Einfluss von Stickstoffmonoxid, Hydroxylradikalen und Peroxynitrit auf DNA-Sch��den, DNA-Reparatur und Mutationen

Im Rahmen dieser Arbeit wurde untersucht ��ber welche Mechanismen und unter welchen Bedingungen Stickstoffmonoxid (NO) und verwandte reaktive Spezies wie Peroxynitrit und Hydroxylradikale zur Krebsentstehung beitragen k��nnen. NO f��hrte an zellfreier DNA kaum zu oxidativen DNA-Sch��den. Peroxynitrit, generiert aus 3-Morpholinosydnonimin (SIN-1), induzierte neben Einzel-strangbr��chen und AP-L��sionen vor allem oxidierte Purinmodifikationen (50 % 8-Hydroxyguanin (8-oxoG)). Hydroxylradikale, freigesetzt aus 4-Hydroxypyridinthion, induzierten neben Einzelstrangbr��chen und AP-L��sionen oxidierte Pyrimidinmodifikationen in der DNA. Nach Transformation und Replikation der gesch��digten DNA in E. coli DT-2 wurden ��berwiegend GC nach AT Transitionen (Hydroxylradikalsch��digung), wahrscheinlich verursacht durch das in der DNA induzierte 5-Hydroxycytidin, bzw. GC nach TA Transversionen (Peroxynitrit), verursacht durch das induzierte 8-oxoG, detektiert. In Zellkulturexperimenten f��hrte endogenes NO, freigesetzt von B6-INOS-Zellen (8��M) nicht zu einem Anstieg der Gleichgewichtsspiegel oxidativer DNA-Sch��den, hatte keinen Einfluss auf deren Induzierbarkeit und Reparatur, die Zellpro-liferation und den Glutathionspiegel, sch��tzte jedoch vor der Induktion von Einzelstrangbr��chen und Mikrokernen durch Wasserstoffperoxid. Exogenes NO, freigesetzt durch den Zerfall von Dipropylentriamin-NONOat, hemmte in Konzentrationen ab 0,5 mM spezifisch die Reparatur oxidativer DNA-Sch��den, nicht jedoch die von Pyrimidindimeren, AP-L��sionen und Einzelstrangbr��chen,und f��hrte in Konzentrationen > 1 mM zu einer Induktion von DNA-Sch��den in den B6-Mausfibroblasten. Dabei ��hnelte das induzierte Schadensprofil sehr dem von SIN-1.

Ma��geschneiderte Kieselgeltr��ger f��r die metallocen-katalysierte Polyolefinsynthese

Die vorliegende Arbeit besch��ftigt sich mit der Synthese und Charakterisierung von por��sen Kieselgelen und ihrem Einsatz als Tr��ger in der heterogenen metallocen-katalysierten Polymerisation von Ethylen. Im Vordergrund stand die Optimierung dieses Prozesses durch das Ma��scheidern der Tr��gereigenschaften unter sonst identischen Polymerisationsbedingungen und das Erforschen des heterogenen Polymerisationsprozesses. Das verwendete Katalysatorsystem (Methylaluminoxan mit Dicyclopentadienylzirkoniumdichlorid) besitzt sehr hohe Aktivit��ten und verbleibt im Falle der heterogenen Reaktionsf��hrung im Produkt. Der Mechanismus verl��uft ��ber mehrere Phasen, wobei besonderes Augenmerk auf die Tr��gerpartikelfragmentierung gelenkt wurde. Es wurden zwei Synthesekonzepte f��r die Herstellung der Tr��ger verfolgt. Im ersten Teil der Arbeit wurden monodisperse unpor��se Kieselgel-Nanopartikel (Monosphere) zu Agglomerattr��gern ��ber einen Spr��htrocknungsprozess aufgebaut. Die Stabilit��t der Agglomerate wurde ��ber den Zusatz von monodispersen Kieselgel-Binderpartikeln w��hrend der Herstellung variiert. Es wurden sowohl die porenstrukturellen als auch morphologischen Eigenschaften der Agglomeratprodukte untersucht und mit den physiko-chemischen Eigenschaften der Nanopartikel korreliert. In einem zweiten Ansatz wurden sph��rische hochpor��se Kieselgele mit abgestufter Porosit��t bei konstanter spezifischer Oberfl��che hergestellt und als Tr��ger in der Polyethylensynthese getestet.

