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排序方式: 共有234条查询结果,搜索用时 15 毫秒
1.
2.
K Sakai Y Miyazaki T Yamane Y Saitoh C Ikawa T Nishihata 《Chemical & pharmaceutical bulletin》1989,37(1):215-217
Some of the Zingiberaceae herbs are known to be useful as stomachics. Water extracts and methanol extracts of eight such herbs were examined in intact unanesthetized rabbits for their effect on gastric secretion. Oral administration of either water extracts or methanol extracts caused a significant decrease in gastric secretion. A significant effect of these extracts appeared at 3 h after administration. The effect of water extracts on gastric secretion was very similar to that of cimetidine, with a significant decrease in acid output. The effect of the methanol extracts was primarily observed as decreased pepsin output. 相似文献
3.
Kenji Tonan Shun-ichi Ikawa 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14):2695-2700
Effect of pressure on conformational equilibria of a small peptide N-acetyl-l-Pro-l-Leu-Gly-NH2 in a chloroform solution has been studied by FTIR spectroscopy. Absorption in the NH stretching region was measured at pressures in the 1–1080 bar range and at 296 K, and decomposed into component bands by least-squares fitting. Intensity ratios of bands which were assigned to a hydrogen-bond-free conformer and intramolecularly hydrogen-bonded conformers with 10- and 13-membered hydrogen bonded rings, respectively, were examined as a function of pressure. It was found that the conformer with the 13-membered ring has definitely smaller partial molar volume than the other two conformers which have nearly the same volume with each other. On the basis of a simple dielectric model, we have shown that the conformer with the 13-membered hydrogen-bonded ring has a considerably large dipole moment which is consistent with the α-helical structure suggested by the previous variable-temperature FTIR study. 相似文献
4.
A palladium-fibroin complex (Pd/Fib) was prepared by soaking silk-fibroin in MeOH solution of Pd(OAc)2 for 2 days (under Ar atmosphere)—4 days (under air). Pd(OAc)2 was gradually absorbed by fibroin and the rapid reduction of fibroin conjugated Pd(OAc)2 proceeded with MeOH as a reductant at room temperature to be the Pd(0) complex. Pd/Fib catalyzed chemoselective hydrogenation of acetylenes, olefins and azides in the presence of aromatic ketones and aldehydes, halides, N-Cbz protective groups and benzyl esters which are readily hydrogenated using Pd/C or Pd/C(en) as a catalyst. 相似文献
5.
6.
Akiko Saito Mana Emoto Akira Tanaka Yuki Doi Kazuaki Shoji Yoshiyuki Mizushina Hiroshi Ikawa Hiromi Yoshida Nobuyasu Matsuura Noriyuki Nakajima 《Tetrahedron》2004,60(52):12043-12049
A simple method for the synthesis of procyanidin B3 substituted with a galloyl group at the 3 and 3″ position is described. Condensation of a benzylated catechin-3-O-gallate electrophile with a nucleophile, catechin and catechin-3-O-gallate, proceeded smoothly and stereoselectively to afford the corresponding dimer gallates, procyanidin B3-3-O-gallate and procyanidin B3-3,3″-di-O-gallate, in good yields. Further, their antioxidant activities on UV-induced lipid peroxide formation, DPPH radical scavenging activity and inhibitory activity of DNA polymerase were also investigated. Among three procyanidin B3 congeners (procyanidin B3, 3-O-gallate and 3,3″-di-O-gallate), the 3,3″-di-O-gallate derivative showed the strongest antioxidant and radical scavenging activity. Interestingly, the 3-O-gallate derivative was the strongest inhibitor of mammalian DNA polymerase with IC50 value of 0.26 μM, although it showed the weakest antioxidant and radical scavenging activity. It became apparent that the presence of a galloyl group at the C-3 position in the proanthocyanidin oligomer was very important for biological activity, however, the antioxidant activity of these compounds was not parallel to the DNA polymerase inhibitory activity. 相似文献
7.
Shimizu H Tada N Ikawa R Kume T Sasaki S 《The journal of physical chemistry. B》2005,109(47):22285-22289
Visual observations through a microscope and in situ Raman measurements have been made for single crystalline ethylene hydrate (EH) and binary methane-ethylene hydrate (MEH) at pressures up to 3.7 GPa and room temperature. Both hydrates showed pressure-induced phase transitions at 1.6, 2.0, and 3.0 GPa for EH and at 1.7, 2.1, and 3.3 GPa for MEH. The cubic sI phase of EH and MEH remains stable up to 1.6 and 1.7 GPa, respectively, which are more widely ranging values than the values for the methane hydrate sI phase. In this sI phase of binary MEH, the cage occupancies by methane and ethylene molecules are investigated from Raman spectra. Above P = 3.0 GPa for EH and 3.3 GPa for MEH, they decomposed by associating with the formation of the polyethylene. 相似文献
8.
[reaction: see text] A selective and catalytic mono-N-alkylation method of both aromatic and aliphatic amines using nitriles as an alkylating agent with Pd/C or Rh/C as a catalyst is described. This method is particularly attractive to provide an environmentally benign and applicable alkylation method of amines without using toxic and corrosive alkylating agents such as alkyl halides and carbonyl compounds. 相似文献
9.
Yoshihiro Itoh Yotaro Morishima Shun-ichi Nozakura 《Photochemistry and photobiology》1984,39(5):603-608
Abstract— Photosensitized reduction of zwitterionic viologen (SPV) and methyl viologen (MV2+ ) was investigated using an amphiliphilic copolymer having phenanthryl and sulfonate groups (APh) as photosensitizer in aqueous solutions. In the presence of triethanolamine the accumulation of SPV * (photoproduct) was found to be faster than that of MV+ . This attributed to the electrostatic repulsion between SPV. and anionic segments of APh. Such difference between SPV and MV2+ was minimized in the case of the related monomer model. Retardation of the back reaction for the APh-SPV system was also demonstrated by laser photolysis, k b = 8.7 × 107 M -1 s-1 for the polymer system as compared to k b = 2.8 × 109 M -1 s-1 for the monomer model system. Strong salt-effects on the yield of the photoreduction and the rate of back reaction confirm the strong electrostatic interaction between the photoproducts and polyanions. This remarkable electrostatic effect of the polyanions was simulated by electrochemical redox reactions by using a graphite electrode coated with APh. 相似文献
10.
Hydrogen bond complex stability between adenine (A) and hydrogen bond equivalents of uracil: 2-pyridone derivatives (UX
X2O) and 3-oxo-1,2,6-thiadiazine-1,1-dioxide derivatives (UX
SO2) was studied, and as the result, the hydrogen bond energy of UX
X2O-A and a complex of UXX
SO2-A, was about 1.5 kcal/mol more stable than that of the corresponding adenine-uracil derivatives complex, respectively. The energy difference between the imide tautomer and enol tautomer was smaller than those of uracil derivatives. UF
SO2 can form a stable complex with A, and its imide tautomer is stable. 相似文献