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291.
Isabella G. Alonso Lais T. Yamane Verônica S. de Freitas-Blanco Luiz F.T. Novaes Michelle Franz-Montan Eneida de Paula Marili V.N. Rodrigues Rodney A.F. Rodrigues Julio C. Pastre 《Tetrahedron》2018,74(38):5192-5199
A 5-step synthesis of spilanthol (affinin) is reported, where the route features complete control of alkene geometry during the assembling of the double bonds, with the use of a Sonogashira cross-coupling reaction, a Z-selective alkyne semi-reduction and a HWE olefination reaction as the key steps. A simplified analogue was also prepared in 4 steps. Both compounds were found to permeate dermatomed pig ear skin through an in vitro Franz-type diffusion cell. The simplified analogue presented a superior anesthetic effect in vivo, using the tail flick model, when compared to spilanthol and to the commercial standard EMLA®. These results suggest that both spilanthol and its analogue could be useful as a topical anesthetic in clinical practice. 相似文献
292.
López-Darias J Pino V Meng Y Anderson JL Afonso AM 《Journal of chromatography. A》2010,1217(46):7189-7197
The functionalized polymeric ionic liquid poly(1-(4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl]imide (poly(VBHDIm(+)NTf(2)(-))) has been used as successful coating in solid-phase microextraction (SPME) to determine a group of fourteen endocrine disrupting chemicals (ECDs), including polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and parabens, in several water samples. The performance of the PIL fiber in direct immersion mode SPME followed by gas chromatography (GC) with flame-ionization detection (FID) is characterized with average relative recoveries higher than 96.1% from deionized waters and higher than 76.7% from drinking bottled waters, with precision values (RSD) lower than 13% for deionized waters and lower than 14% for drinking bottled waters (spiked level of 1 ng mL(-1)), when using an extraction time of 60 min with 20 mL of aqueous sample. Detection limits varied between 9 ng L(-1) and 7 ng mL(-1). A group of real water samples, including drinking waters, well waters, and swimming pool waters, have been analyzed under the optimized conditions. A comparison has also been carried out with the commercial SPME coatings: polydimethylsyloxane (PDMS) 30 μm, and polyacrylate (PA) 85 μm. The functionalized PIL fiber (~12 μm) demonstrated to be superior to both commercial fibers for the overall group of analytes studied, in spite of its lower coating thickness. A normalized sensitivity parameter is proposed as a qualitative tool to compare among fiber materials, being higher for the poly(VBHDIm(+)NTf(2)(-)) coating. Furthermore, the partition coefficients of the studied analytes to the coating materials have been determined. A quantitative comparison among the partition coefficients also demonstrates the superior extraction capability of the functionalized PIL sorbent coating. 相似文献
293.
294.
Luis J. Alías Verónica L. Cánovas A. Gervasio Colares 《General Relativity and Gravitation》2017,49(2):23
In this paper we consider codimension two marginally trapped submanifolds in the family of general Robertson–Walker spacetimes. In particular, we derive some rigidity results for this type of submanifolds which guarantee that, under appropriate hypothesis, the only ones are those contained in slices. We also derive some interesting non-existence results for weakly trapped submanifolds. In particular, we give applications to some cases of physical relevance such as the Einstein-de Sitter spacetime and certain open regions of de Sitter spacetime, including the so called steady state spacetime. Our results will be an application of the (finite) maximum principle for closed manifolds and, more generally, of the weak maximum principle for stochastically complete manifolds. 相似文献
295.
Morales-Florez Víctor Piñero Manuel Braza Verónica del Mar Mesa María Esquivias Luis de la Rosa-Fox Nicolás 《Journal of Sol-Gel Science and Technology》2017,81(2):600-610
Journal of Sol-Gel Science and Technology - This work is a new approach to the study of the structural, mechanical and absorption properties of hybrid organic/inorganic silica-based aerogels.... 相似文献
296.
Verónica Prado Dr. Emilio Lence Dr. Juan A. Vallejo Dr. Alejandro Beceiro Paul Thompson Prof. Alastair R. Hawkins Prof. Concepción González‐Bello 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(8):2758-2768
The phosphoryl‐transfer mechanism of shikimate kinase from Mycobacterium tuberculosis and Helicobacter pylori, which is an attractive target for antibiotic drug discovery, has been studied by 1D 1H and 31P NMR spectroscopy. Metaphosphoric acid proved to be a good mimetic of the metaphosphate intermediate and facilitated the ready and rapid evaluation by NMR spectroscopic analysis of a dissociative mechanism. The required closed form of the active site for catalysis was achieved by the use of ADP (product) or two synthetic ADP analogues (AMPNP, AMPCP). Molecular dynamics simulation studies reported here also revealed that the essential arginine (Arg116/Arg117 in H. pylori and M. tuberculosis, respectively), which activates the γ‐phosphate group of ATP for catalysis and triggers the release of the product for turnover, would also be involved in the stabilisation of the metaphosphate intermediate during catalysis. We believe that the studies reported here will be helpful for future structure‐based design of inhibitors of this attractive target. The approach is also expected be useful for studies on the possible dissociative mechanism of other kinase enzymes. 相似文献
297.
