The effect of electron withdrawing croups on the stability of thiabenzenes

The reactions of p-trifluoromethylphenyllithium with 2,4,6-triarylthiopyrylium perehlorates (Ar = Ph, p-CH₃OC₆H₄, p-NMe₂C₆H₄) have been studied. The initially formed thiabenzenes were not slable enough to he isolated and rearranged readily to their corresponding 4-(p-tri-fluoromethylphenyl)-2,4,6-triarylthiopyrans. The instability of the intermediate thiabenzenes reveals that, in contrast to the stabilization effect of the electron-withdrawing p-chloro- and pentalluorophcnyl groups attached to carbon atoms in sulfur ring, the electron-withdrawing p-lrilluoromethyl group on subsliluenls attached to sulfur decreases the stability of thiabenzenes.     

Synthesis of trimethyl (2S,3R)- and (2R,3R)-[2-H1]-homocitrates and the corresponding dimethyl ester lactones—towards elucidating the stereochemistry of the reaction catalysed by homocitrate synthase and by the Nif-V protein

Trimethyl (2S,3R)- and (2R,3R)-[2-²H₁]-homocitrates, 10b and 10c respectively, and dimethyl (2S,3R)- and (2R,3R)-[2-²H₁]-homocitric lactones, 11b and 11c respectively, have been synthesised from shikimic acid and [2-²H]-shikimic acid by a route which defines the stereochemistry of the two chiral centres in each compound. The NMR spectra of these products will enable the stereochemistry of the biological reaction catalysed by homocitrate synthase and by the protein from the nifV gene to be elucidated.     

Smart Biopolymer-Based Nanocomposite Materials Containing pH-Sensing Colorimetric Indicators for Food Freshness Monitoring

Nanocomposite biopolymer materials containing colorimetric pH-responsive indicators were prepared from gelatin and chitosan nanofibers. Plant-based extracts from barberry and saffron, which both contained anthocyanins, were used as pH indicators. Incorporation of the anthocyanins into the biopolymer films increased their mechanical, water-barrier, and light-screening properties. Infrared spectroscopy and scanning electron microscopy analysis indicated that a uniform biopolymer matrix was formed, with the anthocyanins distributed evenly throughout them. The anthocyanins in the composite films changed color in response to alterations in pH or ammonia gas levels, which was used to monitor changes in the freshness of packaged fish during storage. The anthocyanins also exhibited antioxidant and antimicrobial activity, which meant that they could also be used to slow down the degradation of the fish. Thus, natural anthocyanins could be used as both freshness indicators and preservatives in biopolymer-based nanocomposite packaging materials. These novel materials may therefore be useful alternatives to synthetic plastics for some food packaging applications, thereby improving the environmental friendliness and sustainability of the food supply.     

Novel optical polarizer design based on metasurface nano aperture for biological sensing in mid-infrared regime

Since Metasurfaces are playing important roles in optical devices such as optical polarizers and detectors, in this article, we have proposed a novel shape of nano aperture antenna for mid-infrared applications such as bio-sensing and other potential optical applications based on plasmonic characteristic of the gold layer over the SiN substrate. The transmittance tensor is obtained for vertical and horizontal linear polarization and base on boundary condition of the metasurface, the circular polarizations are extracted which are confirmed by the electric field distributions. We have shown by the parametric studies that the phase difference is altered by the gap and slot width and so with the dimension modification, we are able to achieve circular polarizer in the optical range. The biological materials with a thickness of 80 nm have then been placed over the metasurface layer and the figures of merits have been obtained. We have revealed that when the circular polarization is osculated to the metasurface at a special frequency the linear polarization is obtained in the other side of the metasurface. The nano aperture has been modeled and the finite difference time domain calculations are performed in CST Microwave Studio as a commercial full wave simulation software.     

Quantitative analysis of cement powder by laser induced breakdown spectroscopy

Determination of elemental composition of cement powder plays an important role in the cement and construction industries. In the present paper, Laser induced breakdown spectroscopy (LIBS) is used for measuring the concentration of cement ingredient. Cement powder samples are pressed into pellets. Laser pulses are focused on the surface of pellets. A microplasma is formed in the front of samples. The plasma emission contains information about the elemental composition of the samples. By assumption of local thermodynamic equilibrium (LTE) and using several standard cement samples, a calibration curve is prepared for each element. The major and minor elements of cement such as Ca, Si, K, Mg, Al, Na, Ti, Mn and Sr are qualitatively and quantitatively determined. For verification of LTE conditions, plasma parameters such as plasma electron temperature and electron density are computed. According to the obtained results, the LIBS technique could be a suitable method for determination of elemental composition in the cement production industries.     

