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Adediran S A SA Department of Chemistry, Wesleyan University, Middletown, Connecticut 06459, - - 2006
Beta-lactam antibiotics restrict bacterial growth by inhibiting DD-peptidases. These enzymes catalyze the final transpeptidation step in bacterial cell wall biosynthesis. Although much structural information is now available for these enzymes, the mechanism of the actual transpeptidation reaction has not been studied in detail. The reaction is known to involve a ...
He Zhiqiao - - 2007
Decolorization of the azo dye C.I. Reactive Black 5 (RB5) in solution by a combination of sonolysis and ozonation was investigated. The results showed that the optimum pH for the reaction was 11.0, and both lower and higher pH decreased the decolorization rate. Increasing the initial concentration of RB5 led ...
Liao Wei - - 2007
The objectives of this study were to statistically study the effects of reaction conditions of temperature, acid concentration, and reaction time on manure components of cellulose, hemicellulose, lignin, and nitrogen during dilute acid treatment of dairy manure; and to further optimize the accumulation of cellulose for later enzymatic conversion to ...
Lin Weimin - - 2006
A zinc-mediated chain extension reaction is the key step in the preparation of gamma-keto amides derived from amino acids. The use of tandem reaction sequences, in which the intermediate zinc enolate is trapped with electrophilic reagents, results in the incorporation of alpha-substituents, which mimic the side chains found in natural ...
Hong Wen-Xu - - 2006
[reaction: see text] An efficient total synthesis of (2S,2'S,3aR,3'aR,8aR,8'aR)-6,6'-dichloro-3a,3'a-dihydroxy-1,1',2,2',3,3a,3',3'a,8,8a,8',8'a-dodecahydro-5,5'-bipyrrolo[2,3-b]indole-2,2'-dicarboxylic acid, the central amino acid component of chloptosin (1), is described. Starting from m-chloronitrobenzene, this C(2)-symmetrical amino acid was synthesized by using a 14-step route, in which a Zinin benzidine rearrangement, intramolecular Heck reaction, and selenocyclization and oxidative deselenation served as ...
Brown Allyson J - - 2007
We present the results of our investigations into the use of soluble manganese(IV) as a chemiluminescence reagent, which include a significantly faster method of preparation and a study on the effect of formaldehyde and orthophosphoric acid concentration on signal intensity. Chemiluminescence detection was applied to the determination of 16 analytes, ...
Turpin Estelle - - 2006
Simulation chamber experiments have been carried out at room temperature to investigate the products of the acetone + OH and acetone-d6 + OH reactions using two photoreactors made of Teflon or Pyrex and coupled to GC-FTIR-FID analytical techniques. In the Pyrex chamber, the results demonstrated that the channel forming acetic ...
Miller Matthew P - - 2006
The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport ...
Fricke Michael - - 2007
Dimethylthioarsinic acid (DMTA(V)) has recently been identified in biological, dietary and environmental matrices. The relevance of this compound to the toxicity of arsenic in humans is unknown and further exposure assessment and metabolic studies are difficult to conduct because of the unavailability of a well characterized standard. The synthesis of ...
Van Meenen Ellen - - 2006
Trialkyl phosphites were evaluated for addition reactions to alpha,beta-unsaturated imines. An acidic medium is required to allow consecutive 1,4- and 1,2-addition to occur. In this manner, 3-phosphonyl-1-aminophosphonates, phosphonic acid analogues of glutamate, are obtained in good yields (32-90%). The reaction is mainly influenced by the steric bulk of the nitrogen ...
Lukyanov Dmitry B - - 2006
The conversion of light alkanes to high value aromatics proceeds with a high selectivity over bifunctional, gallium (Ga) containing zeolite catalysts. It is generally agreed that Ga sites are involved in dehydrogenation reaction steps and that the zeolite acid sites catalyze cracking, oligomerization, and cyclization reactions. However, understanding of the ...
Walspurger Stéphane - - 2006
The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed ...
Li Zigang - - 2006
Intermolecular addition of phenols, carboxylic acids, and protected amines to inert olefins can be catalyzed by low concentrations (1-5%) of triflic acid. Functional groups, such as the methoxyl substitution on aromatics, could be tolerated if the concentration of triflic acid and the reaction temperature are controlled appropriately. This reaction provides ...
Clennan Edward L - - 2006
The singlet oxygen ene reactions of four allylic alcohols and for comparison an allylic ether have been examined both in solution and in zeolite Y. Brønsted acid sites in the zeolite were shown to induce decomposition of several of the allylic alcohols. Treatment of the zeolites with pyridine removed these ...
