München, Techn. Univ., Diss., 2002.

Le présent manuscrit de thèse se propose d'étudier l'évolution de l'interaction nucléaire dans les noyaux riches en neutrons de la région du coeur doublement magique de 132Sn via les isotopes de 136Sb, 136Sn et de 138Sn. Le premier chapitre de ce manuscrit présente succinctement certains des isotopes de Sb et de Sn connus à ce jour au delà des fermetures de couches Z=50 et N=82, ainsi que certaines des problématiques rencontrées pour la description des noyaux de cette région par le modèle en couches nucléaire. Le lecteur y trouvera en outre une brève présentation des outils indispensables à la compréhension de tels calculs. Les états excités du 136Sb furent produits à l'Institut Laue-Langevin de Grenoble via le mécanisme de fission induite par neutrons thermiques sur une cible de 241Pu. Les fragments de fission ainsi produits furent séparés par le spectromètre de masse Lohengrin, et une mesure des gammas et des électrons de conversions des fragments de 136Sb permirent la confirmation du précédent spectre expérimental obtenu ainsi que la mesure d'une durée de vie de 31(7) ns pour l'état de spin 4-. Ces éléments sont présentés et discutés en première partie du manuscrit. Les isotopes de 136,138Sn, objets de la seconde partie, furent quant à eux produits par fission d'un faisceau de 238U sur une cible de 9Be au RIBF du RIKEN, à Tokyo. Les séparateurs de masses BigRIPS et ZDS y permirent une séparation et une identification des fragments de fission ainsi produits avant leur implantation dans le détecteur en silicium hautement segmenté WAS3ABi, entouré par l'ensemble de détecteurs en germaniums EURICA. Une première mesure des énergies des transitions 6+ -> 4+, 4+ -> 2+ et 2+ -> 0+ de chacun de ces deux isotopes fut alors réalisée, ainsi que la mesure d'une durée de vie de 46(7) et 219(58) ns pour les états de spins 6+ du 136Sn et du 138Sn respectivement. / Evolution of nuclear structure in the vicinity of the doubly magic nuclei 132Sn will be discussed in this work, through the spectroscopy of 136Sb, 136Sn and 138Sn isotopes. Several Sb and Sn known isotopes beyond the Z=50 and N=82 shell closures will be briefly presented in the first chapter, aswell as some of the problems arising from the current shell model descritpion of nuclei in this region. Reader will also find in the same chapter a brief description of the most important tools needed to understand such calculations. Excited state of 136Sb have been populated at the Institut Laue-Langevin (Grenoble) through thermal neutron-induced fission on a 241Pu target. Fission fragments produced were separated with the Lohengrin mass spectrometer. Conversion electrons and gammas from 136Sb were measured and confirmed the previously proposed schemed. A new 31(7) ns isomer has been measured and assigned to the 4- state. Details of the experiment and analysis are presented in the first part. The second part is devoted to the 136,138Sn isotopes, produced via in-flight fission of 238U on a 9Be target at the RIBF of the RIKEN (Tokyo). Mass separators BigRIPS and ZDS allowed separation and identification of produced fragments, before implantation in the higly segmented silicon detector WAS3ABi surrounded by the germanium array EURICA. The first energy measurement of the 6+ -> 4+, 4+ -> 2+ and 2+ -> 0+ transitions has been performed for each of the 136,138Sn isotopes, aswell as an 46(7) and 219(58) ns half-life for the 6+ state of the 136Sn and 138Sn respectively.

