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Benzoic Acid (benzoic + acid)
Kinds of Benzoic Acid Terms modified by Benzoic Acid Selected AbstractsSynthesis of para -Amino Benzoic Acid,TiO2 Hybrid Nanostructures of Controlled Functionality by an Aqueous One-Step ProcessEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2008Raed Rahal Abstract In situ amino acid surface-modified TiO2 nanoparticle syntheses were performed by a simple one-pot hydrolysis of heteroleptic titanium alkoxide [Ti(OiPr)3(O2CC6H4NH2)]m in water with NnBu4Br. This process allowed precise control of the surface grafting rate by varying the amount of precursors and provided highly functionalized nanomaterials. Their compositions and microstructures were determined by C, H and N elemental analyses, TGA-MS, 13C CP-MAS NMR, XRD, TEM, BET, Raleigh diffusion, FTIR, Raman, XPS and UV/Vis experiments. The results indicated that (i) the aggregation rate increased with an increase in the loading of the organic substrate and (ii) the amino acid is chemisorbed as a carboxylate group onto the TiO2 nanoparticles, which leads to a strong interaction between the amino acid and the TiO2 nanoparticle and good stability of these hybrids. Applications of low-aggregated nanomaterials were demonstrated as efficient protection additive against UVA + UVB radiations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Wide Blue Phase Range in a Hydrogen-Bonded Self-Assembled Complex of Chiral Fluoro-Substituted Benzoic Acid and Pyridine DerivativeADVANCED MATERIALS, Issue 20 2009Wanli He A blue phase with a broad temperature range of about 23.0 °C is easily achieved in a hydrogen-bonded self-assembled complex of chiral fluoro-substituted benzoic acid and pyridine derivative. The success in extending the temperature of blue phase indicates that the hydrogen-bonded self-assembly is a promising new approach to broaden the temperature range of blue phases and to investigate the mystery of blue phases. [source] Catalytic Liquid Phase Oxidation of Toluene to Benzoic AcidCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2008A. Gizli Abstract The production of benzoic acid from toluene in the liquid phase with pure oxygen was studied. Investigations have been carried out with a view to determining the most suitable reaction conditions with respect to operating variables including oxygen flow rate, reaction temperature, batch time and catalyst loading. In a series of batch experiments carried out at 4,atm, the optimum values of mole ratio of oxygen to toluene, temperature, reaction time, and catalyst loading were found to be 2, 157,°C, 2,h and 0.57,g/L, respectively. In addition, a kinetic study was carried out by taking into consideration the optimum reaction conditions. The model dependent on the formation of benzyl radical was found to be feasible for describing the catalytic oxidation of toluene to benzoic acid in the liquid phase. The activation energy was determined as 40,kJ/mol. [source] A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic AcidCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 7 2010Elena Arceo Dr. Shikimic Gimmick: An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method. [source] Rhodium-Mediated Decarboxylative Conjugate Addition of Fluorinated Benzoic Acids: Stoichiometric and Catalytic Transformations,ANGEWANDTE CHEMIE, Issue 36 2009Zhong-Ming Sun Dr. Je nach Bisphosphanligand entsteht bei der Decarboxylierung von 2,6-difluorierten Benzoesäuren mit einem RhI -Katalysator in Gegenwart eines Acrylesters oder Acrylamids bevorzugt das konjugierte Addukt 1 oder das Produkt der Heck-Mizoroki-Arylierung (2; Binap=2,2,-Bis(diphenylphosphanyl)-1,1,-binaphthyl, diop=4,5-Bis(diphenylphosphanylmethyl)-2,2-dimethyl-1,3-dioxolan). [source] Palladium(II)-Catalyzed ortho Alkylation of Benzoic Acids with Alkyl Halides,ANGEWANDTE CHEMIE, Issue 33 2009Yang-Hui Zhang Dr. Wettbewerbsvorteil: Bei der PdII -katalysierten Reaktion von Benzoaten mit Alkylhalogeniden wird eine Aryl-C-H-Bindung aktiviert, bevor die konkurrierende Alkylierung des Carboxylations stattfinden kann. Auf die