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排序方式: 共有346条查询结果,搜索用时 31 毫秒
1.
2.
Cytotoxic activity of marine algae and a cytotoxic principle of the brown alga Sargassum tortile. 总被引:1,自引:0,他引:1
A Numata S Kanbara C Takahashi R Fujiki M Yoneda E Fujita Y Nabeshima 《Chemical & pharmaceutical bulletin》1991,39(8):2129-2131
Partition fractions of hexane, CCl4 and CHCl3 from methanolic extracts of marine algae were each examined for cytotoxic activities against cultured P-388 lymphocytic leukemia cells. Cytotoxic activities were found for partition fractions of 21 species of seaweed. Bioactivity-guided fractionation of the CCl4 partition fraction from Sargassum tortile, exhibiting the most prominent activity, afforded dihydroxysargaquinone (1) and sargatriol (2) previously isolated from this alga. The former was evaluated as a cytotoxic principle, and the latter, showing moderate activity, was suggested to be an artifact derived from 1 during the isolation procedure. 相似文献
3.
We prove that the coinvariant ring of the irreducible Coxeter group of type H4 has the strong Lefschetz property. 相似文献
4.
New triterpenes from a Chinese medicine, goreishi 总被引:1,自引:0,他引:1
A Numata C Takahashi T Miyamoto M Yoneda P M Yang 《Chemical & pharmaceutical bulletin》1990,38(4):942-944
Besides serratagenic acid, three new ursane-type triterpenes, named goreishic acids I (1), II (2), and III (3), were isolated from a Chinese medicine, Goreishi (the feces of Trogopterus xanthipes Milne-Edwards). The structures of 1, 2 and 3 were respectively determined as 2 alpha,3 beta-dihydroxyursa-12,18-dien-28-oic acid, 2 alpha,3 beta-dihydroxy-23-norursa-12,18-dien-28-oic acid and 2 alpha,3 beta-dihydroxy-24-norursa-12,18-dien-28-oic acid on the basis of spectroscopic evidence. 相似文献
5.
Toru Egawa Yukari Kachi Tsuguhide Takeshima Hiroshi Takeuchi Shigehiro Konaka 《Journal of Molecular Structure》2003,658(3):241-251
The molecular structure and conformation of carvone, a compound with a minty odor, were investigated by means of gas electron diffraction supported by theoretical calculations. Electron diffraction patterns were recorded by heating the nozzle up to 128 °C to obtain enough scattering intensity. The infrared spectrum was also measured by using an absorption cell with a path length of 10 m. The obtained molecular scattering intensities were analyzed with the aid of theoretical calculations and infrared spectroscopy. It was revealed that the experimental data are well reproduced by assuming that carvone consists of a mixture of three conformers that have the isopropenyl group in the equatorial position and mutually differ in the torsional angle around the single bond connecting the ring and the isopropenyl group. It was also found that the puckering amplitude of the ring of carvone is close to those of menthol and isomenthol, a minty compound and its nonminty isomer. The determined structural parameters (rg and ∠α) of the most abundant conformer of carvone are as follows: 〈r(C-C)〉=1.520(3) Å; 〈r(CC)〉=1.360(5) Å; r(CO)=1.225(5) Å; 〈r(C-H)〉=1.104(4)Å; 〈∠CC-C〉=121.1(5)°; 〈∠C-C-C〉=110.4(5)°; ∠C-CO-C=117.1(14)°; 〈∠C-C-H〉=111.1(13)°. Angle brackets denote average values and parenthesized values are the estimated limits of error (3σ) referring to the last significant digit. 相似文献
6.
Atsushi Ikeda Masaru Kawaguchi Yoshio Suzuki Tsukasa Hatano Munenori Numata Seiji Shinkai Akio Ohta Makoto Ohta 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):163-170
The calixarene-fullerene interaction,which causes only a slight change in the absorptionspectra, has been substantiated by calorimetricmeasurements: the H° values arecomparable with those obtained from the associationconstants estimated by a spectroscopic method. Furthermore, we determined the association constantbetween homooxacalix[3]arene and [60]fullerenederivatives with a porphyrin moiety by fluorescencespectra. 相似文献
7.
