Synthesis of Zinc Phosphonated Poly(ethylene imine) and Its Fire-Retardant Effect in Low-Density Polyethylene

A novel oligomeric intumescent fire-retardant chelate, zinc phosphonated poly(ethylene imine) (Zn-PEIP), with a variable Zn2+ loading, was synthesized. The chemical structure of Zn-PEIP was confirmed by FTIR, 13C NMR, and 31P NMR spectroscopies. The thermal behavior and fire retardancy of low-density polyethylene (LDPE) containing 25 wt % Zn-PEIPs with different amounts of Zn2+ were investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI) measurements, and cone calorimetry. The TGA results showed that higher concentrations of Zn2+ improved the thermal stability and increased the residue yield of LDPE. However, the data from the LOI and cone calorimetry tests showed that there is an optimum concentration of Zn2+ for the best fire-retardancy performance of LDPE. This behavior is ascribed to the high cross-link density resulting from zinc bridges, preventing normal swelling of the intumescent system. The surface morphology of the char was characterized by digital photography and scanning electron microscopy (SEM). This confirmed the optimum intumescence and coherent and strong barrier layer formation at an intermediate Zn2+ loading

The influence of textile materials on flame resistance ratings of professional uniforms

This study compares the flame speed of different textile materials employed in professional uniforms. Five different garments of aeronauts’ uniforms were analyzed (totaling 200 specimens submitted to flammability tests). Plain weaves and twill weaves composed by 100% CO; 100% PES; 67% PES/33% CO; 50% PES/50% WO; and 55% PES/45%WO were analyzed in the warp and filling directions. The flame speed of each material was determined, and differences in the flame propagation of the fabrics were identified. The lowest flame speed occurred for the material 50% PES/50% WO plain weave and weft direction (0.742 ± 0.140 m/s). The highest flame speed was 3.698 ± 1.806 cm/s for the material 67%PES/33%CO, plain weave and filling direction. Future experiments for reducing the fabric flammability of the uniforms could be related to more closed fabric constructions; mixtures with synthetic fibers to add functionality; changing the direction of the fabric; and changing the weight and torsion of its constituent yarns.São Paulo Research Foundation—FAPESP (“Fundação de Amparo à Pesquisa do Estado de São Paulo”) Grant Number 2016/01331-

Nucleic Acids Res

Site-directed spin labeling is emerging as an essential tool to investigate the structural and dynamical features of RNA. We propose here an enzymatic method, which allows the insertion of a paramagnetic center at a specific position in an RNA molecule. The technique is based on a segmental approach using a ligation protocol with T4 RNA ligase 2. One transcribed acceptor RNA is ligated to a donor RNA in which a thio-modified nucleotide is introduced at its 5'-end by in vitro transcription with T7 RNA polymerase. The paramagnetic thiol-specific reagent is subsequently attached to the RNA ligation product. This novel strategy is demonstrated by introducing a paramagnetic probe into the 55 nucleotides long RNA corresponding to K-turn and Specifier Loop domains from the Bacillus subtilis tyrS T-Box leader RNA. The efficiency of the coupling reaction and the quality of the resulting spin-labeled RNA were assessed by Mass Spectrometry, Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR). This method enables various combinations of isotopic segmental labeling and spin labeling schemes, a strategy that will be of particular interest to investigate the structural and dynamical properties of large RNA complexes by NMR and EPR spectroscopies

Effect of binder on performance of intumescent coatings

This study investigates the role of the polymeric binder on the properties and performance of an intumescent coating. Waterborne resins of different types (vinylic, acrylic, and styrene-acrylic) were incorporated in an intumescent paint formulation, and characterized extensively in terms of thermal degradation behavior, intumescence thickness, and thermal insulation. Thermal microscopy images of charred foam development provided further information on the particular performance of each type of coating upon heating. The best foam expansion and heat protection results were obtained with the vinyl binders. Rheological measurements showed a complex evolution of the viscoelastic characteristics of the materials with temperature. As an example, the vinyl binders unexpectedly hardened significantly after thermal degradation. The values of storage moduli obtained at the onset of foam blowing (melamine decomposition) were used to explain different intumescence expansion behaviors.Funding for this work was provided by FCT-Fundacao para a Ciencia e Tecnologia (Project PTDC/EQU-EQU/65300/2006), and by FEDER/QREN (project RHED) in the - framework of Programa Operacional Factor de Competitividade-COMPETE. Joana Pimenta thanks FCT for PhD Grant SFRH/BDE/33431/2008

