Nanostructured titanate materials with different morphologies,
including layered materials, nanosheets, and nanotubes, were examined
as solid acid catalysts to elucidate the relationship between the
structure and the catalytic properties. The titanate nanotube consists
of a scroll-like layered structure derived from lamellar titanate
nanosheets that exhibits excellent catalytic performance for the Friedel–Crafts
alkylation of toluene with benzyl chloride near room temperature,
exceeding the activities of layered titanates (H2Ti3O7, H0.7Ti1.825□0.175O4·H2O) and nanosheets that
have similar crystal structures to that of the titanate nanotubes.
Fourier transform infrared (FT-IR) spectroscopy and 31P
magic angle spinning nuclear magnetic resonance (31P MAS
NMR) spectroscopy using basic probe molecules have revealed that these
titanate materials possess both Brønsted and Lewis acid sites,
and the Brønsted acid strength of the titanate nanotubes is higher
than that of the titanate nanosheets. The strong Brønsted acidity
of the titanate nanotubes is attributed to lattice distortion due
to scrolling of the lamellar titanate nanosheet, which is evidenced
by Raman spectroscopy and density functional theory calculations.
Furthermore, the mesoporous structure of the titanate nanotubes is
advantageous for acid catalysis, because the reactant molecules are
confined within the nanotubes.
The ion association reaction between aromatic anions and quaternary ammonium ions in aqueous solutions was investigated through mobility changes in capillary electrophoresis. The electrophoretic mobility of aromatic anions decreased with increasing amount of quaternary ammonium salt added to the migrating solutions. The change in mobility of anions due to the ion association was found and was treated with a least-squares method, giving ion association constants. The ion associability order of the isomers of aromatic anions was found to be naphthalene-2,6-dicarboxylate > naphthalene-2,3-dicarboxylate, naphthalene-2-sulfonate > naphthalene-1-sulfonate and terephthalate > isophthalate > phthalate. The order of the ion associability of naphthalene-1,5-and -2,6-disulfonate reversed depending on the alkyl chain length of the pairing cation. The order of ion associability of quaternary ammonium ions was found to be tetraamylammonium > tetrabutylammonium > tetrapropylammonium ≈ octyltrimethylammonium ≈ hexyltrimethylammonium > tetraethylammonium > tetramethylammonium, and suggested that ion association in aqueous solution was governed by the hydrophobicity of the pairing cation.
Cross-allergenicity between five cereal grains including rice, wheat, corn, Japanese millet (Panicum crus-galli L. var. frumentaceum Trin.) and Italian millet (Setaria italica Beauv. var. germanica schrad.) was examined by radioallergosorbent test (RAST) and RAST inhibition assay. There were significant close correlations between every combinations of RAST values for the five cereal grain extracts. RAST inhibition assay of each extract against RAST discs coupled with other cereal grain extracts indicated marked cross-reactivity of IgE binding between these cereal grain extracts. Rice protein 16KD (RP16KD) was shown to be one of major allergens in rice grain extracts by immunoblotting analysis, histamine release assay from human leukocytes and RAST inhibition. Next, the involvement of RP16KD in the cross-allergenicity between these cereals was investigated. RAST values for RP16KD significantly correlated with that for Italian millet as well as rice but not with those for corn and wheat. There was a trend of positive correlation between RAST values for RP16KD and Japanese millet. In the RAST inhibition assay using sera with positive RAST for these five cereal grain extracts and RP16KD, RP16KD inhibited IgE binding to these all cereal discs in a dose-dependent manner. Similarly, all of the five cereal grain extracts showed an effective decrease in IgE binding to the RP16KD disc. These results indicated possible participation of IgE binding structure on RP16KD in cross-allergenicity between these cereal grain extracts in the Poaceae family.
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