Des techniques de séquençage existent pour les biopolymères comme les protéines et l'ADN et ont permis de révolutionner la biologie moderne. Toutefois, des techniques similaires dédiées au séquençage des carbohydrates n'ont pas encore été développées à cause de la complexité de cette classe de biomolécules. Dans ce contexte, nous avons construit un instrument couplant spectroscopie vibrationnelle et spectrométrie de masse (MS/IR) afin de caractériser la structure des carbohydrates grâce à leur signature infrarouge.Dans cette thèse, nous avons démontré que cette métrique permet de différencier les différentes isoméries présentes dans la classe des carbohydrates : la nature des monosaccharides, la position des modifications fonctionnelles ainsi que la régio- et la stéréochimie de la liaison glycosidique. Ensuite la conservation de la structure moléculaire des ions après fragmentation a été démontrée sur des fragments de disaccharides permettant ainsi d'établir les règles du séquençage de carbohydrates par MS/IR. Cette méthode a ensuite été appliquée sur différents oligosaccharides.Enfin dans la dernière partie de ce manuscrit, le potentiel de la spectroscopie IRMPD dans l'infrarouge lointain est exploré pour la résolution des anomères, des isomères et des conformations. Finalement deux approches permettant une séparation en masse et en isomère en amont de l'analyse spectroscopique sont proposées : spectroscopie IRMPD 2 couleurs ou couplage avec la chromatographie liquide / Sequencing techniques have been established for proteins and DNA and have revolutionised modern biology but similar technique do not exist for carbohydrates due to their unique complexity. In this context, we have built an instrument coupling vibrational spectroscopy and mass spectrometry (MS/IR) dedicated to the structural characterization of carbohydrates.In this thesis, we have shown that the IR signature is a powerful metric which is able to resolve simultaneously all carbohydrate isomerisms: the monosaccharide content, the position of functional modifications, the regiochemistry and the stereochemistry of the glycosidic linkage. Then the conservation of the molecular structure of MS fragments has been revealed on disaccharide fragments. Following this demonstration we have established the carbohydrate sequencing rules using MS/IR and applied them for the determination of the sequence of different oligosaccharides.Finally the potential of the IRMPD spectroscopy in the Far-IR range is explored for anomers, isomers and conformations resolution as well as the utilisation of a two colors infrared spectroscopy or the coupling with an HPLC instrument

This work is about the reaction around both isomeres of formylcations, formylcation (HCO+) and isoformylcation (HOC+). In interstellar chemistry these isomeres are of significant importance: radio astronomic measurements have detected the metastabil isomere HOC+ in present of the stabil isomere HCO+ in many objects. The HOC+ was found in photon dominated regions like (SgrB2, NGC 7538 und NGC 2024) as well as in dense clouds like DR21 (OH), W51M, W3 (OH), Orion (3N, 1E)). The ratecoefficiants for reactions forming both isomeres have been measured. Further more the ratecoefficiant for the isomerisation of isoformyl (HOC+) with molecular hydrogen has been measured at 25 K. / In der vorliegenden Arbeit werden Untersuchungen zu dem Ionensystem Formylkationen (HCO+) / Isoformylkationen (HOC+) vorgestellt. In der interstellaren Chemie kommt diesen Isomeren eine hohe Bedeutung zu: neuere radioastronomische Beobachtungen haben das metastabile Ion HOC+ in Anwesenheit des stabilen Isomers HCO+ in einer Vielzahl von interstellaren Umgebungen nachgewiesen. Das HOC+ - Isomer ist in signifikanter Dichte sowohl in Photon - dominierten Gebieten (wie z.B. SgrB2, NGC 7538 und NGC 2024) als auch in Dichten Molekularen Wolken (wie z.B. DR21 (OH), W51M, W3 (OH), Orion (3N, 1E), Orion KL, und G34.3) festgestellt worden. Es konnten die Ratenkoeffizienten für die Bildungsreaktionen beider Isomere bestimmt werden. Des weiteren konnte die Isomerisierung von Isoformylkationen (HOC+) mit Wasserstoff (H2) bei 25 K estimmt werden.

