Preparation,Separation and Identification of Partially Methylated Alditol Acetates for use as Standards in Methylation Analysis

A procedure is described for a simple preparation that produces mixtures of a majority of the possible O-methylated alditol acetate derivatives of neutral monosaccharides. The derivatives can be used as standards to determine both the linkage positions and the precise identities of sugar constituents in cell wall poly-saccharides.     

Screening structure-property correlations and device performance of Ir(III) complexes in multi-layer PhOLEDs

The structure-property correlations of a set of heteroleptic red- and green-emitting Ir(III) complexes with different temperature sensitivities and charge trapping capabilities are described, revealing superb performance in multi-layer phosphorescent organic light-emitting diodes (PhOLEDs) expressed by very high maximum luminous efficiencies up to 36.8 cd A(-1). Using 2-phenylpyridine and with 2-(naphthalen-1-yl)pyridine as the C^N ligand, the resulting red emitting complex featured a maximum luminous efficiency of 10.8 cd A(-1); one of the most excellent device performances within this class of red Ir(III) emitters.     

Dynamics of intermediate filament assembly followed in micro-flow by small angle X-ray scattering

The assembly of intermediate filaments (IFs) is a complex process that can be recapitulated through a series of distinct steps in vitro. The combination of microfluidics and small angle X-ray scattering (SAXS) provides a powerful tool to investigate the kinetics of this process on the relevant timescales. Microfluidic mixers based on the principle of hydrodynamic focusing allow for precise control of the mixing of proteins and smaller reagents like ions. Here, we present a multi-layer device that prevents proteins from adsorbing to the channel walls by engulfing the protein jet with a fluid layer of buffer. To ensure compatibility with SAXS, the device is fabricated from UV-curable adhesive (NOA 81). To demonstrate the successful prevention of contact between the protein jet and the channel walls we measure the distribution of a fluorescent dye in the device by confocal microscopy at various flow speeds and compare the results to finite element method (FEM) simulations. The prevention of contact enables the investigation of the assembly of IFs in flow by gradually increasing the salt concentration in the protein jet. The diffusion of salt into the jet can be determined by FEM simulations. SAXS data are collected at different positions in the jet, corresponding to different salt concentrations, and they reveal distinct differences between the earliest assembly states. We find that the mean square radius of gyration perpendicular to the filament axis increases from 13 nm(2) to 58 nm(2) upon assembly. Thereby we provide dynamic structural data of a complex assembly process that was amenable up to now only by microscopic techniques.     

Rapid synthesis of bis(hetero)aryls by one-pot Masuda borylation-Suzuki coupling sequence and its application to concise total syntheses of meridianins A and G

3-(Hetero)aryl substituted indoles, 7-azaindoles, and pyrroles can be obtained in a very concise fashion via a one-pot Masuda borylation-Suzuki coupling sequence. The concise total syntheses of the marine natural products meridianins A (5) and G (4i) nicely illustrate the utility of this methodology.     

A new acylated triterpene with antimicrobial activity from the leaves of <Emphasis Type="Italic">Rauvolfia vomitoria</Emphasis>

A new acylated tritrepene, 3β-hexadecanoyloxy-lup-20(29)-en-21-ol (1), along with seven known compounds, lupeol (2), betulinic acid (3), ursonic acid (4), -sitosterol (5), β-stigmasterol (6), 3-O-β-D-glucopyranosyl-β-stigmasterol (7), and palmitic acid (8), were isolated from the leaves of Rauvolfia vomitoria (Apocynaceae). Their structures were established on the basis of spectroscopic analysis and chemical evidence. The new acylated triterpene exhibited interesting antimicrobial activity against Candida albicans (a yeast) with the MIC value 64 μg/mL.     

Synthesis and characterization of alternating fluorene–thiophene copolymers bearing ethylene glycol side-chains

Abstract  

New alternating fluorene–thiophene copolymers are introduced bearing polar ethylene glycol-carboxylate functionalities on the thiophene ring to achieve enhanced solubility in polar solvents. Suzuki polycondensation was applied to synthesize a set of three polymers with differing lengths of the ethylene glycol side-chains. The polymers are thermally stable up to temperatures of 300 °C. Solutions of the polymers in CHCl₃ show an absorption maximum at approximately 397 nm and a luminescence maximum of 472 nm in solutions with quantum yield of 30%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels have been determined to be at −5.7 and −2.6 eV, respectively.