CHEMINFORM, Issue 23 2009
Sanjay P. Borikar
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]

ENZYMATIC HYDROLYSIS OF SOYBEAN FOR SOLVENT AND MECHANICAL OIL EXTRACTION

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2000
PRAVEEN C. BARGALE
ABSTRACT Due to inefficient extractability of its low oil content, soybeans are often bypassed in village-scale processing. Soygrits, flakes, and expanded collets were hydrolyzed by proteases, cellulases, and pectinases before oil extraction by solvent and static mechanical pressure. Driselase with multi-enzyme activity and two proteases improved solvent extraction rates but only Driselase enhanced mechanical pressing. Up to 58% of seed oil was pressed from enzyme-hydrolyzed flakes but 88% was pressed from Driselase-treated collets. Either pretreatment is a feasible adjunct to mechanical pressing in small batch operations. [source]

Influence of Aprotic Solvent on Selectivity of an Amperometric Sensor with Nafion Membrane

ELECTROANALYSIS, Issue 5 2006
B. Chachulski
Abstract This paper presents the results of investigation on selectivity of the sulfur dioxide amperometric sensor with Nafion membrane in the presence of carbon monoxide and nitrogen dioxide as the interferents. There have been compared selectivity coefficients, for the sensors containing the following internal electrolytes: solution of sulfuric acid (concentration 5,mol dm,3) in pure water (A) and solution of sulfuric acid (concentration 5,mol dm,3) in mixed solvent dimethylsulfoxide-water with an DMSO: H2O mole ratio of 1,:,2 (B). Values of the selectivity coefficients have been calculated based on the calibration curves. Analysis of both calibration curves and selectivity coefficients plays a significant role in optimization of a working point of a particular sensor. The investigated sensor operates in a three-electrode system, where the working and counter electrodes are vacuum sublimation deposited on the membrane surface. [source]

A Reference Electrode for Electrochemical and Cryoelectrochemical Use in Tetrahydrofuran Solvent

ELECTROANALYSIS, Issue 21 2005
Christopher
Abstract We report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc+) are prepared to give a 4,mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4,mM to 40,,M and 20,°C to ,45,°C respectively. In addition, it is shown by steady,state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc+) otherwise seen in THF is suppressed by ion-pairing with PF using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte. [source]

Electron Transfer Kinetics of Ferrocene at Microcrystalline Boron-Doped Diamond Electrodes: Effect of Solvent and Electrolyte

ELECTROANALYSIS, Issue 4 2003
Shannon Haymond
Abstract Cyclic voltammetric measurements were made using well-characterized microcrystalline boron-doped diamond thin-film electrodes to test the material's responsiveness for ferrocene as a function of scan rate, solvent, and electrolyte composition. Apparent heterogeneous electron transfer rate constants, k°app, of 0.042±0.015, 0.048±0.015, and 0.008±0.002,cm/s were observed in 0.1,M NaClO4/CH3CN, 0.1,M TBAClO4/CH3CN, and 0.1M TBAClO4/CH2Cl2, respectively. These rate constants, obtained using electrodes without any type of pretreatment, are similar to those observed for freshly polished glassy carbon. The results demonstrate that boron-doped diamond is a viable material for the electrochemical analysis of nonaqueous analytes. [source]

Electron-Transfer-Initiated Cascade Cyclizations of Terpenoid Polyalkenes in a Low-Polarity Solvent: One-Step Synthesis of Mono- and Polycylic Terpenoids with Various Functionalities

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004
Mustafa E. Ozser
Abstract A methodology for the one-step synthesis of cyclic polyalkene terpenoids in a low-polarity solvent (dichloromethane) by photoinduced electron transfer (PET) is described. For the efficiency of such processes in low-polarity solvents, the use of the cationic electron acceptor N -methylquinolinium hexafluorophosphate is vital. The first direct cyclizations of farnesol and geranylgeraniol to the corresponding all- trans -fused 6,6- and 6,6,6-cyclic products are also reported. The mechanism of the termination of the cyclizations is also discussed, isotope-labeling experiments having shown that it proceeds through reduction of the final radical to the corresponding anion, followed by protonation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Solvent- and catalyst-free reaction of (aminomethyl)phosphonates with epoxides: Synthesis of novel {[(2-hydroxyethyl)amino]methyl}phosphonates

