Bestimmung von Merthiolate neben anderen Quecksilberverbindungen auf elatographischem Wege

Zusammenfassung Die Anwendung der Elatographie zur Trennung und halbquantitativen Bestimmung von Merthiolate neben anderen Quecksilberverbindungen wird beschrieben. Als Reagens dient Dithizon. Es bilden sich verschiedenartige Komplexe zwischen dem Dithizon und den untersuchten Verbindungen.

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Summary The use of elatography for the separation and semi-quantitative determination of Merthiolate and other mercury compounds is described. Dithizone is applied as reagent. Different kinds of complexes are formed between dithizone and the compounds studied.

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I. Mitteilung: Becker, A.: diese Z. 174, 161 (1960).     

Separation of the radioelements210Pb−210Bi−210Po by spontaneous deposition onto noble metals and verification by Cherenkov and liquid scintillation counting

A method for the separation of²¹⁰Pb,²¹⁰Bi and²¹⁰Po using spontaneous deposition has been developed. The²¹⁰Bi and²¹⁰Po are simultaneously removed by deposition onto nickel foil (copper and tin could also be used but less effectively) while the²¹⁰Po is separated from²¹⁰Bi, after dissolution of the nickel foil, by deposition onto silver foil. The effectiveness of each separation was evaluated by adding aliquot portions of each solution to a cocktail and counting with a liquid scintillation counter. Water was used as the medium to observe the Cherenkov count of the sample solution.     

A fully computer controlled, low cost STM

Summary If one examines the components of a scanning tunneling microscopy system, one finds, that for a great part the computer determines the abilities of it. Once a stable mechanical setup is constructed, it depends on the control part, which features the whole system shows and how convenient one can work with it. Here we present a scanning tunneling microscope which is, as far as possible, computer controlled and can be fully operated from a user surface on the computer. This has been achieved by the use of a two computer concept. The mechanics, electronics and software were self-developed; all other components were selected under the aspect of costs resulting in a low priced and yet high performance system.     

Effects of growth conditions on the surface structure of CdTe studied by a scanning tunneling microscope

Summary CdTe buffer layers are widely used as substrate materials for the molecular beam epitaxial (MBE) growth of Hg_1–x Cd _x Te because of the small lattice mismatch. With the help of a scanning tunneling microscope (STM) and a scanning electron microscope (SEM) the surface topographies of epitaxial CdTe layers grown under different conditions were studied quantitatively. It was found that photoassistance during growth enhances the formation of pyramidal hills with a typical height of 1000 . The use of an excess of Cd completely changes the surface morphology towards 2-dimensional growth and the remaining layer roughness was less than 50 . These initial results suggest that the Cd rich conditions provide a promising method for the growth of large, flat layers.     

Wasserfreies Aluminiumchlorid in der quantitativen Analyse organischer Verbindungen

Zusammenfassung Es wird eine neue Methode zur quantitativen spektrophotometrischen Bestimmung von Äthinyloestradiol beschrieben. Sie basiert auf der Farbreaktion des Steroids mit wasserfreiem Aluminiumchlorid in Nitromethan und ist spezifisch in bezug auf Zersetzungsprodukte. Ein Beispiel für die Bestimmung von Äthinyloestradiol in Tabletten wird angeführt.

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Summary A new method for the quantitative spectrophotometric determination of ethinylestradiol is described. It is based on the colour reaction of the steroid with anhydrous aluminium chloride in nitromethane and is specific in relation to decomposition products. An example for the determination of ethinylestradiol in tablets is shown.

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I. Mitt.: Becker, A., u. A. Kathriner: diese Z. 183, 356 (1961).     

Magnetoresistance and Corbino resistance of iodine doped-polyacetylene

The collinear magneto- and coaxial Corbino resistance of iodine doped polyacetylene have been measured at 4.2 K for doping levels from 7% to 30%. From a comparison of the two sets of data, the “carrier mobility” has been determined. It ranges between 85 and 180 cm²/Vsec, falling with increasing iodine concentration.     

Analysis of Rhizonin Biosynthesis Reveals Origin of Pharmacophoric Furylalanine Moieties in Diverse Cyclopeptides

Rhizonin A and B are hepatotoxic cyclopeptides produced by bacterial endosymbionts (Mycetohabitans endofungorum) of the fungus Rhizopus microsporus. Their toxicity critically depends on the presence of 3-furylalanine (Fua) residues, which also occur in pharmaceutically relevant cyclopeptides of the endolide and bingchamide families. The biosynthesis and incorporation of Fua by non-ribosomal peptide synthetases (NRPS), however, has remained elusive. By genome sequencing and gene inactivation we elucidated the gene cluster responsible for rhizonin biosynthesis. A suite of isotope labeling experiments identified tyrosine and l -DOPA as Fua precursors and provided the first mechanistic insight. Bioinformatics, mutational analysis and heterologous reconstitution identified dioxygenase RhzB as necessary and sufficient for Fua formation. RhzB is a novel type of heme-dependent aromatic oxygenases (HDAO) that enabled the discovery of the bingchamide biosynthesis gene cluster through genome mining.