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51.
Espinoza Catalán L Carrasco Altamirano H Cuellar Fritis M Gallardo Araya C Catalán Marín K 《Molecules (Basel, Switzerland)》2007,12(3):318-327
A selective route for the degradation of the unsaturated side chain of ent-labdanes has been devised, giving two useful synthons: 2beta-acetoxy-14,15,17-trinor-ent-labdane-8,13- dione (5) and 2beta-acetoxy-14,15-dinor-ent-labd-8(17)-en-13-one (7), the use of which for the preparation of terpenylquinone derivatives shall be reported elsewhere. 相似文献
52.
López T Espinoza KA Kozina A Castillo P Silvestre-Albero A Rodriguez-Reinoso F Alexander-Katz R 《Langmuir : the ACS journal of surfaces and colloids》2011,27(7):4004-4009
The sol-gel method was used to synthesize inorganic reservoirs with encapsulated antiepileptic drug phenytoin. The drug release profile was shown to depend on the morphology and surface properties of the matrix. A parameter of the synthesis such as water/alkoxide ratio r(w) was varied in order to investigate its influence on the matrix properties and as a result on the drug release profile. It was found that the specific surface area and crystallization degree decrease with an increase of r(w), whereas the hydroxyl group coverage increases with an increase of r(w). Drug release kinetics studies revealed that the initial release rate increases with an increase of water content in the reaction, whereas the long time release rate first slightly increases with an increase of water content from 4 to 8 and then decreases for r(w) = 16. The interplay of different parameters of the matrix is shown to be responsible for such a dependence and is discussed in the Article. 相似文献
53.
54.
Carrasco H Raimondi M Svetaz L Di Liberto M Rodriguez MV Espinoza L Madrid A Zacchino S 《Molecules (Basel, Switzerland)》2012,17(1):1002-1024
Twenty one phenylpropanoids (including eugenol and safrole) and synthetic analogues, thirteen of them new compounds, were evaluated for antifungal properties, first with non-targeted assays against a panel of human opportunistic pathogenic fungi. Some structure-activity relationships could be observed, mainly related to the influence of an allyl substituent at C-4, an OH group at C-1 and an OCH(3) at C-2 or the presence of one or two NO(2) groups in different positions of the benzene ring. All active compounds were tested in a second panel of clinical isolates of C. albicans and non-albicans Candida spp., Cryptococcus neoformans and dermatophytes. The eugenol derivative 4-allyl-2-methoxy-5-nitrophenol (2) was the most active structure against all strains tested, and therefore it was submitted to targeted assays. These studies showed that the antifungal activity of 2 was not reversed in the presence of an osmotic support such as sorbitol, suggesting that it does not act by inhibiting the fungal cell wall synthesis or assembly. On the other hand, the Ergosterol Assay showed that 2 did not bind to the main sterol of the fungal membrane up to 250 μg mL-1. In contrast, a 22% of fungal membrane damage was observed at concentrations = 1 × MIC and 71% at 4× MIC, when 2 was tested in the Cellular Leakage assay. The comparison of log P and MICs for all compounds revealed that the antifungal activity of the eugenol analogues would not to be related to lipophilicity. 相似文献
55.
T. Aguayo C. Garrido R. E. Clavijo J. S. Gmez‐Jeria C. Araya Monasterio M. Icaza F. Espinoza Moraga M. M. Campos Vallette 《Journal of Raman spectroscopy : JRS》2013,44(9):1238-1245
The Raman and surface enhanced Raman scattering (SERS) spectra of a black dyed silk sample (BDS) were registered. The spectral analysis was performed on the basis of Raman and SERS spectral data of isolated samples of Bombyx mori silk fibroin, its motif peptide component (GAGAGS) and the synthetic reactive black 5 dye (RB5). The macro FT‐Raman spectrum of the silk sample is consistent with a silk II‐Cp crystalline fraction of Bombyx mori silk fibroin; the SERS spectrum is highly consistent with conformational modifications of the fibroin due to the interactions with the Ag nanoparticles. The GAGAGS peptide sequence dominates the Raman spectrum of the silk. The SERS spectrum of the peptide suggests a random coil conformation imposed by the surface interaction; the serine residue in the new conformation is exposed to the surface. Quantum chemical calculations for a model of the GAGAGS–Ag surface predict a nearly extended conformation at the Ag surface. The Raman spectrum of the dye was analysed, and a complete band assignment was proposed; it was not possible to propose a preferential orientation or organization of the molecule on the metal surface. Quantum chemical calculations for a model of the dye interacting with a silver surface predict a rather coplanar orientation of the RB5 on the Ag metal surface. The Raman spectrum of the BDS sample is dominated by signals from the dye; the general spectral behaviour indicates that the dye mainly interacts with the silk through the sulphone (–SO2–) and sulphonate (–SO2–O–) groups. Besides the presence of dye signals, mainly ascribed to the sulphone and sulphonate bands, the SERS spectrum of the BDS sample also displays bands belonging to the amino acids alanine, glycine, serine and particularly tyrosine. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
56.
