In this work we report a simple procedure for synthesis of Cu and Pd catalysts supported on high surface area graphite (HSAG) by wetness impregnation technique, and further generation of metal ...nanoparticles using NaBH4 as reducing agent. The catalysts have been tested in the reduction of 4-nitrophenol to 4-aminophenol, at room temperature, in presence of NaBH4 as hydrogen source. Both Cu and Pd catalysts exhibited exceptionally high catalytic activity with the total degradation of 4-nitrophenol in less than 45 s. Taking into account that Cu is cheaper than Pd, we focused our investigation on studying the catalytic properties of Cu nanoparticles supported over two lab prepared graphene-materials (one N-doped and other undoped) and the commercial HSAG. The maximum catalytic activity was obtained with Cu supported on undoped graphene due to the combination of two parameters: small metal particle size and the unique properties of graphene generated by its electron transference ability. However, recyclability of both Cu/graphene-materials fell after 5 consecutive runs, while Cu/HSAG displayed high stability even after 10 cycles. In order to rationalize these findings, it is postulated that copper nanoparticles in Cu/HSAG are located at the edges of the graphite layers, where a stronger metal-support interaction takes place.
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The analyses of characterization show that the Ru-La interaction facilities the levulinic acid hydrogenation and the reaction rate was a consequence of the amount of Ru active site and the promoting ...effect of Ru-La interaction.
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•The addition of La in Ru/Carbon fiber (Ru1La0.5/CF) enhances the catalytic activity, resulting into a maximum reaction rate of (216.1μmolgcat−1s−1) at 100°C.•The increased reactivity was a consequence of the amount of Ru active site and the promoting effect of Ru-La interaction.•The exact nature of the promotional effect of La in the levulinic acid hydrogenation has been clarified.
A series of La-modified Ru/carbon fiber (CF) catalysts was designed, and used for the conversion of levulinic acid (LA) into γ-valerolactone (GVL) under batch reactor conditions. The dopant of Lanthanum improved the hydrogenation activity from 37.7μmolgcat−1s−1 to 216.1μmolgcat−1s−1 when the mole La/Ru was 0.5 on the catalyst. Even in low temperatures, the Ru1La0.5/CF catalyst also showed a high activity in the hydrogenation of LA. Aiming at a detailed understanding the role of Ru-La interactions in the catalyst, the Ru1Lax/CF catalysts was characterized by the H2-TPR, H2-TPD, CO2-TPD, XPS, TEM and CO chemsorption. The electron density of Ru species has been enhanced by La addition to Ru/CF. The hydrogenation activity was a consequence of the amount of Ru active site and the promoting effect of Ru-La interaction.
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•The ability of copper to promote ethanol dehydrogenation under non-oxidative conditions is much higher than that of silver.•Addition of a low quantity of silver into copper catalyst ...results advantageous to improve metallic dispersion.•Addition of silver into copper catalyst has a negative impact on catalytic activity and null to improve catalytic stability.•Catalytic activity decays during reaction conditions due to fouling but is recovered though thermal treatment under H2 flow.
The physicochemical and catalytic properties of bimetallic AgCu catalysts and their monometallic counterparts supported on a high surface area graphite have been comparatively evaluated in the ethanol dehydrogenation reaction, performed in a continuous-flow reactor. While Cu was incorporated by the incipient wetness impregnation technique, for Ag catalysts two synthesis procedures were explored: incipient wetness impregnation and adsorption of Tollens’ reagent. The catalysts prepared by wetness impregnation exhibited higher metal dispersion, being improved for the bimetallic catalysts in comparison with the monometallic counterparts. The results obtained in the catalytic tests revealed that Cu catalysts is nearly two orders of magnitude more active than Ag catalyst in the dehydrogenation reaction of ethanol on either a turnover frequency or a weight basis, but at the same time both catalysts were 100% selective to acetaldehyde. Whereas selectivity was not affected by the bimetallic composition, there was a substantial decrease in the reaction rate among the bimetallic catalysts as the Cu/Ag ratio diminished, due to blockage of copper surface active sites by silver. Both silver and copper, and the bimetallic catalysts, suffered from deactivation at 523 K, caused by blocking of active sites by adsorbed hydrocarbons on the catalyst surface (fouling). Carbonaceous deposits were removed through a thermal treatment under H2 flow, which allowed the total recovery of the initial catalytic activity.
