Preparation of N-Boc N-Alkyl Glycines for Peptoid Synthesis

A series of N-tert-butoxycarbonylated N-allyl, N-propargyl, N-benzyl or branched N-alkyl glycines, useful building blocks for the synthesis of N-alkyl glycine oligomers, have been prepared by N-alkylation of N-Boc glycine or by a two-step method: reductive alkylation and tert-butoxycarbonylation.     

Theoretical third-order hyperpolarizability of paratellurite from the finite field perturbation method

Density functional theory was used to estimate the third-order hypersusceptibility chi (3) of the alpha-TeO2 paratellurite (as a model structure for TeO2 glass) and the same value for alpha-SiO2 cristobalite (as a model structure for glassy silica). The attempt was made to gain a physical insight into the nature of the extraordinarily high hypersusceptibility of TeO2 glass. A finite field perturbation method implemented in the CRYSTAL code with the "sawtooth" approach was employed. The chi (3) values calculated for alpha-TeO2 were found to be of the same order as that measured for TeO2 glass and much higher than the values computed for alpha-SiO2 which, in turn, were close to that of glassy silica.     

Wavelet bases on a manifold

Using the decomposition method, we present in this paper constructions of multiresolution analyses on a compact Riemannian manifold M of dimension n(n∈N). These analyses are generated by a finite number of basic functions and are adapted to the study of the Sobolev spaces H¹(M) and .     

Crystal chemistry and electronic structure of the metallic lithium ion conductor, LiNiN

The layered ternary nitride LiNiN shows an interesting combination of fast Li+ ion diffusion and metallic behavior, properties which suggest potential applications as an electrode material in lithium ion batteries. A detailed investigation of the structure and properties of LiNiN using powder neutron diffraction, ab initio calculations, SQUID magnetometry, and solid-state NMR is described. Variable-temperature neutron diffraction demonstrates that LiNiN forms a variant of the parent Li3N structure in which Li+ ion vacancies are ordered within the [LiN] planes and with Ni exclusively occupying interlayer positions (at 280 K: hexagonal space group Pm2, a = 3.74304(5) A, c = 3.52542(6) A, Z = 1). Calculations suggest that LiNiN is a one-dimensional metal, as a result of the mixed pi- and sigma-bonding interactions between Ni and N along the c-axis. Solid-state 7Li NMR spectra are consistent with both fast Li+ motion and metallic behavior.     

Fluoroferrate templated with HAmTAZ: X-ray single crystal,thermal behaviour,vibrational study and magnetic characterization

A new metal–organic compound FeF₆(HAmTAZ)₃ which (HAmTAZ = 3-amino-1,2,4-triazole) was hydrothermally synthesized from an equimolar mixture of FeF₂ and FeF₃ with HAmTAZ, aqueous HF and ethanol solvent at 410 K yielded a new hybrid class I fluoroferrate. The structure was characterized by single-crystal X-ray diffraction data. The crystal structure of FeF₆(HAmTAZ)₃ crystallizes in the trigonal system space group R3c with a = b = 12.5230 (6) Å, c = 18.5950 (16) Å, γ = 120° and Z = 6. The structure was built up from isolated octahedral FeF₆ separated by [HAmTAZ]⁺ cations. The thermal analysis has shown that the decomposition undergoes two steps between 475 and 775 K. IR and mass spectrometry have been used to confirm the presence of the organic molecule in the crystal lattice and determine the evacuated vapours during the decomposition, respectively. The magnetization of the title compound has no revealed any ferromagnetic component in the range of magnetic field from ?20 to 20 KOe at room temperature.     

Characterization of Primary Action Mode of Eight Essential Oils and Evaluation of Their Antibacterial Effect against Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli Inoculated in Turkey Meat

