Synthesis of poly(2‐oxazoline)s with side chain methyl ester functionalities: Detailed understanding of living copolymerization behavior of methyl ester containing monomers with 2‐alkyl‐2‐oxazolines

Poly(2‐oxazoline)s with methyl ester functionalized side chains are interesting as they can undergo a direct amidation reaction or can be hydrolyzed to the carboxylic acid, making them versatile functional polymers for conjugation. In this work, detailed studies on the homo‐ and copolymerization kinetics of two methyl ester functionalized 2‐oxazoline monomers with 2‐methyl‐2‐oxazoline, 2‐ethyl‐2‐oxazoline, and 2‐n‐propyl‐2‐oxazoline are reported. The homopolymerization of the methyl ester functionalized monomers is found to be faster compared to the alkyl monomers, while copolymerization unexpectedly reveals that the methyl ester containing monomers significantly accelerate the polymerization. A computational study confirms that methyl ester groups increase the electrophilicity of the living chain end, even if they are not directly attached to the terminal residue. Moreover, the electrophilicity of the living chain end is found to be more important than the nucleophilicity of the monomer in determining the rate of propagation. However, the monomer nucleophilicity can be correlated with the different rates of incorporation when two monomers compete for the same chain end, that is, in copolymerizations. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2649–2661     

Methodological challenges of optical tweezers‐based X‐ray fluorescence imaging of biological model organisms at synchrotron facilities

Recently, a radically new synchrotron radiation‐based elemental imaging approach for the analysis of biological model organisms and single cells in their natural in vivo state was introduced. The methodology combines optical tweezers (OT) technology for non‐contact laser‐based sample manipulation with synchrotron radiation confocal X‐ray fluorescence (XRF) microimaging for the first time at ESRF‐ID13. The optical manipulation possibilities and limitations of biological model organisms, the OT setup developments for XRF imaging and the confocal XRF‐related challenges are reported. In general, the applicability of the OT‐based setup is extended with the aim of introducing the OT XRF methodology in all research fields where highly sensitive in vivo multi‐elemental analysis is of relevance at the (sub)micrometre spatial resolution level.     

Selectivity optimization in green chromatography by gradient stationary phase optimized selectivity liquid chromatography

Stationary phase optimized selectivity liquid chromatography (SOSLC) is a promising technique to optimize the selectivity of a given separation by using a combination of different stationary phases. Previous work has shown that SOSLC offers excellent possibilities for method development, especially after the recent modification towards linear gradient SOSLC. The present work is aimed at developing and extending the SOSLC approach towards selectivity optimization and method development for green chromatography. Contrary to current LC practices, a green mobile phase (water/ethanol/formic acid) is hereby preselected and the composition of the stationary phase is optimized under a given gradient profile to obtain baseline resolution of all target solutes in the shortest possible analysis time. With the algorithm adapted to the high viscosity property of ethanol, the principle is illustrated with a fast, full baseline resolution for a randomly selected mixture composed of sulphonamides, xanthine alkaloids and steroids.     

Discrete series characters for affine Hecke algebras and their formal degrees

We introduce the generic central character of an irreducible discrete series representation of an affine Hecke algebra. Using this invariant we give a new classification of the irreducible discrete series characters for all abstract affine Hecke algebras (except for the types E_n⁽¹⁾{E_{n}^{(1)}} , n=6, 7, 8) with arbitrary positive parameters and we prove an explicit product formula for their formal degrees (in all cases).     

Energy transfer in chiral co-assemblies of triple hydrogen-bonded oligo(p-phenylene vinylene)s and porphyrin

Pi-pi stacking of hydrogen-bonded porphyrin and oligo(p-phenylene vinylene)s (OPVs) yields helical co-assemblies which exhibit energy transfer from OPV to porphyrin.     

Synthesis and partial biological evaluation of a small library of differentially-linked beta-C-disaccharides

The synthesis of a small library of differentially-linked beta-C-disaccharides has been carried out through the use of a radical allylation-RCM strategy. Acids 6 were prepared by Keck allylation of a suitable carbohydrate-based radical precursor, followed by oxidative cleavage of the formed alkene. Dehydrative coupling of these acids with the known olefin alcohol 5 then gave the precursor esters 7 in excellent yield. Methylenation of the esters 7 was followed by RCM and in situ hydroboration-oxidation of the formed glycals to furnish the protected beta-C-disaccharides 10 in good overall yield. Five examples were then deprotected and screened for their efficacy as enzyme inhibitors of beta-glycosidase and against several solid-tumor cell lines for in vitro differential cytotoxicity.     

Micro Analysis on Hallstatt Textiles: Colour and Condition

Due to the special conditions in the Bronze Age and Hallstatt Period salt-mines of Hallstatt, Austria, a large number of archaeological textile fragments, dated from 1400 to 400 BC, can be found. Textiles of good condition from these periods are quite unique. The fibres are identified as wool and most of the fragments still have colours i.e. yellow, green, olive-green, brown, blue and black. To obtain information about the dyeing techniques used in this period, dyestuffs analyses are performed by high performance liquid chromatography coupled to photo diode array detection (HPLC-PDA) and mordant analysis by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). In addition, the condition of the textile fibres is assessed by SEM. The analyses revealed that all textiles were dyed with plant dyes and insect dyes. The yellow plant dyes and the red insect dyes are mordant dyes but the identification of mordants turned out to be difficult. SEM/EDS analyses of small uncontaminated areas on the fibre showed that the elements aluminium, iron and copper are present in many samples. These elements could originate from a mordant or from the mine. The condition of the fibres was assessed by the presence of the characteristic scales on the wool, tears, cuts and particles from the mine. It was found that a relation exists between the copper content of the fibres and their condition. Degraded fibres contain more copper. Black textile fragments which are most possibly coloured by iron gall-black show as well degradation phenomena.