Significance of data treatment and experimental setup on the determination of copper complexing parameters by anodic stripping voltammetry

Different procedures of voltammetric peak intensities determination, as well as various experimental setups were systematically tested on simulated and real experimental data in order to identify critical points in the determination of copper complexation parameters (ligand concentration and conditional stability constant) by anodic stripping voltammetry (ASV). Varieties of titration data sets (Cu_measuredvs. Cu_total) were fitted by models encompassing discrete sites distribution of one-class and two-class of binding ligands (by PROSECE software). Examination of different procedures for peak intensities determination applied on voltammograms with known preset values revealed that tangent fit (TF) routine should be avoided, as for both simulated and experimental titration data it produced an additional class of strong ligand (actually not present). Peak intensities determination by fitting of the whole voltammogram was found to be the most appropriate, as it provided most reliable complexation parameters.Tests performed on real seawater samples under different experimental conditions revealed that in addition to importance of proper peak intensities determination, an accumulation time (control of the sensitivity) and an equilibration time needed for complete complexation of added copper during titration (control of complexation kinetics) are the keypoints to obtain reliable results free of artefacts.The consequence of overestimation and underestimation of complexing parameters is supported and illustrated by the example of free copper concentrations (the most bioavailable/toxic specie) calculated for all studied cases. Errors up to 80% of underestimation of free copper concentration and almost two orders of magnitude overestimation of conditional stability constant were registered for the simulated case with two ligands.     

The production and properties of polylactide composites filled with expanded graphite

Composites have been produced by melt-blending biodegradable polylactide (PLA) with commercially available expanded graphite (EG). Using different techniques of addition, the manifold effects of EG on PLA molecular, thermo-mechanical and fire-retardant properties were evaluated. The EG nanofiller provides PLA composites with competitive functional properties. They have a high rigidity, with Young's modulus and storage modulus increasing with EG content. They also have excellent thermal stability while preserving the glass transition and melting temperature of the original PLA matrix. Purification and pre-dispersion of EG nanofiller proved beneficial for preserving PLA molecular weights and led to improved mechanical performance. The presence of dispersed graphene nanolayers in PLA significantly accelerated the polyester crystallization process. The flame retardant properties also displayed improvements with a large decrease in the maximum rate of heat release as recorded by cone calorimetry, whereas the horizontal burning test (UL94 HB) was successfully passed revealing non-dripping and char formation.     

Structural analysis of an unusual bioactive N-acylated lipo-oligosaccharide LOS-IV in Mycobacterium marinum

Although lipo-oligosaccharides (LOSs) are recognized as major parietal components in many mycobacterial species, their involvement in the host-pathogen interactions have been scarcely documented. In particular, the biological implications arising from the high degree of structural species-specificity of these glycolipids remain largely unknown. Growing recognition of the Mycobacterium marinum-Danio rerio as a specific host-pathogen model devoted to the study of the physiopathology of mycobacterial infections prompted us to elucidate the structure-to-function relationships of the elusive end-product, LOS-IV, of the LOS biosynthetic pathway in M. marinum. Combination of physicochemical and molecular modeling methods established that LOS-IV resulted from the differential transfer on the caryophyllose-containing LOS-III of a family of very unusual N-acylated monosaccharides, naturally present as different diastereoisomers. In agreement with the partial loss of pathogenecity previously reported in a LOS-IV-deficient M. marinum mutant, we demonstrated that this terminal monosaccharide conferred to LOS-IV important biological functions, including macrophage activating properties.     

Development of Amino Acids Functionalized SBA-15 for the Improvement of Protein Adsorption

Ordered mesoporous materials and their modification with multiple functional groups are of wide scientific interest for many applications involving interaction with biological systems and biomolecules (e.g., catalysis, separation, sensor design, nano-science or drug delivery). In particular, the immobilization of enzymes onto solid supports is highly attractive for industry and synthetic chemistry, as it allows the development of stable and cheap biocatalysts. In this context, we developed novel silylated amino acid derivatives (Si-AA-NH₂) that have been immobilized onto SBA-15 materials in biocompatible conditions avoiding the use of toxic catalyst, solvents or reagents. The resulting amino acid-functionalized materials (SBA-15@AA) were characterized by XRD, TGA, EA, Zeta potential, nitrogen sorption and FT-IR. Differences of the physical properties (e.g., charges) were observed while the structural ones remained unchanged. The adsorption of the enzyme lysozyme (Lyz) onto the resulting functionalized SBA-15@AA materials was evaluated at different pHs. The presence of different functional groups compared with bare SBA-15 showed better adsorption results, for example, 79.6 nmol of Lyz adsorbed per m² of SBA-15@Tyr compared with the 44.9 nmol/m² of the bare SBA-15.     

The dehydroxylation of tricalcium aluminate 6-hydrate

The thermal decomposition of tricalcium aluminate 6-hydrate^* has been studied and kinetic parameters determined for each of the two stages in the reaction. The first stage was studied in the temperature range 505-610 K and the second between 950 and 1025 K at partial pressures of water vapour between 0.1 mN m^?2 and 3.2 kN m^?2. For the first stage below 555 K the rate-controlling process is one of nucleation and growth of product phase, which changes at higher temperatures to a diffusion-controlled process. The Arrhenius parameters for each of these processes vary with external water vapour pressure. The second stage of the reaction is controlled by a phase boundary reaction for which Arrhenius parameters are given.     

A benzyloxy group migration under Mitsunobu reaction conditions

When compounds 3a and 3b were subjected to a Mitsunobu reaction with benzoylthymine, the expected substitution products were formed together with the regioisomers corresponding to benzyloxy group migrations.     

Synthesis of [323]-p-octiphenyls: orthogonal functionalization along a rigid-rod scaffold for refined supramolecular architecture

[structure: see text] The synthesis of p-octiphenyls carrying orthogonal tert-butyl esters in the peripheral positions 1(2), 2(2), 3(3), 6(2), 7(3), and 8(2) and either p-methoxybenzyl or benzyl ester substituents in the central positions 4(2) and 5(3) is described. Resolution-enhanced HSQC/HMBC two-dimensional NMR spectroscopy is implemented as an attractive method for the complete characterization of complex p-oligophenyl scaffolds.     

(1R,2s,3S,6R,9S)‐5,5,10,10‐Tetrachloro‐2‐methyltricyclo[7.2.0.03,6]undec‐7‐ene‐4,11‐dione

The title compound, C₁₂H₁₀Cl₄O₂, has a pseudoasymmetric centre at the methyl‐substituted carbon and, in the solid state, a boat‐like conformation.