Aryl Bis‐Sulfonamide Inhibitors of IspF from Arabidopsis thaliana and Plasmodium falciparum

2‐Methylerythritol 2,4‐cyclodiphosphate synthase (IspF) is an essential enzyme for the biosynthesis of isoprenoid precursors in plants and many human pathogens. The protein is an attractive target for the development of anti‐infectives and herbicides. Using a photometric assay, a screen of 40 000 compounds on IspF from Arabidopsis thaliana afforded symmetrical aryl bis‐sulfonamides that inhibit IspF from A. thaliana (AtIspF) and Plasmodium falciparum (PfIspF) with IC₅₀ values in the micromolar range. The ortho‐bis‐sulfonamide structural motif is essential for inhibitory activity. The best derivatives obtained by parallel synthesis showed IC₅₀ values of 1.4 μm against PfIspF and 240 nm against AtIspF. Substantial herbicidal activity was observed at a dose of 2 kg ha^?1. Molecular modeling studies served as the basis for an in silico search targeted at the discovery of novel, non‐symmetrical sulfonamide IspF inhibitors. The designed compounds were found to exhibit inhibitory activities in the double‐digit micromolar IC₅₀ range.     

The simultaneous addition of styrene maleic anhydride copolymer and multiwall carbon nanotubes during melt‐mixing on the morphology of binary blends of polyamide6 and acrylonitrile butadiene styrene copolymer

The effect of simultaneous addition of multiwall carbon nanotubes (MWNTs) and a reactive compatibilizer (styrene maleic anhydride copolymer, SMA) during melt‐mixing on the phase morphology of 80/20 (wt/wt) PA6/ABS blend has been investigated. Morphological analysis through scanning and transmission electron microscopic analysis revealed finer morphology of the blends in presence of SMA + MWNTs. Fourier transform infrared spectroscopic analysis indicated the formation of imide bonds during melt‐mixing. Non‐isothermal crystallization studies exhibited the presence of a majority faction of MWNTs in the PA6 phase of 80/20 (wt/wt) PA6/ABS blend in presence of SMA + MWNTs. Rheological analysis, dynamic mechanical thermal analysis, and thermogravimetric analysis have demonstrated the compatibilization action of simultaneous addition of a reactive compatibilizer (SMA copolymer) and MWNTs in PA6/ABS blends. An attempt has been made to investigate the role of simultaneous addition of SMA copolymer and MWNTs on the morphology of 80/20 (wt/wt) PA6/ABS blend through various characterization techniques. POLYM. ENG. SCI., 55:457–465, 2015. © 2014 Society of Plastics Engineers     

Characterization of glow‐discharge–treated cellulose acetate membrane surfaces for single‐layer enzyme electrode studies

Cellulose acetate membranes (CA) were modified by means of plasma polymerization of ethylene diamine (EDA) and n‐butylamine (n‐BA). The motivation for this work was the application of a modified membrane for the single‐layer enzyme electrode. A tubular reactor with the external radiofrequency (13.56 MHz) excitation was used. Surface modification was performed at 5, 10, and 15 W power (at 27 Pa working pressure) for 5, 10, 15 min. Modified surfaces were characterized in detail by FTIR–ATR, XPS (ESCA), contact angle, and enzyme immobilization activity. The best treatment results were obtained for EDA with 5 W and 30 min and 15 W and 10 min. These results are discussed using surface analysis data. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1341–1352, 2001     

Exploring the Structural Space of the Galectin‐1–Ligand Interaction

Galectin‐1 is a tumor‐associated protein recognizing the Galβ1‐4GlcNAc motif of cell‐surface glycoconjugates. Herein, we report the stepwise expansion of a multifunctional natural scaffold based on N‐acetyllactosamine (LacNAc). We obtained a LacNAc mimetic equipped with an alkynyl function on the 3′‐hydroxy group of the disaccharide facing towards a binding pocket adjacent to the carbohydrate‐recognition domain. It served as an anchor motif for further expansion by the Sharpless–Huisgen–Meldal reaction, which resulted in ligands with a binding mode almost identical to that of the natural carbohydrate template. X‐ray crystallography provided a structural understanding of the galectin‐1–ligand interactions. The results of this study enable the development of bespoke ligands for members of the galectin target family.     

A simple intrinsic measure for rapid crack propagation in bimodal polyethylene pipe grades validated by elastic–plastic fracture mechanics analysis of data from instrumented Charpy impact test

Conventional test procedures, such as the S4 test to analyze the resistance against rapid crack propagation (RCP) of plastic pipe materials are characterized by usage of a lot of material, are far from saving of time and they are‐in need of special experimental set‐ups. Therefore, in the last decade, small‐scale accelerated reliable tests (SMART) are developed ‐ worldwide to overcome the disadvantage of such conventional tests. In this article, fracture mechanics based analysis of instrumented Charpy impact test data for a set of bimodal high‐density polyethylene pipe grades are compared with data of the conventional Charpy impact test. From this comparison the Charpy impact strength at ?30°C comes forth as a robust reproducible measure of the resistance to RCP and it is therefore proposed as a SMART method to rank materials with respect to RCP resistance. POLYM. ENG. SCI., 57:13–21, 2017. © 2016 Society of Plastics Engineers     

