28 research outputs found
Simultaneous Detection of 14 Microcystin Congeners from Tissue Samples Using UPLC- ESI-MS/MS and Two Different Deuterated Synthetic Microcystins as Internal Standards
International audienceCyanobacterial microcystins (MCs), potent serine/threonine-phosphatase inhibitors, pose an increasing threat to humans. Current detection methods are optimised for water matrices with only a few MC congeners simultaneously detected. However, as MC congeners are known to differ in their toxicity, methods are needed that simultaneously quantify the congeners present, thus allowing for summary hazard and risk assessment. Moreover, detection of MCs should be expanded to complex matrices, e.g., blood and tissue samples, to verify in situ MC concentrations, thus providing for improved exposure assessment and hazard interpretation. To achieve this, we applied two synthetic deuterated MC standards and optimised the tissue extraction protocol for the simultaneous detection of 14 MC congeners in a single ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) run. This procedure was validated using plasma and liver homogenates of mice (male and female) spiked with deuterated MC standards. For proof of concept, tissue and plasma samples from mice i.p. injected with MC-LR and MC-LF were analysed. While MC-LF was detected in all tissue samples of both sexes, detection of MC-LR was restricted to liver samples of male mice, suggesting different toxicokinetics in males, e.g., transport, conjugation or protein binding. Thus, deconjugation/-proteinisation steps should be employed to improve detection of bound MC. Key Contribution: The use of deuterated microcystin standards and an improved extraction procedure using UPLC-MS/MS analytics, provides for the simultaneous detection of fourteen microcystin congeners. Thus, it allows more accurate quantitation of total microcystin load of a given sample in complex matrices like blood or tissue, and therefore better hazard interpretation
Die S19 mRNS-Expression in Plattenepithelkarzinomen des oberen Aerodigestivtraktes
Ziel dieser Arbeit war die Analyse von AusmaĂ, HĂ€ufigkeit und Charakter der mRNS-Expression des ribosomalen Proteins S19 (S19) in Head and Neck Squamous Cell Carcinoma (HNSCC). Als Methode wurde die Reverse Transkription-Polymerase Chain Reaction mit spezifischen S19 Primern gewĂ€hlt. Untersucht wurden 18 HNSCC Zelllinien im Vergleich mit 17 benignen Keratinozytenzelllinien sowie 30 HNSCC Gewebeproben im Vergleich mit 8 Referenz-Gewebeproben.
FĂŒr den Vergleich der HNSCC Zelllinien mit den benignen Keratinozytenzelllinien konnten die DDRT-PCR Voruntersuchungen bestĂ€tigt werden: In den HNSCC Zelllinien fand sich eine signifikante S19 mRNS-Repression. Niedrige S19 mRNS-Level korrelierten mit einem stĂ€rker entdifferenzierten Zellbild. FĂŒr die Gewebe zeichnete sich eine Ă€hnliche Tendenz ab - signifikante Ergebnisse konnten jedoch nicht ermittelt werden. Lediglich eine groĂe Karzinomausbreitung korrelierte signifikant mit niedrigen S19 mRNS-Leveln, wodurch die fĂŒr die Zelllinien gewonnenen Ergebnisse gestĂŒtzt werden.
Um zu prĂŒfen, ob die S19 mRNS-Repression lediglich auf verĂ€nderte Ribosomenzahlen zurĂŒckzufĂŒhren war, wurden zwei weiterer ribosomale Proteine, S6 und S14, mit derselben Methodik untersucht. Die mRNS-Expressionslevel aller drei ribosomalen Proteine zeigten hohe Korrelationen. Dies spricht fĂŒr einen Zusammenhang der ribosomalen Rolle des S19 mit seiner mRNS-Repression in HNSCC.
Die Ursachen der S19 mRNS-Repression in HNSCC wurden im Rahmen dieser Arbeit nicht nĂ€her untersucht. UngeklĂ€rt bleibt die Frage, ob die S19 mRNS-Repression Ursache oder Folge der malignen Degeneration ist und ob ribosomale oder extraribosomale Funktionen des S19 betroffen sind. Weitere Untersuchungen sind nötig, um einen möglichen Einsatz des S19 als Tumormarker und Verlaufsparameter oder aber Zielprotein fĂŒr therapeutische Interventionen abzuklĂ€ren
Metabolomic and transcriptomic stress response of Escherichia coli
GC-MS-based analysis of the metabolic response of Escherichia coli exposed to four different stress conditions reveals reduction of energy expensive pathways.Time-resolved response of E. coli to changing environmental conditions is more specific on the metabolite as compared with the transcript level.Cease of growth during stress response as compared with stationary phase response invokes similar transcript but dissimilar metabolite responses.Condition-dependent associations between metabolites and transcripts are revealed applying co-clustering and canonical correlation analysis
Die S19 mRNS-Expression in Plattenepithelkarzinomen des oberen Aerodigestivtraktes
Ziel dieser Arbeit war die Analyse von AusmaĂ, HĂ€ufigkeit und Charakter der mRNS-Expression des ribosomalen Proteins S19 (S19) in Head and Neck Squamous Cell Carcinoma (HNSCC). Als Methode wurde die Reverse Transkription-Polymerase Chain Reaction mit spezifischen S19 Primern gewĂ€hlt. Untersucht wurden 18 HNSCC Zelllinien im Vergleich mit 17 benignen Keratinozytenzelllinien sowie 30 HNSCC Gewebeproben im Vergleich mit 8 Referenz-Gewebeproben.
