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排序方式: 共有427条查询结果,搜索用时 15 毫秒
31.
Masaharu Murata Chifumi Gouda Kentaro Yano Shinichiro Kuroki Tatsuo Suzutani Yoshiki Katayama 《Analytical sciences》2003,19(10):1355-1357
In vitro screening assays are useful techniques for the determination of receptor-mediated activities in environmental samples. In order to define whether environmental chemicals act as an agonist or antagonist to the human estrogen receptor (hER), we have constructed a biosensor based on ligand-inducible interactions between hER and relative proteins on a quartz crystal microbalance (QCM). The his-tagged proteins, which were expressed in E. coli by recombinant DNA technology, were immobilized on an Au-electrode with Ni(II)-mediated chemisorption using the histidine tag and thiol-modified iminodiacetic acid. The resonance-frequency change of the protein-modified electrode was caused by association or dissociation with the hER relative proteins on the surface in the presence of estrogen. These results suggest that this sensor is applicable as a large-scale screening tool for estrogenic compounds. 相似文献
32.
High Intensity Discharge (HID) lamps are difficult to re-ignite rapidly because of the high pressure of metal vapor at high temperatures. We have succeeded in reducing the re-ignition time of high-pressure mercury lamps by using a pre-ionization step where an excess of electrons are generated by UV laser irradiation into the lamp. The effect of changing the laser focal point of the UV laser in the lamp and the position of an auxiliary electrode were also investigated. The time interval for re-ignition was reduced from 230s to 100s by laser irradiation near to the cathode. The results clearly showed that the effect of accelerating the re-ignition time by the pre-ionization step was determined by the behavior of excess electrons generated during the UV laser irradiation. 相似文献
33.
Shinsaku Dobashi Masaharu Kira Ryuichiro Tanaka Yoshinori Izawa Akihide Wada Michikazu Hara 《Analytical sciences》2006,22(4):603-606
The development of molecular spectroscopy has enabled us to select chlorinated aromatic hydrocarbons very rapidly. In particular, the laser ionization TOFMS (time-of-flight mass spectrometry) method is expected to be useful as an on-line, selective, and sensitive method. In the present work, real-time laser ionization TOFMS measurements were carried out on gaseous chlorinated aromatic hydrocarbons. The laser ionization method used resonance-enhanced two-photon ionization with the direct introduction of gas into the vacuum chamber. This method for analyzing aromatic hydrocarbons was developed using a pulsed supersonic molecular beam method. In the context of developing a highly selective and sensitive method, excitation of monochlorinated benzene at lambda = 263.07 nm was found to be effective in the wavelength region from 263 nm to 265 nm. Also the excitation of polychlorinated biphenyls at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. The achievable sensitivity for real-time (1 min) measurements using the laser ionization TOFMS technique was found to be in the ppbV range. 相似文献
34.
35.
Kouji Kuramochi Ryo Takeuchi Masaharu Takemura Kengo Sakaguchi Susumu Kobayashi Fumio Sugawara 《Tetrahedron》2006,62(34):8006-8015
Synthesis of plakevulin A and structure-activity relationships of its related compounds against DNA polymerases is described. We have achieved a total synthesis and revised the structure of plakevulin A. Several analogues including untenone A, manzamenone A, and optically active plakevulin A, were prepared and tested with an enzyme inhibition assay for mammalian DNA polymerases. The effect of the methyl ester moiety, and the substituents at the 1- and 4-positions of plakevulin A on DNA polymerase activities are discussed. 相似文献
36.
We consider parabolic operators of fractional order and their iterates on the upper half space of the euclidean space. We deal with Hilbert spaces of solutions of those parabolic equations. We shall show, in this note, the existence of reproducing kernels and give a formula by using their fundamental solutions. As an application, we also discuss the polyharmonic Bergman spaces and give their reproducing kernels by using the Poisson kernel on the upper half space. 相似文献
37.
Asymmetric Michael reactions of thiols with enones were catalyzed by a Sc(OTf)(3)-chiral bipyridine complex at room temperature in water without using any organic solvents, to afford the desired sulfides in high yields with high enantioselectivities. 相似文献
38.
Bulky tertiary amines, especially dicyclohexylisobutylamine, smoothly reduced α,β-unsaturated ketones in the presence of trichlorosilyl triflate to give the corresponding saturated ketones in excellent yields. Isotope-labeling studies revealed that an α-hydrogen of the amine was transferred to the enones during reduction. 相似文献
39.
Mg isotope fractionation in biogenic carbonates of deep-sea coral, benthic foraminifera, and hermatypic coral 总被引:1,自引:0,他引:1
Yoshimura T Tanimizu M Inoue M Suzuki A Iwasaki N Kawahata H 《Analytical and bioanalytical chemistry》2011,401(9):2755-2769
High-precision Mg isotope measurements by multiple collector inductively coupled plasma mass spectrometry were applied for
determinations of magnesium isotopic fractionation of biogenic calcium carbonates from seawater with a rapid Mg purification
technique. The mean δ26Mg values of scleractinian corals, giant clam, benthic foraminifera, and calcite deep-sea corals were −0.87‰, −2.57‰, −2.34‰,
and −2.43‰, suggesting preferential precipitation of light Mg isotopes to produce carbonate skeleton in biomineralization.
Mg isotope fractionation in deep-sea coral, which has high Mg calcite skeleton, showed a clear temperature (T) dependence from 2.5 °C to 19.5 °C: 1,000 × ln(α) = −2.63 (±0.076) + 0.0138 (±0.0051) × T(R
2 = 0.82, p < 0.01). The δ26Mg values of large benthic foraminifera, which are also composed of a high-Mg calcite skeleton, can be plotted on the same
regression line as that for deep-sea coral. Since the precipitation rates of deep-sea coral and benthic foraminifera are several
orders of magnitude different, the results suggest that kinetic isotope fractionation may not be a major controlling factor
for high-Mg calcite. The Mg isotope fractionation factors and the slope of temperature dependence from deep-sea corals and
benthic foraminifera are similar to that for an inorganically precipitated calcite speleothem. Taking into account element
partitioning and the calcification rate of biogenic CaCO3, the similarity among inorganic minerals, deep-sea corals, and benthic foraminiferas may indicate a strong mineralogical
control on Mg isotope fractionation for high-Mg calcite. On the other hand, δ26Mg in hermatypic corals composed of aragonite has been comparable with previous data on biogenic aragonite of coral, sclerosponges,
and scaphopad, regardless of species differences of samples. 相似文献
40.
Sogawa K Watanabe M Sato K Segawa S Ishii C Miyabe A Murata S Saito T Nomura F 《Analytical and bioanalytical chemistry》2011,400(7):1905-1911
In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic
characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions.
These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming.
In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time
of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples.
Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory
at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were
then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in
the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468),
respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of
bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can
be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined,
and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general,
as well as conventional methods and is a promising technology in clinical laboratories. 相似文献