Synthesis and characterization of metal-chalcogenide MQ 2-Nanoparticles (M = Mo, W, Zr; Q = S, O)

Here, we present the adaptation and optimization of (i) the solvothermal and (ii) the metal-organic chemical vapor deposition (MOCVD) approach as simple methods for the high-yield synthesis of MQ2 (M=Mo, W, Zr; Q = O, S) nanoparticles. Extensive characterization was carried out using X-ray diffraction (XRD), scanning and transmission electron micros��copy (SEM/TEM) combined with energy dispersive X-ray analysis (EDXA), Raman spectroscopy, thermal analyses (DTA/TG), small angle X-ray scattering (SAXS) and BET measurements. After a general introduction to the state of the art, a simple route to nanostructured MoS2 based on the decomposition of the cluster-based precursor (NH4)2Mo3S13���xH2O under solvothermal conditions (toluene, 653 K) is presented. Solvothermal decomposition results in nanostructured material that is distinct from the material obtained by decomposition of the same precursor in sealed quartz tubes at the same temperature. When carried out in the presence of the surfactant cetyltrimethyl��ammonium bromide (CTAB), the decomposition product exhibits highly disordered MoS2 lamellae with high surface areas. The synthesis of WS2 onion-like nanoparticles by means of a single-step MOCVD process is discussed. Furthermore, the results of the successful transfer of the two-step MO��CVD based synthesis of MoQ2 nanoparticles (Q = S, Se), comprising the formation of amorphous precursor particles and followed by the formation of fullerene-like particles in a subsequent annealing step to the W-S system, are presented. Based on a study of the temperature dependence of the reactions a set of conditions for the formation of onion-like structures in a one-step reaction could be derived. The MOCVD approach allows a selective synthesis of open and filled fullerene-like chalcogenide nanoparticles. An in situ heating stage transmission electron microscopy (TEM) study was employed to comparatively investigate the growth mechanism of MoS2 and WS2 nanoparticles obtained from MOCVD upon annealing. Round, mainly amorphous particles in the pristine sample trans��form to hollow onion-like particles upon annealing. A significant difference between both compounds could be demonstrated in their crystallization conduct. Finally, the results of the in situ hea��ting experiments are compared to those obtained from an ex situ annealing process under Ar. Eventually, a low temperature synthesis of monodisperse ZrO2 nanoparticles with diameters of ~ 8 nm is introduced. Whereas the solvent could be omitted, the synthesis in an autoclave is crucial for gaining nano-sized (n) ZrO2 by thermal decomposition of Zr(C2O4)2. The n-ZrO2 particles exhibits high specific surface areas (up to 385 m2/g) which make them promising candidates as catalysts and catalyst supports. Co-existence of m- and t-ZrO2 nano-particles of 6-9 nm in diameter, i.e. above the critical particle size of 6 nm, demonstrates that the particle size is not the only factor for stabilization of the t-ZrO2 modification at room temperature. In conclusion, synthesis within an autoclave (with and without solvent) and the MOCVD process could be successfully adapted to the synthesis of MoS2, WS2 and ZrO2 nanoparticles. A comparative in situ heating stage TEM study elucidated the growth mechanism of MoS2 and WS2 fullerene-like particles. As the general processes are similar, a transfer of this synthesis approach to other layered transition metal chalcogenide systems is to be expected. Application of the obtained nanomaterials as lubricants (MoS2, WS2) or as dental filling materials (ZrO2) is currently under investigation.

