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排序方式: 共有196条查询结果,搜索用时 31 毫秒
21.
Toshiki Yasokawa Ichirou Ishimaru Masahiro Kondo Shigeki Kuriyama Tsutomu Masaki Kaoru Takegawa Naotaka Tanaka 《Optical Review》2007,14(4):161-164
This paper describes a method for measuring the three-dimensional (3D) refractive-index distribution in a single cell. The
method can be used to observe the distribution of cell components without fluorescence staining. The two-dimensional optical
path length distributions from multiple directions are obtained by non-contact rotation of the cell. These optical path lengths
are converted into the line integrals of the refractive index, and the 3D refractive-index distribution is reconstructed by
means of computed tomography. The refractive-index distribution in a breast cancer cell can be measured using a phase-shifting
Mach—Zehnder interferometer in conjunction with proximal two-beam optical tweezers. 相似文献
22.
Mitsuhiro Wada Chieko Morinaka Toshihiko Ikenaga Naotaka Kuroda Kenichiro Nakashima 《Analytical sciences》2002,18(6):631-634
An HPLC method with fluorescence detection for the determination of nitric oxide (NO) in cultivated plant cells (Agave pacifica, Agavaceae) was developed. NO was derivatized in situ with 2,3-diaminonaphthalene (DAN) as a labeling reagent and converted to 1(H)-naphthotriazole. The maximum peak height of the derivative was observed by incubation for 3 h at 25 degrees C with 0.2 mM DAN. Excess reagent in cells was removed by washing 3 times with 5 ml of water. The calibration curve for authentic standard of DAN-NO spiked to cultivated plant cells showed a good linearity (r = 0.995) in the range of 5.0 to 50 pmol/g cell. The detection limit at a signal-to-noise ratio of 3 was 3.4 pmol/g cells. The proposed method was successfully applied to the monitoring of NO concentration with cell growth. The effect of thermal treatment on the concentration of NO in plant cells was also examined. The concentration of NO in cells treated at 5 degrees C for 1 h was significantly higher than that treated at 25 degrees C and 35 degrees C for 1 h (n = 3, p < 0.05). 相似文献
23.
Evaluation of chemiluminescence reagents for selective detection of reactive oxygen species 总被引:2,自引:0,他引:2
Shinya Yamaguchi Kaname Ohyama Maiko Kohno Akira Takadate Naotaka Kuroda 《Analytica chimica acta》2010,665(1):74-27
In order to evaluate the chemiluminescence (CL) reagents for selective detection of reactive oxygen species (ROS), we comprehensively measured the CL responses of 20 CL reagents (three luminol derivatives, two imidazopyrazinone derivatives, eight lophine derivatives, six acridinium ester derivatives and lucigenin) against six types of ROS (superoxide anion: O2−, hydroxyl radical: OH, hydrogen peroxide: H2O2, hypochlorite anion: ClO−, singlet oxygen: 1O2, and nitric oxide: NO). As a result of the screening, it was found that nine CL reagents selectively detected O2− while one CL reagent selectively detected OH. However, no CL reagent had selectivity on the detection of H2O2, ClO−, 1O2 and NO. Our screening results could help to select the most suitable CL reagent for selective determination of different ROS.As an application study, 4-methoxyphenyl-10-methylacridinium-9-carboxylate (MMAC), one of the acridinium ester derivatives, showed high selectivity on the detection of O2−, and thus was applied to the assay of superoxide dismutase (SOD) activity. The dynamic range and detection limit of the developed CL assay were 0.1-10 and 0.06 U mL−1, respectively. Significant correlation (r = 0.997) was observed between the results by the CL assay using MMAC and the spectrophotometric assay using 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt. 相似文献
24.
Akiyuki Hamasaki Akiko Muto Shingo Haraguchi Xiaohao Liu Takanori Sakakibara Takushi Yokoyama Makoto Tokunaga 《Tetrahedron letters》2011,52(51):6869-6872
A treatment of cobalt oxide supported gold nanoparticles (Au/Co3O4) under syngas atmosphere effectively generated a cobalt carbonyl-like active species in the reaction vessel. The preparation of Au/Co3O4 was quite simple and the in situ generated cobalt species could be used as a stable and easy handling alternative for dicobalt octacarbonyl without bothersome purification prior to use. The reactions, which are sensitive to the purity of the dicobalt octacarbonyl, such as the alkoxycarbonylation of epoxides and the Pauson-Khand reaction, smoothly progressed with Au/Co3O4. 相似文献
25.