For the astrophysically relevant molecules, C3 and C6, ab initio calculations are performed to study the geometries of different neutral isomers, the electronic structures of C3 in its ground and excited states, and possible pathways for the reaction C3 + C3 = C6. For C3 we present calculations for the potential energy surfaces of C3 in different electronic configurations, including the singlet ground state, the triplet ground state, and some higher excited states. The geometries studied include triangular shapes with two identical bond lengths, but different bond angles between them. For the singlet and triplet ground states in the linear geometry, the total energies resulting from the mixed density functional-Hartree-Fock and quadratic configuration interaction methods reproduce the experimental values, i.e. the triplet occurs 2.1 eV above the singlet. In the geometry of an equilateral triangle, we find a low-lying triplet state with an energy of only 0.8 eV above the energy of the singlet in the linear configuration, so that the triangular geometry yields the lowest excited state of C3. For the higher excited states up to about 12 eV above the ground state, we apply time-dependent density functional theory. Even though the systematic error produced by this approach is of the order of 0.4 eV, the results give new insight into the potential energy landscape for higher excitation energies. For C6 we consider the known linear states and the lowest state of monocyclic ring. The potential energy surfaces, were built for various pathways for the reaction C3 + C3 = C6. For this investigation we apply a mixed density functional-Hartree-Fock method which gives good results with respect to the experimental values and does not demand much computational time. We have considered collinear and symmetric non-linear as well as some non-symmetric collision schemes of two C3 subunits, producing the 1Ag states of a D2h isomer, one in a cyclic shape, the other in the form of two triangles connected by the corners, and for the non-symmetric scheme the 1A' state of a Cs isomer. To investigate the pathways for the creation of C6 from two C3 we emphasize the importance of the electron configuration for the reacting C3 subunits. As a result we have obtained the following rule: The stable linear as well as the cyclic C6 molecule can only be created in the case when at least one C3 has a partially filled orbital, requiring an excited state with respect to the singlet ground state of C3. / Für die astrophysikalisch bedeutenden Moleküle C3 und C6 werden ab initio Berechnungen von elektronischen Zuständen verschiedener Isomere durchgeführt. Basierend auf der Optimierung verschiedener neutraler Isomere von C3 im Grundzustand und mehreren angeregten Zuständen werden mögliche Wege für die Reaktion C3 + C3 = C6 studiert. Für C3 werden ab initio Berechnungen für die Flächen der potentiellen Energie in verschiedenen elektronischen Konfigurationen durchgeführt, einschließlich des Singulett-Grundzustands, des Triplett-Grundzustands, und einiger höherer Anregungszustände. Die untersuchten Geometrien schließen gleichschenklige Dreiecke mit zwei identischen Bindungslängen ein, wobei der Bindungswinkel dazwischen variiert wird. Die Gesamtenergien, die sich in einem gemischten Hartree-Fock-Dichtefunktional-Verfahren und unter Verwendung der quadratischen Konfigurationswechselwirkung ergeben, reproduzieren die experimentell beobachtete Energiedifferenz von 2.1 eV zwischen dem niedrigsten Triplett-Zustand und dem Singulett-Grundzustand. In der Geometrie des gleichseitigen Dreiecks ergibt sich ein niedrigerliegender Triplett-Zustand mit einer Energie von nur 0.8 eV über der Energie des Singuletts im linearen Isomer, so dass die dreieckige Geometrie den niedrigsten Anregungszustand von C3 ergibt. Für höhere Anregungsenergien bis zu 12 eV über dem Grundzustand wird zeitabhängige Dichtefunktional-Theorie zur Ermittlung der Energie angeregter elektronischer Konfigurationen eingesetzt. Obwohl der von dieser Methode produzierte systematische Fehler von der Größenordnung von 0.4 eV ist, ergeben sich interessante neue Einblicke in die Potentiallandschaft angeregter Zustände. Für C6 betrachten wir das bekannte lineare Isomer und das zyklische Isomer. Der Verlauf der Potentialoberflächen wird für verschiedene Reaktionspfade C3+C3 = C6 untersucht, wobei ein gemischtes Hartree-Fock-Dichtefunktional-Verfahren einesetzt wird. Im Mittelpunkt des Interesses stehen dabei kollineare Anordnungen linearer C3 Moleküle, symmetrische Kollisionen nichtlinearer Reaktanden, sowie einige nichtsymmetrische koplanare Geometrien des Zusammenstosses zweier linearer Moleküle. Als Ergebnis der Reaktionen mit symmetrischen Anordnungen ergibt sich lineares C6 oder zyklisches C6 mit D2h Symmetrie in einem elektronischen Zustand der höchsten Symmetrie 1Ag. Das nicht-symmetrische Reaktionsschema führt zu einem planaren Isomer Cs im Zustand 1A'. Um die Wege für die Bildung von C6 aus zwei C3 zu untersuchen, ist die elektronische Konfiguration der Reaktanden von entscheidender Bedeutung. Als Ergebnis erhält man die folgende Regel: sowohl ein stabiles lineares als auch ein zyklisches C6 Molekül können nur gebildet werden, wenn zumindest eines der C3 Moleküle ein teilweise gefülltes Orbital hat, wofür eine Anregung aus dem Singulett-Grundzustand heraus erforderlich ist.