Edhlund Betsy L - - 2006
The aquatic photochemical degradation of a class of pharmaceuticals known as the nitrofuran antibiotics (furaltadone, furazolidone, and nitrofurantoin) was investigated. Direct photolysis is the dominant photodegradation pathway for these compounds with the formation of a photostationary state between the syn and the anti isomers occurring during the first minutes of ...
Porcheddu Andrea - - 2006
Angeli-Rimini's reaction has been performed for the first time on solid phase. A convenient one-step procedure for the synthesis of hydroxamic acids starting from aldehydes and solid-supported N-hydroxybenzenesulfonamide is reported. The hydroxamates are isolated in good to high yields and purities by simple evaporation of the volatile solvents, after treatment ...
Benyaich Khalid - - 2006
The concentration profiles along the feeding direction of a one side fed gel reactor are analyzed for the iodate-arsenous acid reaction. Multiplicity of inhomogeneous stationary solutions is derived. It is also shown that such profiles may undergo oscillatory bifurcations under long range activation conditions. The bifurcation diagram is analyzed using ...
Egan Timothy J - - 2006
Kinetics of beta-haematin (synthetic malaria pigment) formation from haematin have been studied in the presence of aqueous benzoic acid and derivatives of benzoic acid. Formation of the beta-haematin product is demonstrated by X-ray diffraction and IR spectroscopy. Reactions were followed by determining the fraction of unreacted haematin at various time ...
González-Núñez María E - - 2006
Supercritical carbon dioxide (scCO2) is an efficient reaction medium to perform the Baeyer-Villiger oxidation with hydrated silica-supported potassium peroxomonosulfate (h-SiO2.KHSO5) under flow-through conditions. Hydration modulates the reactivity of the active surface by softening the acidity of the KHSO4 present in the supported reagent. The reaction in scCO2 is much more ...
Yan Zhiqing - - 2006
[reaction: see text] Inspired by allostery in nature, we synthesized cavitand 1 and investigated regulation of its conformational dynamics. Quantitative 1H NMR studies have revealed that the rate of the conformational isomerization of 1 can be modulated using the external addition of acid. As 1 maintains its vase-like conformation in ...
Altieri Katye E - - 2006
Electrospray ionization mass spectrometry (ESI-MS) was used to investigate product formation in laboratory experiments designed to study secondary organic aerosol (SOA) formation in clouds. It has been proposed that water soluble aldehydes derived from aromatics and alkenes, including isoprene, oxidize further in cloud droplets forming organic acids and, upon droplet ...
Zalazar Cristina S - - 2007
The degradation reaction of dichloroacetic acid employing H(2)O(2) and UVC radiation (253.7nm) has been studied in a well mixed reactor operating inside a recycling system. It has been shown that in an aqueous solution no stable reaction intermediates are formed and, at every time during the reaction, two mols of ...
Mehrsheikh Akbar - - 2006
The chlorination reactions of glyphosate and glycine in water were thoroughly studied. Utilizing isotopically enriched (13C and 15N) samples of glycine and glyphosate and 1H, 13C, 31P, and 15N NMR spectroscopy we were able to identify all significant terminal chlorination products of glycine and glyphosate, and show that glyphosate degradation ...
Zamora Rosario - - 2006
The comparative formation of phenylalanine and phenylpyruvic acid in the reaction of 4,5-epoxy-2-decenal with phenylalanine was studied to determine whether epoyalkenals may also degrade amino acids without producing their decarboxylation. Both compounds were produced in the reaction to an extent that depended on the reaction pH, the amount of lipid ...
Hunter Shawn E - - 2006
We conducted an experimental investigation into the kinetics and mechanism of tetrahydrofuran synthesis from 1,4-butanediol via dehydration in high-temperature liquid water (HTW) without added catalyst at 200-350 degrees C. The reaction was reversible, with tetrahydrofuran being produced at an equilibrium yield of 84% (at 200 degrees C) to 94% (at ...
Zhuo Qiongfang - - 2007
The new catalytic decoloration of C.I. Acid Red 3R with electro-coagulation (EC) method assisted by cobalt phosphomolybdate modified kaolin has been studied. The result showed that this process could effectively remove the C.I. Acid Red 3R contained in wastewater and its color removal efficiency could reach up to 98.3% in ...
