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Junker K.,ETH Zurich | Luginbuhl S.,ETH Zurich | Schuttel M.,ETH Zurich | Bertschi L.,Laboratory of Organic Chemistry | And 4 more authors.
ACS Catalysis | Year: 2014

The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was polymerized to poly(PADPA) at 25 °C with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and in the presence of vesicles formed from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as templates. In comparison to the previously studied polymerization of aniline with the same type of enzyme-vesicle system, the polymerization of PADPA is much faster, and considerably fewer enzymes are required for complete monomer conversion. Turbidity measurements indicate that PADPA strongly binds to the vesicle surface before oxidation and polymerization are initiated. Such binding is confirmed by molecular dynamics (MD) simulations, supporting the assumption that the reactions which lead to poly(PADPA) are localized on the vesicle surface. The poly(PADPA) obtained resembles the emeraldine salt form of polyaniline (PANI-ES) in its polaron state with a high content of unpaired electrons, as judged from UV/vis/NIR, EPR, and FTIR absorption measurements. There are, however, also notable spectroscopic differences between PANI-ES and the enzymatically prepared poly(PADPA). Poly(PADPA) appears to be similar to a chemically synthesized poly(PADPA) as obtained in a previous work with ammonium peroxydisulfate (APS) as the oxidant in a mixture of 50 vol % ethanol and 50 vol % 0.2 M sulfuric acid (J. Phys. Chem. B 2008, 112, 6976-6987). ESI-MS measurements of early intermediates of the reaction with TvL and AOT vesicles indicate that the presence of the vesicles decreases the extent of formation of unwanted oxygen-containing species in comparison to the reaction in the absence of vesicles. This is the first information about the differences in the chemical composition of early reaction intermediates when the reaction carried out in the presence of vesicles under optimal conditions is compared with a template-free system. © 2014 American Chemical Society. Source

Madler S.,Laboratory of Organic Chemistry
Analytical and Bioanalytical Chemistry | Year: 2011

The 59th Conference on Mass Spectrometry and Allied Topics of the American Society for Mass Spectrometry (ASMS) was held on June 5, 2011 to June 9, 2011 at the Colorado Convention Center in Denver, Colorado. The conference offered short courses covering the basics of the most important mass spectrometric techniques. It covered several presentations focusing on the latest instrumental developments and applications of mass spectrometry (MS). Other presentations covered several areas such as systems biology/cellular pathways, energy, petroleum and biofuels, drug discovery and development, identification of posttranslational modifications, imaging of biological samples, plant proteomics, and drug metabolism and pharmacokinetics. Several sessions focused on methodological and instrumental developments for H/D exchange, biomolecular structure analysis, microscale and nanoscale separations, LC-MS detection of reactive metabolites, and imaging MS. Source

Merz T.,University of Zurich | Heck T.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Geueke B.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Mittl P.R.E.,University of Zurich | And 4 more authors.
Structure | Year: 2012

The β-aminopeptidase BapA from Sphingosinicella xenopeptidilytica belongs to the N-terminal nucleophile (Ntn) hydrolases of the DmpA-like family and has the unprecedented property of cleaving N-terminal β-amino acid residues from peptides. We determined the crystal structures of the native (αβ)4 heterooctamer and of the 153 kDa precursor homotetramer at a resolution of 1.45 and 1.8 Å, respectively. These structures together with mutational analyses strongly support mechanisms for autoproteolysis and catalysis that involve residues Ser250, Ser288, and Glu290. The autoproteolytic mechanism is different from the one so far described for Ntn hydrolases. The structures together with functional data also provide insight into the discriminating features of the active site cleft that determine substrate specificity. © 2012 Elsevier Ltd All rights reserved. Source

Moussouni S.,Mediterranean Agronomic Institute of Chania | Detsi A.,Laboratory of Organic Chemistry | Majdalani M.,Mediterranean Agronomic Institute of Chania | Makris D.P.,Technological Educational Institute of Larissa | Kefalas P.,Mediterranean Agronomic Institute of Chania
Tetrahedron Letters | Year: 2010

The potential of a crude peroxidase (POD) from onion solid waste as a biocatalyst for the synthesis of a naturally occurring aurone is described. The crude enzyme preparation effectively promotes the cyclization of 2′,3,4,4′,6′-pentahydroxy-chalcone (which is not a natural substrate of onion POD) into aureusidin. © 2010 Elsevier Ltd. All rights reserved. Source

Blokland M.H.,European Union | Van Tricht E.F.,European Union | Van Rossum H.J.,European Union | Sterk S.S.,European Union | And 2 more authors.
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment | Year: 2012

For years it has been suspected that natural hormones are illegally used as growth promoters in cattle in the European Union. Unfortunately there is a lack of methods and criteria that can be used to detect the abuse of natural hormones and distinguish treated from non-treated animals. Pattern recognition of steroid profiles is a promising approach for tracing/detecting the abuse of natural hormones administered to cattle. Traditionally steroids are analysed in urine as free steroid after deconjugation of the glucuronide (and sulphate) conjugates. The disadvantage of this deconjugation is that valuable information about the steroid profile in the sample is lost. In this study we develop a method to analyse steroids at very low concentration levels (ng l~) for the free steroid, glucuronide and sulphate conjugates in urine samples. This method was used to determine concentrations of natural (pro)hormones in a large population (n = 620) of samples from male and female bovine animals and from bovine animals treated with testosterone-cypionate, estradiol-benzoate, dihydroepiandrosterone and pregnenolone. The data acquired were used to build a statistical model applying the multivariate technique 'Soft Independent Modeling of Class Analogy' (SIMCA). It is demonstrated that by using this model the results of the urine analysis can indicate which animal may have had illegal treatment with natural (pro)hormones. ©2012 Taylor & Francis. Source

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