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61.
Chelation of cadmium ions by phytochelatin synthase: role of the cysteine-rich C-terminal. 总被引:1,自引:0,他引:1
Mun'delanji Vestergaard Sachiko Matsumoto Shingo Nishikori Kentaro Shiraki Kazumasa Hirata Masahiro Takagi 《Analytical sciences》2008,24(2):277-281
The interactions between Cd(2+) and the C-terminal region of phytochelatin (PC) synthase using recombinant wild-type and mutant PC synthase were studied. We show that site-directed mutagenesis of Cys residues at C(358)C(359)XXXC(363)XXC(366) motif decreases the number of Cd(2+) and other heavy metal ions interacting with the enzyme, and that the motif binds the metals discriminatingly. The optimum binding ratio of PC synthase to Cd(2+) was also determined. The findings indicate that Cys exists as a free SH residue and that it is involved in the regulation of PC enzyme activity by transferring the metals into closer proximity with the catalytic domain. These results are important in understanding heavy metal detoxification mechanisms in higher plants, a step towards phytoremediated-applications. 相似文献
62.
63.
Asit K. Chandra Shingo Urata Tadafumi Uchimaru Masaaki Sugie Akira Sekiya 《国际化学动力学杂志》2002,34(8):500-507
Kinetics and mechanism of the hydrogen abstraction reaction between trifluoromethyl formate, CF3OCHO, and OH radical have been investigated by using ab initio molecular orbital theory up to G2(MP2) level. The hydrogen abstraction rate constant has been calculated for the first time over a temperature range of 250–450 K by using standard transition state theory including the tunneling correction. Arrhenius parameters of the reaction have been estimated from the temperature dependence of the calculated rate constant. The calculated value for the rate constant (2.0 × 10?14 cm3 molecule?1 s?1) at 298 K is found to be in very good agreement with the recent experimental results. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 500–507, 2002 相似文献
64.
Ikuko Mori Miyuki Ukachi Kimiyo Nagano Hiroyasu Ito Jun Yoshinaga Masataka Nishikawa 《Analytical and bioanalytical chemistry》2010,397(2):463-470
A candidate environmental certified reference material (CRM) for the determination of multielements in tea leaves and materials
of similar matrix, NIES CRM No. 23 Tea Leaves II, has been developed and characterized by the National Institute for Environmental
Studies (NIES), Japan. The origin of the material was tea leaves, which were ground, sieved through a 106-μm mesh, homogenized,
and then subdivided into amber glass bottles. The results of homogeneity and stability tests indicated that the material was
sufficiently homogeneous and stable for use as a reference material. The property values of the material were statistically
determined based on chemical analyses by a network of laboratories using a wide range of methods. Sixteen laboratories participated
in the characterization, and nine certified values and five reference values were obtained. These property values of the candidate
CRM, which are expressed as mass fractions, were close to the median and/or mean values of the mass fractions of elements
in various tea products. The candidate CRM is appropriate for use in analytical quality control and in the evaluation of methods
used in the analysis of tea and materials of similar matrix. 相似文献
65.
Shimizu M Sakakura M Kanehira S Nishi M Shimotsuma Y Hirao K Miura K 《Optics letters》2011,36(11):2161-2163
We report on the formation mechanism of element distribution in glass under high-repetition-rate femtosecond laser irradiation. We simultaneously focused two beams of femtosecond laser pulses inside a glass and confirmed the formation of characteristically shaped element distributions. The results of the numerical simulation in which we considered concentration- and temperature-gradient-driven diffusions were in excellent qualitative agreement with the experimental results, indicating that the main driving force is the sharp temperature gradient. Since the composition of a glass affects its refractive index, absorption, and luminescence property, the results in this study provide a framework to fabricate a functional optical device such as optical circuits with a high-repetition-rate femtosecond laser. 相似文献
66.
In this paper, we will give a simple proof of Theorem of [8] and some applications.This research is partially supported by Grant-in-Aid for Scientific Research. 相似文献
67.
The development of axially chiral dicarboxylic acid catalyzed desymmetrizing asymmetric semipinacol rearrangement of symmetrically substituted six-membered cyclic β-hydroxy-α-diazo esters is reported as a means to give chiral cycloheptanones with good enantioselectivities. 相似文献
68.
69.
A simple approach for determining a liquid structure using X-ray scattering data, in which a liquid structure is uniquely evaluated without construction of any plausible structure models, has been applied to liquid acetonitrile, acetone and cyclohexane. For a pair of molecules, a given point within a molecule is located at the origin with a given molecular orientation. The site of the given point of another molecule is defined by the polar coordinates and the molecular orientation is treated by three Eulerian angles. These parameters are optimized by a non-linear least-squares calculation applied to X-ray scattering data. The reliability of the method was examined by determining the liquid structure of polar acetonitrile and the obtained intermolecular interatomic distances are in good agreement with the previously reported values. The method was then successfully applied to the determination of the liquid structure of acetone and cyclohexane. Especially for nonpolar cyclohexane, the construction of a variety of plausible structural models is very difficult. It was revealed that acetone has an ordered liquid arrangement similar to that found in its crystal, although the intermolecular distances in liquid acetone are different from those in the crystal. On the other hand, the liquid structure of cyclohexane is disordered. 相似文献
70.
As part of our research on benzofurazans (BZs), we have reported the bacterioses of BZs in Escherichia coli, which may be due to O2-. produced within E. coli in the presence of dioxygen (O2). Incubation of E. coli with 4,7-dicyanobenzofurazan (1) lowered the 2,3-dihydroxyisovalerate dehydratase activity detectable in extracts from these cells. Addition of branched chain amino acids such as valine and leucine protected E. coli from growth inhibition by compound 1, though it could not protect E. coli from the damage by paraquat (PQ). Addition of Fe(III)-tris[N-(2-pyridylmethyl)-2-aminoethyl]amine (Fe-TPAA), a novel superoxide dismutase mimic, protected the dehydratase in a dose-dependent manner, which confirms that inactivation of the dehydratase is largely due to production of O2-.. The possibility was discussed that the bacteriostatic effect of compound 1 is due to the inactivation of 2,3-dihydroxyisovalerate dehydratase. 相似文献