Neste trabalho realizamos um estudo do comportamento do momento magnético e do deslocamento isomérico de uma impureza intersticial de Fe em hospedeiros metálicos de valências 4 (Ti, Zr), 3 (Sc, Y). Investigamos também impurezas intersticiais e substitucionais de Mo e Fe em hospedeiros divalentes. Para realizar este estudo fizemos cálculos de estrutura eletrônica utilizando o RS-LMTO-ASA (\"Real Space - Linear Muffin-Tin Orbital - Atomic Spherical Approximation\"), um método de primeiros princípios dentro da aproximação do funcional densidade local, implementado no espaço real. Calculamos o momento magnético no sítio da impureza nos sistemas acima e constatamos que a impureza intersticial de Fe é não magnética nos hospedeiros de valências 4 e 3, e que tanto as impurezas intersticiais como as substitucionais podem apresentar momento magnético nos hospedeiros divalentes. Mostramos que para os sistemas divalentes o momento magnético depende fortemente da relaxação. Os nossos resultados são explicados através de um modelo simples, baseado no modelo de Wolff. Investigamos também o comportamento do deslocamento isomérico no sítio da impureza de Fe nesses vários sistemas. Constatamos que os nossos resultados concordam razoavelmente bem com os dados experimentais e explicam o comportamento das tendências observadas. / In the present work, we have studied the magnetic moments and the behavior of the isomer shift at the interstitial Fe impurity site in Ti, Sc, Zr and Y hosts. We have also investigated interstitial and substitutional Fe and Mo impurities in Ca, Sr and Yb hosts. To perform the calculations, we have used the RS-LMTO-ASA scheme, a first principles method, within the local spin density approximation, implemented in real space. We calculated the magnetic moments at the impurity site in the above systems and all the substitucional impurities are found to be magnetic. The results show that interstitial Fe is non-magnetic in the tri- and tetravalent hosts, but interstitial Fe and Mo impurities could develop local magnetic moment in divalent hosts. \'We show that the magnetic moment at the impurity site in these divalent hosts is strongly dependent on lattice relaxation. The results can be explained using simple arguments based on Wolff model. We have investigated in a systematic way the behavior of the isomer shift of Fe impurities in these systems. We observed that our results are in generally good agreement with experiment and lead to better understanding of the observed trends in terms of the volume occupied by the Fe in each host.

People experience the irritating tearing and burning sensation of lachrymatory factor (LF, propanthial S-oxide) when cutting or chopping onion bulbs. LF is produced by lachrymatory factor synthase (LFS) specifically from 1-propenyl sulfenic acid, a breakdown product of trans-1-propenyl-L-cysteine sulfoxide (1-PRENCSO) by alliinase. This thesis describes strategies to produce a tearless onion by using RNA interference (RNAi) silencing. To determine whether a gene silencing cassette can silence lfs gene transcripts from onion (Allium cepa L.), a crop recalcitrant to genetic transformation, a gene silencing assessment system was developed by using a model plant as a host for the gene of interest. Tobacco (Nicotiana tabacum) plants transgenic for LFS enzyme activity from onion were first produced by introducing a CaMV 35S-onion-lfs gene construct. These plants were then subjected to a second transformation with an RNAi construct directed against the lfs gene sequence. LFS enzyme activity assay showed that the transgenic plants, containing both the lfs gene and the RNAi construct, had significantly reduced LFS activity. This observation was supported by Western analysis for the LFS protein and further validated by quantitative RT-PCR analysis that demonstrated a significant reduction in the lfs transcript level in the dual transformants. This work demonstrated that the RNAi construct is a suitable candidate for the development of a tearless onion. This model plant RNAi system has wide reaching applications for assessment and targeting of plant secondary pathway genes, from poorly studied or recalcitrant plant species, that are important in pharmacological, food and process industries. The functional RNAi vector identified in the model system was transformed into onion. Endogenous lfs transcript levels were successfully reduced by up to 43-fold in six transgenic lines. In consequence, LFS enzyme activity was decreased by up to 1573-fold and this observation was supported by Western analysis for the LFS protein. Furthermore, the production of the deterrent LF upon tissue disruption was reduced up to 67-fold. Subjective olfactory assessment of silenced lines indicated that the pungent odour given off by the leaf and bulb material was much reduced compared with that of non-transgenic counterparts, and that this was replaced by a sweeter milder onion odour. A novel colorimetric assay demonstrated that this silencing had shifted the 1-PRENCSO breakdown pathway so that by reducing LFS protein, more 1-propenyl sulfenic acid was converted into di-1-propenyl thiosulfinate. A consequence of the raised thiosulfinates levels was a marked increase in the downstream production of a non-enzymatically produced zwiebelane isomer that has never previously been identified, and other volatile compounds, di-1-propenyl disulfides and 2-mercapto-3,4-dimethyl-2,3-dihydrothiophenes, which had previously been reported either in small amounts or had not been detected in onions. These raised volatile sulfur compounds provide an explanation for the unique flavour notes of the LF reduced onion and are predicted to have health benefits akin to those found in garlic. These results demonstrated that silencing of LFS enzyme activity by introducing an RNAi construct directed against the lfs gene sequence simultaneously reduced levels of the deterrent LF and increased the desirable thiosulfinates in onions.

