Influence of the network chain orientation on the fracture toughness of a mesogenic epoxy resin modified with CTBN

A biphenol‐type epoxy resin, which had a mesogenic group in the backbone moiety, was modified with carboxy‐terminated butadiene acrylonitrile copolymer (CTBN) as a reactive elastomer, and its fracture toughness was measured. With the addition of CTBN, the fracture toughness of the biphenol‐type epoxy resin significantly increased and became significantly higher than that of a bisphenol A‐type epoxy resin modified with CTBN. The network chain orientation in the cured biphenol‐type epoxy resin system was clearly observed during the fracture process with polarized microscopy Fourier transform infrared measurements, although such a phenomenon was not observed in the bisphenol A‐type epoxy resin system. The high toughness of the cured biphenol‐type system was clearly due to the consumption of the mechanical energy by a large deformation of the matrix resin due to the orientation of the network chains during the fracture process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1198–1209, 2003     

Identification of Shiga toxins in Shiga toxin-producing Escherichia coli using immunoprecipitation and high-performance liquid chromatography-electrospray ionization mass spectrometry

We developed a rapid and reliable identification method for Shiga toxins in Shiga toxin-producing Escherichia coli (STEC) using immunoprecipitation and high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). Polyclonal antisera specific for Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) were raised in rabbits so as to be used for the immunoprecipitation. The immunoprecipitaion was carried out by mixing sample solutions with 50 microl each of the antisera to Stx1 and Stx2 followed by allowing the mixed solutions to stand for 30 min. The quantity required to obtain the immunoprecipitate was more than 0.5 microg of Shiga toxins. HPLC-ESI-MS analysis of the resulting immunoprecipitates provided accurate molecular weight information on Shiga toxins, leading to direct evidence for the presence of these toxins. It requires at most two days to perform our procedure from toxin extraction to measurement of HPLC-ESI-MS whereas the previous method using isolation procedures required about two weeks to complete. The usefulness of the present method has been demonstrated by identifying Stx1, Stx2 and a variant of Stx2 (Stx2e) in the immunoprecipitates prepared from STEC strains.     

Microwave spectroscopic study on the molecular structure and the quadrupole coupling constants of thionyl chloride

Microwave spectra of thionyl chloride, SO³⁵Cl₂ and SO³⁵Cl³⁷Cl, in the frequency range 8–25 GHz have been analyzed. The rotational constants have been obtained from the low J transition frequencies. The r_S coordinates of Cl atoms and the r_o structure have been evaluated with some assumptions: r(S-O) = 1.435 ± 0.011± Å, r(S—Cl) = 2.072 0.005 Å, ∠ OSCl = 108.00 ± 0.06°, ∠ ClSCl = 97.15 ± 0.30°. Nuclear quadrupole coupling constants have been obtained for the SO³⁵Cl₂, species: x_aa = ?25.02 ± 0.04 MHz, x(_bb = ?0.25 ± 0.04 MHz, X_cc = 25.27 ± 0.08 MHz, and X_zz = ?96.75 MHz. The values obtained are compared with those of other workers.     

Umbelliferose Isolated from Cuminum cyminum L. Seeds Inhibits Antigen-Induced Degranulation in Rat Basophilic Leukemia RBL-2H3 Cells

Cuminum cyminum L. (cumin) is an annual plant of the Umbelliferae family native to Egypt. We previously showed that the aqueous extract of cumin seeds suppresses degranulation by downregulating the activation of antigen-induced intracellular signaling molecules in rat basophilic leukemia RBL-2H3 cells. However, the active substances in the extract have not yet been identified. Accordingly, herein, we aimed to ascertain the water-soluble substances present in cumin seeds that inhibit degranulation, which led to the identification of umbelliferose, a characteristic trisaccharide present in plants of the Umbelliferae family. Our study is the first to reveal the degranulation-suppressing activity of umbelliferose, and quantification studies suggest that cumin seed powder contains 1.6% umbelliferose. Raffinose, an isomer of umbelliferose, was also found to significantly suppress antigen-induced degranulation, but less so than umbelliferose. Both umbelliferose and raffinose contain sucrose subunits in their structures, with galactose moieties bound at different sites. These differences in structure suggest that the binding of galactose to the sucrose subunit at the α1-2 bond contributes to its strong degranulation-inhibiting properties.     

Fluorinated and Trifluoromethylated Corannulenes

The syntheses and properties of corannulenes carrying electron‐withdrawing groups (F, CF₃, C₆F₅) are reported. Direct fluorination of corannulene (C₂₀H₁₀) was carried out with xenon difluoride, and the crystal structure of the product was confirmed by the X‐ray analysis. Novel trifluoromethylated corannulenes, including the versatile 4,9‐dibromo‐1,2‐bis(trifluoromethyl)corannulene, were obtained by various established ring‐closing reactions. Besides the use of hexafluorobutyne for the construction of fluoranthenes by Diels–Alder reaction as precursor molecules to form 1,2‐disubstituted corannulenes, bis(pentafluorophenyl)acetylene was employed as dienophile. The molecular structure and crystal packing of a trifluoromethylated corannulene was determined by single‐crystal X‐ray analysis and compared with those known brominated and trifluoromethylated corannulenes. The general electron‐acceptor properties of corannulenes bearing substituents introduced in particular positions by liquid‐phase synthesis are discussed together with published computational results.