843 resultados para Benzyl Alcohol


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Sticholysin I and II (StnI and StnII) are pore-forming toxins that use sphingomyelin (SM) for membrane binding. We examined how hydrogen bonding among membrane SMs affected the StnI- and StnII-induced pore formation process, resulting in bilayer permeabilization. We compared toxin-induced permeabilization in bilayers containing either SM or dihydro-SM (lacking the trans 4 double bond of the long-chain base), since their hydrogen-bonding properties are known to differ greatly. We observed that whereas both StnI and StnII formed pores in unilamellar vesicles containing palmitoyl-SM or oleoyl-SM, the toxins failed to similarly form pores in vesicles prepared from dihydro-PSM or dihydro-OSM. In supported bilayers containing OSM, StnII bound efficiently, as determined by surface plasmon resonance. However, StnII binding to supported bilayers prepared from dihydro-OSM was very low under similar experimental conditions. The association of the positively charged StnII (at pH 7.0) with unilamellar vesicles prepared from OSM led to a concentration-dependent increase in vesicle charge, as determined from zeta-potential measurements. With dihydro-OSM vesicles, a similar response was not observed. Benzyl alcohol, which is a small hydrogen-bonding compound with affinity to lipid bilayer interfaces, strongly facilitated StnII-induced pore formation in dihydro-OSM bilayers, suggesting that hydrogen bonding in the interfacial region originally prevented StnII from membrane binding and pore formation. We conclude that interfacial hydrogen bonding was able to affect the membrane association of StnI- and StnII, and hence their pore forming capacity. Our results suggest that other types of protein interactions in bilayers may also be affected by hydrogen-bonding origination from SMs.

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Os organismos marinhos constituem uma fonte potencial de metabólitos secundários biologicamente ativos. Neste contexto, os micro-organismos isolados de algas marinhas, dentre eles fungos endofíticos, representam alvos para a pesquisa de novas substâncias com potencial farmacológico pronunciado. Substâncias naturais provenientes de espécies de fungos associados às algas marinhas vêm sendo bastante utilizadas em formulações fotoprotetoras devido à ação antioxidante e ao potencial contra a radiação solar. Deste modo, o presente trabalho teve como objetivo a investigação biológica e química dos fungos endofíticos marinhos pertencentes à família Xylariaceae, o Annulohypoxylon stygium, o Cladosporium sp. e o Acremonium implicatum (Hypocreaceae). A princípio, foi realizado um screening para avaliar a absorção de luz ultravioleta na faixa do UVA e UVB pelos extratos obtidos em escala piloto destes fungos endofíticos associados às algas marinhas. O extrato do fungo A. stygium apresentou intensa absorção na região do UV, mostrando-se promissor para a produção de metabólitos secundários com ação fotoprotetora. Além do ensaio proposto, foi realizada a avaliação do potencial antibacteriano e antifúngico da espécie A. stygium. O estudo químico em escala ampliada deste fungo proporcionou o isolamento e identificação de uma substância inédita da classe derivada da 2,5- dicetopiperazina, 3-benzilideno-2-metil-hexahidro-pirrolo [1,2-?] pirazina-1,4-diona (Sf3), e além desta, foram isolados mais quatro metabólitos como, os diasteroisômeros 1-fenil-1,2- propanediol (Sd2) e 1-fenil-1,2-propanediol (Sd3), 1,3-benzodioxole-5-metanol (Sc1), 1,2- propanodiol-1-(1,3-benzodioxol-5-il) (Se1). Ainda foi possível a desreplicação de substâncias via cromatografia gasosa acoplada à espectrometria de massas (CG-EM), entre elas o ácido palmítico, palmitato de metila, ácido metil linoléico, ácido oléico, álcool benzílico e o piperonal. Quanto ao estudo da atividade biológica, não foi observado potencial antibacteriano e antifúngico para os extratos e frações do fungo. Entretanto, notouse um potencial como fotoprotetor in vitro para as frações n-Hexano/AcOEt (2:3) e n- Hexano/AcOEt (1:4) obtidas a partir do extrato do cultivo de 28 dias do fungo A. stygium, extraído com solventes diclorometano/metanol (CH2Cl2/MeOH 2:1) e para a substância (Sf3) isolada do mesmo. Desta forma, o estudo químico e biológico do fungo Annulohypoxylon stygium demonstrou potencial para a produção de metabólitos secundários com atividade fotoprotetora, visto que uma estrutura inédita com esta atividade foi isolada e identificada como produto natural.