HETEROATOM CHEMISTRY, Issue 5 2010
Babak Kaboudin
Uncatalyzed reaction of epoxides with (aminomethyl)phosphonates for the synthesis of novel {[(2-hydroxyethyl)amino]methyl}phosphonates is described. Treatment of (aminomethyl)phosphonates with epoxides without any catalyst and under solvent-free conditions gives novel {[(2-hydroxyethyl)amino]methyl}phosphonates. Using this method, a series of {[(2-hydroxyethyl)amino]methyl}phosphonates was synthesized in good yields. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:284,289, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20615 [source]

Solvent and substituent effects on the reaction of 2- and 4-chloro-3,5-dinitrobenzotrifluorides with substituted anilines

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2009
Basim H. M. Asghar
The solvent effect on a nucleophilic substitution reaction of 2- and 4-chloro-3,5-dinitrobenzotrifluoride with substituted anilines was studied in methanol, acetonitrile, and toluene at 25°C. This reaction is of second order, except 2-chloro-3,5-dinitrobenzotrifluoride in toluene shows third order. The kA values are found to be dependent on the substituent in aniline and give good Hammett correlations. The obtained , values are ,4.07 and ,4.62, for the reaction of anilines with 2-chloro-3,5-dinitrobenzotrifluoride in methanol and acetonitrile, respectively. The , values for the reaction of the anilines with 4-chloro-3,5-dinitrobenzotrifluoride are ,3.38, ,4.11, and ,4.34 in methanol, acetonitrile, and toluene, respectively. The reaction of the former compound with anilines in toluene shows a second order in aniline. The dependence of the reaction on the external base such as DABCO suggests a proton transfer controlling step. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 777,786, 2009 [source]

Solvent and structural effects on the kinetics of the reactions of 2-substituted cyclohex-1-enylcarboxylic and 2-substituted benzoic acids with diazodiphenylmethane

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2007
J. B. Nikoli
The rate constants for the reaction of 2-methyl-cyclohex-1-enylcarboxylic, 2-phenylcyclohex-1-enylcarboxylic, and 2-methylbenzoic and 2-phenylbenzoic acids with diazodiphenyl-methane were determined in 14 various solvents at 30°C. To explain the kinetic results through solvent effects, the second-order rate constants of the examined acids were correlated using the Kamlet,Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The quantitative relationship between the molecular structure and the chemical reactivity has been discussed, as well as the effect of geometry on the reactivity of the examined molecules. The geometric data of all the examined compounds corresponding to the energy minima in solvent, simulated as dielectric continuum, obtained using semiempirical MNDO-PM3 energy calculations. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 664,671, 2007 [source]

Solvent and structural effects on the oxidation of 2,6-diphenyl-piperidin-4-ones by quinolinium chlorochromate

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2002
S. Saravana Kanna
The kinetics of oxidation of 3-R-2,6-diphenyl-piperidin-4-ones (where R = H, Me, Et, and i -Pr) by quinolinium chlorochromate has been studied under pseudo-first-order conditions in different pure (protic and aprotic) solvents. The rate data is correlated with different solvent parameters using linear multiple regression analysis. From the regression coefficients, information on the solvent,reactant and the solvent,transition state interactions is obtained and the solvation models are proposed. Reasons for the difference in reactivity with structure are also discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 585,588, 2002 [source]

The First General and Selective Palladium(II)-Catalyzed Alkoxycarbonylation of Arylboronates: Interplay among Benzoquinone-Ligated Palladium(0) Complex, Organoboron, and Alcohol Solvent

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Yoshihiko Yamamoto
Abstract Methoxycarbonylation of aryl- and alkenylboron compounds was performed using the palladium(II) acetate/triphenylphosphine [Pd(OAc)2/PPh3] catalyst with p -benzoquinone as a stoichiometric oxidant in methanol at ambient temperature to obtain the corresponding methyl esters in good yields. A wide variety of functional groups including various carbonyl functionalities, nitrile, nitro, sulfone, and unprotected pyrrole rings were tolerated in the methoxycarbonlation, while the use of higher alcohols except for tert -butanol afforded various p -chlorobenzoates in moderate to high yields. The catalytic alkoxycarbonylation proceeded without any acid or base additive, and an oxidative transmetalation step is proposed to explain the exceptional efficacy of this protocol. DFT and MP2 calculations support the proposed mechanism. [source]