FĂŒr den Vergleich der HNSCC Zelllinien mit den benignen Keratinozytenzelllinien konnten die DDRT-PCR Voruntersuchungen bestĂ€tigt werden: In den HNSCC Zelllinien fand sich eine signifikante S19 mRNS-Repression. Niedrige S19 mRNS-Level korrelierten mit einem stĂ€rker entdifferenzierten Zellbild. FĂŒr die Gewebe zeichnete sich eine Ă€hnliche Tendenz ab - signifikante Ergebnisse konnten jedoch nicht ermittelt werden. Lediglich eine groĂe Karzinomausbreitung korrelierte signifikant mit niedrigen S19 mRNS-Leveln, wodurch die fĂŒr die Zelllinien gewonnenen Ergebnisse gestĂŒtzt werden.
Um zu prĂŒfen, ob die S19 mRNS-Repression lediglich auf verĂ€nderte Ribosomenzahlen zurĂŒckzufĂŒhren war, wurden zwei weiterer ribosomale Proteine, S6 und S14, mit derselben Methodik untersucht. Die mRNS-Expressionslevel aller drei ribosomalen Proteine zeigten hohe Korrelationen. Dies spricht fĂŒr einen Zusammenhang der ribosomalen Rolle des S19 mit seiner mRNS-Repression in HNSCC.
Die Ursachen der S19 mRNS-Repression in HNSCC wurden im Rahmen dieser Arbeit nicht nĂ€her untersucht. UngeklĂ€rt bleibt die Frage, ob die S19 mRNS-Repression Ursache oder Folge der malignen Degeneration ist und ob ribosomale oder extraribosomale Funktionen des S19 betroffen sind. Weitere Untersuchungen sind nötig, um einen möglichen Einsatz des S19 als Tumormarker und Verlaufsparameter oder aber Zielprotein fĂŒr therapeutische Interventionen abzuklĂ€ren
Putting Rehearsals to the Test
Although the format of the rehearsal is used across a number of disciplines â film and theater as well as fine arts â it has been scarcely considered in historical and contemporary art discourses. With this in mind, Putting Rehearsals to the Test investigates the role and function of the rehearsal as a methodology, modus operandi, medium, site of representation, and reflection on processes of artistic production. As the contributions in this book show, practices of rehearsal put those procedures â sometimes joyful, sometimes troublesome but structurally productive â into the foreground to replace given conventions and regulations with new forms and rules. Shaping working processes (the in-the-making) and products (the making-of) without defined aims and ends, artists, activists, and theorists working with strategies of rehearsal focus on moments of contingency, interruption, recommencement, irregular repetition, uncertainty, and failure within existing systems. Practices of rehearsal, in attempting to transform asymmetric labor divisions, appear as links between aesthetic judgment and social or institutional critique. This book is a critical and timely reappraisal of the methodologies of the rehearsal, and makes a claim for the aesthetic and political potential in the unfinished project
Establishing a Comprehensive Toolbox for Isotopic Labelling Studies on Terpene Synthases
The cumulative doctoral thesis "Establishing a Comprehensive Toolbox for Isotopic Labelling Studies on Terpene Synthases" describes the synthesis and application of isotopically labelled compounds for the systematic in vitro investigation of recombinant terpene synthases to target both cyclisation mechanism and product structure. Methodically, the known approach of enantioselectively deuterated oligoprenyl diphosphate substrates was further developed by the addition of 13C-labelling, which led to a more sensitive detection of the labelled product by NMR. With a stereochemical anchor of known absolute configuration installed in the substrate and untouched by the enzymatic cyclisation mechanism, it is possible to infer the absolute configuration of the terpene product by following the incorporation of deuterium into the diastereotopic hydrogen positions. By combining chemical and enzymatic synthesis, it was finally possible to label every methylene group of the common terpene precursors by 13C and 2H in an enantioselective fashion. These extensions improve both feasibility and robustness of this method, which contributes to the challenging structure elucidation of terpene natural products, including their difficult to address absolute configurations. Depending on the cyclisation mechanism, also the stereochemical course of hydrogen movements can be delineated. Connected to the expanding labelling possibilities, several newly identified terpene synthases from bacteria and fungi have been addressed covering various aspects of their catalysis such as substrate or product specificity, repetitive mechanistic motifs and stereochemical issues. The structural variety of the known and newly identified natural products thereby inspired further studies like tailored labelling experiments, site-directed mutagenesis, chemical modifications and the investigation of EI-MS fragmentation mechanisms. With few publications dealing with other aspects of natural product chemistry such as fungal aromatic volatiles, lignin degradation and selected aspects of the secondary metabolism of marine Roseobacter group bacteria also being included in this work, the main focus lays on a deepened understanding of terpene synthase reactions. The isotopically labelled substrates introduced in this study thereby represent a valuable experimental tool towards a comprehensive picture of these astonishing enzymes that create the largest group of natural products
Heitere Erinnerungen
HEITERE ERINNERUNGEN
Heitere Erinnerungen / Stettenheim, Julius (Public Domain) ( - )
Title page ( - )
Dedication ( - )
I ( - )
II (22)
III (33)
IV (48)
V (61)
VI (74)
VII (86)
VIII (101)
IX (115)
X (131)
XI (149)
XII (164)
XIII (178)
XIV (191)
XV (206)
XVI (220)
XVII (234)
XVIII (255)
XIX (271)
XX (290)
XXI (301)
An meinen Verleger (315)
ColorChart ( -