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排序方式: 共有196条查询结果,搜索用时 15 毫秒
31.
32.
Yamagami C Hamasaki A Kumagai Y Moritoki T Tanahashi T 《Chemical & pharmaceutical bulletin》2005,53(4):398-401
We recently proposed a new hydrogen-accepting scale, S(HA), on the basis of the heat of formation calculated by the conductor-like screening model (COSMO) method. In this work, the same approach was applied to a series of compounds with a common hydrogen-donor group. Thus the S(HA) values for monosubstituted phenols were calculated and used for correlating their log P(oct) values (P(oct): 1-octanol/water partition coefficient) with log P(CL) (P(CL): chloroform/water partition coefficient) and log P(E) (P(E): butyl ether/water partition coefficient). It was demonstrated that the S(HA) parameter works effectively, providing excellent correlations whose physicochemical meanings are well rationalized in terms of hydrogen-bonding characteristics of the substituents. 相似文献
33.
Hideyuki Toyota Tomonori Sasaki Yoshio Jinbo Naotaka Uchitomi 《Journal of Crystal Growth》2008,310(1):78-82
GaSb/AlGaSb multi-quantum well (MQW) structures with an AlSb initiation layer and a relatively thick GaSb buffer layer grown on Si (0 0 1) substrates were prepared by molecular beam epitaxy (MBE). Transmission electron microscopy (TEM) images and high-resolution X-ray diffraction (XRD) patterns indicated definite MQW structures. The photoluminescence (PL) emission around 1.55 μm wavelength was observed for 10.34 nm GaSb/30 nm Al0.6Ga0.4Sb MQW structure at room temperature. Dependence of PL emission energy on GaSb well width was well explained by finite square well potential model. 相似文献
34.
Hamasaki A Yago T Takamasu T Kido G Wakasa M 《The journal of physical chemistry. B》2008,112(11):3375-3379
The magnetic field effects (MFEs) on photoinduced hydrogen abstraction reactions between benzophenone and thiophenol in an ionic liquid, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl) imide (TMPA TFSI), were studied by a nanosecond laser flash photolysis technique under ultrahigh fields of up to 28 T. Extremely large and anomalous stepwise MFEs were observed for the first time. The escape yield of benzophenone ketyl radical decreased with increasing magnetic field strength (B) at 0 T相似文献
35.
Wada M Yokota C Ogata Y Kuroda N Yamada H Nakashima K 《Analytical and bioanalytical chemistry》2008,391(3):1057-1062
A sensitive high-performance liquid chromatography (HPLC)–fluorescence method for determination of morphine (Mor) in rat brain
and blood microdialysates was developed using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. Mor was labeled with DIB-Cl under mild reaction conditions (at room temperature
for 10 min). The separation of DIB-Mor was carried out on an octadecylsilica (ODS) column with CH3CN/0.1 M acetate buffer (pH 5.4) within 14 min. The detection limits of Mor in brain and blood microdialysates at a signal-to-noise
ratio of 3 were 0.4 and 0.6 ng mL−1, respectively. The proposed method was successfully applied to the preliminarily study of potential pharmacokinetic interaction
between Mor and diclofenac. 相似文献
36.
Ohyama K Oyamada K Kishikawa N Ohba Y Wada M Maki T Nakashima K Kuroda N 《Journal of chromatography. A》2008,1208(1-2):242-245
Three new chiral stationary phases with different lengths of l-phenylalanine peptide were prepared by solid-phase synthesis with tert-butoxycarbonyl (Boc)-l-phenylalanine on silica. The effect of phenylalanine peptide length on enantioselectivity was studied. The best separation of R/S-warfarin was achieved by the chiral stationary phase with intermediate peptide length. These stationary phases were found to exist mainly in alpha-helical conformation by using FT-IR spectra. The end-capping reagents for the N-terminus of the peptide were also evaluated. 相似文献
37.
