Stable isotope dilution analysis of the Fusarium mycotoxins deoxynivalenol and 3-acetyldeoxynivalenol

Trichothecenes are secondary metabolites produced by several fungi of the Fusarium genus during their growth period. They inhibit protein biosynthesis in eukaryotic cells resulting in numerous toxic effects such as diarrhea, vomiting, and gastro-intestinal inflammation. Considering its occurrence in food and feedstuff, deoxynivalenol (DON) is one of the most important trichothecenes. We report the synthesis of stable isotope labeled 15-d(1)-deoxynivalenol (15-d(1)-DON) from its natural precursor 3-acetyldeoxynivalenol (3-AcDON) as starting material. Furthermore, a method for the analysis of DON and 3-AcDON using HPLC-MS/MS with stable isotope labeled 15-d(1)-DON and 3-d(3)-AcDON as internal standards has been developed. In total, 18 cereal product samples were analyzed with contamination levels ranging from 10-301 microg/kg for DON and 5-14 microg/kg for 3-AcDON. This is the first report of an isotope dilution MS method for the analysis of type B-trichothecenes.     

Sydnon-äthylene. III. Chemische Reaktionen elektronisch angeregter 4-Styryl-sydnone

Sydnone Ethylenes. III. Chemical Reactions of Excited 4-Styryl-sydnones Dependent on the character of the substituents in the photo reactions of 4-styryl sydnones Z/E-isomerism competes with CO₂-elimination. Excited p-nitrostyryl sydnones exhibit a relatively strong degradation of the bond order in the C C region. Their quantum yields of Z/E-isomerism are therefore much higher than those of compounds with p-substituents of lower acceptor effect. In these compounds the cleavage of the sydnone ring with elimination of carbon dioxide is favoured especially if a methyl group is in 3-position of the sydnone.     

Die Berechnung der Stromverteilung in zylindrischen Leitern mit rechteckigem und elliptischem Querschnitt

Ohne ZusammenfassungDissertation Göttingen.Zum Schlu\ danke ich auch an dieser Stelle Herrn Prof. Reich für die Anregung zu dieser Arbeit, Herrn Prof. Kaluza für sein gro\es Interesse und für das stets in liebenswürdigster Weise gezeigte Entgegenkommen. Erwähnen mu\ ich auch Herrn Dr. Bödewadt, der zu Diskussionen öfter freundlich bereit war und dem ich manche Anregung verdanke.     

Übertragung von Methoden zur Kenngrößenermittlung des selbsttätigen Losdrehens für Versuche am Vibrationsprüfstand nach Junker auf Versuche an einem neuentwickelten Prüfaufbau für Einschraubenverbindungen mit kurzer Klemmlänge unter Verwendung eines Axialpulsers

The self-loosening mechanism can be described and classified using characteristics developed with a Junker vibration test rig. The parameters of critical displacement, critical transverse force and critical angle of rotation gradient Δφ/ΔN are of crucial importance. Under constant boundary conditions the connection will loosen itself, when the threshold value of these critical parameters is exceeded. In the following, the transfer of the methods for determining these critical parameters to a newly developed test setup using an axial test bench for single-bolted joints of the dimensions M12 and M8 with short clamping lengths is investigated.     

Photochemie von Aminoketonen. XV. Photochemische Acylgruppenwanderung in N-Tosyl-β-aminovinyl-phenyl-ketonen

Photochemistry of Aminoketones. XV. Photochemical Acyl Migration in N-Tosyl-β-aminovinyl-phenyl-ketones N-Tosyl-β-aminovinyl-phenyl-ketones 1a – i are prepared in good yields from β-chlorovinyl- phenyl-ketones by reaction with the sodium salts of tosyl amides in dry DMF at room temperature. In contrast to the relatively photostable N, N-dialkyl-β-aminovinyl-aryl-ketones the electronically excited 1 give irreversible chemical reactions within a few minutes. Among other not identified photoproducts the α-tosyl-β-aminovinyl-phenyl-ketones 2 were found. From the experimental results it is evident that the migration of the tosyl group prefers a radical-type two step reaction through an intermediate X / Y of a (1,5)-N→O-tosylrearrangement.     

Spektroskopische Untersuchungen zur Struktur von Silicium-Schwefel-Verbindungen mit mindestens einer Si-S-Bindung – ein Überblick

Spectroscopic Properties of Silicon-Sulfur-Compounds with at least one Si-S-bound – A Review Bond lenghts, bond angles and ²⁹Si-NMR data are tabulated. If possible this parameters are discussed on the bases of covalent radii, electronegativities and other general properties. Qualitative estimations of ²⁹Si-NMR shifts as a function of series of compounds, as a function of ring-size and by comparison with homologous Si-O compounds are suggested. Observations of contrarotating effects of ²⁹Si-NMR shifts in organosubstituted Si-O and Si-S molecules as compared to their hydrogensubstituted counterparts are discussed briefly.     

Ligand Properties of N-Acyl-thiocarbamic-O-alkylesters – A new class of aza-analogous 1,3-thioxoketones

A series of six N-benzoyl-thiocarbamic-O-alkylesters (RMe, Et, i-Pr, Benzyl, n-Hex, n-Dodec; 1–6 ) has been prepared and characterized. They are weak monoprotic acids. The compounds behave as fairly stable and versatile bidentate (O,S)-chelating ligands towards multivalent metal ions e. g. Ni(II), Cu(II), Pb(II) the stability constants of which have been determined in 75 vol% dioxane/water. The molecular structure of bis(O-ethyl-N-benzoylthiocarbamato)nickel(II) 2a is presented. The coordination of the nickel atom is square planar with the two sulphur atoms in cis position.