Copper Nanoparticles on Charcoal for Multicomponent Catalytic Synthesis of 1,2,3-Triazole Derivatives from Benzyl Halides or Alkyl Halides, Terminal Alkynes and Sodium Azide in Water as a "Green" Solvent

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Hashem Sharghi
Abstract A one-pot procedure for synthesis of 1,2,3-triazole derivatives via the three-component coupling (TCC) reaction between terminal alkynes, benzyl or alkyl halides, and sodium azide in the presences of 1,mol% nanoparticles copper/carbon (Cu/C) catalyst has been developed. The catalyst showed high catalytic activity and 1,4-regioselectivity for the [3+2],Huisgen cycloaddition in water as a "green" solvent and good to excellent yields were obtained in all cases. This procedure eliminates the need to handle organic azides, and they are generated in situ. The reaction has a broad scope and is especially practical for the synthesis of new azacrown ether and anthraquinone derivatives of triazole. The heterogeneous catalysts were fully characterized by scanning electron microscopy (SEM), atomic forced microscopy (AFM), X-ray diffraction (XRD), inductively coupled plasma (ICP) analysis and FT-IR experimental techniques. The catalyst was recycled ten times without significant loss of activity. [source]

Cover Picture: Divide et Impera , Multiphase, Green Solvent and Immobilization Strategies for Molecular Catalysis (Adv. Synth.

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006
Catal.
No abstract is available for this article. [source]

PERCEPTION OF TEXTURE AND FLAVOR IN SOUPS BY ELDERLY AND YOUNG SUBJECTS

JOURNAL OF TEXTURE STUDIES, Issue 3 2005
STEFANIE KREMER
ABSTRACT The perception of texture and flavor and their interaction effects in white cream soups were studied in 12 young subjects (18,29 years) and 15 elderly subjects (60,84 years). Eight soup samples (2 × 2 × 2 factorial design) were prepared with or without potato starch, with or without mushroom flavor and with water or with milk. The elderly were less sensitive to changes in the flavor profile of the soups than the young, and their perception of creaminess was reduced. Solvent by flavor interaction effects were independent of age, whereas texture by flavor interaction effects were age specific. Besides the intensities of flavor and texture attributes, pleasantness was also assessed. No indication was found that the contribution of texture and flavor to food appreciation was different for the young and for the elderly in the current study. This study supports the assumption that age-related differences in product perception exist. [source]

Reproducible Solvent,Thermal Synthesis, Controlled Microstructure, and Photoluminescence of REPO4:Eu3+, Tb3+ (RE=Y, La, and Gd) Nanophosphors

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010
Xiuzhen Xiao
By altering the temperature and solvents, we have synthesized hydrated and dehydrated Eu3+/Tb3+ -doped REPO4 (RE=Y, La, and Gd) nanophosphors via a solvo-thermal technology. X-ray powder diffraction and scanning electronic microscopy reveal that they have different structures and different morphologies. REPO4 prepared under subsequent heating at 80°, 120°, and 160°C for 1 day, respectively, present larger particle size than that formed by heating at 160°C for 3 days. Moreover, at the same temperature of 160°C and pH 3, three different solvents (ethanol, N,N -dimethylformamide (DMF), and water) were used, whose influence on the microstructure of LaPO4 has been examined. As a result, LaPO4 samples from anhydrous ethanol solvent show a pure hexagonal phase and nanowire morphology, just like that prepared from the water solvent. On the other hand, the microstructure of LaPO4 samples from DMF,H2O-mixed solvents have been changed: with the increasing volume ratio of DMF to H2O, the crystal phase of LaPO4 has been changed from hexagonal phase to monoclinic phase and the morphology from nanowires to nanoparticles. Finally, the photoluminescence properties of these Eu3+ (Tb3+)-activated rare earth phosphates have been investigated, indicating that the photoluminescent behavior are related to their crystal phases and microstructures. [source]

Nanosized CdSe Particles Synthesized by an Air Pressure Solution Process Using Ethylene-Glycol-Based Solvent