Astolfi Paola - - 2006
The reaction of 2-phenyl- and 1-methyl-2-phenylindole with nitrogen dioxide or with nitrous acid (NaNO2-CH3COOH) in benzene leads mainly to the formation of the isonitroso and 3-nitroso indole derivatives, respectively. When reacted with nitrous acid, 1-methyl-2-phenylindole gives also the corresponding azo-bis-indole in good yields. The reaction of indole with nitrogen dioxide ...
Schirok Hartmut - - 2006
7-Azaindoles are versatile building blocks, especially in medicinal chemistry, where they serve as bioisosteres of indoles or purines. Herein, we are presenting a robust and flexible synthesis of 1,3- and 1,3,6-substituted 7-azaindoles starting from nicotinic acid derivatives or 2,6-dichloropyridine, respectively. Microwave heating dramatically accelerates the penultimate reaction step, an epoxide-opening-cyclization-dehydration ...
Destaillats Hugo - - 2006
Ozone-driven chemistry is a source of indoor secondary pollutants of potential health concern. This study investigates secondary air pollutants formed from reactions between constituents of household products and ozone. Gas-phase product emissions were introduced along with ozone at constant rates into a 198-L Teflon-lined reaction chamber. Gas-phase concentrations of reactive ...
Loh Teck-Peng - - 2006
The work on development of organic reactions that are tolerant to air and moisture, especially that of carbon-carbon bond forming reactions, had only started in the early 1990s. Our laboratory had approached this subject when it was still in its infancy and had developed methodologies for that end. In this ...
Strzelczak Grazyna - - 2007
Aspartic acid (Asp) and asparagine (Asn) are vulnerable amino acids. One-electron addition or withdrawal reactions initiate many deleterious processes involving these amino acids. To study these redox processes we have irradiated by gamma-rays asparagine or aspartic acid in the solid state. The nature of the resulting free radicals was determined ...
Lamorena Rheo B - - 2007
The formation of secondary products during the ozone-initiated oxidations with biogenic VOCs emitted from natural paint was investigated in this study. Mass spectrometry and infrared spectroscopy measurements have shown that the major components of gas-phase chemicals emitted from natural paint are monoterpenes including alpha- and beta-pinenes, camphene, p-cymene, and limonene. ...
Beresford Kenneth J M - - 2006
A variety of homochiral alpha-amino acids have been prepared in good yield via regioselective reaction of higher order cuprates with (2S)-N-para-toluenesulfonylaziridine-2-carboxylic acid 4. The reaction was much less regioselective and low yielding when higher order cuprates were reacted with the more hindered aziridine carboxylic acid 30, the principal products being ...
Joseph Jorly - - 2006
The metal free, single amino acid-catalyzed asymmetric desymmetrization (ADS) of meso-compounds with nitrosobenzene has been investigated using DFT. In this communication, we describe the role of electrostatic and dipole-dipole interactions in amino acid-catalyzed reactions, which has not previously been invoked in discussions of these important reactions.
Contreras-Torres Flavio F - - 2006
Imidazo[1,2-a]pyrazine-3,6-diones are unusual compounds composed of three alpha-amino acid fragments. These bicyclic amidines (BCAs) form under high temperatures or with the use of strong dehydrating reagents. We gave insight into the mechanisms of BCA formation via gas-phase pyrolytic and silica-catalyzed reactions of glycine (Gly) and alpha-aminoisobutyric acid (AIB) with related ...
Laudani Chiara Giulia - - 2006
Octyl oleate is a useful organic compound with several applications in cosmetic, lubricant and pharmaceutical industry. At first, the enzymatic synthesis of n-octyl oleate by direct lipase-catalysed esterification of oleic acid and 1-octanol was investigated in a stirred batch reactor in solvent-free system. A systematic screening and optimisation of the ...
Okuma Kentaro - - 2006
The reaction of adamantane-2-thione with propiolic acid afforded a novel type of cycloadduct, spiro[adamantane-2,2'-6'H-[1,3]-oxathiin]-6'-one (3a), in quantitative yield. The reaction of thiobenzophenone with propiolic acid gave 2,2-diphenyl-6'H-[1,3]-oxathiin]-6'-one and 4-phenyl-3-thia-3,4-dihydronaphthoic acid in 34% and 35% yields, respectively. The reaction might proceed through a concerted process, as confirmed by kinetics. The reaction ...
Beltrán Fernando J - - 2006
The removal of muconic acid (specifically trans-trans-butanedioc acid) with ozone from water has been studied for kinetics purposes. Concentrations of muconic acid of 4.4x10(-4)M are completely removed with ozone in less than 14 and 9 min at pH 3 and 7, respectively, and 3x10(-4)M of ozone in the gas. The ...