This thesis contributes to an increased understanding of the formation of dioxins and dioxin-like compounds in combustion processes. Although emissions to air from waste incineration facilities have been greatly reduced by the use of efficient air pollution control measures, the resulting residues (ashes and filters) are highly toxic and are classified as hazardous waste. The main objective of the work underlying this thesis was to elucidate the formation and chlorination pathways of dioxins and dioxin-like compounds in waste combustion flue gases in the temperature range 640-200°C in a representative, well-controlled laboratory-scale reactor using artificial municipal solid waste. This could contribute to the reduction of harmful emissions to air and also reduce the toxicity of waste incineration residues, thus reducing or even eliminating the need for costly and potentially hazardous after-treatment. A comparison of four different quenching profiles showed that the formation of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) was rapid and mainly occurred in the 640-400°C temperature region, with high dependency on sufficient residence time within a specific temperature region. Prolonged residence time at high temperatures (450/460°C) reduced the PCDD yields, even at lower temperatures along the post-combustion zone. PCDD, PCDF and PCN (polychlorinated naphthalene) isomer distribution patterns indicated contributions from chlorophenol condensation as well as chlorination reactions for all three classes of compounds. The formation of PCDDs was largely influenced by chlorophenol condensation and to some extent by chlorination reactions. For the PCDFs, chlorine substitution adjacent to the oxygen bridges was unfavoured, as demonstrated by the notably lower abundance of 1,9-substituted congeners. This was supported by bidirectional orthogonal partial least squares (O2PLS) modelling. The variable with the greatest influence on the distribution of PCDD congeners was the relative free energy (RΔGf). The O2PLS models displayed distinct clusters, dividing most of the homologues into two or three sub-groups of congeners which seemed to correspond to the probability of origination from chlorophenol condensation. The effects of injection of aromatic structures into the flue gas differed for each class of compounds. Injection of naphthalene increased the formation of monochlorinated naphthalene but the remaining homologues appeared to be unaffected. This was probably due to insufficient residence time at temperatures necessary for further chlorination. Injected dibenzo-p-dioxin was decomposed, chlorinated and re-condensated into PCDDs and PCDFs, whereas injection of dibenzofuran and fluorene reduced the PCDD levels in the flue gas. / Denna avhandling fokuserar på olika aspekter som kan bidra till en ökad förståelse av bildning av dioxiner och dioxin-lika föreningar i förbränningsprocesser. Även om utsläppen till luft från sopförbränningsanläggningar har minskat kraftigt tack vare effektiva rökgasreningsmetoder, så återstår problemet med mycket giftiga rökgasreningsprodukter (askor och filter), vilka klassificeras som farligt avfall. Det huvudsakliga syftet med arbetet bakom denna avhandling var att klarlägga bildnings- och kloreringsvägarna för dioxiner och dioxin-lika föreningar i temperaturintervallet 640-200°C i rökgaser från sopförbränning. Detta kan möjliggöra lösningar för ytterligare emissionsminskningar och en avgiftning av biprodukterna från avfallsförbränning, vilket minskar eller till och med eliminerar behovet av kostsam och riskfylld efterbehandling. Realistiska och välkontrollerade försök har utförts i en lab-skalereaktor där en artificiell hushållssopa har förbränts. En jämförelse av fyra olika temperatur- och uppehållstidsprofiler visade att bildning av polyklorerade dibenso-p-dioxiner (PCDD) och dibensofuraner (PCDF) sker snabbt och huvudsakligen inom temperaturintervallet 640-400°C. Bildningen var starkt beroende av en tillräckligt lång uppehållstid inom ett visst temperaturområde. En förlängd uppehållstid vid höga temperaturer (>450°C) resulterade i minskade halter av PCDD, vilka förhöll sig låga även senare i efterförbränningszonen. Isomermönstren av PCDD, PCDF och PCN (polyklorerade naftalener) visade alla tecken på att härröra från både klorfenolkondensation och kloreringsreaktioner. PCDD-mönstret visade tydliga indikationer på bildning från klorfenoler, och till mindre grad bildning via klorering. För PCDF var klorsubstitution i positioner angränsande till syrebryggan missgynnad, vilket bekräftades av multivariat modellering (O2PLS). Den variabel som starkast påverkade bildningen av