Alkylierung folgte eine intramolekulare Lactonisierung, die weit anwendbare ,- und ,-Benzolactone ergab (siehe Schema). [source] ChemInform Abstract: Chemoselectivity of Cobalt-Catalyzed Carbonylation , A Reliable Platform for the Synthesis of Fluorinated Benzoic Acids.CHEMINFORM, Issue 33 2010Vadim P. Boyarskiy Abstract Methoxycarbonylation of polyhalogenated benzene (I) shows that fluorine substitution is not observed. [source] Two Methods for Direct ortho-Arylation of Benzoic Acids.CHEMINFORM, Issue 51 2007Hendrich A. Chiong Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] DMSO/NaNO2/49% HBr: A Novel and Powerful Oxidant for the Direct Conversion of Primary Benzylamines to Benzoic Acids.CHEMINFORM, Issue 21 2006Ramesh Naik Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Ortholithiation of Unprotected Benzoic Acids: Application for Novel 2-Chloro-6-substituted Benzoic Acid Syntheses.CHEMINFORM, Issue 33 2005Frederic Gohier Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Oxidation of Benzyl Chlorides and Bromides to Benzoic Acids with 30% Hydrogen Peroxide in the Presence of Na2WO4, Na3VO4, or Na2MoO4 under Organic Solvent-Free Conditions.CHEMINFORM, Issue 37 2001Min Shi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Versatile Catalyst for Intermolecular Direct Arylation of Indoles with Benzoic Acids as Arylating ReagentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2010Jun Zhou Coupled together: With a versatile catalyst system (Pd(TFA)2/Ag2CO3/propionic acid) both electron-rich and -deficient benzoic acids serve as arylating reagents for the direct functionalization of a wide rage of indoles by a combination of decarboxylation and CH bond activation. Depending on the nature of the benzoic acids, the reaction occurs selectively at either the C2- or C3-position of indoles, which may arise from two different catalytic pathways (see scheme; TFA=trifluoroacetate). [source] Structure-Based Optimization of Benzoic Acids as Inhibitors of Protein Tyrosine Phosphatase 1B and Low Molecular Weight Protein Tyrosine PhosphataseCHEMMEDCHEM, Issue 6 2009Rosanna Maccari Dr. Abstract We have optimized previously discovered benzoic acids 1, which are active as inhibitors of PTP1B and LMW-PTP, two protein tyrosine phosphatases that have emerged as attractive targets for the development of novel therapeutic agents for the treatment of diabetes, obesity, and cancer. Our efforts led to the identification of new and more potent analogues with appreciable selectivity toward human PTP1B and the IF1 isoform of human LMW-PTP. [source] Application of PC-ANN to Acidity Constant Prediction of Various Phenols and Benzoic Acids in WaterCHINESE JOURNAL OF CHEMISTRY, Issue 5 2008Aziz HABIBI-YANGJEH Abstract Principal component regression (PCR) and principal component-artificial neural network (PC-ANN) models were applied to prediction of the acidity constant for various benzoic acids and phenols (242 compounds) in water at 25 °C. A large number of theoretical descriptors were calculated for each molecule. The first fifty principal components (PC) were found to explain more than 95% of variances in the original data matrix. From the pool of these PC's, the eigenvalue ranking method was employed to select the best set of PC for PCR and PC-ANN models. The PC-ANN model with architecture 47-20-1 was generated using 47 principal components as inputs and its output is pKa. For evaluation of the predictive power of the PCR and PC-ANN models, pKa values of 37 compounds in the prediction set were calculated. Mean percentage deviation (MPD) for PCR and PC-ANN models are 18.45 and 0.6448, respectively. These improvements are due to the fact that the pKa of the compounds demonstrate non-linear correlations with the principal components. Comparison of the results obtained by the models reveals superiority of the PC-ANN model relative to the PCR model. [source] Comparison of ceftibuten transport across Caco-2 cells and rat jejunum mounted on modified ussing chambersBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 7 2003R.M. Menon Abstract Ceftibuten uptake into Caco-2 cells and