Preclinical evaluation of 188 Re-HYNIC-PSMA as a novel therapeutic agent

Journal of Radioanalytical and Nuclear Chemistry - In this study, optimized preparation, quality control, cell assessments and biostribution of 188Re-HYNIC-PSMA in normal rats and tumor bearing...     

Electrochemical "signal-on" reporter for amyloid aggregates

The synthesis and characterization of four new Ferrocene (Fc) bioconjugates, bearing a podant (Lys)-Leu-Val-Phe-Phe motif, namely the hydrophobic sequence of amyloid-β-peptides (Aβ), is reported. The Fc-peptide conjugates are characterized by a reversible redox activity and the ability to undergo hydrophobic and hydrogen bonding interactions. Biomolecular interactions between Fc-bioconjugates with Aβ(12-28) fragments were studied by circular dichroism (CD), transmission electron microscopy (TEM), and electrochemistry. All four Fc-peptides interacted favourable with Aβ(12-28) and prevented fibril formation, the extent of which depended on the length of the peptide and the nature of the C-terminal group. The aggregates obtained for the Aβ(12-28)/Fc-peptide mixtures range from short fibrils to spherical aggregates. We demonstrated that in solution the peptide sequence and peptide charge affect the biomolecular interactions. Fc-peptide interactions with immobilized Aβ(12-28)-Cys films on Au surfaces were detected by measuring the current response of the Fc redox process. The formal redox potential, E(0), at ~440 (10) mV and i(pc)/i(pa) at 0.9 were observed characteristic for the monosubstituted Fc-derivative undergoing a one-electron redox process. On the surface, methyl ester-protected Fc-peptides (1 and 3) interacted only weakly with Aβ(12-28)-Cys films, giving rise to minimal redox activity. In contrast, charged Fc-peptides (2 and 4) gave a significant electrochemical readout following the interaction with Aβ(12-28)-Cys films. Interestingly, the Fc-peptide charge dictates the surface-assisted interactions, while hydrophobic and ionic effects contribute to the overall solution behaviour of the Fc-bioconjugates with Aβ(12-28).     

Synthesis and Characterization of Organosoluble Poly(imide-ether)s with Bulky 2,3-Diaryl Imidazole Moiety: Study Physical,Thermal and Optical Properties

Two new symmetrical diamines were designed and synthesized having different functional groups such as a pair of phenyl ether linkages, 2,3-diaryl substituted imidazole rings and CF₃ groups as pendant, and characterized by FT-IR, ¹H and ¹³C-NMR spectroscopy and elemental analysis. A series of new fluorescent poly(imide-ether)s (PIEs) was prepared by polymerization of the diamines with commercial tetracarboxylic dianhydrides such as pyromellitic dianhydride and 3,3′,4,4′-benzophenone tetracarboxylic dianhydride. The resulting PIEs were amorphous and had intrinsic viscosity [η] in the range of 0.42–0.51 dL/g. The weight average molecular weights (Mw) of these polymers were measured by GPC and were in the range of 28658–35595 g/mol with molecular weight distribution (MWD) of 2.12–2.27. These polymers were readily soluble in a variety of organic solvents and formed low-colored and flexible thin films with cut-off wavelength (λ₀) in the range of 385–420 nm, and all PIEs films exhibited high optical transparency. They also possessed good thermal stability with 10% weight loss temperatures (T_10%) in the range 486–537°C in N₂. The glass transition temperatures (T_g) of PIEs are in the range 251–324°C. These polymers showed fluorescence emission in film and in solution at 459–476 nm with the quantum yields in the range 4–12%.     

Effect of pH on Poly(acrylic acid) Solution Polymerization

The free-radical redox-initiated aqueous solution polymerization of fully and partially neutralized acrylic acid was carried out at room temperature under full exposure to air. The effect of neutralization degree on the polymerization rate and product properties was studied. Increasing neutralization of the reaction mixture with sodium hydroxide resulted in greater conversion of acrylic acid to sodium acrylate. The rate of polymerization, determined from a gravimetric off-line water removal technique, was shown to decrease significantly with decreasing degree of neutralization. Molecular weight also decreased with decreasing degree of neutralization. The glass transition temperature and hydrophilicity of the polymer product decreased with increasing degree of neutralization. In-line infrared monitoring was also used to monitor the reaction progress and was shown to be an effective tool for this purpose.