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2010
Tao Wang
Nanosized CdSe particles were synthesized at a temperature of 115°,175°C by a solution method with air pressure condition. Ethylene glycol (EG) was used as the main solvent and sodium selenite and cadmium nitrate-tetrahydrate as inorganic sources. The influence of refluxing temperature and time on growth morphology and crystallization was investigated by transmission electron microscope, high-resolution transmission electron microscope, and X-ray diffraction. The chemical reaction was deducted based on X-ray photoelectron spectra. The optical absorption property was measured by UV-vis. The CdSe nanoparticles synthesized through this EG solvent system was single wurtzite crystallization and had a nanoscale size below 15 nm diameter with a narrow size distribution. The reduction of Se4+,Se0,Se2,and the disproportionation of Se0 occurred during the synthetic process and dominated the chemical reaction. [source]

Preparation of Crystalline-Oriented Titania Photoelectrodes on ITO Glasses from a 2-Propanol,2,4-Pentanedione Solvent by Electrophoretic Deposition in a Strong Magnetic Field

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2009
Mamiko Kawakita
Crystal-oriented and crack-free thin TiO2 films with a good interfacial adhesion on indium,tin oxide glass substrates for photoelectrodes of dye-sensitized solar cells were fabricated by the constant voltage electrophoretic deposition (EPD) method in a strong magnetic field of 12 T generated by a superconducting magnet. A binder-free suspension for the EPD was prepared by dispersing TiO2 in a mixture of 2-propanol and 2,4-pentanedione (acetylacetone). The electrical conductivity, sedimentation rate, and the electrophoretic mobility were measured at varying ratios of the mixed solution. The optimized state of the suspension exhibiting the highest surface charge potential and producing deposits with the highest green density was obtained at the 50:50 mixing ratio. The TiO2 films were characterized by X-ray diffraction and scanning electron microscopic analyses. [source]

Comparison of Water-Based and Solvent-Based Tape Casting for Preparing Multilayer ZnO Varistors

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008
Lanyi Wang
Water-soluble acrylic was used as the binder of the water-based (aqueous) slurry while polyvinyl butyral was the binder of the solvent-based (nonaqueous) slurry. Both types of slurry exhibited shear thinning properties suitable for tape casting. The casting parameters for them were different when the same thick green sheets were cast. Thermogravimetric analysis was used to find the binder burnout temperatures of the aqueous and nonaqueous green tape. Scanning electron microscopy (SEM) studies revealed that both types of green tapes have smooth defect-free surfaces but the aqueous green tape is denser than the nonaqueous one. The multilayer ZnO varistors prepared by aqueous tape casting display comparable good electrical properties to those prepared by nonaqueous tape casting because both types of ceramic have a uniform, fine grain microstructure with a homogeneous dopant distribution indicated using SEM and transmission electron microscopy. [source]

Physical and Electrochemical Properties of PVdF-HFP/SiO2 -Based Polymer Electrolytes Prepared Using Dimethyl Acetamide Solvent and Water Non-Solvent

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2007
Kwang Man Kim
Abstract Poly[(vinylidene fluoride)- co -hexafluoropropylene]/SiO2 polymer electrolytes were prepared by a phase inversion technique using DMAc solvent and water non-solvent. Cast film electrolytes filled with the same amount of SiO2 using DMAc were also made to compare physical and electrochemical properties. DMAc had a higher solubility to PVdF-based polymers than NMP, and DMAc produced highly porous structures with bigger cavities and influenced the reduction of crystallinity. Due to the highly porous nature of phase inversion membranes, the uptake of electrolyte solution reached more than 400% and room-temperature ionic conductivity was more than 10,3 S,·,cm,1. All of the liquid absorbed, however, did not necessarily contribute to increases in ionic conductivity. This was due to the different conduction modes of lithium cations in a complicated porous structure. Comprehensively optimizing all the properties measured, the phase inversion membrane electrolytes with 10,30 wt.-% SiO2 were the best candidates for use as the polymer electrolyte of lithium rechargeable batteries. [source]

Effect of LiClO4 and LiCl Additives on the Kinetics of Anionic Polymerization of Methyl Methacrylate in Toluene-Tetrahydrofuran Mixed Solvent

