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851.
Dopamine hydroxylation by the copper-superoxo, -hydroperoxo, and -oxo species of dopamine beta-monooxygenase (DBM) is investigated using theoretical calculations to identify the active species in its reaction and to reveal the key functions of the surrounding amino acid residues in substrate binding. A 3D model of rat DBM is constructed by homology modeling using the crystal structure of peptidylglycine alpha-hydroxylating monooxygenase (PHM) with a high sequence identity of 30% as a template. In the constructed 3D model, the CuA site in domain 1 is coordinated by three histidine residues, His265, His266, and His336, while the CuB site in domain 2 is coordinated by two histidine residues, His415 and His417, and by a methionine residue, Met490. The three Glu268, Glu369, and Tyr494 residues are suggested to play an important role in the substrate binding at the active site of DBM to enable the stereospecific hydrogen-atom abstraction. Quantum mechanical/molecular mechanical (QM/MM) calculations are performed to determine the structure of the copper-superoxo, -hydroperoxo, and -oxo species in the whole-enzyme model with about 4700 atoms. The reactivity of the three oxidants is evaluated in terms of density-functional-theory calculations with small models extracted from the QM region of the whole-enzyme model. 相似文献
852.
The electrochemical properties of the nickel-based mercury film electrode (Ni-MFE) were investigated with respect to application of the electrode in the anodic stripping voltammetry (a.s.v.) of heavy metal ions. The hydrogen overpotential at the Ni-MFE is higher than those at MFEs based on other metals, and high enough to get quantitative a.s.v. peaks of lead and cadmium. The mercury film of the Ni-MFE is stable both mechanically and chemically; a.s.v. peaks at a Ni-MFE which had been used fifty times within 300 h after its preparation were identical with those at the freshly prepared electrode. With the Ni-MFE, 5 × 10?10–10?7 M lead(II) and 2 × 10?10–10?7 M cadmium(II) in the solution can be determined with relative standard deviations of 11 and 12%, respectively. These results are comparable to those obtained by a.s.v. at an in situ mercury-plated g]assy carbon electrode. 相似文献
853.
Hisashi Miyafuji Toshiki Nakata Katsunobu Ehara Shiro Saka 《Applied biochemistry and biotechnology》2005,124(1-3):963-971
The water-soluble (WS) portion obtained by supercritical water treatment of lignocellulosics was studied for its fermentability
to ethanol. A fermentation test of the WS portion showed it was not fermented to ethanol. Therefore, a wood characoal treatment
was applied to the WS portion to remove furan and phenolic compounds, which are thought to be the inhibitors to sugar fermentability.
It was found that treatment with wood charcoal can be effective at removing these inhibitors and improving the fermentability
of the WS portion without reducing the levels of fermentable sugars. 相似文献
854.
A new methanodithiomethano-bridged dibenzotrithionin (1) has been synthesized. The electrochemical oxidation of 1 and its analogous compound was studied by cyclic voltammetry. A new type of the sulfur extrusion of 1 was found in the reaction of 1 with concd H2SO4 or 2 equiv of NOPF6 and in its photochemical reaction. 相似文献
855.
856.
Summary The electrolytic behaviour of plutonium ions in a mixture of phosphate and nitrate solutions was studied by flow-coulometry with column electrodes of glassy carbon(GC)-fibers and voltammetry with a GC disc electrode, and compared with that in phosphate-free media. The redox processes, PuO
2
2+
/PuO
2
+
and Pu4+/Pu3+, were demonstrated to be reversible even in the phosphate media and their half wave potentials shifted more negatively due to the formation of PuO2(H2PO4)+ and Pu(HPO4)2. The rate of the irreversible reduction of PuO
2
+
to Pu3+ increased in the presence of phosphoric acid and the quantitative reduction was attained with the column electrode even at +0.35 V vs. saturated KCl-Ag/AgCl. The reduction process of PuO
2
+
was elucidated considering an intermediate Pu(IV)-species, PuO2+, which decomposed into Pu4+ by a post-chemical reaction. Analytical advantages of the use of phosphate media are discussed. 相似文献
857.
Hisashi Morikawa Yoshinori Uwamino Toshio Ishizuka 《Fresenius' Journal of Analytical Chemistry》1990,336(3):210-214
Summary Rare earth elements (REEs) in yttrium oxide were determined by secondary ion mass spectrometry (SIMS) with high sensitivity. The calibration graph approach was employed with chemically prepared standards. Molecular ion interferences derived from the matrix components which limit the superior sensitivity of SIMS were successfully suppressed by an energy filtering technique. The detection limits of the elements ranged from 0.02 to 0.2 g·g-1. 相似文献
858.
Hirata KS Kajita T Kifune T Kihara K Nakahata M Nakamura K Ohara S Oyama Y Sato N Takita M Totsuka Y Yaginuma Y Mori M Suzuki A Takahashi K Tanimori T Yamada M Koshiba M Suda T Miyano K Miyata H Takei H Kaneyuki K Nagashima Y Suzuki Y Beier EW Feldscher LR Frank ED Frati W Kim SB Mann AK Newcomer FM Van Berg R Zhang W Fukugita M 《Physical review letters》1988,61(23):2653-2656
859.
[reaction: see text] The reaction of nitroso compounds with enolates, "the nitroso aldol reaction", occurs in high yield to generate alpha-hydroxyamino carbonyl compounds. Yields range from 42% to 98% with N-selectivity >99:1 from commercially available aromatic or aliphatic nitroso compounds and a variety of alkali metal or tin enolates. 相似文献
860.
We prepared test solutions which contained 80% (v/v) ethanol and 0.2% (w/v) chlorhexidine (CH) or benzalkonium chloride (BC) with or without a dibasic acid diester. After complete evaporation of the ethanol from the solution on filter paper, an overnight broth culture (Staphylococcus aureus) was repeatedly inoculated onto the filter paper, and viable bacterial counts were measured at 5 min after the last inoculation. By comparison with viable counts for CH or BC alone, we estimated the potentiating effects of dibasic acid diester on the bactericidal activity of CH or BC, and confirmed that this activity of the two disinfectants was potentiated in the presence of certain compounds in the homologs of di-n-butyl esters of aliphatic dibasic acid, and di-alkyl esters of adipic and phthalic acid. Diisobutyl adipate, one of the most effective diesters, substantially enhanced the bactericidal activities of benzethonium chloride, cetyl pyridinium chloride and didecyl dimethyl ammonium chloride, as well as CH and BC, but not those of polyhexamethylene biguanide or alkyldiaminoethyl glycinate. The potentiating effects of dibasic acid diesters observed for both CH and BC seemed to be affected by the hydrophobic character of these diesters themselves and are also expressed well by a particular quadratic equation as a function of these characters: namely, capacity factors, as determined by high-performance liquid chromatography. 相似文献