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61.
Theoretical aspects of the MS Xα method are analyzed. It is shown that real field self-consistency is not achieved in an MS Xα calculation and some consequences of this fact are discussed. The approximations involved in the use of the transition-state procedure to evaluate ionization and excitation energies from a MS Xα calculation are presented in some detail and commented. 相似文献
62.
This determination of salicylate in blood serum is based on application of an immobilized enzyme electrode. Salicylate hydroxylase (E.C.1.14.13.1) is chemically immobilized onto a pig intestine mounted on an oxygen electrode. The signals are monitored amperometrically and the resulting output voltage is read using a simple adapter. The experimental parameters and possible interferences are discussed. Samples containing 1.0 × 10?5?1.87 × 10?3 M (1.6–300 μg ml?1) salicylate were assayed with relative standard deviations between 1.3% and 6% and recoveries between 98.7 and 103%. Results obtained by the proposed method and by the established clinical method for randomly spiked pooled serum samples correlated well (r = 0.99). 相似文献
63.
Paula?Messina Marcela?A.?Morini Pablo?C.?SchulzEmail author 《Colloid and polymer science》2003,281(7):695-698
The hydration of micellised sodium dehydrocholate molecules was determined by viscosity measurements. It was found that there are 39 water molecules for each micellised surfactant molecule. About ten water molecules may be attributed to the hydration of the sodium carboxylate group. By assignation of two water molecules to each of the three carbonyl groups, the total hydration of a micellised sodium dehydrocholate molecule was estimated as about 16 water molecules. The remaining 23 water molecules per micellised sodium dehydrocholate molecule may be attributed to water trapped in the structure of micelles. 相似文献
64.
Jarmila Štetinová Rudolf Kada Miloslava Dandárová Marcela Krublová Ján Leśko 《Chemistry of Heterocyclic Compounds》1995,31(10):1231-1233
Substituted ]-(6-methoxy-2-benzothiazolyt)-2-pyridones were prepared from 2-amino-6-methoxybenzathiazate through N-(6-methoxy-2-benzothiazotyl) cyanvorearmileaznd-3-aryl-N-(6-methoxy-2-benzothiazolyt)-2-cyano-2-propenamides. The cyclization of the latter with malonodinitrile in the presence of piperidine gave the corresponding pyridones. The structures of the synthesized compounds were confirmed by1H NMR and mass spectral data.Department of Organic Chemistry, Mass Spectrometry Laboratory, Slovak Technical University, 812 37 Bratislava, Slovakia. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1402–1404, October, 1995. Original article submitted August 24, 1995. 相似文献
65.
A. G. Taranto J. W. de M. Carneiro F. G. de Oliveira M. T. de Araujo C. R. Correa 《Journal of Molecular Structure》2002,580(1-3):207-215
Artemisinin is a sesquiterpene lactone with an endoperoxide function that is essential for its antimalarial activity. Endoperoxides are supposed to act on heme leading to the reduction of the peroxide bond and production of radicals, which can be responsible for killing the parasite. The geometries of artemisinin, radical anions and neutral species generated by rearrangement after reduction of the peroxide bond were fully optimized with the AM1 and PM3 semi-empirical methods, in order to characterize the intermediates formed during the process. Among the radicals calculated along the pathway for reductive decomposition of artemisinin, the secondary radical centered on carbon C4 has the highest stability when compared to other radicals that can be achieved either by hydrogen migration to the original O-centered radical or by homolytic break of C–C bond. This suggests that the C4-centered radical may be the species responsible for killing the parasite, as has been indicated previously in experimental studies. 相似文献
66.
The potentiometric determination of zinc in chloride solutions with a coated wire electrode is described. The electroactive membrane contains the chlorozincate(II) salt of Aliquat 336S in poly (vinyl chloride). The electrode shows a useful response over the range 10-5 M–10-1 M zinc(II) in 3 M total chloride solutions in the pH range 1.5–6. The electrode is more responsive to the divalent tetrachlorozincate(II) than to the monovalent trichlorozincate(II) species. Applications in compleximetric titrations, and to the analysis of zinc oxide and zinc concentrates are reported. 相似文献
67.