Entwicklung und Charakterisierung von Gassterilisationsprozessen am Beispiel der Oberfl��chensterilisation mittels Wasserstoffperoxid und Ethylenoxid

Bei der Auswahl einer Sterilisationsmethode stehen, gem���� den Vorgaben des Europ��ischen Arzneibuches, die Sterilisation mittels Hitze (Dampf bzw. Hei��luft) oder ionisierender Strahlung im Vordergrund. Diese so genannten Referenzverfahren verf��gen neben einem breiten Wirkungsspektrum ��ber eine hohe Effektivit��t und zeichnen sich durch eine gute Reproduzierbarkeit aus. H��ufig jedoch verbieten die physikalisch ��� chemischen Eigenschaften des zu sterilisierenden Gutes eine Anwendung der Referenzverfahren. In derartigen F��llen muss nach geeigneten Alternativverfahren gesucht werden, will man eine aseptische Herstellung vermeiden. Besonders bei thermolabilen G��tern hat sich der Einsatz von gasf��rmigen Agenzien mit keimt��tender Wirkung bew��hrt. Bei entsprechenden Rahmenbedingungen ist hier eine Sterilisation unterhalb der Raumtemperatur m��glich. Die vorliegende Arbeit untersucht die Anwendbarkeit der Ethylenoxidsterilisation bzw. der Sterilisation mittels gasf��rmigen Wasserstoffperoxids (Vapour Phase Hydrogen Peroxide) auf verschiedene Materialoberfl��chen am Beispiel zweier aktueller Anwendungen aus der pharmazeutischen Industrie. Dabei werden die Vor- und Nachteile der beiden Verfahren aufgezeigt und in Relation zu den Referenzverfahren gestellt. Im Rahmen der abschlie��enden mikrobiologischen Leistungsbeurteilung beider Verfahren werden verschiedene methodische Ans��tze, wie Halbzyklus und Fraction Negative Analysis zur Anwendung gebracht und bewertet.

Hypersonic elastic excitations in soft mesoscopic structures

This dissertation is devoted to the experimental exploration of the propagation of elastic waves in soft mesoscopic structures with submicrometer dimensions. A strong motivation of this work is the large technological relevance and the fundamental importance of the subject. Elastic waves are accompanied by time-dependent fluctuations of local stress and strain fields in the medium. As such, the propagation phase velocities are intimately related to the elastic moduli. Knowledge of the elastic wave propagation directly provides information about the mechanical properties of the probed mesoscopic structures, which are not readily accessible experimentally. On the other hand, elastic waves, when propagating in an inhomogeneous medium with spatial inhomogeneities comparable to their wavelength, exhibit rather rich behavior, including the appearance of novel physical phenomena, such as phononic bandgap formation. So far, the experimental work has been restricted to macroscopic structures, which limit wave propagation below the KHz range. It was anticipated that an experimental approach capable of probing the interplay of the wave propagation with the controlled mesoscopic structures would contribute to deeper insights into the fundamental problem of elastic wave propagation in inhomogeneous systems. The mesoscopic nature of the structures to be studied precludes the use of traditional methods, such as sound transmission, for the study of elastic wave propagation. In this work, an optical method utilizing the inelastic scattering of photons by GHz frequency thermally excited elastic waves, known as Brillouin light scattering spectroscopy (BLS), was employed. Two important classes of soft structures were investigated: thin films and colloidal crystals. For the former, the main interest was the effect of the one-dimensional (1D) confinement on the wave propagation due to the presence of the free-surface or interface of the layer and the utilization of these waves to extract relevant material parameters. For the second system, the primary interest was the interaction of the elastic wave and the strong scattering medium with local resonance units in a three-dimensional (3D) periodic arrangement.

