Untersuchung von Mehl und Brot

Ohne Zusammenfassung     

Design, synthesis, and biological evaluation of potent discodermolide fluorescent and photoaffinity molecular probes

[structure: see text] The design, synthesis, and biological evaluation of a series of (+)-discodermolide molecular probes possessing photoaffinity and fluorescent appendages has been achieved. Stereoselective olefin cross-metathesis comprised a key tactic for construction of two of the molecular probes. Three photoaffinity probes were radiolabeled with tritium.     

Redox protein-polymer films for simultaneous determination of ascorbic Acid and hydrogen peroxide

Layer by layer films of protein and redox polymer were constructed and used to simultaneously analyze ascorbic acid and hydrogen peroxide. The films were made using hemoglobin and poly[4-vinylpyridine Os(bipyridine)(2)Cl]-co-ethylamine (Pos-Ea). The film growth was monitored using cyclic voltammetry, quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Reversible pairs of oxidation-reduction peaks were observed using cyclic voltammetry corresponding to the Os(II)/Os(III) from redox polymer and HbFe(III)/HbFe(II) redox couples at 0.35 and -0.25 V vs. Ag/AgCl, respectively. The two redox centers were independent of each other. This enabled the simultaneous and independent determination of ascorbic acid and hydrogen. Peak currents were linearly related to concentration for both analytes in a mixture. The linear range of ascorbic acid was 0 - 1 mM (R(2) = 0.9996, n = 5) at scan rate of 50 mV s(-1) (sensitivity 3.5 microA/mM) while hydrogen peroxide linear range was 1.0 - 10.0 microM (R(2) = 0.991, n = 6) with sensitivity of 1.85 microA/microM.     

Annulation of pyrrole: application to the synthesis of indolizidine alkaloids

The nucleophilicity of pyrrole has been exploited to rapidly assemble the bicyclic skeleton of the indolizidine alkaloids. The key sequence is the annulation of a second ring onto pyrrole from a γ-lactone and has been exploited in the synthesis of the natural products (±)-monomorine and (±)-indolizidine 209D.     

Simple One‐Pot Syntheses of Water‐Soluble Bis(acyl)phosphane Oxide Photoinitiators and Their Application in Surfactant‐Free Emulsion Polymerization

The sodium salt of the new bis(mesitoyl)phosphinic acid (BAPO‐OH) can be prepared in a very efficient one‐pot synthesis. It is well soluble in water and hydrolytically stable for at least several weeks. Remarkably, it acts as an initiating agent for the surfactant‐free emulsion polymerization (SFEP) of styrene to yield monodisperse, spherical nanoparticles. Time‐resolved electron paramagnetic resonance (TR‐EPR) and chemically induced electron polarisation (CIDEP) indicate preliminary mechanistic insights.

     

Pyridine modified polyethylene copolymer compatibilizer for melt blended carbon nanotube composites: effects of chain structure and matrix viscosity

The electrical percolation threshold of different polyethylene/carbon nanotube nanocomposites was studied as a function of chain structure, matrix viscosity, and the effect of compatibilizer. The lower the viscosity of the matrix the lower is the percolation threshold, regardless of the chain architecture and degree of crystallization. To improve dispersion a series of acrylic acid copolymer are introduced into the system. The highest concentration of acid co‐monomer that maintain miscibility with the polyethylene matrix is 5 wt.%. The compatibilizer in its pristine form does not have a significant effect on dispersion and on volume resistivity. When the acidic copolymer was modified with aminomethylpyridine, in order to facilitate π–π interaction with the nanotubes, a 4‐decade reduction was recorder for the high viscosity matrices at 10 wt.% compatibilizer loading. Copyright © 2014 John Wiley & Sons, Ltd.     

The calculation of chemical shifts in conjugated molecules

Within the context of pi-electron theory an expression for the proton chemical shifts in conjugated molecules is derived via a current density approach. Using London integral approximations the method is applied to benzene and naphthalene. Provided a particular form of the London Approximation is used, theoretical values in good agreement with experiment are obtained.