C. B. Zamboni L. C. Oliveira L. Dalaqua Jr J. Mesa 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):331-334
Summary Neutron activation analysis technique, using Au as flux monitor, was applied to determine element concentrations of Ca, K,
Na, Mg, Mn and Sr in certified reference material (NIST 1400 Bone Ash). The results were compared with those using comparative
INAA and they were compatible. The same results were obtained using the recommended k0 factors, in order to obtain the activation cross section as input in concentration for the same reference material. Some
applications in the health area aiming clinical evaluation in bone samples of medium and small-sized animals were performed
and the viability of using this methodology was discussed. 相似文献
68.
In the present contribution, a new automated on-line hydride generation methodology was developed for dibutyltin and tributyltin speciation at the trace level, using a programmable temperature-vaporizing inlet followed by capillary gas chromatography coupled to mass spectrometry in the selected ion-monitoring mode acquisition (PTV-GC/MS(SIM)). The methodology involves a sequence defined by two running methods, the first one configured for hydride generation with sodium tetrahydroborate as derivatising agent and the second configured for speciation purposes, using a conventional autosampler and data acquisition controlled by the instrument's software. From the method-development experiments, it had been established that injector configuration has a great effect on the speciation of the actual methodology, particularly, the initial inlet temperature (-20 degrees C; He: 150 ml/min), injection volume (2 microl) and solvent characteristics using the solvent venting mode. Under optimized conditions, a remarkable instrumental performance including very good precision (RSD < 4%), excellent linear dynamic range (up to 50 microg/ml) and limits of detection of 0.12 microg/ml and 9 ng/ml, were obtained for dibutyltin and tributyltin, respectively. The feasibility of the present methodology was validated through assays upon in-house spiked water (2 ng/ml) and a certified reference sediment matrix (Community Bureau of Reference, CRM 462, Nr. 330 dibutyltin: 68+/-12 ng/g; tributyltin: 54+/-15 ng/g on dry mass basis), using liquid-liquid extraction (LLE) and solid-phase extraction (SPE) sample enrichment and multiple injections (2 x 5 microl) for sensitivity enhancement. The methodology evidenced high reproducibility, is easy to work-up, sensitive and showed to be a suitable alternative to replace the currently dedicated analytical systems for organotin speciation in environmental matrices at the trace level. 相似文献
69.
Hiléia K. S. Souza V. R. da Silveira F. M. M. Borges Dulce M. A. Melo H. Scatena Jr. O. A. de Oliveira A. G. Souza 《Journal of Thermal Analysis and Calorimetry》2007,87(2):433-436
Thermal behavior of rare earth nitrate complexes
with 2-azacyclononanone (AZA) with Ln(NO3)3·3(AZA)
composition (where Ln=Gd, Er and Ho) was
analyzed in kinetic point of view. Kinetic parameters were calculated from
thermogravimetric data. All obtained results were similar. The first decomposition
step was representative to the loss of ligand and the residue was essentially
Ln2O3. Furthermore, a reaction
path was proposed for the thermal decomposition of the Ln(NO3)3·3(AZA). 相似文献
70.
Immobilization of protein on ferromagnetic Dacron 总被引:1,自引:0,他引:1
A. M. A. Carneiro LeÃo E. A. Oliveira L. B. Carvalho 《Applied biochemistry and biotechnology》1991,31(1):53-58
Ferromagnetic Dacron (polyethyleneterephthalate) is proposed as a matrix to immobilize proteins covalently. Dacron in powder was magnetized by reacting ferrous (Fe+2) and ferric (Fe+3) ions with its hydrazide form at pH 8.3. Ferromagnetic hydrazide Dacron was converted to ferromagnetic azide Dacron and amyloglucosidase (E.C. 3.2.1.3) was covalently bound through the latter group. The catalytic property of the enzyme was preserved (8% of the specific activity estimated for the soluble enzyme) and all the magnetic amyloglucosidase Dacron derivative was recovered by using a magnetic field. No activity was detected in the supernatant. 相似文献