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•Metronidazole (MNZ) and trimethoprim (TMP) were adsorbed on nanocarbon materials.•Four nanocarbon materials were commercial high surface area graphite.•Three nanocarbons were ...synthesized from graphene oxide (GO) and reduced GO.•Except for GO, the nanomaterials adsorption capacity increased with surface area.•Adsorption of MNZ and TMP was predominantly due to π-π dispersive interactions.
The adsorption of metronidazole (MNZ) and trimethoprim (TMP) antibiotics from water on nanomaterials synthesized from graphene oxide and graphite, was examined thoroughly. The effect of the physicochemical properties and surface area onto the adsorption capacity of the nanomaterials was studied in detail. The nanocarbon materials used were graphene oxide (GO), and GO reduced in inert medium (rGO) or ammonia (N-rGO), and four high surface area graphites (HSAG100, HSAG300, HSAG400, HSAG500). The nanomaterials characterization was performed by transmission and scanning electron microscopy, N2 physisorption, TG-profiles and X-ray diffraction. The increasing order of the nanomaterial adsorption capacity toward MNZ was: HSAG100 < HSAG300 < N-rGO < HSAG400 < HSAG500 < GO < rGO and toward TMP was: HSAG100 < N-rGO ≈ HSAG300 < HSAG400 < HSAG500 ≈ rGO < GO; and except for GO, the adsorption capacity of the nanomaterials increased almost linearly with the surface area. At T = 25 °C, the maximum mass adsorbed of MNZ and TMP on GO were 190 and 218 mg/g, at pH 7 and pH 10, respectively. The adsorption of TMP and MNZ on GO corroborated the presence of different adsorption mechanisms dependent on antibiotic speciation and pH. The adsorption of both antibiotics on the materials based on graphite and reduced graphene oxide was predominantly due to π-π dispersive interactions.
Blocking Ras inhibition as an antitumor strategy Marín-Ramos, Nagore I.; Ortega-Gutiérrez, Silvia; López-Rodríguez, María L.
Seminars in cancer biology,
February 2019, 2019-Feb, 2019-02-00, 20190201, Letnik:
54
Journal Article
Recenzirano
Ras proteins are among the most frequently mutated drivers in human cancer and remain an elusive pharmaceutical targeting. Previous studies have improved the understanding of Ras structure, ...processing, and signaling pathways in cancer cells and have opened new possibilities for inhibiting Ras function. In this review we discuss the most recent advances towards inhibiting Ras activity with small molecules, highlighting the two approaches: (i) compounds that bind directly to Ras protein and (ii) inhibitors of the enzymes involved in the post-translational modifications of Ras. In the former, we analyze the most recent contributions in each of the main classes of Ras direct binders, including the different types of nucleotide exchange inhibitors, allosteric compounds, and molecules that interfere with the interaction between Ras and its effectors. In the latter, we examine the compounds that inhibit Ras activation by blocking any of its post-translational modifications. Also, a special focus is made on those molecules that have progressed the farthest from medicinal chemistry and drug development points of view. Finally, the current scene regarding the clinical trials of Ras inhibitors, together with the future promising avenues for further development of the challenging Ras field are reviewed.
Ni, Cu and Ni-Cu catalysts supported on high surface area graphite were synthesized by incipient wet impregnation. Also, the effect of doping the graphite support with alkali oxides (Li, Na and K) ...was studied. The catalysts were tested in the formic acid decomposition reaction to produce hydrogen. The bimetallic Ni-Cu catalyst doped with K showed the best catalytic performance with 100% conversion of formic acid at 130 °C and a 95% of selectivity to hydrogen. The turnover frequency (TOF) of the catalysts follows the order: Ni-Cu/K > NiCu/Na > Ni-Cu > Ni-Cu/Li. While the order for the apparent activation energy values is: Ni-Cu > Ni-Cu/Li > Ni-Cu/Na > Ni-Cu/K. The mechanism of the reaction is approached by programmed temperature surface reaction (TPSR) experiments and attenuated total reflectance (ATR). The greater catalytic activity of the Ni-Cu catalyst doped with potassium is ascribed to the lower stability of the formate, bicarbonate and carbonate species on its surface.
