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991.
The membrane destabilizing and fusogenic properties of the synthetic peptide VP3(110-121), corresponding to an immunogenic sequence of the hepatitis A virus (HAV) VP3 capsid protein, were studied. By tryptophan fluorescence and acryalmide quenching it was demonstrated that the peptide binds liposomes of POPC-SM-DPPE (47 + 39 + 14) and POPC-SM-DPPE-DOTAP (40 + 33 + 12 + 15) and penetrates the membrane, at both neutral and acidic pH (POPC = 1-palmitoyl-2-oleoylglycero-sn-3-phosphocholine; SM = sphingomyelin; DPPE = 1,2-dipalmitoylphosphatidylethanolamine; DOTAP = 1,2-dioleoyl-3-trimethylammoniumpropane). VP3(110-121) did not have membrane-destabilizing properties at neutral pH. Acid-induced destabilization of the vesicles was demonstrated by fluorescence techniques and dynamic light scattering. VP3(110-121) induced aggregation of POPC-SM-DPPE-DOTAP (40 + 33 + 12 + 15) vesicles, lipid mixing and leakage of vesicle contents, all consistent with fusion of vesicles. In POPC-SM-DPPE (47 + 39 + 14) vesicles, at acidic pH, VP3(110-121) induced membrane destabilization with leakage of contents but without aggregation of vesicles or lipid mixing. The peptide only showed fusogenic properties when bound to the vesicles at neutral pH before acidification to pH below 6.0, and no effect was seen if the peptide was added to vesicles already set at acidic pH. These results may have physiological significance in the mechanism of infection of host hepatic cells by HAV. 相似文献
992.
M. Reháková A. Sopková J. Lokaj 《Journal of inclusion phenomena and macrocyclic chemistry》1992,14(1):47-54
The aim of this study was the preparation of natural zeolitic materials doped with iodine and its ions. Natural zeolite from an East Slovakian deposit was used. The content of iodine in the zeolitic products depended on the experimental conditions used for the preparation. The products and their intermediates obtained at 100, 200, 400 and 900°C were identified. 相似文献
993.
J. A. Infantes M. D. Luque de Castro M. Valcárcel 《Fresenius' Journal of Analytical Chemistry》1991,339(1):58-61
Summary Two methods based on the use of the normal and stopped-flow injection modes were developed for the determination of oxalate based on its inhibitory effect on the catalytic action of Fe(III) on the 2,4-diaminophenol/hydrogen peroxide system. The linear determination ranges achieved were between 0.2 and 12.0 g ml–1 and between 0.2 and 40.0 g ml–1, the precision was ±5.4%, and ±3.5%, and the sampling rate was 30 and 20 samples h–1 for the normal and stopped-flow method, respectively. Both methods have been applied to the determination of oxalate in urine with excellent results. 相似文献
994.
Summary The reactions of MCl4 (M = Ti or V) with R2P(S)P(S)R2 (R = Me or Et) yield hexacoordinate complexes MCl4 · R2P(S)P(S)R2 (M = Ti or V; R = Me or Et), whereas similar reactions with VOCl3 lead to reduction of vanadium and give rise to the vanadium(IV) pentacoordinated complexes: VOCl2-R2P(S)P(S)R2 (R = Me or Et). All the compounds have been characterized by elemental analyses, i.r., visible and e.p.r. spectra, which show thecis-chelate character of these ligands, although in the complexes containing Et4P2S2 the i.r. spectra indicates that thegauche conformation of the ligand is implicated in bonding to the metal. The occupation of the sixth coordination site in pentacoordinate complexes, VOCl2 · R2P(S)P(S)R2, by different donor solvents, has been studied by means of visible and e.p.r. spectra. 相似文献
995.
Summary Nickel(II) xanthates react with amines to form nickel(II) dithiocarbamates and thiourethanes, both products of nucleophilic substitution at the sp2 carbon atom. If the reaction is conducted under carbon monoxide the nickel and sulphur-containing byproduct of thiourethane formation is transformed partly into Ni(CO)4. 相似文献
996.
Semiautomatic and automatic amperometry and constant-current potentiometry were used to follow the course of catalytic titration of gold(III) with potassium iodide. The Ce(IV)-As(III) system in the presence of sulfuric acid was used as the indicator reaction. The possibilities of the application of two types of graphite electrodes were investigated. The effect of concentration of the indicator reaction components, and the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 80–900 μg of gold(III) were determined with a relative standard deviation less than 1.1%. The results obtained are in good agreement with those of comparable methods. 相似文献
997.