The current study aims to evaluate the antimicrobial activity of eight essential oils (EOs) against multidrug-resistant Escherichia coli strains, producing extended-spectrum β-lactamase (ESBL) enzymes and isolated from foods. Disc-diffusion assay showed that the inhibition diameters generated by EOs varied significantly among the tested EOs and strains. In fact, EOs extracted from Thymus capitaus, Eucalyptus camaldulensis, Trachyspermum ammi and Mentha pulegium exerted an important antimicrobial effect against tested strains, with the diameters of inhibition zones varied between 20 and 27 mm. Moreover, minimal inhibition and bactericidal concentration (MIC and MBC) values demonstrated that T. capitatus EOs generate the most important inhibitory effect against E. coli strains, with MIC values ranging from 0.02 to 0.78%. Concerning the mode of action of T. capitatus EO, the obtained data showed that treatment with this EO at its MIC reduced the viability of E. coli strains, their tolerance to NaCl and promoted the loss of 260-nm-absorbing material. In addition, in the presence of T. capitatus EO, cells became disproportionately sensitive to subsequent autolysis. Moreover, the inhibitory effect of T. capitatus was evaluated against two E. coli strains, experimentally inoculated (10⁵ CFU/g) in minced turkey meat, in the presence of two different concentrations of EO (MIC and 2 × MIC), and stored for 15 days. In both samples, EO exerted a bacteriostatic effect in the presence of concentrations equal to MIC. Interestingly, at 2 × CMI concentration, the bactericidal activity was pronounced after 15 days of storage. Our results highlighted that the use of essential oils, specially of T. capitatus, to inhibit or prevent the growth of extended-spectrum β-lactamase (ESBL)-producing E. coli in food, may be a promising alternative to chemicals.     

Hyperbranched aramids by direct polyamidation of two reactant systems: Synthesis and properties

Some A₂ + B₃ and A₃ + B₃ reagent pairs have been used for the direct polyamidation reaction leading, besides the network formation, to hyperbranched aramid structures. Depending on the chosen experimental conditions, variable amounts of a sol fraction having close similarities with the hyperbranched aramid structures derived from the polyamidation of AB₂ monomers, have indeed been obtained. Solubility of the sol fraction in various organic solvents, as well as its thermal properties and its capability of enzyme fixation, have been determined for the various systems under investigation. Future developments are envisaged.     

Synthesis of hyperbranched aromatic polyamides by direct polycondensation

Some hyperbranched aromatic polyamides have been synthesized by direct polycondensation using the modified Higashi's method. Structures of the above polymers have been realized taking in proper account the analogies with amide group sequences of poly(p-phenyleneterephthalamide) (PPDT) and poly(p-benzamide) (PBA). Therefore, AB₂- type monomers as well as suitable combinations of different bi- and trifunctional reactants (AA + B₃) (e.g., p-phenylenediamine + trimesic acid or other trifunctional acids) have been considered. For the latter systems, network formation has been minimized. In the present paper, our results on their direct polyamidation together with some preliminary characterization data on the resultant hyperbranched aramids are given.     

Neuropeptidomics: Comparison of parallel reaction monitoring and data‐independent acquisition for the analysis of neuropeptides using high‐resolution mass spectrometry

Targeted peptide quantitation by mass spectrometry is a rapidly emerging field. Traditionally it relied on the development and validation of multiple reaction monitoring assays that could comply with a high level of sensitivity, specificity, accuracy and reproducibility in complex biological samples. However, with the introduction of high‐resolution mass spectrometers, other acquisition modes could provide more comprehensive datasets for identification and quantification but also for in‐depth data mining. The objective of this study was to evaluate two analytical approaches, parallel‐reaction monitoring (PRM) and data‐independent analysis (DIA) using a hybrid Quadrupole–Orbitrap mass spectrometer for the quantification of neuropeptides in animal spinal cord tissues. Mouse spinal cord tissues were harvested, homogenized and neuropeptides extracted using a C₁₈ solid‐phase extraction protocol. Chromatography was achieved using a Thermo Biobasic C₈ 100 × 1 mm (5 μm) column. The initial mobile phase conditions consisted of acetonitrile and water (both containing 0.1% of formic acid) at a ratio of 5:95. An 11 min linear gradient was applied up to a ratio of 50:50 and maintained for 3 min. The flow rate was fixed at 75 μL/min and 2 μL of sample was injected. Mass spectrometry analyses were performed using a Thermo Q Exactive Plus MS using PRM and DIA approaches. Quantitative data using an isotopic dilution and a label‐free strategy were obtained for both methods and statistically compared. Using both approaches, we were able to clearly detect endogenous neuropeptides. However, with DIA, mass spectra alone could not distinguish Leu‐Enk and Met‐Enk. We used a Bland–Altman plot (Difference plot) to analyze the agreement between both approaches and no systematic bias was observed. Further statistical analyses, including variance analysis, showed more variability in DIA compared with PRM mode. Further analyses were performed using a label‐free approach and confirmed an increase of the variance using a DIA approach.