intestinal brush border membrane vesicles is mediated by the dipeptide transport system (PEPT1). The apical to basolateral transport characteristics of ceftibuten across Caco-2 cells and rat jejunum mounted on a modified Ussing chamber was examined. Mannitol was used as a paracellular marker along with trans-epithelial electrical resistance (TEER) for monitoring tight junction permeability. Transport across Caco-2 cells and rat jejunum mounted on a modified Ussing chamber was linear across the concentration range 0.25,10 mm. The net flux of mannitol and ceftibuten was higher across rat jejunum compared with Caco-2 cells. At a donor concentration of 0.25 mm, ceftibuten transport across Caco-2 cells was found to be pH dependent. Glycyl proline, a dipeptide, and 2,4- dinitrophenol, an energy poison, caused a reduction in the permeability of 0.25 mm ceftibuten across Caco-2 cells. Benzoic acid and adipic acid also inhibited transcellular transport of ceftibuten. At a donor concentration of 0.25 mm, passive paracellular transport accounts for about 60% and the active carrier mediated mechanism accounts for about 40% of ceftibuten transport across Caco-2 cells. None of the inhibitors however, had a significant effect on ceftibuten transport across rat jejunum mounted on a modified Ussing chamber at a donor concentration of 0.25 mm. In the concentration range 0.25,10 mm, ceftibuten is predominantly transported by paracellular mechanisms across rat jejunum and a mixture of active and passive transport across Caco-2 cells. Copyright © 2003 John Wiley & Sons, Ltd. [source] Transporters involved in apical and basolateral uptake of ceftibuten into Caco-2 cellsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 8 2002Rajeev M. Menon Abstract Ceftibuten uptake from the apical and basolateral side of Caco-2 cells grown on transwells was studied. Uptake into the cells showed concentration dependent saturation. The apical transporter(s) showed a higher capacity and lower affinity for ceftibuten than the basolateral transporter(s). Uptake was inhibited in the presence of higher pH and in the presence of 2,4-dinitro phenol (DNP). A proton gradient had a greater effect on the apical than on the basolateral transporter. Glycyl proline, a dipeptide transport system (PEPT1) substrate, inhibited ceftibuten uptake into Caco-2 cells. Benzoic acid, a monocarboxylic acid (MCT) transporter substrate also exhibited a strong inhibition of ceftibuten uptake, but acetic acid had no effect. Adipic acid inhibited apical uptake of ceftibuten but had no effect on the basolateral uptake. None of the inhibitors had a significant effect on ceftibuten uptake in absence of a pH gradient. Addition of inhibitors in presence of DNP led to a greater decrease in ceftibuten uptake, when compared to the effect of DNP alone, indicating a facilitated diffusion process. These results indicate that ceftibuten uptake in Caco-2 cells involve multiple transport pathways. Apical uptake is mediated by an energy dependent carrier-mediated process and an energy independent facilitated diffusion process. The apical transport system is different from the basolateral transporter. Copyright © 2002 John Wiley & Sons, Ltd. [source] A Direct, Biomass-Based Synthesis of Benzoic Acid: Formic Acid-Mediated Deoxygenation of the Glucose-Derived Materials Quinic Acid and Shikimic AcidCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 7 2010Elena Arceo Dr. Shikimic Gimmick: An alternative biomass-based route to benzoic acid from the renewable starting materials quinic acid and shikimic acid is described. Benzoic acid is obtained selectively using a highly efficient, one-step formic acid-mediated deoxygenation method. [source] Synthesis, Spectroscopic Studies, and Crystal Structures of Phenylorganotin Derivatives with [Bis(2,6-dimethylphenyl)amino]benzoic Acid: Novel Antituberculosis AgentsHELVETICA CHIMICA ACTA, Issue 8 2004Vaso Dokorou The novel triphenyl adduct of 2-[(2,6-dimethylphenyl)amino]benzoic acid (HDMPA; 1), i.e., [SnPh3(DMPA)] (2), the dimeric tetraorganostannoxane [Ph2(DMPA)SnOSn(DMPA)Ph2]2 (3), and the monomeric