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1.
2.
O. N. Oliveira Jr. G. F. Leal Ferreira 《Applied Physics A: Materials Science & Processing》1987,42(3):213-217
Surface-potential measurements carried out in negatively corona charged 12 m samples of fluorethylenepropylene (Teflon FEP) showed the following characteristics: 1) with a constant charging current, the potential initially rises linearly, and then sublinearly; 2) the potential saturates irrespectively of the charging process and 3) practically no potential decay is observed after switching off the corona. These results have been interpreted in terms of an usual model (field-independent trapping time) for charge transport in insulators, with saturable deep traps in both surface and bulk of the sample and a relatively high electron mobility in order to prevent free-space charge accumulation. The partial differential equations derived from the model are numerically solved and it was found that only the product of the mobility with the trapping time is relevant to the fitting of experimental results, provided that >10–8 cm2/Vs. A field-dependent trapping time model leads to poorer fittings. 相似文献
3.
Sexual attraction in the silkworm moth: structure of the pheromone-binding-protein-bombykol complex 总被引:14,自引:0,他引:14
BACKGROUND: Insects use volatile organic molecules to communicate messages with remarkable sensitivity and specificity. In one of the most studied systems, female silkworm moths (Bombyx mori) attract male mates with the pheromone bombykol, a volatile 16-carbon alcohol. In the male moth's antennae, a pheromone-binding protein conveys bombykol to a membrane-bound receptor on a nerve cell. The structure of the pheromone-binding protein, its binding and recognition of bombykol, and its full role in signal transduction are not known. RESULTS: The three-dimensional structure of the B. mori pheromone-binding protein with bound bombykol has been determined by X-ray diffraction at 1.8 A resolution. CONCLUSIONS: The pheromone binding protein of B. mori has six helices, and bombykol binds in a completely enclosed hydrophobic cavity formed by four antiparallel helices. Bombykol is bound in this cavity through numerous hydrophobic interactions, and sequence alignments suggest critical residues for specific pheromone binding. 相似文献
4.
5.
Determination of macrolide antibiotics by liquid chromatography 总被引:7,自引:0,他引:7
The liquid chromatographic separation of seven macrolides used in food producing animals in the European Union has been studied. Separation was performed by using an end-capped high-purity silica-based C18 column and mobile phases consisting of phosphate buffer (pH 2.5)–acetonitrile mixtures. The effect of pH and acetonitrile percentage on the separation was examined. Two UV-based detection systems, wavelength programming and diode array, were assayed. Detection limits were in the range 6–33 μg l−1 for spiramycin, tilmicosin, tylosin, kitasamicin and josamicin and about 400 μg l−1 for erythromycin and oleandomycin. The suitability of the method for multiresidue determination of the five macrolides is demonstrated by the analysis of spiked samples of chicken muscle. 相似文献
6.
L. C. Machado A. A. L. Marins E. J. B. Muri J. A. S. Lacerda V. O. Balthar P. F. Fulvio J. C. C. Freitas 《Journal of Thermal Analysis and Calorimetry》2004,75(2):615-621
This paper presents the reactions of synthesis between the ligand sodium diphenylamine-4-sulfonate and the lanthanum(III)
chloride hydrated. The compounds (LaCl3)2·(C12H10NSO3Na)3·2(CH3CH2OH) (A) and (LaCl3)·(C12H10NSO3Na)·(CH3CH2OH)·12H2O (B) were obtained using the solvents ethanol and methanol (synthesis A) and ethanol and water (synthesis B). The produced
compounds and the ligand were characterized by thermogravimetric and differential thermogravimetric analysis, IR spectroscopy
and elemental analysis of sodium, carbon, hydrogen, nitrogen, sulfur, chlorine and lanthanum, whereas the residues from thermal
decomposition were investigated by X-ray diffractometry.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Variations of densities and viscosities with temperature and composition are reported for binary liquid mixtures containing propionic acid+aniline (I),+o-toluidine (II),+o-anisidine (III), and+o-chloroaniline (IV). Entropies S
m and enthalpies H
m of activation as functions of the composition of the mixtures, as well as free energies of activation G
m at 10, 20, 30, 40, and 50°C and different compositions were calculated by means of Eyring's equation. The formation of activated complexes between the components of these binary mixtures is postulated and claimed to result from acid-base and hydrogen bonding exchange interactions. 相似文献
8.
