticancer agents that must be transported into cells. These drugs accumulate in the nucleus where they intercalate with DNA, thereby interfering with DNA replication in turn leading to cell death. Anthracyclines are used for treating a variety of cancers including leukemia, lymphomas, breast, lung, and ovarian. Despite evidence for active uptake of anthracyclines, the specific transporter has not been identified. Using the ovarian cancer cell line TOV2223G, we show that substrates reported for the organic cation transporter OCT1, such as ergothioneine, thiamine and phenformin, partially compete with uptake of daunorubicin, but not of L-carnitine, i.e., a high affinity substrate transported by hCT2 and OCTN2. These findings exclude the involvement of the L-carnitine organic cation family of transporters in anthracycline uptake. Moreover, we show that OCT1 actively mediates high affinity (Km ~ 5 μM) transport of daunorubicin into TOV2223G cells, whereas micromolar amounts of choline completely abolish drug uptake. shRNA-mediated downregulation of OCT1 causes defective uptake of daunorubicin, as well as significant resistance to the drug, as compared to the vector control. Transfection of HEK293T cells with a plasmid expressing OCT1 as a GFP fusion protein revealed that OCT1-EYFP was predominantly localized to the plasma membrane. These transfected cells manifested nearly 5-fold increased uptake of daunorubicin compared to the empty vector control. In summary, we show for the first time that human OCT1 is a high affinity transporter for anthracyclines. As such, we postulate that OCT1 status represents a critical determinant in the response of cancer cells to chemotherapy with anthracyclines

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

The Matimba and soon to be completed Medupi power stations located in close proximity to the town of Lephalale are a cause for environmental concern due to the known effects that coal combustion has on air, soil and water quality. The Medupi power station is currently being constructed, while the Matimba power station may have already negatively altered the water quality of the rivers especially those downwind of the power stations. The Lephalala (perennial river, upwind), the Mokolo (perennial river, upwind) and Matlabas (seasonal river, downwind) Rivers were selected due to the locations relative to the power stations. The concentrations and flux of cations and sulphate ions within the rivers in the Waterberg District Municipality were investigated for any seasonal or annual patterns using monthly data from a single sampling station along each river. Data for the concentrations of sodium, potassium, magnesium, calcium, ammonium and sulphate were analysed in conjunction with river discharge, rainfall and ambient temperature data available for each hydrological year from 1999 to 2010. The data were converted to seasonal and annual values in order to determine the influence of the quality and quantity of coal combusted as well as climatic variables (rainfall, temperature and discharge) on ion fluxes measured. Sodium was the dominant cation in all rivers, reaching a maximum concentration of 0.0015 mol.ℓ-1 (in 2007), 0.0007 mol.ℓ-1 (in 2007) and 0.0006 mol.ℓ-1 (in 2001) in the Lephalala, Mokolo and Matlabas Rivers, respectively. Other cation concentrations were four times lower in the Lephalala and Mokolo Rivers, while they were eight times lower in the Matlabas Rivers. Sulphate concentrations were approximately nine, five and 15 times lower than the cation concentrations measured within the Lephalala, Mokolo and Matlabas Rivers, respectively. The mean summed cation flux was highest in the Lephalala River (0.0015 ± 0.0010 Eq.ℓ-1), which was approximately 1.7 and 2.1 times higher than summed cation fluxes measured in the Mokolo (0.0009 ± 0.0002 Eq.ℓ-1) and Matlabas (0.0007 ± 0.0006 Eq.ℓ-1) Rivers. Cation fluxes were highest during the rainfall season (summer and spring) in the river closest to the Matimba power station (Mokolo Rivers) while summed cation flux in the Lephalala and Mokolo Rivers (located further away from the power station) showed no specific seasonality. It was, however, noted that the cation fluxes during spring and winter were elevated for both rivers, possibly indicating

Orientador: Carlos Alexandre Costa Crusciol / Banca: Dirceu Maximino Fernandes / Banca: Luis Reynaldo F. Alleoni / Banca: Edson Lazarini / Banca: Julio Cezar F. dos Santos / Resumo: Atualmente vem existindo interesse na calagem superficial, sem prévia incorporação, para implantação do sistema de plantio direto (SPD). Dessa forma, objetivou-se avaliar a quantidade, a qualidade e os efeitos de resíduos de diferentes plantas de cobertura, com e sem calagem superficial, sobre os atributos químicos no perfil do solo e as respostas do milho e da soja, no SPD em fase de implantação em região de inverno seco. O experimento foi realizado nos anos agrícolas de 1999/00, 2000/01 e 2001/02 na FCA/UNESP-Botucatu (SP), em Nitossolo Vermelho Distroférrico. O delineamento experimental foi em blocos ao acaso, com parcelas subdivididas e quatro repetições. As parcelas foram constituídas pelos tratamentos de cobertura vegetal, sendo: 1-sorgo de Guiné vermelho, 2-sorgo de Guiné branco/preto, 3-milheto, 4-painço, 5-vegetação espontânea e 6-sem vegetação. Nas subparcelas foram admitidos dois níveis de saturação por bases: A- a original do solo e B- visando a elevação da V% a 70 (recebendo inicialmente uma aplicação superficial de calcário e posterior reaplicação). Foi utilizado um calcário dolomítico faixa D (filler). As coberturas vegetais foram dessecadas aos 53, 56 e 50 dias após a emergência... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Interest has been on the rise toward surface liming, without previous incorporation, during no-till system implementation. The objective was thus to evaluate the amount, quality, and effects of residues of different ground cover plants, either with or without surface liming, on the soil profile's chemical attributes, and the responses of corn and soybean, under no-till system at the implementation stage in a dry-winter region. The experiment was conducted during the 1999/00, 2000/01, and 2001/02 cropping seasons at FCA/UNESP-Botucatu (SP), on a Red Nitosol (Alfisol). The experimental design was organized as random blocks, with split-plots and four replicates. Plots consisted of ground cover plant treatments, as follows: 1-red broomcorn millet, 2- white/black broomcorn millet, 3- millet, 4- fall panicum, 5-spontaneous vegetation, and 6-no vegetation. Two base saturation levels were admitted in the subplots: A- the soil's original value, and B- a value that would raise V% to 70 (initially receiving one surface lime application and a later reapplication). Ground cover plants were desiccated at 53, 56, and 50 days after emergence, in the three cropping years... (Complete abstract, click electronic address below) / Doutor