Synthesis and characterization of polyfunctional crosslinking agents for cyanate resins

An efficient crosslinking monomer for a mixed cyanate/epoxy resin system, bisphenol-A-monocyanate monoglycidyl ether 3 , has been synthesized and characterized. The intermediate compound, the monoglycidyl ether of bisphenol-A 2 , was also isolated and purified by extraction and chromatographic separation using a silica gel column. The cyanate functional group in the crosslinking monomer 3 can be cured easily by heat to form a triazine structure 8 , but the epoxy functional group in the crosslinking monomer 3 can not be cured without affecting the cyanate group because the latter is more reactive both under heat and basic conditions. A practical approach for the application of the crosslinking monomer 3 is discussed and tested. Most interestingly, under heat curing, a very tough and strong resin material was produced from this crosslinking mixed resin mixture. By using a secondary amine, diethylamine, as a curing agent, the cyanate groups in the crosslinking monomer 3 react to form the structures 11 or 12 , depending on the molar ratio of monomer 3 to diethylamine. A bifunctional crosslinking agent for a mixed cyanate (thermoset) and polyolefin (thermoplastic) resin system, 2-allylphenyl cyanate 16 , has also been synthesized and characterized. Like 3 , 2-allylphenyl cyanate 16 easily forms the crosslinking triazine compound 17 upon heating. 17 is a crystalline solid with mp = 110–111°C. As a crosslinking agent, 2-allylphenyl cyanate 16 reacts not only with itself, but also with other cyanates to form heterogeneous triazine rings, exemplified by triazines 18 and 19 . Even though it does not self polymerize through the allyl double bond, it can copolymerize with an other olefinic monomer, such as methyl methacrylate, to form a crosslinked and insoluble polymer. © 1995 John Wiley & Sons, Inc.     

Mitigating Effect of Lindera obtusiloba Blume Extract on Neuroinflammation in Microglial Cells and Scopolamine-Induced Amnesia in Mice

Lindera obtusiloba Blume (family, Lauraceae), native to Northeast Asia, has been used traditionally in the treatment of trauma and neuralgia. In this study, we investigated the neuroinflammatory effect of methanol extract of L. obtusiloba stem (LOS-ME) in a scopolamine-induced amnesia model and lipopolysaccharide (LPS)-stimulated BV2 microglia cells. LOS-ME downregulated the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, inflammatory cytokines, and inhibited the phosphorylation of nuclear factor kappa-B (NF-ĸB) and extracellular signal-regulated kinase (ERK) in LPS-stimulated BV2 cells. Male C57/BL6 mice were orally administered 20 and 200 mg/kg of LOS-ME for one week, and 2 mg/kg of scopolamine was administered intraperitoneally on the 8th day. In vivo behavioral experiments (Y-maze and Morris water maze test) confirmed that LOS-ME alleviated cognitive impairments induced by scopolamine and the amount of iNOS expression decreased in the hippocampus of the mouse brain. Microglial hyper-activation was also reduced by LOS-ME pretreatment. These findings suggest that LOS-ME might have potential in the treatment for cognitive improvement by regulating neuroinflammation.     

The singlet-triplet separation in CF2: state-of-the-art ab initio calculations and Franck-Condon simulations including anharmonicity.

Geometrical parameters, vibrational frequencies and relative electronic energies of the X2B1 state of CF2- and the X1A1 and ?3B1 states of CF2 have been calculated. Core-electron effects on the computed minimum-energy geometries and relative electronic energies have been investigated, and relativistic contributions to the computed relative electronic energies calculated. Potential energy functions of the X2B1 state of CF2- and the X1A1 and ?3B1 states of CF2 have been determined, and anharmonic vibrational wavefunctions of these states calculated variationally. Franck-Condon factors including anharmonicity and Duschinsky rotation have been computed and used to simulate the ?-X emission spectrum of CF2 determined by S. Koda [Chem. Phys. Lett. 1978, 55, 353] and the 364 nm laser photodetachment spectrum of CF2- obtained by R. L. Schwartz et al. [J. Phys. Chem. A 1999, 103, 8213]. Comparison between theory and experiment shows that the theoretical approach benchmarked in the present study is able to give highly reliable positions for the CF2(X1A1) + e <-- CF2-(X2B1) and CF2(?3B1) + e <-- CF2-(X2B1) bands in the photoelectron spectrum of CF2- and a reliable singlet-triplet gap for CF2. It is therefore concluded that the same theoretical approach should give reliable simulated CCl2(X1A1) + e <-- CCl2-(X2B1) and CCl2(?3B1) + e <-- CCl2-(X2B1) bands in the photodetachment spectrum of CCl2- and a reliable singlet-triplet gap for CCl2.     