NMR studies on supramolecular aggregates in solution and the solid state

The aim of this work presented here is the characterization of structure and dynamics of different types of supramolecular systems by advanced NMR spectroscopy. One of the characteristic features of NMR spectroscopy is based on its high selectivity. Thus, it is desirable to exploit this technique for studying structure and dynamics of large supramolecular systems without isotopic enrichment. The observed resonance frequencies are not only isotope specific but also influenced by local fields, in particular by the distribution of electron density around the investigated nucleus. Barbituric acid are well known for forming strongly hydrogen-bonded complexes with variety of adenine derivatives. The prototropic tautomerism of this material facilitates an adjustment to complementary bases containing a DDA(A = hydrogen bond acceptor site, D = hydrogen bond donor site) or ADA sequences, thereby yielding strongly hydrogen-bonded complexes. In this contribution solid-state structures of the enolizable chromophor "1-n-butyl-5-(4-nitrophenyl)-barbituric acid" that features adjustable hydrogen-bonding properties and the molecular assemblies with three different strength of bases (Proton sponge, adenine mimetic 2,6-diaminopyridine (DAP) and 2,6-diacetamidopyridine (DAC)) are studied. Diffusion NMR spectroscopy gives information over such interactions and has become the method of choice for measuring the diffusion coefficient, thereby reflecting the effective size and shape of a molecular species. In this work the investigation of supramolecular aggregates in solution state by means of DOSY NMR techniques are performed. The underlying principles of DOSY NMR experiment are discussed briefly and more importantly two applications demonstrating the potential of this method are focused on. Calix[n]arenes have gained a rather prominent position, both as host materials and as platforms to design specific receptors. In this respect, several different capsular contents of tetra urea calix[4]arenes (benzene, benzene-d6, 1-fluorobenzene, 1-fluorobenzene-d5, 1,4-difluorobenzene, and cobaltocenium) are studied by solid state NMR spectroscopy. In the solid state, the study of the interaction between tetra urea calix[4]arenes and guest is simplified by the fact that the guests molecule remains complexed and positioned within the cavity, thus allowing a more direct investigation of the host-guest interactions.

Design und Synthese ma��geschneiderter funktioneller Rylenfarbstoffe

Die vorgelegte Dissertation besch��ftigt sich mit der Darstellung und Untersuchung von funktionellen Farbstoffen auf der Basis von Rylendiimiden. Diese Substanzklasse zeichnet sich durch gute Funktionalisierbarkeit, hohe chemische und photochemische Stabilit��t sowie durch hohe Fluoreszenzquantenausbeuten und Extinktionskoeffizienten aus. Rylendiimide spielen eine bedeutsame Rolle in den modernen Materialwissenschaften. Ein Schwerpunkt der Arbeit liegt auf der Synthese und Untersuchung von neuen Perylendiimiden (PDI) im Hinblick auf eine Anwendung in der organischen Elektronik. Das Substitutionsmuster der PDI hat einen signifikanten Einflussrnauf deren supramolekulares Verhalten und die Leistungsf��higkeit in elektronischen Bauteilen. Durch das Einf��hren neuer Substituenten konnten weitergehende Erkenntnisse ��ber das supramolekulare Verhalten der PDI gewonnenrnwerden. Multichromophore sind wichtige Modellsysteme zur Untersuchung vonrnEnergietransportprozessen und Einzelphotonenquellen. Daher liegt ein weiterer Schwerpunkt auf der Synthese multichromophorer PDI-Systeme. Neben der Darstellung definierter dendritischer Nanoteilchen auf Basis von Poly(phenylenethinylen)-Dendrimeren besch��ftigt sich dieser Teil auch mit der Synthese hochverzweigter ethinylverkn��pfter Polymere auf Basis von PDI-Monomeren. Aufgrund ihrer au��ergew��hnlichen photochemischen Eigenschaften spielen Perylen- und Terrylendiimide eine wichtige Rolle als Fluoreszenzmarker.rnDaher besch��ftigt sich ein weiterer Aspekt dieser Arbeit mit der Synthese vonrnFluoreszenzmarkern, die sowohl in Polymerisationsreaktionen als auch inrnbiologischen Systemen Anwendung finden k��nnen.

Windkanalstudien zum Graupelwachstum und Bestimmung von Retentionskoeffizienten verschiedener Spurengase w��hrend der Bereifung

