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81.
82.
The surface states of ganglioside GM1 (GM1)/dipalmitoylphosphatidylcholine (DPPC)/dioleoylphosphatidylcholine (DOPC) monolayers having various compositions were investigated using atomic force microscopy (AFM), and the effect of the composition on the surface states of the membrane was examined. The AFM images for the ternary system showed a DPPC-rich phase containing GM1 in the DOPC matrix, which indicated that the morphology varied as the composition of the monolayers changed. The AFM images for the GM1/DPPC/DOPC monolayers having (2:9:9) and (4:18:9) molar ratios showed a percolation pattern similar to that observed for the GM1/DPPC (1:9) monolayer. The AFM image for the GM1/DPPC/DOPC (2:18:9) monolayer showed a dotted pattern with a high topography. Monolayers having a higher content of DOPC than DPPC and/or having a higher content of GM1 showed dot-like domains in the DPPC-rich phase containing GM1. In conclusion, the surface states of GM1/DPPC/DOPC monolayers changed depending on the composition. These results may be related to a diversity of GM1 in various organs. 相似文献
83.
Ismail IS Ito H Hatano T Taniguchi S Yoshida T 《Chemical & pharmaceutical bulletin》2004,52(9):1145-1147
Two new additional trijugin-type limonoids, sandrapins D (4) and E (5), which are analogues of the previously reported sandrapins A-C (1-3), were isolated as minor components from the leaves of Sandoricum koetjape (Meliaceae), and their structures were elucidated on the basis of MS and NMR spectral data. 相似文献
84.
Yumiko Ohta Shoko Yokoyama Hideki Sakai Masahiko Abe 《Colloids and surfaces. B, Biointerfaces》2004,33(3-4):191-197
The interaction between ganglioside GM1 (GM1) and
--dipalmitoylphosphatidylcholine (DPPC) in mixed monolayers was investigated using surface pressure measurements and atomic force microscopy (AFM), and the effects of GM1, surface pressure and temperature on the properties of the membranes were examined. Mixed GM1/DPPC monolayers were deposited on mica using the Langmuir–Blodgett (LB) technique for AFM. GM1 and DPPC were miscible below the 0.2 mole fraction of GM1 and there was attractive interaction between GM1 and DPPC. The AFM images for the GM1/DPPC monolayers (XGM1 < 0.2) at 30 mN m−1 and 25 °C indicated a percolation pattern which means a micro phase separation: namely, the mixed film composed of GM1 and DPPC phase-separated from the DPPC liquid-condensed film. The AFM images for the mixed monolayers at 33 mN m−1 indicated a specific morphology when the surface pressure was varied from 30 to 40 mN m−1. The percolation pattern in the AFM image at 25 °C came to be destroyed with increasing temperature and completely disappeared at 45 °C. The change in the morphology of mixed GM1/DPPC monolayers on varying the surface pressure and temperature is thought to be related to signal transduction and a preventive mechanism against viral infections in the human body. 相似文献
85.
Takanori Suzuki Shoko Tanaka Hiroki Higuchi Hidetoshi Kawai Kenshu Fujiwara 《Tetrahedron letters》2004,45(46):8563-8567
The long C-C bonds (1.614(2)-1.630(2) Å) in newly prepared title donors 2-6 are cleaved upon two-electron oxidation to afford the bond-dissociated dicationic dyes 22+-62+, whose electron affinities are stronger than the corresponding biphenyl-2,2′-diyl dications 12+ due to the spatial proximity of two xanthenylium units. Not only UV-vis but also fluorescence spectra changed drastically upon electrolysis since only colorless neutral donors are fluorescent. 相似文献
86.
The ring-cleavage reactions of a series of benzocycloalkenes were studied using an ArF excimer laser. Product formation was significantly suppressed in the presence of nitrogen; therefore, the presence of vibrationally excited states (hot molecules), as intermediates, was indicated. The product of highly strained benzocyclobutene was linearly proportional to the laser fluence, whereas those of benzocyclopentene and benzocyclohexene were proportional to the square of the laser fluence in the presence of nitrogen. These phenomena cannot be understood as photochemical bond cleavage in the electronic excited state, but instead appear to be the result of single- and two-photon reactions of hot molecules. The dissociation rate constants were evaluated by a statistical rate theory under the assumption that the reaction occurred from the hot molecule. The reaction rate of highly strained benzocyclobutene was predicted to be faster than the collisional rate with foreign gas, even if it had vibrational energy equivalent to one photon; however, the reaction rates of less strained benzocyclohexene were expected to compete with the collisional rate when the vibrational energy was equivalent to two photons. Benzocyclopentene was an intermediate case and showed both single- and two-photon reactions. The dissociation rate constant of 1.4 x 10(6) s(-1) was successfully obtained from benzocyclopentene under collision-free conditions. This value was in fair agreement with the calculated value. The different dissociation rate constants of the molecules were well-explained in terms of the strain energy. Although the strain energy varies in a wide range (10-130 kJ mol(-1)), the simple model of the calculations reproduced the observed values of the CH2-CH2 bond dissociation in strained benzocycloalkenes. 相似文献
87.
Yamazaki S Morikawa S Iwata Y Yamamoto M Kuramoto K 《Organic & biomolecular chemistry》2004,2(21):3134-3138
A novel cyclization reaction of ethenetricarboxylate derivative aromatic compounds in the presence of various Lewis acids gave benzo-annulated cyclic compounds such as oxindole and benzofuran derivatives via Friedel-Crafts intramolecular Michael addition in high yields. For example, the reaction of diethyl 2-[(N-methyl-N-phenylcarbamoyl)methylene]malonate (1a) in the presence of ZnCl2 at room temperature gave diethyl 2-(1-methyl-2-oxoindolin-3-yl)malonate (2a) in 98% yield. The reactions also proceeded with a catalytic amount of a Lewis acid such as AlCl3, ZnCl2, ZnBr2, Sc(OTf)3, or InBr3. 相似文献
88.
Sakamoto R Murata M Kume S Sampei H Sugimoto M Nishihara H 《Chemical communications (Cambridge, England)》2005,(9):1215-1217
A new platinum complex with both an azo-bound dithiolato ligand and an azobenzene-bound bipyridine ligand exhibits tristability reversibly controllable using different energy lights. 相似文献
89.
Hydrogen dynamics in one-dimensional hydrogen bonded organic antiferroelectric, co-crystal of 5,5’-dimethyl-2,2’-bipyridine (55DMBP) and chloranilic acid (H2ca), was investigated by use of 2H high resolution solid-state NMR. The two types of hydrogen bonds O-H …N and N+-H …O? in the antiferroelectric phase were clearly observed as the splitting of the side band of the 2H MAS NMR spectra of the acid-proton deuterated compound 55DMBP-D 2ca. The temperature dependence of the spin-lattice relaxation time was measured of the N+-H and O-H deuterons, respectively. It was suggested that the motion of the O-H deuteron is already in the antiferroelectric phase in the fast-motion regime in the NMR time scale, while that of the N+-H deuteron is a slow motion. In the high-temperature paraelectric phase, the both deuterons become equivalent and the fast motion of the deuterons in the NMR time scale is taking place with the activation energy of 7.9 kJ mol?1. 相似文献
90.
A nitrogen-directed regioselective homocoupling reaction of aromatic compounds has been found to be catalyzed by a ruthenium complex in the presence of methallyl acetate as a hydrogen scavenger. 相似文献