Spectroscopic study of copper(II)--wheat straw cell wall residue surface complexes

The sorption of copper(II) by wheat straw cell wall residue (CWR) was studied and revealed a relatively stable surface complexation on the acid sites of the substrate (carboxylic and phenolic moieties). The copper binding capacity at pH = 5.75 and ionic strength of 0.1 M was evaluated at 63 micromol x g(-1) CWR. The Langmuir and Freundlich isotherm equations were then used to describe the partitioning behavior for the system at different pH values. Batch experiments have been achieved in the presence of calcium in order to mimic the calcareous soil of the Champagne region. A competitive effect on copper complexation has been shown, which is presumably due to the calcium ability to form outer-sphere complexes far less stable than copper(II) ones. Electron spin resonance and X-ray absorption spectroscopy were combined to obtain information on the geometry and structure of Cu bound to CWR. At least two different binding sites for Cu2+ were found to take place in CWR. From ESR parameters, we deduced that copper(II) ions, when complexed with CWR, are coordinated in a square-planar arrangement with four oxygen-containing groups. EXAFS and XANES experiments revealed that Cu(II) is surrounded by four oxygen atoms, with an average Cu-O equatorial distance equal to 1.94 A.     

Response of a Lactobacillus plantarum human isolate to tannic acid challenge assessed by proteomic analyses

Scope : To gain insight on the mechanisms used by intestinal bacteria to adapt and resist the antimicrobial action of dietary tannins and identify targets for tannic acid in Lactobacillus plantarum. Methods and results : A proteomic analysis of an L. plantarum human isolate exposed to the tannic acid challenge was undertaken. Tannic acid targeted proteins involved in outstanding processes for bacterial stress resistance including cyclopropanation of membrane lipids, stress response at population scale and maintenance of cell shape. To respond to this aggression, tannic acid‐misfit cells of L. plantarum challenged with tannic acid reorganized their metabolic capacity to economize energy and express proteins involved in oxidative stress defense and cell wall biogenesis, indicating that the injury incurred by tannic acid was based on oxidative damage and disruption of the cell envelope. The induction of 3‐octaprenyl‐4‐hydroxybenzoate carboxy‐lyase, which is sensitive to changes in redox conditions and involved in ubiquinone biosynthesis in other bacteria, suggests for a tannic acid‐induced redox imbalance. Conclusion : The results reveal the adaptation of a gastrointestinal isolate of L. plantarum to tannic acid and identify antibacterial targets for this dietary compound. This provides the basis for the selection of tannin‐resistant microorganisms and their use to obtain health benefits from tannin‐containing diets.     

Measurement of enzymatic activity and specificity of human and avian influenza neuraminidases from whole virus by glycoarray and MALDI-TOF mass spectrometry

Influenza neuraminidases hydrolyze the ketosidic linkage between N-acetylneuraminic acid and its adjacent galactose residue in sialosides. This enzyme is a tetrameric protein that plays a critical role in the release of progeny virions. Several methods have been described for the determination of neuraminidase activity, usually based on colorimetric, fluorescent, or chemiluminescent detection. However, only a few of these tests allow discrimination of the sialyl-linkage specificity (i.e., α2-3- versus α2-6-linked sialyllactosides) of the neuraminidase. Herein we report a glycoarray-based assay and a MALDI-TOF study for assessing the activity and specificity of two influenza neuraminidases on whole viruses. The human A(H3N2) and avian A(H5N2) neuraminidase activities were investigated. The results from both approaches demonstrated that α2-3 sialyllactoside was a better substrate than α2-6 sialyllactoside for both viruses and that H5N2 virus had a lower hydrolytic activity than H3N2.     

Experimental methodology to study tribological aspects of deep drawing — application to aluminium alloy sheets and tool coatings

To optimise the contact between aluminium alloy sheets and coated HSS steel tools during deep drawing operation, we present an experimental methodology to decompose an extended slippage by using a strip drawing test with cylindrical tools in multipassing mode. We show in this paper the role of transfer films formed on the tool surface on the evolution of both friction coefficient and surface topography of the metal sheet.     