Am vertikalen Windkanal der Johannes Gutenberg-Universit��t Mainz wurden physikalische und chemische Bereifungsexperimente durchgef��hrt. Dabei lagen die Umgebungstemperaturen bei allen Experimenten zwischen etwa -15 und -5��C und der Fl��ssigwassergehalt erstreckte sich von 0,9 bis etwa 1,6g/m��, typische Bedingungen f��r Mischphasenwolken in denen Bereifung stattfindet. Oberfl��chentemperaturmessungen an wachsenden h��ngenden Graupelpartikeln zeigten, dass w��hrend der Experimente trockene Wachstumsbedingungen herrschten.rnZun��chst wurde das Graupelwachstum an in einer laminaren Str��mung frei schwebenden Eispartikeln mit Anfangsradien zwischen 290 und 380��m, die mit fl��ssigen unterk��hlten Wolkentr��pfchen bereift wurden, studiert. Ziel war es, den Kollektionskern aus der Massenzunahme des bereiften Eispartikels und dem mittleren Fl��ssigwassergehalt w��hrend des Wachstumsexperimentes zu bestimmen. Die ermittelten Werte f��r die Kollektionskerne der bereiften Eispartikel erstreckten sich von 0,9 bis 2,3cm��/s in Abh��ngigkeit ihres Kollektorimpulses (Masse * Fallgeschwindigkeit des bereifenden Graupels), der zwischen 0,04 und 0,10gcm/s lag. Bei den Experimenten zeigte sich, dass die hier gemessenen Kollektionskerne h��her waren im Vergleich mit Kollektionskernen fl��ssiger Tropfen untereinander. Aus den aktuellen Ergebnissen dieser Arbeit und der vorhandenen Literaturwerte wurde ein empirischer Faktor entwickelt, der von dem Wolkentr��pfchenradius abh��ngig ist und diesen Unterschied beschreibt. F��r die untersuchten Gr����enbereiche von Kollektorpartikel und fl��ssigen Tr��pfchen k��nnen die korrigierten Kollektionskernwerte in Wolkenmodelle f��r die entsprechenden Gr����en eingebunden werden.rnBei den chemischen Experimenten zu dieser Arbeit wurde die Spurenstoffaufnahme verschiedener atmosph��rischer Spurengase (HNO3, HCl, H2O2, NH3 und SO2) w��hrend der Bereifung untersucht. Diese Experimente mussten aus technischen Gr��nden mit h��ngenden Eispartikeln, dendritischen Eiskristallen und Schneeflocken, bereift mit fl��ssigen Wolkenl��sungstr��pfchen, durchgef��hrt werden.rnDie Konzentrationen der L��sung, aus der die Wolkentr��pfchen mit Hilfe von Zweistoffd��sen erzeugt wurden, lagen zwischen 1 und 120mg/l. F��r die Experimente mit Ammoniak und Schwefeldioxid wurden Konzentrationen zwischen 1 und 22mg/l verwendet. Das Schmelzwasser der bereiften h��ngenden Graupel und Schneeflocken wurden ionenchromatographisch analysiert und zusammen mit der bekannten Konzentration der bereifenden Wolkentr��pfchen konnte der Retentionskoeffizient f��r jeden Spurenstoff bestimmt werden. Er gibt die Menge an Spurenstoff an, die bei der Phasenumwandlung von fl��ssig zu fest in die Eisphase ��bergeht. Salpeters��ure und Salzs��ure waren nahezu vollst��ndig retiniert (Mittelwerte der gesamten Experimente entsprechend 99��8% und 100��9%). F��r Wasserstoffperoxid wurde ein mittlerer Retentionskoeffizient von 65��17% bestimmt. rnDer mittlere Retentionskoeffizient von Ammoniak ergab sich unabh��ngig vom Fl��ssigwassergehalt zu 92��21%, w��hrend sich f��r Schwefeldioxid 53��10% f��r niedrige und 29��7% f��r hohe Fl��ssigphasenkonzentrationen ergaben. Bei einigen der untersuchten Spurenstoffe wurde eine Temperaturabh��ngigkeit beobachtet und wenn m��glich durch Parametrisierungen beschrieben.rn

Does quantification of USPIO uptake-related signal loss allow differentiation of benign and malignant normal-sized pelvic lymph nodes?