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Sticholysin II (StnII) is a pore-forming toxin that uses sphingomyelin (SM) as the recognition molecule in targeting membranes.After StnII monomers bind to SM, several toxin monomers act in concert to oligomerize into a functional pore. The regulation of StnII binding to SM, and the subsequent pore-formation process, is not fully understood. In this study, we examined how the biophysical properties of bilayers, originating from variations in the SM structure, from the presence of sterol species, or from the presence of increasingly polyunsaturated glycerophospholipids,affected StnII-induced pore formation. StnII-induced pore formation, as determined from calcein permeabilization, was fastest in the pure unsaturated SM bilayers. In 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/saturated SM bilayers (4:1 molar ratio), pore formation became slower as the chain length of the saturated SMs increased from 14 up to 24 carbons. In the POPC/palmitoyl-SM (16:0-SM) 4:1 bilayers, SM could not support pore formation by StnII if dimyristoyl-PC was included at 1:1 stoichiometry with 16:0-SM, suggesting that free clusters of SM were required for toxin binding and/or pore formation. Cholesterol and other sterols facilitated StnII-induced pore formation markedly, but the efficiency did not appear to correlate with the sterol structure. Benzyl alcohol was more efficient than sterols in enhancing the pore-formation process, suggesting that the effect on pore formation originated from alcohol-induced alteration of the hydrogen-bonding network in the SM-containing bilayers. Finally, we observed that pore formation by StnII was enhanced in the PC/16:0-SM 4:1 bilayers, in which the PC was increasingly unsaturated. We conclude that the physical state of bilayer lipids greatly affected pore formation by StnII. Phase boundaries were not required for pore formation, although SM in a gel state attenuated pore formation.

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Catalytically active heterogeneous catalysts have been prepared via microwave deposition of iron oxide nanoparticles (0.5–1.2 wt%) on MCM-41 type silica materials with different morphologies (particles, helical and spheres). This methodology leads to iron oxide nanoparticles composed by a mixture of FeO and Fe2O3 species, being the Fe(II)/Fe(III) peak ratio near to 1.11 by XPS. DRUV spectroscopy indicates the presence of tetrahedral coordinated Fe3+ in the silica framework of the three catalysts as well as some extraframework iron species in the catalysts with particle and sphere-like morphologies. The loading of the nanoparticles does neither affect the mesopore arrangement nor the textural properties of the silica supports, as indicated by SAXS and nitrogen adsorption/desorption isotherms. A detailed investigation of the morphology of the supports in various microwave-assisted catalyzed processes shows that helical mesostructures provide optimum catalytic activities and improved reusabilities in the microwave-assisted redox (selective oxidation of benzyl alcohol) catalyzed process probably due to a combination of lower particle size and higher acidity in comparison with the supports with particle and sphere morphology.

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The objective of this research was to investigate the oxidation of organic compounds in molten alkali metal hydroxides containing manganates. It has been shown that controlled oxidation can be readily achieved with high specificity to give products in high yield with very short reaction times. The concurrent changes in the melt were monitored using a vibrating platinum indicator electrode with a quazi-reference electrode which was successfully developed for use in molten (Na-K)OH eutectic at 523K. Henry's Law constants for water in the molten eutectic system (Na-K)OH have been measured and used to calculate the water concentration in the melt. The electrochemistry of manganates in molten (Na-K)OH eutectic at 523K has been studied using the vibrating platinum electrode, and the existence of the species Mn(II), Mn(II!), Mn(IV), Mn(V) and Mn(VI) in such melts has been investigated at various water concentrations. The half-wave potentials of the voltammetric waves were measured versus the cathodic limit of the melt. The stability of Mn(V) or Mn(VI) in the melt was achieved by varying the water concentration. A range of organic chemicals has been passed through molten (Na-K)OH at 523K and the reactions of these chemicals with the melt have been studied. The same organics were then passed through molten (Na-K)OH containing stabilized Mn(V) or Mn{VI) without violent reaction. Methanol, allyl alcohol, propane 1, 2 diol, I-heptene and acetone were oxidized by Mn(V) and Mn(VI). Ethanol was only oxidized by Mn(VI), isopropanol and benzyl alcohol were only oxidized by Mn(V). Npropanol, butanol, 2 methyl propan-2-ol, n-hexane, n-heptane toluene and cyclohexane were unchanged by both Mn(V) and Mn(VI). Detailed experiments have been performed on the reactions of ethanol, iso-propanol and methanol in molten (Na-K)OH containing stabilized Mrt(V) or Mn(VI), and reaction mechanisms have been postulated. Ethanol and iso-propanol were oxidized to acetaldehyde and acetone respectively with a potential for useful chemical process. The oxidation of methanol could be developed as a basis for an industrial methanol disposal process.

