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排序方式: 共有649条查询结果,搜索用时 156 毫秒
641.
A new heptadentate Schiff base, containing an inner N3O2 and an outer O2O2 site, has been obtained by the reaction of 3-formylsalicylic acid and diethylenetriamine. By reaction of this ligand with copper(II), nickel(II) or uranyl(VI) salts, mononuclear and dinuclear complexes have been synthesized. The mononuclear complexes can act as ligands towards a second metal ion giving rise to homodinuclear or heterodinuclear complexes. The enlargement of the inner coordination chamber allows the synthesis of dinuclear uranyl(VI) species, impossible to obtain with the inner N2O2 site of the ligands previously employed. The equatorial pentacoordination of the UO22+ group in the outer O2O2 chamber is reached with the coordination of a solvent molecule to the central metal ion. The electrochemical behaviour of some complexes prepared is also reported. 相似文献
642.
643.
Silvano Monarca Donatella Feretti Alberto Zanardini Massimo Moretti Milena Villarini Berthold Spiegelhalder Ilaria Zerbini Umberto Gelatti Eugenio Lebbolo 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2001,490(2)
This research was designed to examine the presence of mutagenic/carcinogenic compounds in airborne pollutants in the rubber industry using an integrated chemical/biological approach. Inhalable airborne particulate matter (PM-10: <10 μm) was collected in four rubber factories using a high-volume sampler equipped with a cascade impactor for particle fractionation. The organic extracts of two different fractions (0.5–10 μm and <0.5 μm) were examined for mutagenicity with the Ames test and for in vitro DNA-damaging activity in human leukocytes by single-cell microgel electrophoresis (Comet assay). The extracts were also studied by gas chromatography/mass spectrometry (GC/MS) for polycyclic aromatic hydrocarbon (PAH) content. Nitrosamines in ambient air were sampled on cartridges and analysed by GC with a thermal energy analyser (TEA) detector. Airborne volatile genotoxins were monitored in situ using a clastogenicity plant test (Tradescantia/micronuclei test). The results showed that airborne particulates were mainly very fine (<0.5 μm) and that trace amounts of genotoxic nitrosamines (N-nitrosodimethylamine: 0.10–0.98 μg/m3; N-nitrosomorpholine: 0.77–2.40 μg/m3) and PAH (total PAH: 0.34–11.35 μg/m3) were present in air samples. Some extracts, particularly those obtained from the finest fractions, were mutagenic with the Ames test and genotoxic with the Comet assay. In situ monitoring of volatile mutagens using the Tradescantia/micronuclei test gave positive results in two working environments. The results showed the applicability of this integrated chemical–biological approach for detecting volatile and non-volatile genotoxins and for monitoring genotoxic hazards in the rubber industry. 相似文献
644.
Calf lens crystallin messenger RNA''s contain polynucleotide sequences rich in adenylic acid 总被引:2,自引:1,他引:1
Gianni Piperno Umberto Bertazzoni Anton J.M. Berns Hans Bloemendal 《Nucleic acids research》1974,1(2):245-255
Calf lens messenger fractions have been purified on poly(dT)-cellulose. The purified RNA's have been analyzed as nucleosides by a method which can be used on a micro-scale with highly reproduceble results. Both the 10S and 14S lens mRNA contain poly A sequences. The poly A content found in 14S mRNA cannot account for the excess nucleotides in this message. 相似文献
645.
646.
Maria Armida Rossi Clelia Di Mauro Hermann Esterbauer Fulvio Fidale Mario Umberto Dianzani 《Cell biochemistry and function》1994,12(4):275-280
A comparison has been made between the effects of 4-hydroxy-2,3-trans-nonenal (HNE) and 4-hydroxy-2,3-trans-octenal (HOE), two lipid peroxidation products, on the basal and GTPgammaS-stimulated activities of phosphoinositide-specific phospholipase C (PL-C) of rat polymorphonuclear leukocytes. PL-C activity was determined in vitro by measuring the hydrolysis of [3H] phosphatidylinositol-4,5-bis-phosphate (PtdIns-P2) added as exogenous substrate to neutrophil plasma membranes. PL-C was activated by concentrations of HNE ranging from 10?8 to 10?6 M both in the presence and in the absence of 2 × 10?5 M GTPgammaS; HOE stimulated the enzymatic activity between 10?11 and 10?8 M ; maximal stimulation was given by 10?11 M HOE plus GTPgammaS. The aldehyde concentrations able to accelerate PtdIns-P2 breakdown displayed a good correspondence with those which have been reported to stimulate the oriented migration of rat neutrophils. Pretreatment of neutrophils with pertussis toxin prevented the stimulation of PL-C by 10?11 M HOE and by HOE plus GTPgammaS. Our results suggest that the chemotactic action of HNE and HOE might depend on the activation of PL-C; furthermore a regulatory G protein appears to be involved in the acceleration of PtdIns-P2 turnover by HOE. 相似文献
647.
Summary The growth of Cyanidium caldarium on nitrate and ammonia as nitrogen sources was studied at different temperatures from 21 to 54°C.Algal growth occurred at temperatures of 24° C or above when ammonia was the nitrogen source, whereas with nitrate, growth occurred at 30° C or above. The optimum and the maximum growth temperatures were 45 and 54° C respectively on both substrates.Arrhenius plots show that the logarithm of the growth rate is not linear with the reciprocal of absolute temperature, but exhibit sharply defined breaks at 30° C on ammonia and at 40° C on nitrate.It is assumed that below 40° C, when Cyanidium grows on nitrate, the utilization of this substrate represents the master reaction which controls the growth rate of the alga. 相似文献
648.
The structure of horse liver alcohol dehydrogenase 总被引:11,自引:0,他引:11
649.
Keith Dobney Anton Ervynck Umberto Albarella Peter Rowley-Conwy 《Journal of Zoology》2004,264(2):197-208