Amberlyst 15-catalyzed cyclizations of propargylic silanes

A very efficient and simple route to bicyclic ketones using propargylic silanes is described. The cyclization is initiated by a trace of Amberlyst 15 that is added to a reaction vessel. Stirring at room temperature and non-aqueous work-up yielded several bicyclic ketones in high chemical yields containing the synthetically very useful terminal allene.     

The HEATOX Project

HEATOX is the acronym for a European Union-funded project entitled Heat-Generated Food Toxicants: Identification, Characterization, and Risk Minimization. Acrylamide will be the main experimental focus, but identification of unknown toxicants in heated carbohydrate-rich foods will also be attempted. The project includes research on formation chemistry, food technology, analytical methods, hazard characterization, and exposure assessment. The results will finally be used in risk assessment and risk management advice.     

Magnetic Separation Immunoassay for Digoxin in Plasma with Flow Injection Fluorescence Detection

Immunoassay (IA) is a sensitive and selective approach for low level quantitation of drugs. Magnetic separation immunoassays use magnetic beads to facilitate the separation of bound labeled antigens from free antigens in solution. Digoxin was chosen for this study because low level analysis (ngmL^–1) in biological samples isrequired, antibodies to digoxin were commercially available and derivatization procedures for fluorescence labeling were well established. A competitive immunoassay format was used in this study. Streptavidin coated magnetic beads were attached to biotinylated anti-digoxin antibodies for the separation. The inhibition curve for off-line magnetic separation immunoassay of digoxin in spiked plasma was characterized and the dynamic range of the curve was 0.25–2.5ngmL^–1. A power fit weighted by the inverse of concentration was found to provide the best fit to the data (r=0.9934). The percent RSDs for the two controls, 0.8 and 2.2ngmL^–1, were 9.95% and 20.62% (n=6) and the percent errors were 11.75% and 22.63% (n=6), respectively. The limit of detection (LOD) in plasma is 0.14ngmL^–1. The dynamic range of the inhibition curve for on-line magnetic separation immunoassay of digoxin was 0.5–15ngmL^–1 of digoxin. A quadratic fit was found to provide the best fit to the data (r=0.9937). The percent RSDs for the two controls, 4.0 and 12ngmL^–1, were 14.1% and 10.7% (n=6) and the percent errors were 5.8% and 3.3% (n=6) from the spiked value, respectively. The LOD was estimated to be 0.44ngmL^–1 (determined as two times the standard deviation of the blank, n=6). The on-line method has the advantages of being relatively easy to automate in the continuous flow mode and is adaptable for use in conjunction with HPLC separations.     

Influence of ice and snow covers on the UV exposure of terrestrial microbial communities: dosimetric studies

Bacillus subtilis spore biological dosimeters and electronic dosimeters were used to investigate the exposure of terrestrial microbial communities in micro-habitats covered by snow and ice in Antarctica. The melting of snow covers of between 5- and 15-cm thickness, depending on age and heterogeneity, could increase B. subtilis spore inactivation by up to an order of magnitude, a relative increase twice that caused by a 50% ozone depletion. Within the snow-pack at depths of less than approximately 3 cm snow algae could receive two to three times the DNA-weighted irradiance they would receive on bare ground. At the edge of the snow-pack, warming of low albedo soils resulted in the formation of overhangs that provided transient UV protection to thawed and growing microbial communities on the soils underneath. In shallow aquatic habitats, thin layers of heterogeneous ice of a few millimetres thickness were found to reduce DNA-weighted irradiances by up to 55% compared to full-sky values with equivalent DNA-weighted diffuse attenuation coefficients (K(DNA)) of >200 m(-1). A 2-mm snow-encrusted ice cover on a pond was equivalent to 10 cm of ice on a perennially ice covered lake. Ice covers also had the effect of stabilizing the UV exposure, which was often subject to rapid variations of up to 33% of the mean value caused by wind-rippling of the water surface. These data show that changing ice and snow covers cause relative changes in microbial UV exposure at least as great as those caused by changing ozone column abundance.     

Polylactides - degradable polymers for fibres and films

Modification of a poly(L-lactide) (PLLA) base resin, by treatment with peroxides and compounding with plasticisers, yield resins which can be processed by conventional techniques and equipment to thin blown films, fibres and nonwoven fabrics having properties comparable to those of corresponding PP and PE samples. Film samples have tensile strength between 30 and 50 MPa, elongation at break around 250%, and puncture resistance, measured as dart drop values, of 12 g/μm. Fibres can be spun to filaments or directly to nonvowen fabrics by spun-bond techniques. These fabrics have mechanical properties comparable to polypropylene materials. The polymer products are readily degraded in a compost to carbon dioxide, water and biomass.     

Calcium-induced noncovalently linked tetramers of MRP8 and MRP14 detected by ultraviolet matrix-assisted laser desorption/ionization mass spectrometry

MRP8 and MRP14 are members of the S100 family of calcium-binding proteins which play an important role during calcium-induced activation of phagocytes. Both proteins form noncovalently associated complexes as a prerequisite for biological functions. The exact stoichiometric composition of these complexes, however, has not been completely clarified yet. In the present study we show for the first time by ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI-MS) the calcium-induced formation of noncovalently associated (MRP8/MRP14)2 tetramers. Furthermore, we could determine posttranslational modifications of MRP8 and MRP14, the stoichiometric proportion of the two known MRP14 isoforms in the complexes as well as the number of calcium ions bound to the single MRP8 and MRP14 monomers and tetramers. MRP14 showed a higher affinity for calcium than MRP8. Upon complex formation the calcium binding increased to maximal saturation of the known EF hands in the complexed forms. Calcium-induced stabilization of the MRP8/MRP14 complexes was confirmed by DSC studies. Our results extend scope and application of UV-MALDI-MS by allowing identification of noncovalent protein complexes, the identification of minor alterations of subunits in such complexes as well as the determination of bound calcium ions.     

Nanostructure of epicuticular plant waxes: Self-assembly of wax tubules

A “surface science approach” is used to investigate the growth process of tubular wax structures on plant leaves: natural epicuticular wax from nasturtium leaves, mainly consisting of (S)-nonacosan-10-ol, has been recrystallized on artificial substrates of different structure and polarity, namely HOPG, glass and silicon oxide, and the growth process and structure have been studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result the tubular structure as found on the living leaves is reproduced independent of the nature of the substrate and the way of wax deposition. Prerequisite for tubule formation, however, is the admixture of a few percent of alkyl-diols to the nonacosan-10-ol as shown with artificial mixtures of both components.