Catalytic and stereoselective glycosylations using glycosyl fluorides are described: 1) activation of armed glycosyl fluorides by trityl tetrakis(pentafluorophenyl)borate [TrB(C6F5)4] catalyst in trifluoromethylbenzene (BTF)-pivalonitrile ('BuCN)(5:1) to afford the corresponding disaccharides in high yields with good to high β-stereoselectivity; 2) activation of disarmed glycosyl fluorides by the combined use of silver tetrakis(pentafluorophenyl)borate [AgB(C6F5)4] and stannous chloride (SnCl2) or stannic chloride (SnCl4); and 3) selective α or β glycosylation using glycosyl fluoride by an appropriate choice of erotic acid catalysts and solvents. Also, the effect of counter anions of erotic acid catalysts on controlling the stereo-selectivities of glycosylation is newly noted. Finally, efficient one-pot sequential syntheses of trisaccharide, F1α antigen, and branched heptasaccharide are demonstrated.
An analytical expression for the orbit of a dust particle ejected from a comet is derived as the two-body problem by including solar radiation pressure effects. Then deviations of the semi-major axis, the eccentricity and the epoch of the perihelion passage of the particle from those of the comet are expressed as functions of a parameter depending on the ejection velocity, the size of the particle and the true anomaly at the ejection point. Furthermore, numerical values are computed for comet 55P/Tempel-Tuttle which has produced Leonid meteor showers. Finally, perturbations due to Jupiter, Saturn and Uranus are roughly computed and an idea to predict meteor showers is proposed.
U1B3.3 monoclonal antibody (mAb) was established by immunizing a rat with the tMK-2U lymphoma cell line, derived from athymic nude mice. U1B3.3 mAb recognizes some T cell populations, B cells and natural killer (NK) cells. U1B3.3+ T cells express CD3/T cell receptor (TCR) complex at a unique intensity: between that of TCR-intermediate cells (TCRint cells) and TCRbright cells. TCRint cells strongly express the interleukin-2 receptor β chain (IL-2Rβ), but almost all U1B3.3+ T cells express high or low levels of IL-2Rβ. When purified U1B3.3+ NK1.1-T cells were cultured with IL-2, approximately 14% of the cells acquired expression of NK1.1 molecules, which are expressed on NK cells and natural killer T (NKT) cells. Furthermore, U1B3.3+ NK1.1-T cells killed tumor cells after culture with IL-2. These results indicate that U1B3.3 mAb recognizes a precursor of NK1.1+ cytotoxic T cells generated by IL-2.