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71.
The mass spectra of 1,2-cycloaddition products obtained from the benzophenone photosensitized irradiation of 2,3-dimethyl maleic and citraconic anhydride in several thiophen derivatives are prsented and discussed. 相似文献
72.
Peix A Rivas R Velázquez E Mateos PF Martínez-Molina E Muñoz-Herrera A Gómez-Alonso A Velázquez E 《Electrophoresis》2005,26(23):4402-4410
The random intergenic spacer analysis is a recently developed technique for the study of microbial populations. The bacterial intergenic spacer (ITS) is located between 16S rRNA and 23S rRNA genes and presents different length and sequence among bacterial species. Therefore, the amplicons can be separated by electrophoresis commonly performed at low voltage during several hours. Although this technique is especially useful for unculturable microorganisms, it has not been applied before to clinical sample analysis. As these samples have a limited number of bacterial species, the size of the gels may be reduced to facilitate their handling and to reduce the running time. To obtain maximum separation among the ITS bands, we analysed in this work different electrophoretical conditions including staircase electrophoresis, a technique based on the application of several voltage steps. The results obtained showed a different behaviour of the electrical resistance during the performance of submarine horizontal and vertical staircase electrophoresis. In the first case the resistance decreased during most of the running time whereas in the second case it increased. Here, we show that the performance of horizontal staircase electrophoresis reduces the running time more than 80% with respect to conventional electrophoresis at low voltages. This procedure was applied to the separation of ITS bands from bacterial DNA present in a tissue from a vocal cord biopsy. The sequencing of these bands allowed their identification. This new procedure may be very useful in the rapid diagnosis of bacteria present in human, animal and plant tissues. 相似文献
73.
The assignment of the carbon-13 nmr resonances of a series of oxetanes derived from the photoaddition of benzophenone and 2-naphthaldehyde to furan and some of its methyl derivatives and of benzophenone to 2,5-dimethylthiophene has been made. The assignments were made by chemical shift arguments, by the use of C-13 labelling when required and different decoupling techniques. This information may be useful in the identification of new compounds with analogous carbon skeleton. 相似文献
74.
S. Yez Vilar A. Castro‐Couceiro B. Rivas‐Murias A. Fondado J. Mira J. Rivas M. A. Searís‐Rodríguez 《无机化学与普通化学杂志》2005,631(11):2192-2196
The dielectric properties of mixed‐oxide CaMn7O12 are reported. This compound exhibits a high dielectric constant at room temperature (ε′r> 104), for frequencies up to 104 Hz, values that make it very attractive for potential applications provided that its rather high losses can be minimized. Complex plane analysis of the obtained data reveal an important extrinsic contribution to these high ε′r values; and also that the intrinsic dielectric constant of this material is ε′r,∞ ≈ 30, a value rather high for this type of compounds, that could be related to the electronic process of charge‐ordering present in this oxide below 440 K. 相似文献
75.
76.
Ana T. Rufino Ana Ramalho Adelaide Sousa Jos Miguel P. Ferreira de Oliveira Paulo Freitas Manuel A. Gonzalez Gmez Yolanda Pieiro-Redondo Jos Rivas Flix Carvalho Eduarda Fernandes Marisa Freitas 《Molecules (Basel, Switzerland)》2021,26(21)
Silver nanoparticles (AgNP) have been increasingly incorporated into food-related and hygiene products for their unique antimicrobial and preservative properties. The consequent oral exposure may then result in unpredicted harmful effects in the gastrointestinal tract (GIT), which should be considered in the risk assessment and risk management of these materials. In the present study, the toxic effects of polyethyleneimine (PEI)-coated AgNP (4 and 19 nm) were evaluated in GIT-relevant cells (Caco-2 cell line as a model of human intestinal cells, and neutrophils as a model of the intestinal inflammatory response). This study also evaluated the putative protective action of dietary flavonoids against such harmful effects. The obtained results showed that AgNP of 4 and 19 nm effectively induced Caco-2 cell death by apoptosis with concomitant production of nitric oxide, irrespective of the size. It was also observed that AgNP induced human neutrophil oxidative burst. Interestingly, some flavonoids, namely quercetin and quercetagetin, prevented the deleterious effects of AgNP in both cell types. Overall, the data of the present study provide a first insight into the promising protective role of flavonoids against the potentially toxic effects of AgNP at the intestinal level. 相似文献
77.