Hamasaki T Kashiwagi T Imada T Nakamichi N Aramaki S Toh K Morisawa S Shimakoshi H Hisaeda Y Shirahata S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7354-7364
There are few reports on the physiological effects of metal nanoparticles (nps), especially with respect to their functions as scavengers for superoxide anion radical (O2(.-)) and hydroxyl radical (.OH). We tried to detect the scavenging activity of Pt nps using a hypoxanthine-xanthine oxidase system for O2(.-) and using a Fenton and a UV/H2O2 system for .OH. Electron spin resonance analysis revealed that 2 nm particle size Pt nps have the ability to scavenge O2(.-) and .OH. The calculated rate constant for the O2(.-)-scavenging reaction was 5.03 +/- 0.03 x 10(7) M (-1) s (-1). However, the analysis of the Fenton and UV/H 2O 2 system in the presence of Pt nps suggested that the .OH-scavenging reaction cannot be determined in both systems. Among particle sizes tested from 1 to 5 nm, 1 nm Pt nps showed the highest O2(.-)-scavenging ability. Almost no cytotoxicity was observed even after adherent cells (TIG-1, HeLa, HepG2, WI-38, and MRC-5) were exposed to Pt nps at concentrations as high as 50 mg/L. Pt nps scavenged intrinsically generated reactive oxygen species (ROS) in HeLa cells. Additionally, Pt nps significantly reduced the levels of intracellular O2(.-) generated by UVA irradiation and subsequently protected HeLa cells from ROS damage-induced cell death. These findings suggest that Pt nps may be a new type of antioxidant capable of circumventing the paradoxical effects of conventional antioxidants. 相似文献
38.
Naoya Kishikawa Nobuhiro Ohkubo Kaname Ohyama Kenichiro Nakashima Naotaka Kuroda 《Analytical and bioanalytical chemistry》2009,393(4):1337-1343
A sensitive and selective chemiluminescence assay for the determination of quinones was developed. The method was based on
generation of reactive oxygen species through the redox reaction between quinone and dithiothreitol as reductant, and then
the generated reactive oxygen was detected by luminol chemiluminescence. The chemiluminescence was intense, long-lived, and
proportional to quinone concentration. It is concluded that superoxide anion was involved in the proposed chemiluminescence
reaction because the chemiluminescence intensity was decreased only in the presence of superoxide dismutase. Among the tested
quinones, the chemiluminescence was observed from 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 1,4-naphthoquinone, whereas
it was not observed from 9,10-anthraquinone and 1,4-benzoquinone. The chemiluminescence property was greatly different according
to the structure of quinones. The chemiluminescence was also observed for biologically important quinones such as ubiquinone.
Therefore, a simple and rapid assay for ubiquinone in pharmaceutical preparation was developed based on the proposed chemiluminescence
reaction. The detection limit (blank + 3SD) of ubiquinone was 0.05 μM (9 ng/assay) with an analysis time of 30 s per sample.
The developed assay allowed the direct determination of ubiquinone in pharmaceutical preparation without any purification
procedure.
Figure Chemiluminescence generated through the redox cycle of quinone 相似文献
39.
Total synthesis of cytotoxic marine alkaloids, lamellarins D, L, and N, has been achieved by using Hinsberg-type pyrrole synthesis and palladium-catalyzed Suzuki-Miyaura coupling of the 3,4-dihydroxypyrrole bistriflate 6 as the key reactions. The total yields of lamellarins D, L, and N from the common intermediate 6 are 54, 58, and 50%, respectively. 相似文献
40.
Yuka Akimura Toshiki Maruyama Naotaka Yoshinaga Satoshi Chiba 《Acta Physica Hungarica A》2006,27(2-3):355-358
We study the hadron-quark phase transition in a molecular dynamics (MD) of quark degrees of freedom. The hadron state at low density and temperature, and the deconfined quark state at high density and temperature are observed in our model. We investigate the equations of state and draw the phase diagram at wide baryon density and temperature range. We also discuss the transport property, e.g. viscosity, of $q\bar q$ matter. It is found that the ratio of the shear viscosity to the entropy density is less than one for quark matter. 相似文献