Self-Association of an Activating Natural Killer Cell Receptor, KIR2DS1

As a major component of the innate immune system, natural killer cells are responsible for activating the cytolytic killing of certain pathogen-infected or tumor cells. The self-recognition of natural killer cells is achieved in part by the killer cell immunoglobulin-like receptors (KIRs) protein family. In the current study, using a suite of biophysical methods, we investigate the self-association of an activating KIR, KIR2DS1. This KIR is of particular interest because when in the presence of the HLA-Cw6 protein, KIR2DS1 becomes a major risk factor for psoriasis, an autoimmune chronic skin disease. Using circular dichroism spectroscopy, dynamic light scattering, and atomic force microscopy, we reveal that KIR2DS1 self-associates in a well-defined fashion. Our novel results on an activating KIR allow us to suggest a working model for the KIR2DS1- HLA class I molecular mechanism

Designing of polylactide/clay nanocomposites for textile applications: effect of processing conditions, spinning and characterization

peer reviewedAn experimental study was carried out to design polylactide (PLA)-clay nanocomposites for developing fibers. PLA and 1-10 wt % of a selected organomodified bentonite (Bentone® 104-B104) were melt mixed to examine the effect of processing conditions (temperature, shear, residence time) on the morphology of performed polymer nanocomposites (PNC). Because of a good compatibility with PLA matrix, the dispersion of B104 occurred under different conditions without difficulty, and a similar morphology was obtained. The results obtained showed that at low temperature of mixing, the shear stress exerted on polymer has a key role on the extent of intercalation and delamination. Upscale experiments were further performed using optimized conditions and 4 wt % B104 was added to PLA matrix by melt blending to produce PNC for spinning. Then, the recovered PNC were melt spun to produce multifilaments yarns, and it was demonstrated that surprisingly, it is not necessary to use a plasticizer to spin a blend with 4 wt % B104. The properties of the yarns have been studied in terms of clay dispersion as well as thermal, mechanical, and shrinkage properties. B104 could be added up to 4 wt % into PLA without detrimentally sacrificing the tensile strength of melt-spun filaments, especially at high draw ratio. Interestingly, the PNC-based multifilaments were knitted and the flammability studied using cone calorimeter at 35 kW/m2. A strong decrease, up to 46%, of the heat release rate was measured

(Plasticized) polylactide/clay nanocomposite textile : thermal, mechanical, shrinkage and fire properties

peer reviewedVarious quantities of Cloisite® 30B (from 1% to 4% in weight) have been added to a polylactide matrix by melt blending to produce polylactide-based nanocomposites. Then, these blends have been melt-spun to produce multifilaments yarns. It is demonstrated that it is necessary to use a plasticizer to spin a blend with 4% in weight of Cloisite® 30B. The properties of these yarns have been studied (dispersion of the clay, thermal, mechanical and shrinkage properties). A decrease of the tensile properties is observed when the quantity of Cloisite® 30B increases, but an improvement of the thermal and shrinkage properties is highlighted. These multifilaments have been knitted and the flammability studied using cone calorimeter at 35 kW/m2. A strong decrease, up to 38%, of the heat release rate has been measured

A strong 13C chemical shift signature provides the coordination mode of histidines in zinc-binding proteins

International audienceZinc is the second most abundant metal ion incorporated in proteins, and is in many cases a crucial component of protein three-dimensional structures. Zinc ions are frequently coordinated by cysteine and histidine residues. Whereas cysteines bind to zinc via their unique Sγ atom, histidines can coordinate zinc with two different coordination modes, either Nδ1 or Nε2 is coordinating the zinc ion. The determination of this coordination mode is crucial for the accurate structure determination of a histidine-containing zinc-binding site by NMR. NMR chemical shifts contain a vast amount of information on local electronic and structural environments and surprisingly their utilization for the determination of the coordination mode of zinc-ligated histidines has been limited so far to 15N nuclei. In the present report, we observed that the 13C chemical shifts of aromatic carbons in zinc-ligated histidines represent a reliable signature of their coordination mode. Using a statistical analysis of 13C chemical shifts, we show that 13Cδ2 chemical shift is sensitive to the histidine coordination mode and that the chemical shift difference δ{13Cε1} - δ{13Cδ2} provides a reference-independent marker of this coordination mode. The present approach allows the direct determination of the coordination mode of zinc-ligated histidines even with non-isotopically enriched protein samples and without any prior structural information