Bukh Christian - - 2006
A laccase from the fungus Trametes villosa (TviL) was investigated in order to elucidate the reaction mechanism of the reduction of dioxygen to water performed by this blue multi-copper oxidase. The ability of TviL to activate dioxygen was studied by stopped-flow experiments and under steady-state conditions. In the stopped-flow experiments ...
Ross David S - - 2006
The Arrhenius parameters for the initiating reactions in butane thermolysis and the formation of soot, reliable to at least 3000 K, have been applied to the question of the survival of amino acids in cometary impacts on early Earth. The pressure/temperature/time course employed here was that developed in hydrocode simulations ...
Grimm Ronald L - - 2006
The recently developed technique of field-induced droplet ionization (FIDI) is applied to study interfacial chemistry of a single droplet. In a new variation of the FIDI method, 1-2-mm-diameter droplets hang from a capillary and undergo heterogeneous reactions between solution-phase analytes and gas-phase species. Following a specified reaction time, the application ...
Tsvetkova Boika - - 2006
The kinetics of esterification of 7-theophyllineacetic acid with diethylene glycol monomethyl ether in the presence of dicyclohexylcarbodiimide and 4-dimethylaminopyridine as catalyst was studied. According to the known mechanism, besides the main process, the side-reaction of intramolecular rearrangement with formation of pharmacologically active N-acylurea occurs. The course of the main and ...
Chen Yan Xia - - 2006
The potential of in-situ Fourier transform infrared (FTIR) spectroscopy measurements in an attenuated total reflection configuration (ATR-FTIRS) for the evaluation of reaction pathways, elementary reaction steps, and their kinetics is demonstrated for formic acid electrooxidation on a Pt film electrode. Quantitative kinetic information on two elementary steps, formic acid dehydration ...
Papajak Ewa - - 2006
dl-2-Haloacid dehalogenase from Pseudomonas sp. 113 is a unique enzyme because it acts on the chiral carbons of both enantiomers, although its amino acid sequence is similar only to that of d-2-haloacid dehalogenase from Pseudomonas putida AJ1 that specifically acts on (R)-(+)-2-haloalkanoic acids. Furthermore, the catalyzed dehalogenation proceeds without formation ...
García B - - 2006
The acid-catalyzed hydrolysis reactions of the antiinflammatory drugs indomethacin and acemethacin were investigated at 25.0 degrees C in a number of strongly concentrated perchloric acid media. The reaction rates were evaluated by UV measurements, and the intermediate species were detected by UV-vis, 1H NMR, 13C NMR, and mass spectroscopy measurements. ...
Wen Bin - - 2007
The esterification of palmitic acid with vitamin C in the presence of concentrated sulfuric acid as the solvent and catalyst by means of 25 kHz ultrasonic irradiation to obtain l-ascorbyl 6-palmitate is studied. By using ultrasound the dissolution rate of the reactants can be accelerated greatly, the reaction time of ...
Abubakar Saifudin M - - 2006
Phosphorus modification of a HZSM-5 (MFI) zeolite by wet impregnation has long been known to decrease aromatic formation in methanol conversion chemistry. We prepared and studied a catalyst modified by introducing trimethylphosphine under reaction conditions followed by oxidation. Magic-angle spinning (MAS) NMR shows that extensive dealumination occurs, resulting in a ...
Nunes Fernando M - - 2006
In this work, the galactomannans from roasted coffee infusions were purified by 50% ethanol precipitation, anion exchange chromatography, and phenylboronic acid-immobilized Sepharose chromatography. Specific enzymatic hydrolysis of the beta-(1-->4)-D-mannan backbone allowed us to conclude that the galactomannans of roasted coffee infusions are high molecular weight supports of low molecular weight ...
Rahman S H A - - 2007
Oil palm empty fruit bunch fiber is a lignocellulosic waste from palm oil mills. It is a potential source of xylose which can be used as a raw material for production of xylitol, a high value product. The increasing interest on use of lignocellulosic waste for bioconversion to fuels and ...
Jang Myoseon - - 2006
A predictive model for secondary organic aerosol (SOA) formation by both partitioning and heterogeneous reactions was developed for SOA created from ozonolysis of alpha-pinene in the presence of preexisting inorganic seed aerosols. SOA was created in a 2 m3 polytetrafluoroethylene film indoor chamber under darkness. Extensive sets of SOA experiments ...
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