Alkyl- und Arylsulfensäureanilide durch Cycloelimierung von Propen aus N-Aryl-S-isopropyl-sulfimiden

A series of N-aryl-S-isopropyl-S-alkyl- or aryl-sulfimides has been prepared and transformed into alkyl- or arylsulfenanilides, respectively, by thermal cycloelimination of propene.

     

Interactions between co-expressed <Emphasis Type="Italic">Arabidopsis</Emphasis> sucrose transporters in the split-ubiquitin system

Background  

The Arabidopsis genome contains nine sucrose transporter paralogs falling into three clades: SUT1-like, SUT2 and SUT4. The carriers differ in their kinetic properties. Many transport proteins are known to exist as oligomers. The yeast-based split ubiquitin system can be used to analyze the ability of membrane proteins to interact.     

Biomolecular self-assembly of micrometer sized silica beads on patterned glass substrates

A self-assembly process for the two-dimensional arrangement of micrometer sized silica beads on glass slides was developed. It is based on the hybridization of two single stranded DNA-oligonucleotides to a DNA double helix. To prepare for the self-assembly process the silica beads as well as the glass slides were modified covalently with matching DNA-molecules. The patterned areas on the slides were defined by printing DNA-molecules with an optimized micro contact printing procedure using agarose gel stamps. In the following hybridization experiment the addressed beads self-assemble selectively on the matching areas of the glass substrate. Control experiments with mismatching DNA-oligonucleotides showed that silica beads tend to adhere strongly to the glass surfaces. Washing conditions must be controlled carefully to differentiate between hybridized beads and non-specifically bound beads. With regard to the use of this method in microelectronic chip assembly it could be shown that the salt concentration during the hybridization step can be reduced drastically without affecting the hybridization reaction.     

Zur Synthese von isocamphananalogem Ephedrin

The synthesis of two new bicyclic phenylethylamine derivatives with potentially simpathomimetic effects is described. The synthesis of the isocamphane analogous apoephedrine (4) starts from the bicyclic methylketone5 and leads via its -bromoderivative6 and the corresponding tosylamidoketone8 to4. The synthesis of the title compound2 has been accomplished by preparing the -oximinoketone19 from the bicyclic ethylketone15 with subsequent reduction to the amino alcohol derivative20 and final selective monomethylation by theJohnstone procedure via the corresponding trifluoroacetamide.

Herrn Prof. Dr.K. Kratzl mit den besten Wünschen zum 70. Geburtstag gewidmet.     

Rheological investigation of starch polysaccharide gelation

Small-amplitude dynamic measurements of aqueous starch polysaccharide solutions are performed by a Bohlin controlled-stress rheometer with air bearing. Three classes of starch polysaccharides–native starches, fractions of starches and hydrolysed starches–are compared in their molecular composition and rheological properties during and after the gelation process. Viscoelastic properties of solutions and gels are recorded in dependence on temperature and time, yielding storage and loss moduli during and after sol-gel transition. Hot concentrated aqueous solutions are cooled down from 90 °C to 5 °C at a rate of 1 °C/min. Measurements are carried out at 0,1 Hz and 5% strain amplitude deformation. The typical course of the moduli of gelling starch polysaccharide solutions shows a liquid-like behavior (G” > G') in the upper temperature level between 60 and 90 °C, a jumpwise increase with ensuing intersection of G' and G” below 60 °C and a solid-like behavior (G' > G”) at lower temperatures with a slightly in time growing storage modulus. Storage and loss moduli depend on molecular composition and concentration of the substance. The process of starch polysaccharide aggregation is discussed with regard to theories of physical gelation by Ross-Murphy and Winter.