X-ray Photoelectron Spectra of Poly(2-vinylpyridine) and its Adduct with Boron Trifluoride

The sources of interactions at an interface and in solution have been subjects which have occupied both experimentalists and theorists for some time. Several types of interactions, e.g. donor-acceptor,^1–6 have been suggested to explain deviations in adhesion and solution data from that predicted from London dispersion forces. The experimentalist has employed both infrared spectroscopy and calorimetry to measure donor-acceptor interactions. It is the purpose of this note to show that X-ray photoelectron spectroscopy (XPS) can be used also to detect donor-acceptor interactions in polymeric systems.     

Interaction of the Adhesive Protein Mefp-1 and Fibrinogen with Methyl and Oligo (Ethylene Glycol)-terminated Self-assembled Monolayers

The interaction of fibrinogen and Mefp-1, the adhesive protein of the common blue mussel Mytilus edulis, with methyl- and oligo(ethylene oxide) (OEG)-terminated self-assembled monolayers (SAMs) has been investigated by Fourier Transform Infrared Reflection (FT-IRAS) analysis. The measurements on the hydrophobic surfaces show that the underlying SAM is structurally undisturbed when the proteins adhere. Mefp-1 is used as an attachment factor (Cell-Tak^TM) in cell cultures and in biomedical applications, and it is of interest to determine if OEG-terminated surfaces are inert towards Cell-Tak-mediated cell adhesion. We find that, when Langmuir transfer of a protein film at the liquid/air interface is avoided, the moderately hydrophilic hydroxyhexa (ethylene oxide) and methoxytri(ethylene oxide) undecanethiolate SAMs prepared on Au substrates are protein resistant. The inertness of the OEG-terminated surfaces does not depend on any specific protein present in solution, but rather appears to be a general phenomenon that is independent of the specific structure or chemistry of the macromolecule.     

The Influence of Polyunsaturated Fatty Acids on the Phospholipase D Isoforms Trafficking and Activity in Mast Cells

The impact of polyunsaturated fatty acid (PUFA) supplementation on phospholipase D (PLD) trafficking and activity in mast cells was investigated. The enrichment of mast cells with different PUFA including α-linolenic acid (LNA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid (LA) or arachidonic acid (AA) revealed a PUFA-mediated modulation of the mastoparan-stimulated PLD trafficking and activity. All PUFA examined, except AA, prevented the migration of the PLD1 to the plasma membrane. For PLD2 no PUFA effects on trafficking could be observed. Moreover, PUFA supplementation resulted in an increase of mastoparan-stimulated total PLD activity, which correlated with the number of double bonds of the supplemented fatty acids. To investigate, which PLD isoform was affected by PUFA, stimulated mast cells were supplemented with DHA or AA in the presence of specific PLD-isoform inhibitors. It was found that both DHA and AA diminished the inhibition of PLD activity in the presence of a PLD1 inhibitor. By contrast, only AA diminished the inhibition of PLD activity in the presence of a PLD2 inhibitor. Thus, PUFA modulate the trafficking and activity of PLD isoforms in mast cells differently. This may, in part, account for the immunomodulatory effect of unsaturated fatty acids and contributes to our understanding of the modulation of mast cell activity by PUFA.     

Synthese von Oligo(p‐phenylen‐m‐pyridindiyl)en

Oligomers ( 7 , 9 , 11 , and 13a ‐ c ), which consist of an alternate sequence of 1,4‐linked benzene rings and 2,4‐linked pyridine rings, were prepared from the corresponding oligochalcones. Each enone segment reacts with phenacylpyridinium bromide ( 3 ) and ammonium acetate ( 4 ) to yield a pyridine building block. Propoxy sidechains attached on the benzene rings of the chalcones reduce to some extent the yield of the cyclization reactions (40–68%) but enhance the solubility of the oligomers. Cross conjugation leads to a moderate bathochromic shift of the absorption with increasing number of repeating units.     