Ultrasmall superparamagnetic iron oxide (USPIO) particles are promising contrast media, especially for molecular and cellular imaging besides lymph node staging owing to their superior NMR efficacy, macrophage uptake and lymphotropic properties. The goal of the present prospective clinical work was to validate quantification of signal decrease on high-resolution T(2)-weighted MR sequences before and 24-36 h after USPIO administration for accurate differentiation between benign and malignant normal-sized pelvic lymph nodes. Fifty-eight patients with bladder or prostate cancer were examined on a 3 T MR unit and their respective lymph node signal intensities (SI), signal-to-noise (SNR) and contrast-to-noise (CNR) were determined on pre- and post-contrast 3D T(2)-weighted turbo spin echo (TSE) images. Based on histology and/or localization, USPIO-uptake-related SI/SNR decrease of benign vs malignant and pelvic vs inguinal lymph nodes was compared. Out of 2182 resected lymph nodes 366 were selected for MRI post-processing. Benign pelvic lymph nodes showed a significantly higher SI/SNR decrease compared with malignant nodes (p < 0.0001). Inguinal lymph nodes in comparison to pelvic lymph nodes presented a reduced SI/SNR decrease (p < 0.0001). CNR did not differ significantly between benign and malignant lymph nodes. The receiver operating curve analysis yielded an area under the curve of 0.96, and the point with optimal accuracy was found at a threshold value of 13.5% SNR decrease. Overlap of SI and SNR changes between benign and malignant lymph nodes were attributed to partial voluming, lipomatosis, histiocytosis or focal lymphoreticular hyperplasia. USPIO-enhanced MRI improves the diagnostic ability of lymph node staging in normal-sized lymph nodes, although some overlap of SI/SNR-changes remained. Quantification of USPIO-dependent SNR decrease will enable the validation of this promising technique with the final goal of improving and individualizing patient care.

Cannabinoid receptor trafficking in peripheral cells is dynamically regulated by a binary biochemical switch

The cannabinoid G protein-coupled receptors (GPCRs) CB��� and CB��� are expressed in different peripheral cells. Localization of GPCRs in the cell membrane determines signaling via G protein pathways. Here we show that unlike in transfected cells, CB receptors in cell lines and primary human cells are not internalized upon agonist interaction, but move between cytoplasm and cell membranes by ligand-independent trafficking mechanisms. Even though CB receptors are expressed in many cells of peripheral origin they are not always localized in the cell membrane and in most cancer cell lines the ratios between CB��� and CB��� receptor gene and surface expression vary significantly. In contrast, CB receptor cell surface expression in HL60 cells is subject to significant oscillations and CB��� receptors form oligomers and heterodimers with CB��� receptors, showing synchronized surface expression, localization and trafficking. We show that hydrogen peroxide and other nonspecific protein tyrosine phosphatase inhibitors (TPIs) such as phenylarsine oxide trigger both CB��� receptor internalization and externalization, depending on receptor localization. Phorbol ester-mediated internalization of CB receptors can be inhibited via this switch. In primary human immune cells hydrogen peroxide and other TPIs lead to a robust internalization of CB receptors in monocytes and an externalization in T cells. This study describes, for the first time, the dynamic nature of CB receptor trafficking in the context of a biochemical switch, which may have implications for studies on the cell-type specific effects of cannabinoids and our understanding of the regulation of CB receptor cell surface expression.

Non-invasive method to predict viscosity and size using total internal reflection fluorescence microscopy (TIRFM) system

This study develops an automated analysis tool by combining total internal reflection fluorescence microscopy (TIRFM), an evanescent wave microscopic imaging technique to capture time-sequential images and the corresponding image processing Matlab code to identify movements of single individual particles. The developed code will enable us to examine two dimensional hindered tangential Brownian motion of nanoparticles with a sub-pixel resolution (nanoscale). The measured mean square displacements of nanoparticles are compared with theoretical predictions to estimate particle diameters and fluid viscosity using a nonlinear regression technique. These estimated values will be confirmed by the diameters and viscosities given by manufacturers to validate this analysis tool. Nano-particles used in these experiments are yellow-green polystyrene fluorescent nanospheres (200 nm, 500 nm and 1000 nm in diameter (nominal); 505 nm excitation and 515 nm emission wavelengths). Solutions used in this experiment are de-ionized (DI) water, 10% d-glucose and 10% glycerol. Mean square displacements obtained near the surface shows significant deviation from theoretical predictions which are attributed to DLVO forces in the region but it conforms to theoretical predictions after ~125 nm onwards. The proposed automation analysis tool will be powerfully employed in the bio-application fields needed for examination of single protein (DNA and/or vesicle) tracking, drug delivery, and cyto-toxicity unlike the traditional measurement techniques that require fixing the cells. Furthermore, this tool can be also usefully applied for the microfluidic areas of non-invasive thermometry, particle tracking velocimetry (PTV), and non-invasive viscometry.