Dr. Laura Abad Galán Dr. David Aguilà Dr. Yannick Guyot Dr. Verónica Velasco Dr. Olivier Roubeau Dr. Simon J. Teat Dr. Massimiliano Massi Dr. Guillem Aromí 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7288-7299
The ligand H3L (6-[3-oxo-3-(2-hydroxyphenyl)propionyl]pyridine-2-carboxylic acid), which exhibits two different coordination pockets, has been exploited to engender and study energy transfer (ET) in two dinuclear [LnIIILnIII′] analogues of interest, [EuYb] and [NdYb]. Their structural and physical properties have been compared with newly synthesised analogues featuring no possible ET ([EuLu], [NdLu], and [GdYb]) and with the corresponding homometallic [EuEu] and [NdNd] analogues, which have been previously reported. Photophysical data suggest that ET between EuIII and YbIII does not occur to a significant extent, whereas emission from YbIII originates from sensitisation of the ligand. In contrast, energy migration seems to be occurring between the two NdIII centres in [NdNd], as well as in [NdYb], in which YbIII luminescence is thus, in part, sensitised by ET from Nd. This study shows the versatility of this molecular platform to further the investigation of lanthanide-to-lanthanide ET phenomena in defined molecular systems. 相似文献
298.
Verónica Almeida-Marrero Marta Mascaraque María Jesús Vicente-Arana Prof. Ángeles Juarranz Prof. Tomás Torres Dr. Andrés de la Escosura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(37):9634-9642
In the endeavor of extending the clinical use of photodynamic therapy (PDT) for the treatment of superficial cancers and other neoplastic diseases, deeper knowledge and control of the subcellular processes that determine the response of photosensitizers (PS) are needed. Recent strategies in this direction involve the use of activatable and nanostructured PS. Here, both capacities have been tuned in two dendritic zinc(II) phthalocyanine (ZnPc) derivatives, either asymmetrically or symmetrically substituted with 3 and 12 copies of the carbohydrate sialic acid (SA), respectively. Interestingly, the amphiphilic ZnPc-SA biohybrid ( 1 ) self-assembles into well-defined nanoaggregates in aqueous solution, facilitating cellular internalization and transport whereas the PS remains inactive. Within the cells, these nanostructured hybrids localize in the lysosomes, as usually happens for anionic and hydrophilic aggregated PS. Yet, in contrast to most of them (e. g., compound 2 ), hybrid 1 recovers the capacity for photoinduced ROS generation within the target organelles due to its amphiphilic character; this allows disruption of aggregation when the compound is inserted into the lysosomal membrane, with the concomitant highly efficient PDT response. 相似文献
299.
Patricio Hermosilla-Ibáñez Juan Costamagna Andrés Vega Verónica Paredes-García Eric Le Fur 《Journal of Coordination Chemistry》2014,67(23-24):3940-3952
In the present work, the synthesis and structural characterization of two new polyoxovanadoborate (BVO) frameworks, based on the [V12B18O60H6]10? polyanion, are reported, K(H3O)(enH2)4[V12B18O60H6]·9.60H2O (1) and Li8(NH4)2[V12B18O60H6]·8.02H2O (2). Both compounds are obtained in a mixed valence ratio of 10VIV/2VV. Framework 1 is characterized by potassium ions coordinated by the BVO cluster and ethylenediammonium and hydronium ions as charge-compensating agents. In framework 2, the BVO clusters are coordinating lithium ions and the charge is compensated by ammonium ions. Using the SHAPE 2.1 program, it was possible to calculate the best geometry for the existing lithium and potassium ions. For 2, the lithium ions are five-coordinate, best described by a square pyramid (SPY-5), while the coordination sphere around the potassium ions in 1 are six-coordinate. For 1, the coordination sphere of the existing potassium ions in the framework can be described as trigonal prism (TPR-6). Calculations were also done for a previously reported cluster [Na10[(H2O)V12B18O60H6]·18H2O] (3), in which the sodium ions are six-coordinate but in two different geometries, these being octahedral and TPR-6. The influence of the interactions of the alkali ions with the [V12B18O60H6]10? polyanion, on the vanadate and borate absorption bands observed in the infrared spectra, is discussed. 相似文献
300.
In Situ and Theoretical Studies for the Dissociation of Water on an Active Ni/CeO2 Catalyst: Importance of Strong Metal–Support Interactions for the Cleavage of O–H Bonds
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Dr. Javier Carrasco Dr. David López‐Durán Dr. Zongyuan Liu Dr. Tomáš Duchoň Dr. Jaime Evans Dr. Sanjaya D. Senanayake Dr. Ethan J. Crumlin Prof. Dr. Vladimir Matolín Dr. José A. Rodríguez Dr. M. Verónica Ganduglia‐Pirovano 《Angewandte Chemie (International ed. in English)》2015,54(13):3917-3921
Water dissociation is crucial in many catalytic reactions on oxide‐supported transition‐metal catalysts. Supported by experimental and density‐functional theory results, the effect of the support on O? H bond cleavage activity is elucidated for nickel/ceria systems. Ambient‐pressure O 1s photoemission spectra at low Ni loadings on CeO2(111) reveal a substantially larger amount of OH groups as compared to the bare support. Computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO2(111) compared with pyramidal Ni4 particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni2+ species by accommodating electrons in localized f‐states. The fast dissociation of water on Ni/CeO2 has a dramatic effect on the activity and stability of this system as a catalyst for the water‐gas shift and ethanol steam reforming reactions. 相似文献