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003
Mahua G. Dhara
Abstract The kinetics of anionic polymerization of MMA has been studied at ,78,°C in toluene-THF (9:1 v/v) using 1,1,-diphenylhexyl lithium as initiator in the presence of lithium perchlorate and lithium chloride as Lewis acid additives. The control of the polymerization is lost in the absence of additives as evident from the non-linear first-order time-conversion plot and polymers with broad multimodal molecular weight distribution. The presence of LiClO4 and LiCl in 10:1 and 5:1 ratio, respectively, over the initiator brings about sufficient control, yielding polymers of narrow unimodal distribution throughout the polymerization. The reaction in the presence of the additives follows first-order kinetics free of termination and transfer. Moreover, the order with respect to the active centers is found to be almost unity, which signifies a probable disaggregation of ion-pairs to a single complexed propagating species. GPC elugrams at different conversions for MMA polymerization in the presence of LiClO4. [source]

Sphere-to-Rod Transition of Micelles formed by the Semicrystalline Polybutadiene- block -Poly(ethylene oxide) Block Copolymer in a Selective Solvent

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010
Adriana M. Mihut
Abstract We present a morphological study of the micellization of an asymmetric semicrystalline block copolymer, poly(butadiene)- block -poly(ethylene oxide), in the selective solvent n -heptane. The molecular weights of the poly(butadiene) (PB) and poly(ethylene oxide) (PEO) blocks are 26 and 3.5,kg,·,mol,1, respectively. In this solvent, micellization into a liquid PEO-core and a corona of PB-chains takes place at room temperature. Through a thermally controlled crystallization of the PEO core at ,30,°C, spherical micelles with a crystalline PEO core and a PB corona are obtained. However, crystallization at much lower temperatures (,196,°C; liquid nitrogen) leads to the transition from spherical to rod-like micelles. With time these rod-like micelles aggregate and form long needles. Concomitantly, the degree of crystallinity of the PEO-cores of the rod-like micelles increases. The transition from a spherical to a rod-like morphology can be explained by a decrease of solvent power of the solvent n -heptane for the PB-corona chains: n -Heptane becomes a poor solvent at very low temperatures leading to a shrinking of the coronar chains. This favors the transition from spheres to a morphology with a smaller mean curvature, that is, to a cylindrical morphology. [source]

Chlorophyll a Self-assembly in Polar Solvent,Water Mixtures ,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000
Radka Vladkova
ABSTRACT The conversion of chlorophyll a (Chl a) monomers into large aggregates in six polar solvents upon addition of water has been studied by means of absorption, fluorescence spectroscopy and fluorescence lifetime measurements for the purpose of elucidating the various environmental factors promoting Chl a self-assembly and determining the type of its organization. Two empirical solvent parameter scales were used for quantitative characterization of the different solvation properties of the solvents and their mixtures with water. The mole fractions of water f1/2 giving rise to the midpoint values of the relative fluorescence quantum yield were determined for each solvent, and then various solvent,water mixture parameters for the f1/2 values were compared. On the basis of their comparison, it is concluded that the hydrogen-bonding ability and the dipole,dipole interactions (function of the dielectric constant) of the solvent,water mixtures are those that promote Chl a self-assembly. The influence of the different nature of the nonaqueous solvents on the Chl aggregation is manifested by both the different water contents required to induce Chl monomer , aggregate transition and the formation of two types of aggregates at the completion of the transition: species absorbing at 740,760 nm (in methanol, ethanol, acetonitrile, acetone) and at 667,670 nm (in pyridine and tetrahydrofuran). It is concluded that the type of Chl organization depends on the coordination ability and the polarizability (function of the index of refraction) of the organic solvent. The ordering of the solvents with respect to the f1/2 values,methanol < ethanol < acetonitrile < acetone < pyridine < tetrahydrofuran,yielded a typical lyotropic (Hofmeister) series. On the basis of this solvent ordering and the disparate effects of the two groups of solvents on the Chl a aggregate organization, it is pointed out that the mechanism of Chl a self-assembly in aqueous media can be considered a manifestation of the Hofmeister effect, as displayed in the lipid-phase behavior (Koynova et al., Eur. J. Biophys. 25, 261,274, 1997). It relates to the solvent ability to modify the bulk structure and to distribute unevenly between the Chl,water interface and bulk liquid. [source]

Rubber plasticizers from degraded/devulcanized scrap rubber: A method of recycling waste rubber,