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Various monoacrylic compounds containing a hindered phenol function (e.g.3,5-di-tert.-butyl-4-hydroxy benzyl alcohol, DBBA and vinyl-3-[3',5'-di-tert.-butyl-4-hydroxy phenyl] propionate, VDBP), and a benzophenone function (2-hydroxy-4-[beta hydroxy ethoxy] benzophenone, HAEB) were synthesised and used as reactive antioxidants (AO's) for polypropylene (PP). These compounds were reacted with PP melt in the presence of low concentration of a free radical generator such a peroxide (reactive processing) to produce bound-antioxidant concentrates. The binding reaction of these AO's onto PP was found to be low and this was shown to be mainly due to competing reactions such as homopolymerisation of the antioxidant. At high concentrations of peroxide, higher binding efficiency resulted, but, this was accompanied by melt degradation of the polymer. In a special reactive processing procedure, a di- or a trifunctional reactant (referred to as coagent), e.g.tri-methylol propane tri-acrylate, Tris, and Divinyl benzene, DVB, were used with the antioxidant and this has led to an enhanced efficiency of the grating reaction of antioxidants on the polymer in the melt. The evidence suggests that this is due to copolymerisation of the antioxidants with the coagent as well as grafting of the copolymers onto the polymer backbone. Although the 'bound' AO's containing a UV stabilising function showed lower overall stabilisation effect than the unbound analogues before extraction, they were still much more effective when subjected to exhaustive solvent extraction. Furthermore, a very effective synergistic stabilising activity when two reactive AO's containing thermal and UV stabilising functions e.g. DBBA and HAEB, were reactively processed with PP in the presence of a coagent. The stabilising effectiveness of such a synergist was much higher than that of the unbound analogues both before and after extraction. Analysis using the GPC technique of concentrates containing bound-DBBA processed in the presence of Tris coagent showed higher molecular weight (Mn), compared to that of a polymer processed without the coagent, but was still lower than that of the control processed PP with no additives. This indicates that Tris coagent may inhibit further melt degradation of the polymer. Model reactions of DBBA in liquid hydrocarbon (decalin) and analysis of the products using FTIR and NMR spectroscopy showed the formation of grafted DBBA onto decalin molecules as well as homopolymerisation of the AO. In the presence of Tris coagent, copolymerisation of DBBA with the Tris inevitably occured; which was followed by grafting of the copolymer onto the decalin, FTIR and NMR results of the polymer concentrates containing bound-DBBA processed with and without Tris, showed similar behaviour as the above model reactions. This evidence supports the effect of Tris in enhancing the efficiency of the reaction of DBBA in the polymer melt. Reactive procesing of HAEB in polymer melts exhibited crosslinking formation In the early stages of the reaction, however, in the final stage, the crosslinked structure was 'broken down' or rearranged to give an almost gel free polymer with high antioxidant binding efficiency.

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Siliceous mesoporous molecular sieves (SBA-15) have been functionalised with propylsulfonic acid groups by both co-condensing 3-mercaptopropyltrimethoxysilane with the solid at the synthesis (sol-gel) stage and by grafting the same compound to pre-prepared SBA-15, followed, in both cases, by oxidation to sulfonic acid. The acidic and catalytic properties of the supported sulfonic acids prepared in the two ways have been compared, using ammonia adsorption calorimetry and the benzylation reaction between benzyl alcohol and toluene. Using a combination of X-ray photoelectron spectroscopy and other analytical techniques, the level of functionalisation and the extent of subsequent oxidation of tethered thiol to sulfonic acid, both in the bulk and close to the surface of SBA-15 particles, have been assessed. The research shows that the co-condensing route leads to higher levels of functionalisation than the grafting route. The extent of oxidation of added thiol to acid groups is similar using the two routes, about 70% near the surface and only 50% in the bulk. Comparison is made with polymer supported sulfonic acid catalysts, Amberlysts 15 and 35, and Nafion. Nafion shows the highest acid strength and the highest specific catalytic activity of all materials studied. Amongst the other materials, average acid strengths are broadly similar but there appears to be a relationship between the concentration of acid sites on the catalysts and their specific activity in the benzylation reaction. A model is proposed to explain this, in which clustering of sulfonic acid groups, even to a small extent, leads to disproportionately enhanced catalytic activity. © 2009 Elsevier B.V. All rights reserved.

