Capillary electrophoretic resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit

Summary A simple capillary electrophoretic method with UV detection has been developed for resolution of the enantiomers of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, the key flavor compounds in strawberry fruit. The separation was performed in fused-silica capillaries (30/40.2 cm long×50μm i.d.) with running buffer consisting of 50mm ammonium acetate, pH 4.0, containing 20mm heptakis-(2,3-O-diacetyl-6-O-sulfato)-β-cyclodextrin (HDAS-β CD). The applied potential was 10 kV, the temperature 25°C, and detection was at 280 nm. The method was used to determine the enantiomer ratio of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) isolated from strawberry fruits and from the yeastZygosaccharomyces rouxii. The formation of enantiomerically enriched(+)-DMHF byZ. rouxii was demonstrated for, the first time.     

Helical structure and threshold voltage of cholesteric-nematic phase change at different anchoring conditions

The helical structure of cholesteric mixed systems and their electro-optical behaviour are studied at planar and pretilted surface orientation. The results indicate that the influence of the forces of wall orientation is decreased by the helical structure. To prove this model strong and weak anchoring conditions of the molecules in the cholesteric mixture at the substrate surface are realized. Also the behaviour of the electro-optical threshold voltage at different surface conditions supports the assumptions concerning the helical structure.     

Influence of Additives and Surface Topography on the Alignment of Nematic Liquid Crystals

Observations of the influence of a simultaneous action of different surface topographies and polar or nonpolar additives in small concentration on the alignment properties of liquid crystal molecules are reported. The additive dependence of the threshold behaviour of planar aligned liquid crystal cells is also studied.     

Robust and accurate filtered spherical harmonics expansions for radiative transfer

We present a novel application of filters to the spherical harmonics (P_N) expansion for radiative transfer problems in the high-energy-density regime. The filter we use is based on non-oscillatory spherical splines and a filter strength chosen to (i) preserve the equilibrium diffusion limit and (ii) vanish as the expansion order tends to infinity. Our implementation is based on modified equations that are derived by applying the filter after every time step in a simple first-order time integration scheme. The method is readily applied to existing codes that solve the P_N equations. Numerical results demonstrate that the solution to the filtered P_N equations are (i) more robust and less oscillatory than standard P_N solutions and (ii) more accurate than discrete ordinates solutions of comparable order. In particular, the filtered P₇ solution demonstrates comparable accuracy to an implicit Monte Carlo solution for a benchmark hohlraum problem in 2D Cartesian geometry.     

Ueber neue Methoden der quantitativen Analyse

Ohne Zusammenfassung     

Cinnamide Derivatives of d‐Mannose as Inhibitors of the Bacterial Virulence Factor LecB from Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic Gram‐negative pathogen with high antibiotic resistance. Its lectin LecB was identified as a virulence factor and is relevant in bacterial adhesion and biofilm formation. Inhibition of LecB with carbohydrate‐based ligands results in a decrease in toxicity and biofilm formation. We recently discovered two classes of potent drug‐like glycomimetic inhibitors, that is, sulfonamides and cinnamides of d‐mannose. Here, we describe the chemical synthesis and biochemical evaluation of more than 20 derivatives with increased potency compared to the unsubstituted cinnamide. The structure–activity relationship (SAR) obtained and the extended biophysical characterization allowed the experimental determination of the binding mode of these cinnamides with LecB. The established surface binding mode now allows future rational structure‐based drug design. Importantly, all glycomimetics tested showed extended receptor residence times with half‐lives in the 5–20 min range, a prerequisite for therapeutic application. Thus, the glycomimetics described here provide an excellent basis for future development of anti‐infectives against this multidrug‐resistant pathogen.