adduct [SnPh2(DMPA)2] (4), where DMPA is monodeprotonated HDMPA, have been prepared and structurally characterized by means of IR, 1H-NMR, and 13C-NMR spectroscopy. The structures of 1 and 2 have been determined by X-ray crystallography. Single-crystal X-ray-diffraction analysis of 1 revealed that there are two molecules in the asymmetric unit, HD1 and HD2, differing in conformation, both forming centrosymmetric dimers linked by H-bonds between the carboxylic O-atoms. X-Ray analysis of 2 revealed a pentacoordinate structure containing Ph3Sn coordinated to the carboxylato group. Significant CH/, interactions and intramolecular H-bonds stabilize the structures of 1 and 2, which self-assembled via CH/, and ,/, -stacking interactions. The Ph3Sn adduct 2 was found to be a promising antimycobacterial lead compound, displaying activity against Mycobacterium tuberculosis H37Rv. The cytotoxiciy in the Vero cell line is also reported. [source] ChemInform Abstract: Catalytic Asymmetric Intramolecular Hydroamination of Alkynes in the Presence of a Catalyst System Consisting of Pd(0)-Methyl Norphos (or Tolyl Renorphos)-benzoic Acid.CHEMINFORM, Issue 16 2009Meda Narsireddy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Towards a Tunable Tautomeric Switch in Azobenzene Biomimetics: Implications for the Binding Affinity of 2-(4,-Hydroxyphenylazo)benzoic Acid to StreptavidinCHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2008Joan-Antoni Farrera Dr. Abstract The tautomeric equilibria of 2-(4,-hydroxyphenylazo)benzoic acid (HABA) and 2-(3,,5,-dimethyl-4,-hydroxyphenylazo)benzoic acid (3,,5,-dimethyl-HABA) have been studied by a combination of spectroscopic and computational methods. For neutral HABA in solvents of different polarity (toluene, chloroform, DMSO, DMF, butanol, and ethanol) the azo tautomer (AT) is largely predominant. For monoanionic HABA, the hydrazone tautomer (HT) is the only detected species in apolar solvents such as toluene and chloroform, while the AT is the only detected species in water and a mixture of both tautomers is detected in ethanol. Comparison of the results obtained for HABA and its 3,,5,-dimethylated derivative shows that dimethylation of the hydroxybenzene ring shifts the tautomeric preferences towards the hydrazone species. These findings have been used to examine the differences in binding affinity to streptavidin, as the lower affinity of HABA can be explained in terms of the larger energetic cost associated with the tautomeric shift to the bioactive hydrazone species. Overall, these results suggest that a balanced choice of chemical substituents, embedding environment, and pH can be valuable for exploitation of the azo,hydrazone tautomerism of HABA biomimetics in biotechnological applications. [source] ChemInform Abstract: A Simple and Efficient Synthesis of 2-(N-Phenylamino)benzoic Acids.CHEMINFORM, Issue 26 2002M. H. Chen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Development of HPLC and NACE methods for the simultaneous determination of benzoic and sorbic acids in sour snap beans containing oilELECTROPHORESIS, Issue 22 2007Po Han Abstract The practical methods were developed for the simultaneous determination of benzoic acid (BA) and sorbic acid (SA) in sour snap bean samples containing oil. BA and SA in the samples were extracted by ultrasonication with water, followed by cleanup procedures with precipitation for removing the potential proteins and with petroleum ether liquid,liquid extraction for removing the edible oil contained in the samples. The HPLC method was developed using Supelco C18 (250,mm×4.6,mm id, 5,,m) as column, MeOH,20,mM NH4Ac (25:75 v/v) at 1.0,mL/min as the mobile phase and 230,nm as the detection wavelength. The optimal NACE method was established with a running buffer of 20.0,mM NH4Ac in 95% MeOH (pH*,10.6), and an applied voltage of ,30,kV over a capillary of 50,,m id×48.5,cm (40,cm to the detector window), which gave a baseline separation of BA and SA, and as well as of the blank matrix within ca. 10,min. Both HPLC and NACE methods gave the relatively lower limits of quantification at