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191.
R Pietruszko C de Zalenski H Theorell 《Acta chemica Scandinavica. Series B: Organic chemistry and biochemistry》1976,(7):595-599
ADH from human liver forms binary complexes with NADH, associated with a blue shift of the peak of the fluorescence emission of NADH. The wavelength shift is the same for all isoenzymes but the accompanying intensification of the fluorescence is different. The fluorescence is further increased by the formation of the very tight ternary enzyme-NADH-isobutyramide complexes. These properties are similar to those for the horse liver ADH, as well as the molecular weight of E=40 000 per active site of the dimer molecule (EE). "Stopped-flow" determined velocity constants (ER in equilibrium E+R) were found to be in good agreement with ethanol activity constants previously determined by activity measurement, confirming the validity of the ordered ternary complex mechanism also for the human ADH. No single isoenzyme activity as high as that reported by Mourad and Woronick or Drum has been found. 相似文献
192.
De Wasch K De Brabander HF Van de Wiele M Vercammen J Courtheyn D Impens S 《Journal of chromatography. A》2001,910(1):79-86
Direct gas chromatographic methods to analyse phenylurea pesticides are discouraged by the thermal instability of these compounds, that in conventional hot splitless inlet systems leads to extensive and irreproducible formation of isocyanates and amines. However a careful control of the operating conditions, like the inlet temperature, the pressure and the presence of suitable chemical additives (as acetic acid, low-molecular-mass amines, organic anhydrides) can either: (i) minimise the thermal decomposition enabling the direct GC-MS analysis of phenylureas, or (ii) lead to reproducible conversion to isocyanates. Experimental design was employed to study the effect of the experimental variables on the thermal transformation of phenylurea pesticides in splitless inlet system. Two strategies were alternatively optimised: (i) the minimisation of degradation reactions to increase the signal of phenylureas; (ii) the maximisation of the degradation to isocyanates that are in turn determined. The maximal yields in isocyanate were obtained with high inlet temperatures, low carrier flows in the injection phase and the presence of acetic anhydride. By contrast, the use of relatively low inlet temperatures, high carrier flows during the injection and the presence of an amine maximise the response of the parent compounds. 相似文献
193.
A method is described for the precise determination of carbon and hydrogen in milligram, amounts of sample. The method is based on the manometric measurement of the amounts of carbon dioxide and water formed on combustion. A precision mercury manometer is used in which pressures are converted to mercury volumes. The latter are measured with the aid of a commercial piston-type buret using a photo-electric level indication. 相似文献
194.
Kaczmarek K Walczak B de Jong S Vandeginste BG 《Journal of chemical information and computer sciences》2002,42(6):1431-1442
Automatic alignment (matching) of two-dimensional gel electrophoresis images is of primary interest in the evolving field of proteomics. In the present study, feature-based matching techniques, in their classical and robust versions, are described, and an automatic method of fuzzy alignment (FA) is introduced. This method allows automatic matching of two gel images with different numbers of features with unknown correspondence. Performance of FA is tested on simulated and real data sets. 相似文献
195.
A method for the quantitative preconcentration of lead based on an existing batch process was developed for implementation in a flow system including a flame AAS detector. Lead can be quantitatively preconcentrated as pyrrolidinedithiocarbamate or dithizonate on an activated carbon minicolumn. The chelates are eluted in methyl isobutyl ketone and introduced directly into the nebuliser-burner. An enrichment factor of 50 is typically obtained for a preconcentration time of 2 min (lead can be determined at concentrations between 15 and 400 ng/ml), which results in a throughput of ca. 25 samples per hr. The sensitivity achieved with the two reagents is similar, but the selectivity provided by APDC exceeds that of dithizone. Based on the results obtained in the determination of lead in reference materials (minerals and skim milk), the proposed APDC method is applicable to real samples. 相似文献
196.
In applying non-destructive neutron-activation analysis for gold and uranium in spiked low-grade ore samples, the following extrapolated unspiked concentrations were measured: 0.278 ± 0.015 ppm gold (chemical assay: 0.202 ± 0.020 ppm gold); 25.1 ± 1.1 ppm uranium (chemical assay value: 19.5 ±2.0 ppm uranium). Different approaches to the fitting of results, and the influence of spiking non-uniformity, are discussed. 相似文献
197.
L. A. M. Rodriguez H. M. van Looy J. A. Gabant 《Journal of polymer science. Part A, Polymer chemistry》1966,4(8):1917-1926
The following reactions, carried out in the absence of solvents, has been studied: α-TiCl3 + Al(CH3)3 at 20°C., β-TiCl3 + Al(CH3)3 at 65°C., α-TiCl3 + Al(CH3)2Cl at 20 and 65°C., and α-TiCl3 + Al(C2H5)3 between 30 and 65°C. It appears that a general reaction mechanism, such as discussed in the preceding paper of this series, applies to all these reactions between TiCl3 and aluminum alkyls. The differences in overall stoichiometry between some of these systems may be linked to differences in stability of the intermediate Ti? C bonds. In the case of α-TiCl3 + Al(CH3)2Cl, alkylation is probably accompanied by fixation of the AlCH3Cl2 on the nonvolatile product. 相似文献
198.
Optimum conditions have been established for formation and extraction of indium-Rhodamine complexes, and limits of detection found for fluorimetric determination of gallium and indium by means of Rhodamine dyes, using the excitation with pulsed laser and xenon arc sources. 相似文献
199.
An accurate method for the determination of inorganic sulphate in synthetic detergents has been developed. After addition of a cationic surface-active agent (cetyl pyridinium chloride) to an anionic detergent, sulphate can be determined by means of indirect titration with EDTA, using a mixture of Metalphthalein and Naphthol Green B as indicator. 相似文献
200.