PCDD var relativa fria energin (RΔGf). Modellerna visade på en distinkt gruppering av PCDD- och PCDF-kongenerna i två eller tre grupper för varje kloreringsgrad, och föreslås vara relaterad till sannolikheten för respektive kongen att bildas via klorfenolkondensation. Injektion av aromatiska kolstrukturer i rökgaskanalen gav upphov till skilda effekter. Injektion av naftalen ökade bildningen av monoklorerad naftalen medan resterande homologer inte verkade påverkas, sannolikt på grund av för kort uppehållstid för ytterligare klorering. Dibenso-p-dioxin spjälkades sannolikt till fenoliska fragment som klorerades och sedan återkondenserades till PCDD och PCDF, medan dibensofuran och fluoren kraftigt reducerade PCDD-koncentrationerna.

Perfluoroalkyl compounds (PFCs) are a group of chemical surfactants most notably used in non-stick and stain-resistance applications. Due to their wide-spread use and inherent resistance to degradation, several PFCs have become persistent environmental contaminants. Despite the high concentrations of PFCs reported in wild birds and their eggs, very little is known about the toxicological effects they have on avian species. This thesis investigates the developmental toxicity of PFCs in an avian model species: the domestic chicken (Gallus gallus domesticus). Egg injection experiments were performed to assess the in ovo toxicity of perfluorooctane sulfonate (technical grade, T-PFOS), perfluorooctanoic acid (PFOA), perfluorodecane sulfonate (PFDS) and perfluoroundecanoic acid (PFUdA). Real-time RT-PCR was then used to measure the transcription of candidate biomarker genes in the liver tissue of day 20 embryos. Candidate genes were selected based on their responsiveness to PFC exposure in previously conducted in vitro screening assays. In ovo exposure to PFOS resulted in a dose-dependent decrease in embryo pipping success (a measure of hatching success) with an LD50 of 93 μg/g (3.54 μg/g-672,910 μg/g, 95% confidence interval), however the expression of peroxisome proliferator-activated receptor alpha (PPARα)-regulated genes was not affected in liver tissue as hypothesized. PFOA, PFDS and PFUdA had no effect on the pipping success of chicken embryos. The expression of cytochrome P450 1A4 (CYP1A4) and liver fatty acid binding protein (L-FABP) mRNA increased in embryo liver tissue following in ovo exposure to PFUdA but was only statistically significant at 10 μg/g, which is several orders of magnitude higher than concentrations reported in wild bird eggs. The isomer-specific accumulation of PFOS in chicken embryo livers was also investigated using an in-port derivatization gas-chromatography/mass spectrometry (GC-MS) method. Prior to incubation, chicken eggs were injected with T-PFOS, composed of 63% linear isomer (L-PFOS) and 37.3% branched isomers. The isomer profiles in day-20 embryo liver tissue showed up to 20% enrichment in the proportion of L-PFOS, compared to T-PFOS, with a corresponding decrease in the proportion of branched isomers. This enrichment was inversely proportional to dose. Finally, the transcriptional profiles of cultured chicken embryonic hepatocytes (CEH) exposed to either T-PFOS or L-PFOS were compared using Agilent 4x44k Chicken (V2) Gene Expression microarrays. At equal concentrations (10 μM), T-PFOS altered the expression of significantly more genes (340 genes, >1.5 fold change, false discovery rate adjusted p<0.05) compared to L-PFOS (130 genes). Functional analysis showed that L-PFOS and T-PFOS affected genes involved in lipid metabolism, cellular growth and proliferation, and cell-cell signaling. Pathway and interactome analysis suggested that gene expression may be affected through RXR, oxidative stress response, TP53 signaling, MYC signaling, Wnt/β-catenin signaling and PPARγ and SREBP receptors. In all functional categories and pathways examined, T-PFOS had a more pronounced disruptive effect on transctional regulation than L-PFOS. In summary, egg injection experiments showed that T-PFOS (but not linear PFOA, PFDS or PFUdA) may affect the hatching success of the chicken at environmentally relevant concentrations. It was also demonstrated that the accumulation of PFOS in embryonic liver is isomer specific, and leads to an enrichment of L-PFOS. The increased transcriptional disruption caused by T-PFOS in cultured hepatocytes over L-PFOS suggests that the branched isomers may be largely responsible for the toxicological effects of PFOS. Combined, the results from this thesis demonstrate the importance of considering PFOS isomer burdens during risk assessment. In addition, gene expression analysis identified several candidate mechanisms for PFOS toxicity.