Hydroxylation of naphthalene by aromatic peroxygenase from Agrocybe aegerita proceeds via oxygen transfer from H2O2 and intermediary epoxidation

Agrocybe aegerita peroxidase/peroxygenase (AaP) is an extracellular fungal biocatalyst that selectively hydroxylates the aromatic ring of naphthalene. Under alkaline conditions, the reaction proceeds via the formation of an intermediary product with a molecular mass of 144 and a characteristic UV absorption spectrum (A(max) 210, 267, and 303 nm). The compound was semistable at pH 9 but spontaneously hydrolyzed under acidic conditions (pH<7) into 1-naphthol as major product and traces of 2-naphthol. Based on these findings and literature data, we propose naphthalene 1,2-oxide as the primary product of AaP-catalyzed oxygenation of naphthalene. Using (18)O-labeled hydrogen peroxide, the origin of the oxygen atom transferred to naphthalene was proved to be the peroxide that acts both as oxidant (primary electron acceptor) and oxygen source.

The antioxidant glutathione in the fish cell lines EPC and BCF-2: response to model pro-oxidants as measured by three different fluorescent dyes

Reduced glutathione (GSH) protects cells against injury by oxidative stress and maintains a range of vital functions. In vitro cell cultures have been used as experimental models to study the role of GSH in chemical toxicity in mammals; however, this approach has been rarely used with fish cells to date. The present study aimed to evaluate sensitivity and specificity of three fluorescent dyes for measuring pro-oxidant-induced changes of GSH contents in fish cell lines: monochlorobimane (mBCl), 5-chloromethylfluorescein diacetate (CMFDA) and 7-amino-4-chloromethylcoumarin (CMAC-blue). Two cell lines were studied, the EPC line established from a skin tumour of carp Cyprinus carpio, and BF-2 cells established from fins of bluegill sunfish Lepomis macrochirus. The cells were exposed for 6 and 24 h to low cytotoxic concentrations of pro-oxidants including hydrogen peroxide, paraquat (PQ), copper and the GSH synthesis inhibitor, L-buthionine-SR-sulfoximine (BSO). The results indicate moderate differences in the GSH response between EPC and BF-2 cells, but distinct differences in the magnitude of the GSH response for the four pro-oxidants. Further, the choice of GSH dye can critically affect the results, with CMFDA appearing to be less specific for GSH than mBCl and CMAC-blue.

A new Time-Of-Flight Mass Spectrometer (TOF-MS) for noble gas analysis

Noble gas analysis in early solar system materials, which can provide valuable information about early solar system processes and timescales, are very challenging because of extremely low noble gas concentrations (ppt). We therefore developed a new compact sized (33 cm length, 7.2cm diameter, 1.3 L internal volume) Time-of-Flight (TOF) noble gas mass spectrometer for high sensitivity. We call it as Edel Gas Time-of-flight (EGT) mass spectrometer. The instrument uses electron impact ionization coupled to an ion trap, which allows us to ionize and measure all noble gas isotopes. Using a reflectron set-up improves the mass resolution. In addition, the reflectron set-up also enables some extra focusing. The detection is via MCPs and the signals are processed either via ADC or TDC systems. The objective of this work is to understand the newly developed Time-Of-Flight (TOF) mass spectrometer for noble gas analysis in presolar grains of the meteorites. Chapter 1 briefly introduces the basic idea and importance of the instrument. The physics relevant to time-of-flight mass spectrometry technique is discussed in the Chapter 2 and Chapter 3 will present the oxidation technique of nanodiamonds of the presolar grains by using copper oxide. Chapter 4 will present the details about EGT data analysis software. Chapter 5 and Chapter 6 will explain the details about EGT design and operation. Finally, the performance results will be presented and discussed in the Chapter 7, and whole work is summarized in Chapter 8 and also outlook of the future work is given.