Synthesis and magnetorheological characteristics of ribbon‐like,polypyrrole‐coated carbonyl iron suspensions under oscillatory shear

One of the crucial problems of classical magnetorheological (MR) fluids is their high rate of sedimentation. This disadvantage may be substantially eliminated using core‐shell particles. The aim of this study is to prepare spherical carbonyl iron (CI) particles coated with conducing polymer polypyrrole (PPy) with ribbon‐like morphology. Scanning electron microscopy proved the formation of the ribbon‐like layer onto CI particles while Fourier transform infrared spectroscopy confirmed the chemical structure of PPy. The magnetic properties observed via vibrating sample magnetometer showed decreased magnetization saturation of core‐shell‐structured particles due to the existence of non‐magnetic surface layer. MR measurements performed under oscillatory shear flow as a function of the applied magnetic flux density, temperature, and particle concentration showed that core‐shell particle‐based MR suspension exhibits sufficient MR performance for practical applications. Moreover, the suspension stability is promoted significantly when core‐shell particles are used as a dispersed phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interfacial chemistry using a bifunctional coupling agent for enhanced electrical properties of carbon nanotube based composites

A bifunctional coupling agent (BCA) containing one oxazoline and one benzoxazinone group was applied to promote a reaction between polyamide 12 (PA12) and multiwalled carbon nanotubes (MWCNTs) during melt mixing. With this modification, the MWCNT content needed for the electrical percolation was significantly reduced by more than a factor of three. For amino functionalized MWCNT–PA12 composites adding 1 wt.% BCA electrical percolation was reached at only 0.37 wt.% MWCNTs compared to 1.0 wt.% without BCA. With the help of a model reaction, the covalent attachment of the BCA to the MWCNTs could be shown by thermogravimetric analysis (TGA) and via fluorescence spectroscopy. Model compounds were applied containing either only the oxazoline or the benzoxazinone group to show that the better electrical properties in the PA12–MWCNT composites were a result of a covalent bond between the polymer and the nanotube which only takes place when the BCA was used. In addition, significantly higher electrical conductivity values were obtained by the addition of BCA as well with amino functionalized as with nonmodified commercial MWCNTs. This surprising result was attributed to the significant hydroxy group content on the surface of those commercial MWCNTs.     

Polyethylene multiwalled carbon nanotube composites

Polyethylene (PE) multiwalled carbon nanotubes (MWCNTs) with weight fractions ranging from 0.1 to 10 wt% were prepared by melt blending using a mini-twin screw extruder. The morphology and degree of dispersion of the MWCNTs in the PE matrix at different length scales was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and wide-angle X-ray diffraction (WAXD). Both individual and agglomerations of MWCNTs were evident. An up-shift of 17 cm⁻¹ for the G band and the evolution of a shoulder to this peak were obtained in the Raman spectra of the nanocomposites, probably due to compressive forces exerted on the MWCNTs by PE chains and indicating intercalation of PE into the MWCNT bundles. The electrical conductivity and linear viscoelastic behaviour of these nanocomposites were investigated. A percolation threshold of about 7.5 wt% was obtained and the electrical conductivity of PE was increased significantly, by 16 orders of magnitude, from 10⁻²⁰ to 10⁻⁴ S/cm. The storage modulus (G′) versus frequency curves approached a plateau above the percolation threshold with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behaviour. The ultimate tensile strength and elongation at break of the nanocomposites decreased with addition of MWCNTs. The diminution of mechanical properties of the nanocomposites, though concomitant with a significant increase in electrical conductivity, implies the mechanism for mechanical reinforcement for PE/MWCNT composites is filler-matrix interfacial interactions and not filler percolation. The temperature of crystallisation (T_c) and fraction of PE that was crystalline (F_c) were modified by incorporating MWCNTs. The thermal decomposition temperature of PE was enhanced by 20 K on addition of 10 wt% MWCNT.     

Anionic polymerization of acrylates. XIV. Synthesis of MMA/acrylate block copolymers initiated with ester-enolate/tert-alkoxide complex

Diblock copolymers of methyl methacrylate (MMA) with 2-ethylhexyl, butyl, ethyl or tert-butyl acrylate (EtHA, BuA, EtA, t-BuA) have been prepared by the ligated anionic polymerization initiated with methyl 2-lithioisobutyrate (MIB-Li) in the presence of an excess of Li tert-butoxide (t-BuOLi) in toluene/THF mixture at −60 or −78 °C. The copolymers, prepared at −60 °C, show MWD with a hint of bimodality, indicating partial deactivation of the living PMMA upon addition of acrylic monomer. At −78 °C, the extent of this deactivation is distinctly lower, the formed block copolymers, in particular, poly(MMA-b-EtHA), have unimodal MWD and exhibit tails only in the lower-molecular-weight region. Poly(MMA-b-EtHA)s were extracted with acetonitrile dissolving PMMA; very small parts of the crude products dissolved, whereas prevailing parts remained as solids documenting thus formation of block copolymer in a high yield. Surprisingly, the highest amount of self terminated PMMA was found in block copolymerization of MMA with t-BuA at both the temperatures, the products of which had clearly bimodal MWDs. This finding is shortly discussed on the basis of relatively slow propagation of t-BuA in comparison with EtHA, BuA and EtA.