Spaltungen mittels Diazonium verbindungen und Chinonimidchlorid, 12. Mitt.: Über die Strukturzuordnung bei Azokupplungsprodukten des Resorcins

Zusammenfassung Es wird die Struktur der beiden möglichen isomeren Bis-(p-nitrobenzolazo)-resorcinverbindungen1 und4 mittels gezielter Azokupplung geeigneter Modellsubstanzen und durch NMR-spektroskopische Messungen festgelegt.

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The structures of the two possible isomeric bis(p-nitrophenylazo)-resorcinol derivatives1 and4 have been determined by diazo coupling of suitable model compounds and by n.m.r. spectroscopic studies.

     

Synthesis of ornithine lactams via diastereoselective photocyclization of 2-amino-4-oxo-4-phenyl-butanoyl amines

The diastereoselective synthesis of ornithine lactams 6-9 via photoinduced -hydrogen abstraction followed by cyclization of the corresponding 1,6-biradicals is described. A highly asymmetric 1,4-induction is observed.     

Characterization of carotenoids and carotenoid esters in red pepper pods (Capsicum annuum L.) by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

Carotenoids and carotenoid esters were extracted from red pepper pods (Capsicum annuum L.) without saponification. Among the 42 compounds detected, 4 non-esterified, 11 mono- and 17 diesters were characterized based on their retention times, UV/Vis spectra and their fragmentation patterns in collision-induced dissociation experiments in atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Positive and negative ion mode measurements were used for the characterization of major and minor carotenoids and their esters. Capsanthin esterified with lauric, palmitic and myristic acids represented the predominant compounds in the red pepper extracts. Additionally, three beta-cryptoxanthin and one zeaxanthin monoester were tentatively identified in red pepper pods for the first time. Furthermore, the specific fragmentation patterns of capsanthin-laurate-myristate and capsanthin-myristate-palmitate were used for the distinction of both regioisomers. The results obtained from LC-DAD-APCI-MSn experiments demonstrated that the carotenoid profile of red pepper pods is considerably more complex than considered hitherto.     

Strong local electron correlations in high-temperature superconductors: Mean-field description of the metal-insulator transition

A realistic model of a Cu?O-plane, as the important structural element of high-temperature superconductors, is discussed with emphasis on strong local electron correlations. The Coulomb repulsion of electrons on oxygen sites as well as the one on copper sites is assumed very large, so that a systematic approximation scheme can be based on canonical transformations for elimination of both of these interactions. The resulting multiplet-J-model encorporates correlated hopping as leading processes and interactions between local spins as next leading ones. Here we concentrate on the leading terms and study transitions between a metallic phase and a charge transfer insulator phase via bosonization and mean field theory. The full selfconsistent one particle spectra are derived for the metal and the doped charge transfer insulator. Near the phase transition an analytic solution is given. Numerical calculations are based on realistic tight binding bands and include the influence of van Hove singularities. Physical implications, some formal aspects of mean-field theory and the connection to other approaches a are discussed.     

Influence of exchange fields in hybrid pairing superconductors II. Selfconsistent ground states

A previously investigated model of a two band superconductor with hybrid pairing and molecular fields is enlarged by exchange interactions generating those fields. The fields are calculated selfconsistently in molecular field approximation at zero temperature. They turn out to stabilise the previously found new state of gapless superconductivity and non vanishing spin polarization for a wide range of exchange couplings, in particular for zero external field.Dedicated to B. Mühlschlegel on the occasion of his 60th birthdayWork performed within the research program of Sonderforschungsbereich 125 Aachen-Jülich-Köln     

Stable isotope-free quantitative shotgun proteomics combined with sample pattern recognition for rapid diagnostics

Mass spectrometry (MS) has become a powerful tool for the quantitative analysis of complex protein samples. A high-throughput strategy for the comparative analysis of multiple protein samples with high complexity becomes more and more important. Two strategies, spectral count and peak intensity, for label-free MS analysis of prefractionated complex mixtures have been described recently to be useful for quantitation. Here we compare both strategies for rapid and quantitative 1-D shotgun LC/MS/MS analyses of highly complex protein mixtures using silica-based monolithic columns. First, we validated linearity and sensitivity of these methods by spiking varying amounts of an internal standard protein in a complex plant protein extract. Secondly, quantitative data of proteins of Medicago truncatula nodules were visualized with independent components analysis using data either obtained from spectral count or peak integration performed with commercial software. Spectral count showed apparent advantages over peak integration because several peptides per protein are automatically averaged, the linear dynamic range of quantitation increases in complex matrices and the number of quantified proteins surpasses the number of proteins using peak integration. Thus, for the need of rapid comparative analysis of highly complex protein samples, spectral count enables sample pattern recognition and identification of biomarkers in nongel based proteomic studies.