Colloidal Co nanoparticles supported on SiO2: Synthesis, characterization and catalytic properties for steam reforming of ethanol

Colloidal Co nanoparticles with sizes in the 3–8 nm range were obtained by thermal decomposition of Co₂(CO)₈ in the presence of ligands and impregnated on SiO₂ to prepare SiO₂-supported Co nanocatalysts. The catalysts showed activity for the steam reforming of ethanol with higher values for smaller Co particles. H₂ adsorption results and Fourier transform infrared spectroscopy of adsorbed CO suggested that the fraction of accessible Co sites also depended on the synthesis conditions. Precipitation of the Co nanoparticles with methanol instead of ethanol before impregnation had a positive effect on the density of accessible Co sites to catalysis; similar result was verified by increasing the thermal treatment temperature under H₂ flow before the reaction. Based on the distribution of products with temperature of reaction, a mechanism for steam reforming of ethanol on SiO₂-supported Co nanocatalysts is suggested.     

Biochemical Investigation of the Interaction of pICln,RioK1 and COPR5 with the PRMT5–MEP50 Complex

The PRMT5–MEP50 methyltransferase complex plays a key role in various cancers and is regulated by different protein–protein interactions. Several proteins have been reported to act as adaptor proteins that recruit substrate proteins to the active site of PRMT5 for the methylation of arginine residues. To define the interaction between these adaptor proteins and PRMT5, we employed peptide truncation and mutation studies and prepared truncated protein constructs. We report the characterisation of the interface between the TIM barrel of PRMT5 and the adaptor proteins pICln, RioK1 and COPR5, and identify the consensus amino acid sequence GQF[D/E]DA[E/D] involved in binding. Protein crystallography revealed that the RioK1 derived peptide interacts with a novel PPI site.     

Chemical Recycling of Carbon Fiber Reinforced Epoxy Composites Using Mild Conditions

The increased use of carbon fiber reinforced thermosets generates more waste and end-of-life products. However, an efficient recycling method for the expensive carbon fibers has not yet been developed. The selective decomposition of amine-cured epoxy resin under mild conditions is presented. A two-step method was investigated to decompose the epoxy resin. The optimum parameters were initially determined using a model compound. By analysis of the reaction products, a cleavage of the C–N bond according to the Cope elimination could be proven. Therefore, the Cope elimination is suggested as the main step of the decomposition of amine-cured epoxy resins in presence of hydrogen peroxide. By dissolving the resin, it is possible to recover resin-free fibers with unimpaired mechanical properties.     

Effects of H<Subscript>2</Subscript> Atmospheres on Sintering of Low Alloy Steels Containing Oxygen-Sensitive Masteralloys

Processing of novel sintered steels with compositions including oxygen-sensitive elements requires deep understanding of the chemistry of sintering. The use of H₂ atmospheres alleviates the oxygen transference from the base powder to the oxygen-sensitive particles. However, in H₂, methane formation at 700–1200°C causes dramatic homogeneous decarburization of the part that affects both mechanical behavior and dimensional stability. The intensity and the critical temperatures of this effect depend strongly on the alloying elements, being significantly enhanced in presence of Si. When combining the alloying elements as Fe-Mn-Si masteralloys, methane formation is enhanced around 760°C due to the high Mn content (40 wt.%) in the masteralloys. Nevertheless, the benefits of H₂ towards oxide reduction can still be advantageously used if diluting it in the form of N₂-H₂ atmospheres, or if limiting the use of H₂ to temperatures below 500°C. Thus, decarburization due to methane formation can be successfully controlled.     

Blends of thermoplastic polyurethane and maleic-anhydride grafted polyethylene. I: Morphology and mechanical properties

Thermoplastic polyurethane elastomers (TPU) and polyethylene (PE) form immiscible blends with an extremely low compatibility. In order to improve the dispersion, stability, and properties of these blends, polyethylene was grafted with maleic anhydride (PE-g-MA). Subsequently, it was blended with a commercial polyester - type TPU in a twin-screw extruder. With PE-g-MA as blend component, the particle size was dramatically reduced in comparison with PE. Coalescence was significantly reduced and the increase in particle size with composition was less pronounced than in blends with PE. In addition, the phase adhesion and the mechanical properties were improved by using PE-g-MA as minor component. Grafting of the MA onto the PE leads to a decrease of the molecular weight, the melt viscosity, and the mechanical properties of the pure PE. Hence, the reactive blend system exhibits a lower viscosity ratio. Comparison of these results with those from uncompatibilized blends with different viscosity ratios revealed that the reduction in viscosity ratio has a big influence on the blend morphology and because of that on the mechanical properties. In addition, there is a further effect on morphology and properties caused by the reduction in interfacial tension, which results from the compatibilizer formed at the interface.