Dünnschichtchromatographie an Salzen von Heteropolysäuren

Zusammenfassung In Fortsetzung früherer Arbeiten wurde die Verwendbarkeit von Oxingermanododekamolybdat und Pyridingermanododekamolybdat als Dünnschichtträgermaterial bei der Auftrennung von Uran-Spaltprodukten untersucht. Eine spezifische Abtrennung des Cäsiums von den Spaltprodukten⁹⁵Zr/⁹⁵Nb,¹⁰⁶Ru,⁹⁰Sr/⁹⁰Y und¹⁴⁴Ce mit Hilfe von 0,01-m Ammoniumacetat-ÄDTA bzw. 0,001-m Ammoniumacetat-ÄDTA wurde durchgeführt.

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Summary In continuation of previous studies, an investigation was made of the possibility of employing oxine germanomolybdate and pyridine germanomolybdate as thin layer carrying material in the separation of uranium fission products. A specific separation of cesium from the fission products⁸⁵Zr/⁹⁵Nb,¹⁰⁶Ru,⁹⁰Sr/⁹⁰Y,¹⁴⁴Ce was carried out with the aid of 0,01M ammonium acetate-EDTA or 0,001M ammonium acetate-EDTA.

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Résumé Faisant suite au travail précédent, on a étudié expérimentalement les possibilités d'application du germanomolybdate d'oxine et de pyridinium comme substance-support pour couche mince dans le cas de la séparation des produits de fission de l'uranium. On a effectué une séparation spécifique du césium des produits de fission⁸⁵Zr/⁹⁵Nb,¹⁶⁶Ru,⁹⁰Sr/⁹⁰Y et¹⁴⁴Ce par le système EDTA-acétate d'ammonium 0,01M ou EDTA-acétate d'ammonium 0,001M.

     

Beitrag zur Trennung von Alkalimetallen auf chromatographischem Wege

Zusammenfassung Die Ionenaustauscheigenschaften einer Reihe von Heteropolysäuresalzen wurden untersucht (Ammoniumphosphor-12-molybdänsäure, Ammoniumarseno-12-molybdänsäure, Ammoniumgermano-12-molybdänsäure, Oxingermano-12-molybdänsäure und Oxinphosphor-12-molybdänsäure). Natrium, Kalium, Rubidium und Cäsium wurden auf imprägniertem Papier bzw. auf einer Dünnschicht getrennt.

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Summary The ion exchange characteristics were studied of a number of salts of heteropoly acids (ammonium 12-molybdophosphoric acid, ammonium 12-molybdoarsenic acid, ammonium 12-molybdogermanic acid, oxine 12-molybdophosphoric acid, oxine 12-molybdophosphoric acid). Sodium, potassium, rubidium, and cesium were separated on impregnated paper or on a thin layer.

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Résumé On a étudié les propriétés échangeuses d'ions d'une série de sels d'hétéropolyacides (phosphomolybdate-12 d'ammonium, arséniomolybdate12 d'ammonium, germanomolybdate-12 d'ammonium, germanomolybdate12 d'oxinium et phosphomolybdate-12 d'oxinium). On a séparé le sodium, le potassium, le rubidium et le césium sur papier imprégné ou sur couche mince.

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Herrn Prof. Dr.A. Franke mit den besten Wünschen zum90. Geburtstag gewidmet.     

Determination of benzyl isothiocyanate metabolites in human plasma and urine by LC-ESI-MS/MS after ingestion of nasturtium (Tropaeolum majus L.)

A liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated to determine the concentration of benzyl isothiocyanate (BITC) metabolites in human plasma and urine. In this study, the following BITC metabolites have been considered: BITC–glutathione, BITC–cysteinylglycine, BITC–cysteine, and BITC–N-acetyl-l-cysteine. The assay development included: (1) synthesis of BITC conjugates acting as reference substances; (2) sample preparation based on protein precipitation and solid-phase extraction; (3) development of a quantitative LC-MS/MS method working in the multiple-reaction monitoring mode; (4) validation of the assay; (5) investigation of the stability and the reactivity of BITC conjugates in vitro; (6) application of the method to samples from a human intervention study. The lower limits of quantification were in the range of 21–183 nM depending on analyte and matrix, whereas the average recovery rates from spiked plasma and urine were approximately 85 and 75 %, respectively. BITC conjugates were found to be not stable in alkaline buffered solutions. After consumption of nasturtium, containing 1,000 μM glucotropaeolin, the primary source of BITC, quantifiable levels of BITC–NAC, BITC–Cys, and BITC–CysGly were found in human urine samples. Maximum levels in urine were determined 4 h after the ingestion of nasturtium. With regard to the human plasma samples, all metabolites were determined including individual distributions. The work presented provides a validated LC-MS/MS method for the determination of BITC metabolites and its successful application for the analysis of samples collected in a human intervention study.

Fabrication of p/n heterojunctions by electrochemical deposition of Cu2O onto TiO2 nanotubes

This work describes the TiO₂ nanotubes formation by anodic oxidation under different experimental conditions and the following attempts to optimize the electrochemical deposition of Cu₂O within the nanotubular structure. The as-formed Cu₂O/TiO₂ interface is a p/n junction that could be used in various light-assisted devices. The effect of the F^– concentration, the polarization duration and the post-thermal treatment on the TiO₂ nanotubes is recalled. Then the electrochemical deposition of cuprous oxide is investigated by cyclic voltammetry and the influence of the pH on the morphology and crystal structure is studied. Finally, potential pulses were applied to optimize the Cu₂O film morphology in order to improve the nanotubes covering.     

Fatty acyl-CoA reductases of birds

Background

Adenine and guanine phosphates are involved in a number of biological processes such as cell signaling, metabolism and enzymatic cofactor functions. Binding sites in proteins for these ligands are often detected by looking for a previously known motif by alignment based search. This is likely to miss those where a similar binding site has not been previously characterized and when the binding sites do not follow the rule described by predefined motif. Also, it is intriguing how proteins select between adenine and guanine derivative with high specificity.

Results

Residue preferences for AMP, GMP, ADP, GDP, ATP and GTP have been investigated in details with additional comparison with cyclic variants cAMP and cGMP. We also attempt to predict residues interacting with these nucleotides using information derived from local sequence and evolutionary profiles. Results indicate that subtle differences exist between single residue preferences for specific nucleotides and taking neighbor environment and evolutionary context into account, successful models of their binding site prediction can be developed.

Conclusion

In this work, we explore how single amino acid propensities for these nucleotides play a role in the affinity and specificity of this set of nucleotides. This is expected to be helpful in identifying novel binding sites for adenine and guanine phosphates, especially when a known binding motif is not detectable.     

Über die Lösungen linearer Differentialgleichungen mit ganzen Funktionen als Koeffizienten

Ohne Zusammenfassung