Adina Borbély Dr. Eduard Figueras Ana Martins Dr. Lizeth Bodero Dr. André Raposo Moreira Dias Dr. Paula López Rivas Dr. Arianna Pina Dr. Daniela Arosio Dr. Paola Gallinari Dr. Marcel Frese Dr. Christian Steinkühler Prof. Dr. Cesare Gennari Prof. Dr. Umberto Piarulli Prof. Dr. Norbert Sewald 《ChemistryOpen》2019,8(6):737-742
RGD-cryptophycin and isoDGR-cryptophycin conjugates were synthetized by combining peptidomimetic integrin ligands and cryptophycin, a highly potent tubulin-binding antimitotic agent across lysosomally cleavable Val-Ala or uncleavable linkers. The conjugates were able to effectively inhibit binding of biotinylated vitronectin to integrin αvβ3, showing a binding affinity in the same range as that of the free ligands. The antiproliferative activity of the novel conjugates was evaluated on human melanoma cells M21 and M21-L with different expression levels of integrin αvβ3, showing nanomolar potency of all four compounds against both cell lines. Conjugates containing uncleavable linker show reduced activity compared to the corresponding cleavable conjugates, indicating efficient intracellular drug release in the case of cryptophycin-based SMDCs. However, no significant correlation between the in vitro biological activity of the conjugates and the integrin αvβ3 expression level was observed, which is presumably due to a non-integrin-mediated uptake. This reveals the complexity of effective and selective αvβ3 integrin-mediated drug delivery. 相似文献
78.
Vargas F Zoltan T Rivas C Ramirez A Cordero T Díaz Y Izzo C Cárdenas YM López V Gómez L Ortega J Fuentes A 《Journal of photochemistry and photobiology. B, Biology》2008,92(2):83-90
We have synthesized two naphthyl ester quinolone derivates and determined their ability to generate reactive oxygen species (ROS) such as (1)O(2), ()OH, H(2)O(2) upon photolysis with UV-A light. The ability of cinoxacin (1) and nalidixic acid (2), and their naphthyl ester derivatives (3 and 4) to generate a dose-dependent amount of singlet oxygen and ROS (()(-)O(2), ()OH) in cell-free systems was detected by histidine assay and by luminol-enhanced chemiluminescence (LCL), respectively. Their electronic absorption and emission spectra were quantified and their photostability was determined. Their tendency to generate peroxidic derivative species showed the following order: 3>4; in contrast, their ability to generate singlet oxygen was 4>3 and these were better sensitizers than their parent quinolones 1 and 2. The antibacterial activity in darkness and under irradiation of compounds 3 and 4 was tested on Escherichia coli and compared with that of their parent compounds. An enhanced antibacterial activity by irradiation of the naphthyl esters of cinoxacin and nalidixic acid on E. coli was observed. 相似文献
79.
Electrochemical Sensor for the Quantification of Dopamine Using Glassy Carbon Electrodes Modified with Single‐Wall Carbon Nanotubes Covalently Functionalized with Polylysine 下载免费PDF全文
Alejandro Gutiérrez Aurélien Gasnier María L. Pedano Jose Miguel Gonzalez‐Dominguez Alejandro Ansón‐Casaos Javier Hernández‐Ferrer Laura Galicia María D. Rubianes María T. Martínez Gustavo A. Rivas 《Electroanalysis》2015,27(7):1565-1571
We report a dopamine electrochemical sensor based on the modification of glassy carbon electrodes (GCE) with polylysine‐functionalized single‐wall carbon nanotubes (SWCNT‐PLys). The resulting electrodes (GCE/SWCNT‐PLys) showed a significant improvement in the electrooxidation of dopamine with drastic decrease in the peak potentials separation and important enhancement in the associated currents. Dopamine was detected by differential pulse voltammetry‐adsorptive stripping with medium exchange at nanomolar levels even in the presence of high excess of ascorbic and uric acids. The sensor was successfully used for the quantification of dopamine in urine samples enriched with the neurotransmitter. 相似文献
80.
C. Mateo-Mateo C. Vázquez-Vázquez M.C. Buján-Núñez M.A. López-Quintela D. Serantes D. Baldomir J. Rivas 《Journal of Non》2008,354(47-51):5236-5237
Cobalt ferrite–poly(N-vinyl-2-pyrrolidone) nanocomposites were prepared by drying a dispersion of cobalt ferrite (CoFe2O4) nanoparticles and poly(N-vinyl-2-pyrrolidone). Magnetic measurements indicate a superparamagnetic behavior. Zero-field-cooling magnetization experiments at 100 Oe show different trends depending on the CoFe2O4 nanoparticles size. For the smaller ones (3.9 nm), the blocking temperatures shift to lower temperatures with increasing concentration; however, this shift is not observed for the larger ones (6.6 nm). These differences can be related to the anisotropy constant of the CoFe2O4 nanoparticles and the interparticle dipolar interactions. 相似文献