Roberto Cesareo Angel D. Bustamante Julio S. Fabian Sandra Del Pilar Zambrano Walter Alva Luis Z. Chero Maria C. Del Carmen Espinoza Rosendo R. Rodriguez Marco F. Seclen Fidel V. Gutierrez Edgard B. Levano Juan A. Gonzales Marcia A. Rizzutto Enrico Poli Cristiane Calza Marcelino Dos Anjos Renato Pereira De Freitas Ricardo T. Lopes Carlos Elera Izumi Shimada Victor Curay Maria G. Castillo Giovanni E. Gigante Gabriel M. Ingo Fabio Lopes Ulla Holmquist David Diestra 《Applied Physics A: Materials Science & Processing》2013,113(4):889-903
Three types of alloys were recognized when analyzing pre-Columbian artifacts from the North of Peru: gold, silver, and copper alloys; gilded copper and silver; silvered copper; tumbaga, i.e., copper or silver enriched on gold at the surface by depletion gilding. In this paper, a method is described to differentiate gold alloys from gilded copper and from copper–gold tumbaga, and silver alloys from silvered copper and copper–silver tumbaga. This method is based on the use of energy-dispersive X-ray fluorescence, i.e., on a sophisticated analysis of XRF-spectra carrying out an accurate determination of Cu(K α /K β ), Ag(K α /K β ), Au(L α /L β ), and Au-L α /Cu-K α or Ag-K α /Cu-K α ratios. That implies a dedicated software for the quantitative determination of the area of X-ray peaks. This method was first checked by a relevant number of standard samples and then it was applied to pre-Columbian alloys from the North of Peru. 相似文献
57.
L. Rojas-Blanco M.D. UrzúaR. Ramírez-Bon F.J. Espinoza Beltrán 《Applied Surface Science》2012,258(6):2103-2106
In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min. 相似文献
58.
Rosa Linares Xchitl N. Acua Gabriela Rosas Elizabeth Vieyra Deyra A. Ramírez Andrea Chaparro Julieta A. Espinoza Roberto Domínguez Leticia Morales-Ledesma 《Molecules (Basel, Switzerland)》2021,26(18)
In rats with polycystic ovary syndrome (PCOS) induced by injection of estradiol valerate (EV), unilateral or bilateral section of the vagus nerve restores ovulatory function in 75% of animals, suggesting that the vagus nerve participates in the development of PCOS. Since the vagus nerve is a mixed nerve through which mainly cholinergic-type information passes, the objective of the present study was to analyze whether acetylcholine (ACh) is involved in the development of PCOS. Ten-day-old rats were injected with 2.0 mg EV, and at 60 days of age, they were microinjected on the day of diestrus in the bursa of the left or right ovary with 100 or 700 mg/kg of ovarian weight atropine, a blocker of muscarinic receptors, and sacrificed for histopathological examination after the surgery. Animals with PCOS microinjected with 100 mg of atropine showed a lack of ovulation, lower serum concentrations of progesterone and testosterone, and cysts. Histology of the ovaries of animals microinjected with 700 mg of atropine showed corpus luteum and follicles at different stages of development, which was accompanied by a lower concentration of progesterone and testosterone. These results allow us to suggest that in animals with PCOS, ACh, which passes through parasympathetic innervation, is an important component in the persistence and development of the pathophysiology. 相似文献
59.
J.L. Maxwell M.R. Black C.A. Chavez K.R. Maskaly M. Espinoza M. Boman L. Landstrom 《Applied Physics A: Materials Science & Processing》2008,91(3):507-514
This work demonstrates that two or more elements of negligible solubility (and no known phase diagram) can be co-deposited
in fiber form by hyperbaric-pressure laser chemical vapor deposition (HP-LCVD). For the first time, Hg-W alloys were grown
as fibers from mixtures of tungsten hexafluoride, mercury vapor, and hydrogen. This new class of materials is termed normally-immiscible
materials (NIMs), and includes not only immiscible materials, but also those elemental combinations that have liquid states
at exclusive temperatures. This work also demonstrates that a wide variety of other binary and ternary alloys, intermetallics,
and mixtures can be grown as fibers, e.g. silicon-tungsten, aluminum-silicon, boron-carbon-silicon, and titanium-carbon-nitride.
In addition, pure metallic fibers of aluminum, titanium, and tungsten were deposited, demonstrating that materials of high
thermal conductivity can indeed be grown in three-dimensions, provided sufficient vapor pressures are employed. A wide variety
of fiber properties and microstructures resulted depending on process conditions; for example, single crystals, fine-grained
alloys, and glassy metals could be deposited.
PACS 81.15.Fg; 81.05.Bx; 81.05.Je; 81.15.Gh 相似文献
60.