Water-soluble supramolecular bowls formed by intra-clipping of resorcin[4]arene-based ligands with Pd(II) ions

Bowl-shaped superstructures have been constructed by intra-clipping of resorcin[4]arene derivatives with two equivalents of (en)Pd(NO3)2 in water. The binding phenomena of the aromatic carboxylates were proven to be both enthalpically and entropically favoured.     

Gene silencing by siRNA microhydrogels via polymeric nanoscale condensation

The first attempt to prepare biologically active siRNA-based microhydrogels is reported. The self-assembled microhydrogels were fabricated using sense/antisense complementary hybridization between single-stranded linear and Y-shaped trimeric siRNAs. The siRNA microhydrogels were condensed using a popular cationic polymer such as LPEI to form compact, stable siRNA/polymeric nanoparticles that exhibited superb cellular uptake efficiency and gene silencing activity.     

Indirect conductimetric detection of amino acids after liquid chromatographic separation

A liquid chromatographic method using indirect conductimetric detection is proposed for the determination of low levels of organic compounds, which does not require any special functional characteristics of the analyte. The signal detected is proportional to the molar concentration of the analyte and independent of its nature. The detector response is linearly dependent on analyte concentrations over at least three orders of magnitude. The basis of the detection is to create a conducting background, which will decrease on elution of the organic compounds. The theory of the method is discussed, with special reference to the quantitative displacement of the conducting species of the mobile phase from the column by the analyte on sample injection. The proposed method has been applied to study the chromatographic behaviour of twenty-one amino acids, where a 5 -μm Econosil CN column was used as the stationary phase with a mixture of water-acetonitrile-tetrahydrofuran (70:20:3) containing 1 mM perchloric acid or trichloroacetic acid as the mobile phase. The proposed method allows as little as 10 ng of each amino acid to be determined.     

DFT and ab initio calculations on two reactions between hydrogen atoms and the fire suppressants 2-H heptafluoropropane and CF3Br

Reaction enthalpies and barrier heights of the reactions CF3Br+H-->CF3+HBr {reaction (1)} and CF3CHFCF3+H-->CF3CFCF3+H2 {reaction (2)} have been calculated at the near state-of-the-art ab initio level, and also by employing the B3LYP, BH&HLYP, BB1K, MPW1K, MPWB1K and TPSS1KCIS functionals. In addition, the integrated molecular orbital+molecular orbital (IMOMO) method has been used to study reaction (2). The ab initio benchmark values of the reaction enthalpy (298 K) and barrier height (0 K) of reaction (2) are reported for the first time {-(0.7+/-0.7) and 13.3+/-0.5 kcal/mole respectively}. When density functional theory (DFT) results are compared with ab initio benchmarks for both reactions (1) and (2), the MPWB1K functional is found to have the best performance of the six functionals used. The IMOMO method with the RCCSD/aug-cc-pVTZ and/or RCCSD(T)/aug-cc-pVTZ levels, as the high levels of calculation on the model system, gives reaction enthalpies and barrier heights of reaction (2), which agree with ab initio benchmark values to within 1 kcal/mole. Computed key geometrical parameters and imaginary vibrational frequencies of the transition state structures of reactions (1) and (2) obtained at different levels of calculation are compared. The magnitudes of the computed imaginary vibrational frequencies of the transition states of both reactions considered are found to be very sensitive to the levels of calculation used to obtain them. The heat of formation (298 K) of CF3CFCF3 calculated at the near state-of-the-art level has a value of -(318+/-3) kcal/mole.     

Rapid authentication of Gastrodiae rhizoma by direct ionization mass spectrometry

In this study, direct ionization mass spectrometry (DI-MS) for rapid authentication of Gastrodiae rhizoma (known as Tianma in Chinese), a popular herbal medicine, has been developed. This method is rapid, simple and allows direct generation of characteristic mass spectra from the raw herbal medicines with the application of some solvents and a high voltage. The acquired DI-MS spectra showed that gastrodin, parishin B/parishin C and parishin, the major active components of Gastrodiae rhizoma, could be found only in genuine Gastrodiae rhizoma samples, but not in counterfeit samples, thus allowing rapid authentication of Gastrodiae rhizoma. Moreover, wild and cultivated Gastrodiae rhizoma could be classified and Gastrodiae rhizoma from different geographical locations could be differentiated based on their different intensity ratios of characteristic ions or principal component analysis (PCA). This method is simple, rapid, reproducible, and can be extended to analyze other herbal medicines.