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221.
Mitamura K Sakai T Nakai R Wakamiya T Iida T Hofmann AF Ikegawa S 《Analytical and bioanalytical chemistry》2011,400(7):2061-2072
Previous work from this laboratory has reported the chemical synthesis of N-acetylcysteine (NAC) conjugates of natural bile acids (BAs) and shown that such novel conjugates can be formed in vivo in
rats to which NAC has been administered. The subsequent fate of such novel conjugates is not known. One possible biotransformation
is sulfation, a major pathway for BAs N-acylamidates in patients with cholestatic liver disease. Here, we report the chemical synthesis of the 3-sulfates of the
S-acyl NAC conjugates of five natural BAs (cholic, chenodeoxycholic, deoxycholic, ursodeoxycholic, and lithocholic). We also
measured the sulfation of N-acetylcysteine–natural bile acid (BA-NAC) conjugates when they were incubated with a rat liver cytosolic fraction. The chemical
structures of the BA-NAC 3-sulfates were confirmed by proton nuclear magnetic resonance, as well as by means of electrospray
ionization-linear ion trap mass spectrometry with negative-ion detection. Upon collision-induced dissociation of singly and
doubly charged deprotonated molecules, structurally informative product ions were observed. Using a triple-stage quadrupole
instrument, selected reaction monitoring analyses by monitoring characteristic transition ions allowed the achievement of
a highly sensitive and specific assay. When BA-NACs were incubated with a rat liver cytosolic fraction to which 3’-phosphoadenosine
5’-phosphosulfate was added, sulfation occurred, but the dominant reaction was hydrolysis of the S-acyl linkage to form the unconjugated BAs. Subsequent sulfation occurred at C-3 on the unconjugated BAs that had been formed
from the BA-NACs. Such sulfation was proportional to the hydrophobicity of the unconjugated bile acid. Thus, NAC conjugates
of BAs as well as their C-3 sulfates if formed in vivo are rapidly hydrolyzed by cytosolic enzymes. 相似文献
222.
Shigeo Kawai 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(6):2284-2295
In this paper, we consider a functional on the space of maps between Riemannian manifolds, and give some results for its stationary maps. 相似文献
223.
Hyoe Takata Tatsuo Aono Keiko Tagami Shigeo Uchida 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):795-799
For safety assessments of geological repositories of nuclear waste, understanding of uranium (U) fate in estuarine areas is
important because U chemical behavior in the areas is expected to be complex. Environmental transfer parameters such as sediment–water
distribution coefficients (K
d) and concentration ratios (CRs) for marine organisms are useful in mathematical models for the assessment. However, due to
its low concentration in estuarine water, K
d and CF data for U are scarce. Thus we studied a rapid method for separation and concentration of U from estuarine water samples
using NOBIAS-CHELATE PA1 resin columns followed by inductively coupled plasma mass spectrometry (ICP-MS) for U measurement.
Chemical recovery was about 100% at pH of 5.7 ± 0.1 from the water samples and alkali and alkaline earth metals were removed.
The method was used to measure U concentrations in estuarine water samples collected at eight Japanese estuarine areas; they
ranged from 0.1 to 3.8 μg L−1. We also measured U concentrations in sediment and marine organism samples by ICP-MS after acid digestion. Using these values,
we observed K
d (range: 39–284 L kg−1) and CRs (0.86–52 L kg−1 for macroalgae, 0.087–15 L kg−1 for crustaceans, and 0.52–93 L kg−1 for molluscs). 相似文献
224.
Jian Zheng Hyoe Takata Keiko Tagami Tatsuo Aono Kazuhiro Fujita Shigeo Uchida 《Microchemical Journal》2012
A simple and rapid analytical method to measure total iodine in seawater using sector-filed ICP-MS is presented here. The new method avoided tedious and complicated organic iodine decomposing and redox treatment. In addition, no pre-concentration and separation operations are needed. The seawater was diluted 100-fold with 0.5% TMAH prior to SF-ICP-MS analysis. Te was added as internal standard. Due to the high sensitivity of SF-ICP-MS, excellent detection limit of 0.23 ng ml? 1 in original seawater was obtained. By applying this newly developed method, for the first time, the total iodine concentrations in Japanese coastal seawaters in 14 estuaries were investigated. An average value of 58.26 ± 6.30 ng ml? 1 (n = 59) for total iodine concentration was obtained for future study on the estimation of sediment–water distribution coefficients and the concentration ratios from water to organisms in Japanese coastal marine environment. 相似文献
225.
Yuya Maekawa Taku Sakaguchi Hiroshi Tsuchikawa Shigeo Katsumura 《Tetrahedron letters》2012,53(7):837-841
The thermal 6-endo cyclization of N-sulfonyl-2,4-dienamide compounds to produce 4,6-disubstituted 2-piperidinone is described. The observed remarkable substituent effect due to the N-sulfonyl and C3 ethoxycarbonyl groups for acceleration of this 6-endo cyclization strongly suggests that the reaction would proceed via the 6π-azaelectrocyclization of the intermediary imidic acid. On the contrary, the corresponding 5-formyl and 5-acetyl derivatives rapidly cyclized at room temperature to produce the 5-exo cyclized products. 相似文献
226.
Kajikawa T Okumura S Iwashita T Kosumi D Hashimoto H Katsumura S 《Organic letters》2012,14(3):808-811
Fucoxanthin exhibits high energy transfer efficiencies to Chlorophyll a (Chl a) in photosynthesis in the sea. In order to reveal how each characteristic functional group, such as the length of the polyene chain, allene, and conjugated carbonyl groups, of this marine natural product are responsible for its remarkably efficient ability, the total synthesis of fucoxanthin by controlling the stereochemistry was achieved. The method established for fucoxanthin synthesis was successfully applied to the synthesis of the C42 longer chain analogue. 相似文献
227.
Speckle is a random distribution of a radiant power density or an irradiance on the observation plane (retina of observers in the laser display) due to the interference of randomly phase-modulated wavefronts. Since a color is synthesized by the superposition of red-green-blue (RGB) primary-color lasers in laser displays, if the speckle patterns of RGB lasers are uncorrelated with each other, then the fluctuation in radiant power density results in a change in color received by the observer. We name this random distribution of color “color speckle”. The distribution of color on the xy chromaticity diagram is investigated for speckle patterns of various speckle contrasts. We demonstrate a numerical simulation of color speckle. Then, we derive the theoretical expressions of the variance and covariance of the distribution of xy chromaticity under the assumption of low speckle contrast. 相似文献
228.
Yasushi?TomitaEmail author Koji?Suzuki Tatsuo?Fukui Hironori?Tokita Shigeo?Kubota 《Optical Review》2014,21(1):90-93
The measurement of the nonuniform intensity distribution of scattered light by a moving diffuser using an integrating sphere, which lowers the effective numerical aperture of the projection lens and affects the lowest speckle contrast, is reported. A comparison of the effective numerical apertures realized by several diffusers revealed that JIS #600 or #800 diffusers are most appropriate for efficient speckle reduction 相似文献
229.
The thermal degradation mechanism of tetrabrominated epoxy resin was investigated in order to explain its flame retardant mechanism. From the results obtained it was concluded that the flame retardant mechanisms are 1) a lowering of temperature through degradation and 2) the formation of hydrogen bromide and its role in catalysis in the condensation reaction of the resin. These mechanisms were investigated by the pyrolysis behavior of the resin by gas chromatography, thermal gravimetric analysis, and differential thermal analysis studies. 相似文献