Shin-ichi Hirano Toshinobu Yogo Wataru Sakamoto Seiji Yamada Tomoyuki Nakamura Tomoe Yamammto Hiroyuki Ukai Kouichi Banno Tomoko Nakafuku Yukari Ando 《Journal of Sol-Gel Science and Technology》2003,26(1-3):35-41
Nano sized crystalline particles/polymer hybrids were synthesized form designed metal-organic precursors. The newly developed method is composed of the synthesis of organic matrix by polymerization and the in situ nucleation and growth of crystalline oxide particles in the organic matrix below 100°C. The design of metal-organic precursor modified with polymerizable ligand and the selection of reaction conditions does influence the size and crystallinity of ceramic particles in organic matrix. The nano-sized magnetic particle/polymer hybrid exhibits the interesting feature of superparamagnetism and quantum size effect. The crystalline particles of BaTiO3/, PbTiO3/, and KNbO3/polymer hybrids behave to be dielectric and show the typical electro-rheological behavior. 相似文献
8.
Numata M Asai M Kaneko K Bae AH Hasegawa T Sakurai K Shinkai S 《Journal of the American Chemical Society》2005,127(16):5875-5884
We have found that single-chain schizophyllan and curdlan (s-SPG and s-curdlan, respectively) can dissolve as-grown and cut single-walled carbon nanotubes (ag-SWNTs and c-SWNTs, respectively) in aqueous solution. The vis-NIR spectra of the composites suggest that c-SWNTs are dissolved as a bundle, whereas ag-SWNTs exist as one or only a few pieces in the tubular hollow constructed by the helical structure inherent to these beta-1,3-glucans. EDX and CLSM measurements and TEM observation established that the distribution map of these polysaccharides overlaps well with the image of SWNTs, indicating that these two components form a composite. Very interestingly, when c-SWNTs were dissolved with the aid of s-SPG or s-curdlan in water, a clear periodical structure with inclined stripes, as detected by AFM, appeared on the fibrous composite surface. Because this periodical structure has never been recognized for the composites with other water-soluble polymers, one can regard that s-SPG or s-curdlan wraps c-SWNTs constructing a helically twined structure. High-resolution TEM observation of an ag-SWNTs/s-SPG composite gave a clearer image in that two s-SPG chains twine one ag-SWNT and the helical motif is right-handed. When this sample was subjected to the AFM measurement, the composite showed the 2-3 nm height. This height implies that one piece of ag-SWNT is included in the s-SPGs helical structure. As a summary, it has been established that beta-1,3-glucans such as s-SPG and s-curdlan not only dissolve SWNTs but also create a novel superstructure on the surface. 相似文献
9.
A flow-injection system is described for the determination of d-mannitol. Mannitol dehydrogenase is immobilized on poly(vinyl alcohol) beads and packed in a column (5 cm × 4 mm i.d.). The NADH formed is detected fluorimetrically. The response is linear between 5 × 10?7 and 1 × 10?4 M mannitol and the detection limit is 1 × 10?7 M. The throughput is 30 samples per hour. The reactor is stable for at least 8 weeks. 相似文献
10.
The oxygen ions of the β-VOPO4 catalyst were exchanged with an
tracer by a reduction–oxidation method and by a catalytic oxidation of but-1-ene using
2. The bands at 992 and 900 cm−1 were more shifted to lower frequencies than those at 1076 and 1002 cm−1. Applying the correlation between the Raman bands and stretching vibrations in the literature, the exchanged oxygen species were estimated. The results suggest that the P–O–V vacancies corresponding to 992 and 900 cm−1 were responsible for reoxidation and the V=O oxygen corresponding to the 1002 cm−1 band of β-VOPO4 was not. The (VO)2P2O7 was oxidized to β-VOPO4 by O2 above 823 K. The insertion position of oxygen was determined at the bands at 992 and 900 cm−1 of β-VOPO4 using
2, which is the same as the exchanged position. 相似文献