Gleison Gonalves Ferreira Ana Carolina Sousa Quaresma Dayse Lúcia do Nascimento Brando Andrey Moacir do Rosario Marinho Jos Edson de Sousa Siqueira Kamila Leal Correa Jos Otvio Carrra Silva-Júnior Sandro Percario Maria Fni Dolabela 《Molecules (Basel, Switzerland)》2023,28(1)
Cancer is a multifactorial organic dysfunction for which great efforts are being devoted in searching for new treatments and therapeutic adjuvants. Annona muricata is a fruit that has promising activity against several types of cancer, as it contains acetogenins, the metabolite group associated with this action. Thus, the objective of this study was to evaluate, in experimental models, the toxic behavior of an extract and fraction rich in acetogenins from A. muricata seeds and study the acetogenin, Annonacin, in silico. Phytochemical characterization was made by thin layer chromatography, spectroscopy in the infrared region and nuclear magnetic resonance. Toxicity was evaluated by tests of Allium cepa and Artemia salina, and in silico studies using the SwissDock servers DockThor, PharmMapper, ADMETLab, PreADME, Osiris and ProTox. The extract and fraction showed genotoxic activity against meristematic cells of A. cepa, reducing the mitotic index; however, the extract produced great deleterious effects on the system, even causing cell necrosis. In A. Saline, the extract was more toxic than the fraction, but both samples were considered toxic. Annonacin was effectively linked to complex I, and presented different activities regarding toxicity. Thus, the results of this study are promising, highlighting the anticancer potential of acetogenins. 相似文献
9.
Dr. Saida Majdoub Dr. Zoltán Garda Alexandre C. Oliveira Dr. Inga Relich Agnès Pallier Dr. Sara Lacerda Dr. Christelle Hureau Dr. Carlos F. G. C. Geraldes Dr. Jean-François Morfin Dr. Éva Tóth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2009-2020
Metal chelates targeted to amyloid peptides are widely explored as diagnostic tools or therapeutic agents. The attachment of a metal complex to amyloid recognition units typically leads to a decrease in peptide affinity. We show here that by separating a macrocyclic GdL chelate and a PiB targeting unit with a long hydrophobic C10 linker, it is possible to attain nanomolar affinities for both Aβ1-40 (Kd=4.4 nm ) and amylin (Kd=4.5 nm ), implicated, respectively in Alzheimer's disease and diabetes. The Scatchard analysis of surface plasmon resonance data obtained for a series of amphiphilic, PiB derivative GdL complexes indicate that their Aβ1-40 or amylin binding affinity varies with their concentration, thus micellar aggregation state. The GdL chelates also affect peptide aggregation kinetics, as probed by thioflavin-T fluorescence assays. A 2D NMR study allowed identifying that the hydrophilic region of Aβ1-40 is involved in the interaction between the monomer peptide and the Gd3+ complex. Finally, ex vivo biodistribution experiments were conducted in healthy mice by using 111In labeled analogues. Their pancreatic uptake, ∼3 %ID g−1, is promising to envisage amylin imaging in diabetic animals. 相似文献
10.
Daniela P. Mesquita Cristiano Leal Jorge R. Cunha Adrian Oehmen A. Luís Amaral Maria A.M. Reis Eugénio C. Ferreira 《Analytica chimica acta》2013
The present study focuses on predicting the concentration of intracellular storage polymers in enhanced biological phosphorus removal (EBPR) systems. For that purpose, quantitative image analysis techniques were developed for determining the intracellular concentrations of PHA (PHB and PHV) with Nile blue and glycogen with aniline blue staining. Partial least squares (PLS) were used to predict the standard analytical values of these polymers by the proposed methodology. Identification of the aerobic and anaerobic stages proved to be crucial for improving the assessment of PHA, PHB and PHV intracellular concentrations. Current Nile blue based methodology can be seen as a feasible starting point for further enhancement. Glycogen detection based on the developed aniline blue staining methodology combined with the image analysis data proved to be a promising technique, toward the elimination of the need for analytical off-line measurements. 相似文献