Perfluoroalkyl compounds (PFCs) are a group of chemical surfactants most notably used in non-stick and stain-resistance applications. Due to their wide-spread use and inherent resistance to degradation, several PFCs have become persistent environmental contaminants. Despite the high concentrations of PFCs reported in wild birds and their eggs, very little is known about the toxicological effects they have on avian species. This thesis investigates the developmental toxicity of PFCs in an avian model species: the domestic chicken (Gallus gallus domesticus). Egg injection experiments were performed to assess the in ovo toxicity of perfluorooctane sulfonate (technical grade, T-PFOS), perfluorooctanoic acid (PFOA), perfluorodecane sulfonate (PFDS) and perfluoroundecanoic acid (PFUdA). Real-time RT-PCR was then used to measure the transcription of candidate biomarker genes in the liver tissue of day 20 embryos. Candidate genes were selected based on their responsiveness to PFC exposure in previously conducted in vitro screening assays. In ovo exposure to PFOS resulted in a dose-dependent decrease in embryo pipping success (a measure of hatching success) with an LD50 of 93 μg/g (3.54 μg/g-672,910 μg/g, 95% confidence interval), however the expression of peroxisome proliferator-activated receptor alpha (PPARα)-regulated genes was not affected in liver tissue as hypothesized. PFOA, PFDS and PFUdA had no effect on the pipping success of chicken embryos. The expression of cytochrome P450 1A4 (CYP1A4) and liver fatty acid binding protein (L-FABP) mRNA increased in embryo liver tissue following in ovo exposure to PFUdA but was only statistically significant at 10 μg/g, which is several orders of magnitude higher than concentrations reported in wild bird eggs. The isomer-specific accumulation of PFOS in chicken embryo livers was also investigated using an in-port derivatization gas-chromatography/mass spectrometry (GC-MS) method. Prior to incubation, chicken eggs were injected with T-PFOS, composed of 63% linear isomer (L-PFOS) and 37.3% branched isomers. The isomer profiles in day-20 embryo liver tissue showed up to 20% enrichment in the proportion of L-PFOS, compared to T-PFOS, with a corresponding decrease in the proportion of branched isomers. This enrichment was inversely proportional to dose. Finally, the transcriptional profiles of cultured chicken embryonic hepatocytes (CEH) exposed to either T-PFOS or L-PFOS were compared using Agilent 4x44k Chicken (V2) Gene Expression microarrays. At equal concentrations (10 μM), T-PFOS altered the expression of significantly more genes (340 genes, >1.5 fold change, false discovery rate adjusted p<0.05) compared to L-PFOS (130 genes). Functional analysis showed that L-PFOS and T-PFOS affected genes involved in lipid metabolism, cellular growth and proliferation, and cell-cell signaling. Pathway and interactome analysis suggested that gene expression may be affected through RXR, oxidative stress response, TP53 signaling, MYC signaling, Wnt/β-catenin signaling and PPARγ and SREBP receptors. In all functional categories and pathways examined, T-PFOS had a more pronounced disruptive effect on transctional regulation than L-PFOS. In summary, egg injection experiments showed that T-PFOS (but not linear PFOA, PFDS or PFUdA) may affect the hatching success of the chicken at environmentally relevant concentrations. It was also demonstrated that the accumulation of PFOS in embryonic liver is isomer specific, and leads to an enrichment of L-PFOS. The increased transcriptional disruption caused by T-PFOS in cultured hepatocytes over L-PFOS suggests that the branched isomers may be largely responsible for the toxicological effects of PFOS. Combined, the results from this thesis demonstrate the importance of considering PFOS isomer burdens during risk assessment. In addition, gene expression analysis identified several candidate mechanisms for PFOS toxicity.