about 0.01,0.02 and 0.04,0.05,mg/kg, respectively, whereas the overall recoveries were larger than 85.0%. The proposed methods have been successfully applied to measure 15 real sour bean samples and the content profile of BA and SA in sour bean samples was obtained and evaluated. [source] Determination of the chiral and achiral related substances of methotrexate by cyclodextrin-modified micellar electrokinetic chromatographyELECTROPHORESIS, Issue 16 2004Roberto Gotti Abstract A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4-diamino-6-(hydroxymethyl)pteridine, aminopterine hydrate, 4-[N -(2-amino-4-hydroxy-6-pteridinylmethyl)- N -methylamino] benzoic acid, 4-[N -(2,4-diamino-6-pteridinylmethyl)- N -methylamino] benzoic acid, and the distomer D -MTX is presented. The MEKC separation of these compounds was optimized by applying a step-by-step approach. The addition of ,-CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high-resolution factor between the peaks adjacent to the main component (L -MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD-MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM ,-CD in a mixture of 50 mM borate buffer, pH 9.30-methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93,106% recovery) in the determination of L -MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D -MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets. [source] Vapor pressures and enthalpies of sublimation of 17 polychlorinated dibenzo- p -dioxins and five polychlorinated dibenzofuransENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2004Xian-Wei Li Abstract An apparatus for vapor pressure measurement with a very small cell by the mass-loss Knudsen effusion technique was tested with solid benzoic acid and anthracene. The vapor pressure and enthalpy of sublimation results of the two reference compounds were in good agreement with accepted literature data. The vapor pressures at different temperatures of 17 polychlorinated dibenzo- p -dioxins (including dibenzo- p -dioxin) and five polychlorinated dibenzofurans (including dibenzofuran) were measured with the apparatus, and the enthalpies of sublimation of the 22 dioxins and furans were derived from the temperature dependence of vapor pressure. The results were systematically compared with the literature data. [source] 13C-breath tests for clinical investigation of liver mitochondrial functionEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 9 2010Ignazio Grattagliano Eur J Clin Invest 2010; 40 (9): 843,850 Abstract Background, Mitochondria play a major role in cell energetic metabolism; therefore, mitochondrial dysfunction inevitably participates in or even determines the onset and progression of chronic liver diseases. The assessment of mitochondrial function in vivo, by providing more insight into the pathogenesis of liver diseases, would be a helpful tool to study specific hepatic functions and to develop rational diagnostic, prognostic and therapeutic strategies. Design, This review focuses on the utility of breath tests to assess mitochondrial function in humans and experimental animals. Results, The introduction in the clinical setting of specific breath tests may allow elegantly and noninvasively overcoming the difficulties caused by previous complex techniques and might provide clinically relevant information, i.e the effects of drugs on mitochondria. Substrates meeting this requirement are alpha-keto-isocaproic acid and methionine that are both decarboxylated by mitochondria. Long-and medium-chain fatty acids that are metabolized through the Krebs cycle, and benzoic acid which undergoes glycine conjugation, may also reflect the function of mitochondria. Conclusions, Breath tests to assess in vivo mitochondrial function in humans represent a potentially useful diagnostic and prognostic tool in clinical investigation. [source] Designed Assembly and Structures and Photoluminescence of a New Class of Discrete ZnII Complexes of 1H -1,10-Phenanthroline-2-oneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2006Jie-Peng Zhang Abstract The hydrothermal reaction of 1H -1,10-phenanthroline-2-one (Hophen), zinc acetate, benzoic acid (Hba), and triethylamine (3.0 mL) yields the tetranuclear complex [Zn4(,3 -OH)2(ophen)4(ba)2] (2), which features a chair-like Zn4(,3 -OH)2 cluster with two ba ligands centrosymmetrically oriented. [(OAc){Zn3(,3 -OH)(ophen)3}(ox){Zn3(,3 -OH)(ophen)3}(OAc)] (3; ox = oxalate) was isolated when less triethylamine (1.0 mL) was used. Two Zn3(,3 -OH)(ophen)3 clusters in 3 are linked together by an oxalate to form a dumbbell-like structure in which the acetate and oxalate ligands point outward from the Zn3(,3 -OH)(ophen)3 cluster with an acute bending angle. A geometric analysis reveals that Zn3(,3 -OH)(ophen)3 and dicarboxylate with an obtuse bending angle cannot form an infinite zigzag chain, whereas the ring isomer can. With isophthalate (ipa), thiophene-2,5-dicarboxylate (tda), and 4,4,-oxybis(benzoate) (oba) instead of the acetate of 3 three new complexes, namely [{Zn3(,3 -OH)(ophen)3}(ipa)2{Zn3(,3 -OH)(ophen)3}]·0.5H2O (4), [{Zn3(,3 -OH)(ophen)3}(tda)2{Zn3(,3 -OH)(ophen)3}] (5), and [{Zn3(,3 -OH)(ophen)3}(oba)2{Zn3(,3 -OH)(ophen)3}] (6), were obtained in which two Zn3(,3 -OH)(ophen)3 clusters are linked by a pair of ipa, tda, or oba ligands to form isostructural, cluster-based 2:2 metallomacrocycles. Photoluminescence studies of 2,6 revealed that their luminescent properties are derived from ophen-based ,-,* excited states. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] In Situ Synthesis, Characterization of SiPMo-X, and Different Catalytic Properties of SiPMo-X and SiPW-XEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2006Chunfeng Shi Abstract SBA-15 frameworks with encapsulated Keggin type heteropolyacids (HPAs) were synthesized in situ under strongly acidic conditions (pH,<,0). During the hydrolysis of tetraethyl orthosilicate (TEOS), a P- and a Mo source were added into the initial sol,gel system to form Keggin type HPAs. The texture of the final products was studied by the N2 adsorption,desorption isotherms and transmission electron microscopy (TEM), and their structure was systematically characterized by X-ray diffraction (XRD), UV/Vis diffuse reflectance- (DRS), infrared- (IR), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Characterization results suggest that the samples show very ordered hexagonal mesostructure, and the HPAs that are incorporated into the framework of meso-silica are insoluble during catalysis. Results of catalytic tests indicate that the materials demonstrated catalytic activity comparable with or even surpassing those of the bulk HPAs in catalytic tests implementing chemical reactions of bulky molecules (1,3,5-triisopropylbenzene cracking, esterification of benzoic acid with tert -butyl alcohol, and 2,3,6-trimethylphenol hydroxylation with H2O2). Additionally, some other properties, such as easy separation and stability when recycled, ensure their potential applications in the chemical industries. Here, we report not only the in situ synthesis and characterization of SiPMo-X, but also the difference in the catalytic properties of SiPMo-X and SiPW-X. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Inhibition of lipid peroxidation by anthocyanins, anthocyanidins and their phenolic degradation productsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 1 2007Jonathan E. Brown Abstract Food components that delay or prevent biomolecule oxidation may be relevant in shelf life extension as well as disease prevention. Anthocyanins are a potentially important group of compounds, but they are prone to degradation both in vitro and in vivo, producing simple phenols. In this study, eight structurally related (poly)phenols [anthocyan(id)ins and phenolic acids] were examined for their ability to inhibit lipid oxidation at physiologically relevant concentrations (100,1000,nM) using the Cu2+ -mediated low-density lipoprotein oxidation model. Interaction between each (poly)phenol and Cu2+ ions was also investigated. (Poly)phenols with an ortho -dihydroxy group arrangement, i.e. cyanidin-3-glucoside, cyanidin and protocatechuic acid, were the most effective within