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271.
J. Takada T. Sumino K. Nishimura Y. Tanaka M. Akaboshi 《Journal of Radioanalytical and Nuclear Chemistry》1996,214(2):103-116
The lanthanides (REE) in 142 fern leaves collected from several sampling sites in Japan have been determined by neutron activation analysis, and the correlations between any two REEs in the logarithmic scattering diagram were examined. The relationship was expressed by the general formula, Y=aX+b with a correlation coefficient R. A strong positive correlation was seen between any two REEs in the diagram with a regression coefficient and a correlation coefficient close to unity. However, between Eu or Tb and other REEs the relationship was split into two lines with the same correlation coefficient. From the intercept b, the relative abundance of the two elements was determined for each REE and compared with those in hickory and tobacco leaves. These findings indicated that the abundance pattern of fern leaves is quite different from those of hickory and tobacco leaves. Namely, the relative abundance of La and Ce was quite similar in the three plants, but the abundance of the other REEs (Nd, Sm, Gd, Dy and Lu) was considerably lower in ferns than in hickory and tobacco leaves. For Eu and Tb the higher values obtained in fern leaves coincided with those of the two plants. 相似文献
272.
A trace amount of molybdenum(VI) can be determined by using its catalytic effect on the oxidation of iodide to iodine by hydrogen peroxide in acidic medium. Addition of ascorbic acid added to the reaction mixture produces the Landolt effect, i.e., the iodine produced by the indicator reaction is reduced immediately by the ascorbic add. Hence the concentration of iodide begins to decrease once all the ascorbic acid has been consumed. The induction period is measured by monitoring the concentration of iodide ion with an iodide ion-selective electrode. The reciprocal of the induction period varies linearly with the concentration of molybdenum(VI). The most suitable pH and concentrations of hydrogen peroxide and potassium iodide are found to be 1.5, 5 and 10mM, respectively. An appropriate amount of ascorbic acid is added to the reaction mixture according to the concentration of molybdenum(VI) in the sample solution. A calibration graph with good proportionality is obtained for the molybdenum(VI) concentration range from 0.1 to 160 μM. Iron(III), vanadium(IV), zirconium(IV), tungsten(VI), copper(II) and chromium(VI) interfere, but iron(III) and copper(II) can be masked with EDTA. 相似文献
273.
We developed a new convenient method for generation of an abasic site at the 3'-terminus of an oligonucleotide. This method uses a 1-deaza-2'-deoxyguanosine residue, which easily undergoes depurination under acidic conditions. The abasic site of the oligonucleotide can be further modified with external functional groups. We report herein the chemical stability of 1-deaza-2'-deoxyguanosine in the oligodeoxynucleotide and the application to the postsynthetic modification of an oligonucleotide by utilizing the chemical property of 1-deaza-2'-deoxyguanosine. [Structure: see text] 相似文献
274.
Kanazawa H Okada A Igarashi E Higaki M Miyabe T Sano T Nishimura R 《Journal of chromatography. A》2004,1031(1-2):213-218
This study demonstrated the analysis of midazolam and its metabolites by liquid chromatography-mass spectrometry (LC-MS) with a sonic spray ionization (SSI) interface. The analytical column was a YMC-Pak Pro C18 (50 mm x 2.0 mm i.d.) using 10 mM ammonium acetate (pH 4.8)-methanol (1:1) at a flow rate of 0.2 ml min(-1). The drift voltage was 100 V. The sampling aperture was heated at 110 degrees C and the shield temperature was 230 degrees C. The lower limits for the detection of midazolam and 1'-hydroxymidazolam were 26.3 and 112.76 pg injected, respectively. The calibration curves for midazolam and 1'-hydroxymidazolam were linear in the range of 0.1-5 microg ml(-1). Within-day relative standard deviations was less than 7%. The method was applied to the determination of midazolam in monkey plasma, and the analysis of midazolam and its metabolites in an in vitro study with recombinant cytochrome P450 (CYP) 3A4. This method is sufficiently sensitive and useful to elucidate the kinetics of midazolam metabolite formation. We also investigated the effect of propofol on the metabolism of midazolam using recombinant CYP3A4. Propofol competitively inhibited the metabolism of midazolam to 1'-hydroxymidazolam by CYP3A4. 相似文献
275.
276.
Shiratori H Ohno T Nozaki K Yamazaki I Nishimura Y Osuka A 《The Journal of organic chemistry》2000,65(25):8747-8757
Three sets of dyads, in which a zinc-porphyrin (ZP) electron donor is connected to an aromatic diimide electron acceptor,either pyromellitimide (PI) or naphthalene-1,8:4,5-tetracarboxylic acid diimide (NI), via a boronate-ester bridge, a piperidine bridge, and a 1,3-dioxolane bridge, respectively, were prepared for the purpose of control of intramolecular electron transfer (ET) by acid-base reactions at the connecting bridge. Boronate-ester bridge is a Lewis acidic site and confers a chance to regulate intramolecular ET reaction upon base coordination. This has been demonstrated by suppression of photoinduced ET from ZP to PI or NI in highly electron-pair donating solvents or upon addition of a fluoride anion. To extend this strategy to control of ET-path selectivity, we prepared triad 18, which consists of a ZP donor bearing NI and PI acceptors at similar distances through a boronate-ester bridge and an acetal bridge, respectively. Photoexcitation of 18 in a free form led to intramolecular ET from (1)()ZP preferentially to NI, but the ET path was completely switched toward PI in F(-)-coordinated form without a serious drop in the rate, constituting a novel ET-switching molecular system. 相似文献
277.
Y Usui N Nishimura N Kobayashi T Okanoue M Kimoto K Ozawa 《Journal of chromatography. A》1989,489(2):291-301
A sensitive and precise method for measuring endogenous phylloquinone (K1) and menaquinone (MK-n) in human liver was developed, based on gradient elution high-performance liquid chromatography using platinum-black catalyst reduction and fluorimetric detection. Subnanogram levels of vitamin K compounds in 1 g of liver specimen were detectable. We measured vitamin K concentrations in 38 human resected livers. K1 and MK-4 to MK-13 were detected. The concentrations of MK-10 to MK-12 in livers with chronic hepatitis (n = 10) and cirrhosis (n = 22) were significantly lower than in normal livers (n = 6). It is suggested that the decreased concentrations indicate functional damage of the hepatocytes. 相似文献
278.
279.
280.
Rhodium/chiral diene-catalyzed asymmetric methylation of N-sulfonylarylimines with trimethylboroxine
Takahiro Nishimura Akram Ashouri Yusuke Ebe Yuko Maeda Tamio Hayashi 《Tetrahedron: Asymmetry》2012,23(9):655-658
A hydroxorhodium complex coordinated with a chiral diene ligand catalyzed the asymmetric addition of trimethylboroxine to N-sulfonylarylimines to give high yields of chiral 1-aryl-1-ethylamines with high enantioselectivity. 相似文献