Fujii S Mochizuki M Aono K Hamasaki S Murakami R Nakamura Y 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):12902-12909
Polystyrene (PS) latex particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) hair (PDEA-PS particles) were synthesized by dispersion polymerization and characterized in terms of diameter, diameter distribution, morphology, chemical composition, surface chemistry, and pH-response using scanning electron microscopy (SEM), elemental microanalysis, (1)H nuclear magnetic resonance spectroscopy, the laser diffraction method, and zeta potential measurements. The hairy particles can act as pH-responsive stabilizers of aqueous foams by adsorption at the air-water surface. Above pH 8.0, where particles have nonprotonated PDEA hair, which is relatively hydrophobic, particle-stabilized foams are stable for at least 1 month. Optical microscopy and SEM confirmed that flocculated PDEA-PS latex particles were adsorbed at the air-water interface and stabilized the aqueous foams. At pH 6.1 and 7.1, relatively stable foams can be prepared that remain stable for at least 24 h. SEM studies indicated that the PDEA-PS particles were adsorbed at the air-water interface as a monolayer at pH 6.1. At pH 5.1 and 3.1, where the particles have cationic water-soluble PDEA hairs with hydrophilic character, no foam was formed. Rapid defoamation can be induced by lowering the solution pH; the addition of acid caused the in situ protonation of 2-(diethylamino)ethyl methacrylate residues, which impart water-soluble hydrophilic character to the PDEA hair, and the PDEA-PS particles desorbed from the air-water interface. The foaming and defoaming cycles could be repeated at least five times. 相似文献
26.
Vitamin K is a fat-soluble vitamin involved in blood coagulation and bone metabolism. The detection and monitoring of vitamin K homologues in rheumatoid arthritis (RA) patients is a challenging problem due to the smaller concentrations of vitamin K and the presence of several interfering medications. Therefore, this study aimed to develop a new highly sensitive and selective chemiluminescence (CL) method designated to quantify vitamin K homologues in plasma of RA patients including phylloquinone (PK, vitamin K1), menaquinone-4 (MK-4, vitamin K2) and menaquinone-7 (MK-7, vitamin K2). The method was based on the unique photochemical properties of vitamin K homologues that were exploited for selective luminol CL reaction. The correlation coefficients of 0.998 or more were obtained in the concentration ranges of 0.1-100 ng mL−1 vitamin K homologues. The detection limits were 0.03-0.1 ng mL−1 in human plasma for vitamin K homologues. The developed HPLC-CL system was successfully applied for selective determination of vitamin K homologues in plasma of RA patients. The developed method may provide a useful tool for monitoring vitamin K homologues in different clinical studies such as RA, osteoporosis and hepatocellular carcinoma in which vitamin K is intervented. 相似文献
27.
Ichikawa T Yoshio M Hamasaki A Kagimoto J Ohno H Kato T 《Journal of the American Chemical Society》2011,133(7):2163-2169
Thermotropic bicontinuous cubic (Cub(bi)) liquid-crystalline (LC) compounds based on a polymerizable ammonium moiety complexed with a lithium salt have been designed to obtain lithium ion-conductive all solid polymeric films having 3D interconnected ionic channels. The monomer shows a Cub(bi) phase from -5 to 19 °C on heating. The complexes retain the ability to form the Cub(bi) LC phase. They also form hexagonal columnar (Col(h)) LC phases at temperatures higher than those of the Cub(bi) phases. The complex of the monomer and LiBF(4) at the molar ratio of 4:1 exhibits the Cub(bi) and Col(h) phases between -6 to 19 °C and 19 to 56 °C, respectively, on heating. The Cub(bi) LC structure formed by the complex has been successfully preserved by in situ photopolymerization through UV irradiation in the presence of a photoinitiator. The resultant nanostructured film is optically transparent and free-standing. The X-ray analysis of the film confirms the preservation of the self-assembled nanostructure. The polymer film with the Cub(bi) LC nanostructure exhibits higher ionic conductivities than the polymer films obtained by photopolymerization of the complex in the Col(h) and isotropic phases. It is found that the 3D interconnected ionic channels derived from the Cub(bi) phase function as efficient ion-conductive pathways. 相似文献
28.
Kaname Ohyama Kana Oyamada Naoya Kishikawa Mitsuhiro Wada Yoshihito Ohba Kenichiro Nakashima Naotaka Kuroda 《Chromatographia》2011,74(5-6):467-470
Characteristics of the chiral stationary phase with poly(l-phenylalanine) peptide selector, which was in ??-helical state, was reported. Since environmental factors affect peptide conformation, the changes in enantioselectivity were examined depending on column temperature and mobile phase conditions (ionic strength, pH, mobile phase composition). Column temperature and pH drastically affected the enantioselectivity. Based on these changes, the relation between chiral recognition and secondary structure of the peptide selector was discussed. The column stability during sequential analysis under different separation conditions was also evaluated. 相似文献
29.
Takuo Okuchi Naotaka Tomioka Narangoo Purevjav Jun Abe Stefanus Harjo Wu Gong 《高压研究》2013,33(2):273-280
Neutron powder diffraction measurements of 0.9 mm3 of mixture of deuterated brucite and pressure medium were conducted at pressures to 2.8 GPa, using an opposed anvil cell and a medium-resolution diffractometer at Japan Proton Accelerator Research Complex pulsed neutron source. Spurious-free diffraction patterns were successfully obtained and refined to provide all structural parameters including Debye–Waller factors. Tilting of hydroxyl dipoles of brucite toward one of the three nearest-neighbor oxygen anions was confirmed to be substantial at pressure as low as 1.5 GPa. By this application, technical feasibility to analyze such a small sample has been newly established, which would be useful to extend the applications of neutron diffraction at high pressures. 相似文献
30.