Contreras Ricardo R. Fontal Bernardo Bahsas Alí Suárez Trino Reyes Marisela Bellandi Fernando Nava Flor Cancines Pedro 《Transition Metal Chemistry》2004,29(1):51-55
The synthesis of [benzyl-N,N-alkylbis(2-amino-1-cyclopentencarbodithioate)]MII [alkyl = ethene (L2) and propene, (L3) and M = Cu, Ni and Co] complexes and their characterization (u.v.–vis., FT-IR, 1H-n.m.r., mass spectra and cyclic voltametry) are reported. 相似文献
998.
Trace elements in small sample volumes of saliva were determined by coupling a high efficiency direct injection nebulizer to inductively coupled plasma mass spectrometry and employing quantification by isotope dilution. Aliquots of 0.4 ml of human saliva were mixed with 0.1 ml of concentrated nitric acid and diluted to 2 ml with water. Sample solutions were spiked with an isotopic solution enriched in 135Ba, 112Cd, 65Cu, 206Pb and 66Zn. The amount of each isotope added to the samples and the measurement procedure were adjusted to attain precise analytical results calculated from the isotope ratios 135Ba/138Ba, 112Cd/114Cd, 65Cu/63Cu, 206Pb/208Pb and 66Zn/68Zn. Data acquisition for Ba, Cu and Zn isotopes was performed for a single sample injection of 50 microl and in another sample injection the Cd and Pb isotopes were measured. Concentrations ranging from 5.0 to 16 microg l(-1) for Ba, from 0.50 to 1.1 microg l(-1) for Cd, from 6.0 to 50 microg l(-1) for Cu, from 0.8 to 18.8 microg l(-1) for Pb and from 46.0 to 230 microg l(-1) for Zn were found in saliva samples. Detection limits of 0.11, 0.03, 0.40, 0.05 and 0.59 microg l(-1) were determined for Ba, Cd, Cu, Pb and Zn, respectively. The concentrations found by isotope dilution were in agreement with those of the completely digested samples quantified by external calibration. The direct analysis of 30 samples per hour was attained with the proposed procedure, avoiding time-consuming digestion steps, contamination risks and matrix effects. 相似文献
999.
M. S. Rahman M. Parre?o R. Bossi A. B. Payá-Pérez B. Larsen 《Fresenius' Journal of Analytical Chemistry》1998,360(5):556-563
Six extraction methods for the analysis of PCBs (CB-28, CB-52, CB-101, CB-118, CB-138, CB-153 and CB-180) in sewage sludge
were tested. A certified reference material (CRM 392) was used for the evaluation of the performance of the methods. Soxhlet-Dean-Starch
with toluene as solvent, Soxhlet with hexane:acetone (2:3), cold digestion/saponification with 2 mol/L KOH in methanol followed
by partition with hexane, and sonicated liquid-solid extraction with hexane:acetone (1:1) produced accurate results (97%,
93%, 104%, and 88%, respectively) with acceptable precisions (6.2%, 6.8%, 15% and 12%, respectively). Results in close agreement
with the certified value for all congeners were obtained by treatment with BF3-methanol prior to partition with dichloromethane. However, this is a tedious procedure and involves the use of hazardous
compounds. Cyclic steam distillation produced results with an accuracy of around 80% and a good precision (5.2%). The very
low consumption of solvents and other expensive chemicals by this technique and the possibility of analyzing the extract directly
without clean-up make it an interesting alternative to the more sophisticated methods. Column elution with dichloromethane
was found to be less efficient (61%), but it is a rapid, direct method with a low consumption of solvents and it may therefore
serve as screening method.
Received: 29 April 1997 / Revised: 30 July 1997 / Accepted: 6 August 1997 相似文献
1000.
Prásilová J 《Talanta》1966,13(11):1567-1571
A substoichiometric method for the determination of heavy rare earths (holmium, thulium) has been developed. After the addition of a substoichiometric amount of EDTA to the test sample of rare earth labelled with its radioactive isotopes, the negatively charged complex formed was separated by passage through a column of Dowex 50 x 8. Interfering metals can be removed by preliminary cupferron and diethylammonium diethyldithiocarbamate extraction. Concentrations of rare earth down to 4 x 10(-7)g 5 ml have been determined. 相似文献