Syllabic priming in lexical decision and naming tasks: The syllable congruency effect re-examined in French.

This study investigated the role of the syllable in visual recognition of French words. The syllable congruency procedure was combined with masked priming in the lexical-decision task (Experiments 1 and 3) and the naming task (Experiment 2). Target words were preceded by a nonword prime sharing the first three letters that either corresponded to the syllable (congruent condition), or not (incongruent condition). When primes were displayed for 67 ms, similar results were found in both the lexical decision and the naming tasks. Consonant-vowel targets such as BA.LANCE were recognised more rapidly in the congruent condition than in the incongruent and control conditions, while consonant-vowel-consonant targets such as BAL.CON were recognised more rapidly in the congruent and incongruent conditions than in the control condition. When a 43-ms SOA was used in the lexical-decision task, no significant priming effect was obtained. The results are discussed in an interactive-activation model incorporating syllable units. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical reactions affecting halloysite dispersion in epoxy nanocomposites

Halloysite nanotubes (HNTs) have attracted a technologic and scientific attention as reinforcements of epoxy-based nanocomposites. However, their reported interaction with epoxy matrices is varied and the controlled dispersion of HNTs is still a challenge. In this work, we study the effect of chemical reactions taking place in the dispersion process of halloysite and their possible influence in the composite's properties. HNTs' surface was modified through an alkaline treatment and by grafting two aminosilanes with different chain lengths and functionality numbers. Evidence of homopolymerization and degradation reactions was found, depending on the surface treatment. The rheological study indicated that an interconnected network can be achieved in epoxy/HNTs blends depending on the surface chemical characteristics of the nanofillers and the blending method. The better dispersion was accomplished when ultrasonicating with the aid of a solvent. Nevertheless, the mechanical properties of the nanocomposites are not warranted by selecting a dispersion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47979.     

Mechanical reliability of Ce0.8Gd0.2O2−δ-FeCo2O4 dual phase membranes synthesized by one-step solid-state reaction

Ce_0.8Gd_0.2O_2−δ-FeCo₂O₄ composites are attractive candidate materials for high-purity oxygen generation providing robust chemical stability. Aiming for future industrial applications, a feasible solid-state reaction process with one thermal processing step was used to synthesize 50 wt% Ce_0.8Gd_0.2O_2−δ:50 wt% FeCo₂O₄ and 85 wt% Ce_0.8Gd_0.2O_2−δ:15 wt% FeCo₂O₄ composites. Mechanical reliabilities of the sintered membranes were assessed based on the characterized mechanical properties and subcritical crack growth behavior. In general, the fracture strengths of as-sintered membranes were reduced by tensile residual stresses and microcracks. In particular, the enhanced subcritical crack growth behavior, which leads to limited stress tolerance and high failure probability after a 10-year operation, was evaluated in more detail. Further materials and processing improvements are needed to eliminate the tensile stress and microcracks to warrant a long-term reliable operation of the composites.     

Design and synthesis of a new type of non steroidal human aromatase inhibitors

The structure-activity relationship study of one of recently described aromatase inhibitors, compound 1 (MR20814), allowed us to design some related derivatives as potential new inhibitors. Among those we synthesized, chlorophenylpyridylmethylenetetrahydroindolizinone 5 (MR20492) exhibited in vitro a ten-fold higher inhibition of the enzyme (IC50 = 0.2 +/- 0.0 microM and Ki = 10.3 +/- 3.3 nM).     

New direct coupling configuration between TE/sub 01 delta / dielectric resonator modes

A new geometric configuration is presented to carry out negative coupling between dielectric resonators (DRs) acting in their dipolar TE/sub 01 delta / mode. These DRs are coupled in a direct manner so that transmission lines, metallic screws or irises as usually used become unnecessary.<>