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41.
A new method to improve the analysis of phytochelatins and their precursors (cysteine, gamma-Glu-Cys, and glutathione) derivatized with monobromobimane (mBrB) in complex biological samples by capillary zone electrophoresis is described. The effects of the background electrolyte pH, concentration, and different organic additives (acetonitrile, methanol, and trifluoroethanol) on the separation were studied to achieve optimum resolution and number of theoretical plates of the analyzed compounds in the electropherograms. Optimum separation of the thiol peptides was obtained with 150 mM phosphate buffer at pH 1.60. Separation efficiency was improved when 2.5% v/v methanol was added to the background electrolyte. The electrophoretic conditions were 13 kV and capillary dimensions with 30 cm length from the inlet to the detector (38 cm total length) and 50 microm inner diameter. The injection was by pressure at 50 mbar for 17 s. Under these conditions, the separation between desglycyl-peptides and phytochelatins was also achieved. We also describe the optimum conditions for the derivatization of biological samples with mBrB to increase electrophoretic sensitivity and number of theoretical plates. The improved method was shown to be simple, reproducible, selective, and accurate in measuring thiol peptides in complex biological samples, the detection limit being 2.5 microM glutathione at a wavelength of 390 nm. 相似文献
42.
The reactions of the 3-methoxy-isoxazole quinones 1 and 9 in a highly polar solution of dimethyl sulfoxide have been studied. Quinones of type 2, 4/11, 5/12, 6 and 7/13 have been isolated; nmr measurements give a detailed insight into the reaction mechanism. 相似文献
43.
A99Tc-ADP complex was prepared when KTcO4 was reduced in aquous medium by SnCl2, Na2S2O4, NaBH4 or Zn in the presence of ADP in excess. The resulting solution was studied by chromatography and spectrophotometry. Electrochemical reduction and substitution on [TcIII(tu)6]3+ were investigated as alternative synthetic routes. The anionic Tc-ADP complex was isolated as a solid. Cerimetric titrations confirmed the oxidation state +3 for the central atom. IR and1H-NMR data showed that the purine base is bonded to the Tc central atom but not the ribose moiety. No oxo groups seemed to be directly bonded to the Tc atom. The complex is rather stable in neutral solutions. However, it decomposes to pertechnetate and TcO2 at extreme pH values. 相似文献
44.
N. S. Prostakov A. V. Varlamov M. Torres B. N. Anisimov M. A. Ryashentseva 《Chemistry of Heterocyclic Compounds》1982,18(3):283-284
3-Methyl-4-benzyl-2,6-diphenylpiperidine was obtained by hydrogenation of 3-methyl-4-benzyl-2,6-diphenylpyridine in the presence of rhenium heptasulfide; this confirms the common character of the method of selective hydrogenation of aryl(aralkyl)-substituted pyridine bases to give similarly substituted piperidines. Dehydrocyclization of this pyridine base by heating with sulfur leads to 10-mercapto-1,3-diphenyl-2-azaanthracene, which was obtained under the same conditions from 1,2-diphenyl-1,2-bis(3-methyl-2,6-diphenyl-4-pyridyl)ethane.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 375–376, March, 1982. 相似文献
45.
A. González Arias C. Torres C. de
Francisco J. M. Muñoz P. Hernández
Gómez O. Alejos O. Montero J. I. Iñiguez 《Journal of Thermal Analysis and Calorimetry》2006,86(1):195-198
The article discusses theory and experiment about the measurement of
defect concentration in Ti-substituted yttrium iron garnet by means of thermogravimetry
techniques. The two possible cases arising from oxygen interchange with atmosphere,
oxygen vacancies and interstitial cations, may be analyzed quantitatively
from the derived expressions. The possibility of another type of defects being
present in the samples, not associated to oxygen evolution, is not excluded.
Measurements were carried out in air and CO2 for different
Ti contents. The substitution tends to increase slightly the defect parameter
θ in YIG, while a CO2 reducing atmosphere is
much more effective than the Ti substitution for increasing θ. Calculations
for a given single-phased sample sintered in air show two possibilities: a
deficit of one oxygen atom for every 2.5 unit cells of 96 atoms, or one excess
cation for every 3.5 cells. Other samples show very similar results. The accuracy
involved in the measurements is about 2–3%. 相似文献
46.
47.
The synthesis and structural characterisation of a thermally stable novel three-dimensional microporous copper silicate open-framework are described; the material is capable of undergoing reversible zeolitic water removal without destruction of the framework. 相似文献
48.
Simulation of aerated lagoon using artificial neural networks and multivariate regression techniques
Karla Patricia Oliveira-Esquerre Aline C. da Costa Roy Edward Bruns Milton Mori 《Applied biochemistry and biotechnology》2003,106(1-3):437-449
The aim of this study was to develop an empirical model that provides accurate predictions of the biochemical oxygen demand
of the output stream from the aerated lagoon at International Paper of Brazil, one of the major pulp and paper plants in Brazil.
Predictive models were calculated from functional link neural networks (FLNNs), multiple linear regression, principal components
regression, and partial least-squares regression (PLSR). Improvement in FLNN modeling capability was observed when the data
were preprocessed using the PLSR technique. PLSR also proved to be a powerful linear regression technique for this problem,
which presents operational data limitations. 相似文献
49.
50.