their class, extending the lag phase to oxidation by 137, 255 and 402%, respectively (at 1000,nM). At the same concentration, trihydroxy-substituted compounds (delphinidin and gallic acid) were of intermediate efficacy, extending the lag phase by 175 and 38%, respectively. Compounds with the 4'-hydroxy-3',5'-methoxy arrangement (i.e. malvidin-3-glucoside and malvidin) were the least effective (3 and 58% extension, respectively), while syringic acid (4-hydroxy-3,5-dihydroxy benzoic acid) was pro-oxidant (lag phase shortened by 31%). (Poly)phenols with the ortho -dihydroxy arrangement chelated Cu2+ ions, which in part explains their greater efficacy over the other (poly)phenols in this model oxidation system. However, differences in their hydrogen-donating properties and their partitioning between lipid and hydrophilic phases are also relevant in explaining these structure-activity relationships. [source] Glutamate-induced elevations in intracellular chloride concentration in hippocampal cell cultures derived from EYFP-expressing miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2004Jennifer E. Slemmer Abstract The homeostasis of intracellular Cl, concentration ([Cl,]i) is critical for neuronal function, including ,-aminobutyric acid (GABA)ergic synaptic transmission. Here, we investigated activity-dependent changes in [Cl,]i using a transgenetically expressed Cl, -sensitive enhanced yellow-fluorescent protein (EYFP) in cultures of mouse hippocampal neurons. Application of glutamate (100 µm for 3 min) in a bath perfusion to cell cultures of various days in vitro (DIV) revealed a decrease in EYFP fluorescence. The EYFP signal increased in amplitude with increasing DIV, reaching a maximal response after 7 DIV. Glutamate application resulted in a slight neuronal acidification. Although EYFP fluorescence is sensitive to pH, EYFP signals were virtually abolished in Cl, -free solution, demonstrating that the EYFP signal represented an increase in [Cl,]i. Similar to glutamate, a rise in [Cl,]i was also induced by specific ionotropic glutamate receptor agonists and by increasing extracellular [K+], indicating that an increase in driving force for Cl, suffices to increase [Cl,]i. To elucidate the membrane mechanisms mediating the Cl, influx, a series of blockers of ion channels and transporters were tested. The glutamate-induced increase in [Cl,]i was resistant to furosemide, bumetanide and 4,4,-diisothiocyanato-stilbene-2,2,-disulphonic acid (DIDS), was reduced by bicuculline to about 80% of control responses, and was antagonized by niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB). We conclude that membrane depolarization increases [Cl,]i via several pathways involving NFA- and NPPB-sensitive anion channels and GABAA receptors, but not through furosemide-, bumetanide- or DIDS-sensitive Cl, transporters. The present study highlights the vulnerability of [Cl,]i homeostasis after membrane depolarization in neurons. [source] Optimization of the Azobenzene Scaffold for Reductive Cleavage by Dithionite; Development of an Azobenzene Cleavable Linker for Proteomic ApplicationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Geoffray Leriche Abstract In this paper we conducted an extensive reactivity study to determine the key structural features that favour the dithionite-triggered reductive cleavage of the azo,arene group. Our stepwise investigation allowed identification of a highly reactive azo,arene structure 25 bearing a carboxylic acid at the ortho position of the electron-poor arene and an ortho - O -alkyl-resorcinol as the electron-rich arene. Based on this 2-(2,-alkoxy-4,-hydroxyphenylazo)benzoic acid (HAZA) scaffold, the orthogonally protected difunctional azo,arene cleavable linker 26 was designed and synthesized. Selective linker deprotection and derivatization was performed by introducing an alkyne reactive group and a biotin affinity tag. This optimized azo,arene cleavable linker led to a total cleavage in less than 10 s with only 1 mM dithionite. Similar results were obtained in biological media. [source] | |||||||||||||||||||||||||||||||||||||