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•High purity hydrogen has been obtained through formic acid decomposition.•Non-noble Ni-Cu catalysts supported over high surface area graphite have been used.•The effect of doping the graphite support with an alkaline (Li, Na, K) was studied.•The alkalines can promote the reaction at mild temperatures.•The Ni-Cu catalyst doped with K showed the best catalytic performance.
Achieving high selectivity is one of the major challenges in heterogeneous catalysis, being carbon materials universally employed as catalysts support due to their so-called “inert” nature. However, ...due to the complexity of its intrinsic characteristics, there are still several factors to bear in mind when selecting the appropriate carbon support. In this work we demonstrate that the remaining sulfur impurities in one type of commercial carbon nanofibers (CNFs) drastically alter the catalytic properties of palladium by triggering electro-deficient active sites. Two as-received CNFs thermally processed at different severity degrees, namely PS and HHT, were used to support Pd nanoparticles through the wet impregnation technique using palladium nitrate as precursor. The proof of principle is demonstrated through two transformation reactions of biomass platform molecules: the hydrogenation of 5-hydroxymethylfurfural, performed in a batch-type reactor, and the ethanol dehydrogenation/decarbonylation reaction, carried out in a continuous flow fixed-bed reactor. In both reactions, Pd/PS was substantially more selective than its sulfur-free counterpart Pd/HHT, and one of the most selective in comparison with the state-of-the-art Pd catalysts. This finding makes available a simple, easy and green strategy to design carbon-supported Pd catalysts for selective hydrogenation and dehydrogenation reactions.
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Blockade of Ras activity by inhibiting its post-translational methylation catalyzed by isoprenylcysteine carboxylmethyltransferase (ICMT) has been suggested as a promising antitumor strategy. ...However, the paucity of inhibitors has precluded the clinical validation of this approach. In this work we report a potent ICMT inhibitor, compound 3 UCM-1336, IC50 = 2 μM, which is selective against the other enzymes involved in the post-translational modifications of Ras. Compound 3 significantly impairs the membrane association of the four Ras isoforms, leading to a decrease of Ras activity and to inhibition of Ras downstream signaling pathways. In addition, it induces cell death in a variety of Ras-mutated tumor cell lines and increases survival in an in vivo model of acute myeloid leukemia. Because ICMT inhibition impairs the activity of the four Ras isoforms regardless of its activating mutation, compound 3 surmounts many of the common limitations of available Ras inhibitors described so far. In addition, these results validate ICMT as a valuable target for the treatment of Ras-driven tumors.
Commercial carbon nanotubes (CNT), were used as supports to prepare Ni/CNT catalysts with a 15 wt% Ni loading and NiCu x /CNT catalysts with Cu loadings of x : 1.5, 2.25, 3.0 and 3.75 wt% were ...prepared. The catalysts were characterized by N 2 physisorption, H 2 -temperature programmed reduction (TPR), transmission electron microscopy (TEM), STEM-HAADF and X-ray photoelectron spectra (XPS), and they were evaluated in the conversion of guaiacol at 573 K and 5 MPa H 2 pressure for 4 h in a batch reactor. The characterization showed that Ni–Cu alloys were formed which existed along with Ni, Cu and NiO entities. The Ni metallic particle size was lower upon increasing Cu content, however the increased proportion of NiO species and the coverage of Ni sites with Cu diminished the intrinsic activity. The addition of Cu also decreased the hydrogenolysis and deoxygenation ability for the catalysts up to 3 wt% of Cu, which can be related to the lower size of Ni ensembles. Beyond that percentage, the selectivity was modified and it was attributed to changes in the Ni dispersion.
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