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Propylsulfonic acid derivatised SBA-15 catalysts have been prepared by post modification of SBA-15 with mercaptopropyltrimethoxysilane (MPTMS) for the upgrading of a model pyrolysis bio-oil via acetic acid esterification with benzyl alcohol in toluene. Acetic acid conversion and the rate of benzyl acetate production was proportional to the PrSO3H surface coverage, reaching a maximum for a saturation adlayer. Turnover frequencies for esterification increase with sulfonic acid surface density, suggesting a cooperative effect of adjacent PrSO3H groups. Maximal acetic acid conversion was attained under acid-rich conditions with aromatic alcohols, outperforming Amberlyst or USY zeolites, with additional excellent water tolerance.

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The study of green chemistry is dedicated to eliminating or reducing toxic waste. One route to accomplish this goal is to explore alternative reaction conditions and parameters resulting in the development of more benign synthetic routes and reagents. The primary focus of this research is to find optimal reaction conditions for the oxidation of a primary alcohol to an aldehyde. As a case study, the oxidation of benzyl alcohol to benzaldehyde, a common industrial process, was examined. Traditionally carried out using the Jones Reagent, commonly referred to as chromium (IV) oxide or chromium trioxide (CrO3) in sulphuric acid, a great deal of research went into utilizing less toxic reagents, such as MnO2 or KMnO4 supported on a clay base. This research has led to an improvement on these alternatives, using a lithium chloride (LiCl) catalyst in a montmorillonite K10 clay solid phase, together with the oxidizing agent hydrogen peroxide, as even greener alternatives to these traditional oxidizing agents. Experiments were carried out to determine the lifetime of this LiCl/clay system as compared to MnO2 and KMnO4, to investigate its ability to catalyze the oxidation of other aromatic alcohols (such as 4-methoxybenzyl alcohol and diphenylmethanol), and to further improve the system’s adherence to green chemistry principles. Green solvent alternatives were examined by replacing the toluene solvent with dimethylcarbonate (DMC), and reaction conditions were optimized to improve product yield. It was determined that the LiCl/H2O2 system was, in most cases, equally as effective at catalyzing the oxidation of benzyl alcohol to benzaldehyde. Although the catalyst and oxidizing agent eliminated the toxic waste generated from chromium reagents, it offered significant challenges in product isolation, because of an aqueous-organic phase separation.

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Diffuse reflectance and laser-induced techniques were used to study photochemical and photophysical processes of benzil adsorbed on two solid powdered supports, microcrystalline cellulose and beta-cyclodextrin. In both substrates, a distribution of ground-state benzil conformers exists, largely dominated by skew conformations where the carbonyl groups are twisted one to the other. Room temperature phosphorescence was observed in air-equilibrated samples in both cases. The decay times vary greatly and the largest lifetime was obtained for benzil/beta-cyclodextrin, showing that this host's cavity accommodates benzil well, enhancing its room temperature phosphorescence. Triplet - triplet absorption of benzil entrapped in cellulose was detected and benzil ketyl radical formation also occurred. With benzil included into beta-cyclodextrin, and following laser excitation, benzoyl radicals were detected on the millisecond timescale. Product analysis and identification of laser-irradiated benzil samples in the two hosts clearly showed that the main degradation photoproducts were benzoic acid and benzaldehyde. The main differences were a larger benzoic acid/benzaldehyde ratio in the case of cellulose and the formation of benzyl alcohol in this support.

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Typically adolescents' friends are considered a risk factor for adolescent engagement in risk-taking. This study took a more novel approach, by examining adolescent friendship as a protective factor. In particular it investigated friends' potential to intervene to reduce risk-taking. 540 adolescents (mean age 13.47 years) were asked about their intention to intervene to reduce friends' alcohol, drug and alcohol-related harms and about psychosocial factors potentially associated with intervening. More than half indicated that they would intervene in friends' alcohol, drug use, alcohol-related harms and interpersonal violence. Intervening was associated with being female, having friends engage in overall less risk-taking and having greater school connectedness. The findings provide an important understanding of increasing adolescent protective behavior as a potential strategy to reduce alcohol and drug related harms.

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An improved synthetic route to α(1→3)/α(1→2)-linked mannooligosaccharides has been developed and applied to a more efficient preparation of the potent anti-angiogenic sulfated pentasaccharide, benzyl Manα(1→3)-Manα(1→3)-Manα(1→3)-Manα(1→2)-Man hexadecasulfate, using only two monosaccharide building blocks. Of particular note are improvements in the preparation of both building blocks and a simpler, final deprotection strategy. The route also provides common intermediates for the introduction of aglycones other than benzyl, either at the building block stage or after oligosaccharide assembly. The anti-angiogenic activity of the synthesized target compound was confirmed via the rat aortic assay.