POLYMER ENGINEERING & SCIENCE, Issue 7 2004
Amiya R. Tripathy
Seeking a solution to the problem of disposing scrap tires, we attempted to depolymerize or degrade vulcanized rubber scrap such that the resulting pseudo-liquid material could be used as an extender/plasticizer in virgin rubber compounds. As degraded natural rubber (DNR) and degraded styrene-butadiene rubber (DSBR) are polymeric in nature (confirmed from gel-permeation chromatography (GPC) and differential scanning calorimetry (DSC) results), they can be unique substitutes for typical rubber plasticizers (oil). DNR-loaded samples have shown better mechanical property retention after aging and a lower extractable content in acetone than the respective oil-plasticized samples. Solvent swelling in toluene and 100% modulus values indicate that DNR-added rubber vulcanizates undergo a phase adhesion between the rubber matrix and the degraded polymer, as well as incurring extra reinforcement due to particulate carbon black present in the degraded rubber. Polym. Eng. Sci. 44:1338,1350, 2004. © 2004 Society of Plastics Engineers. [source]

DNA and RNA in Anhydrous Media: Duplex, Triplex, and G-Quadruplex Secondary Structures in a Deep Eutectic Solvent,

ANGEWANDTE CHEMIE, Issue 36 2010
Irena Mamajanov
Verlockende Aussichten! Tiefeutektische Solventien (DESs) sind nichtflüchtige Medien, die sich für viele chemische Reaktionen eignen. In einem wasserfreien DES bilden Nucleinsäuren Duplex-, Triplex- und G-Quadruplex-Strukturen (die sich teilweise von denen in wässrigen Medien unterscheiden), sodass katalytische Nucleinsäuren und Enzym-Nucleinsäure-Komplexe vielleicht auch in diesen Solventien genutzt werden können. [source]

Systematic Metal Variation and Solvent and Hydrogen-Gas Storage in Supramolecular Nanoballs,

ANGEWANDTE CHEMIE, Issue 47 2009
Martin
Ballspiele: Selbstorganisierte diskrete metallosupramolekulare Nanobälle (siehe Bild) mit verschiedenen zweiwertigen Metallionen sind ähnlich porös wie manche Metall-organischen Netzwerke. Durch stufenweises Entfernen von Lösungsmittelmolekülen werden Metallzentren zugänglich, die dann mit organischen Molekülen funktionalisiert werden können; die Hohlräume zwischen den Bällen haben eine hohe Affinität für Wasserstoffgas. [source]

High performance liquid chromatographic,mass spectrometric assay for the quantitation of BMS-204352 in dog K3EDTA plasma

BIOMEDICAL CHROMATOGRAPHY, Issue 3 2002
Ming Yao
A high performance liquid chromatographic-mass spectrometric (LC/MS) assay was developed and validated for the determination of BMS-204352 in dog K3EDTA plasma. A 0.5,mL aliquot of control plasma was spiked with BMS-204352 and internal standard (IS) and buffered with 1,mL of 5,mM ammonium acetate. The mixture was then extracted with 3,mL of toluene. After separation and evaporation of the organic phase to dryness using nitrogen at 40°C, the residue was reconstituted in the mobile phase and 25,µL of the sample were injected onto a Hypersil C18 column (2,×,50,mm; 3,µm) at a flow rate of 0.5,mL/min. The mobile phase was consisted of two solvent mixtures (A and B). Solvent A was composed of 5,mM ammonium acetate and 0.1% triethylamine in 75:25 v/v water:methanol, pH adjusted to 5.5 with glacial acetic acid, and solvent B was 5,mM ammonium acetate in methanol. A linear gradient system was used to elute the analytes. The mass spectrometer was programmed to admit the de-protonated molecules at m/z 352.7 (IS) and m/z 357.9 (BMS-204352). Standard curves of BMS-204352 were linear (r2,,,0.998) over the concentration range of 0.5,1000,ng/mL. The mean predicted quality control (QC) concentrations deviated less than 5.1% from the corresponding nominal values (ie 4, 80, 400 and 2000,ng/mL); the within- and between-assay precision of the assay were within 5.5% relative standard deviation. Stability of BMS-204352 was confirmed after at least three freeze/thaw cycles and BMS-204532 was stable in dog plasma when stored frozen at or below ,20°C for at least 16 weeks in spiked QC samples and for at least 4 1/2 weeks for in vivo study samples. BMS-204352 and IS were stable in the injection solvent at room temperature for at least 24,h. The assay was applied to delineate the pharmacokinetic disposition of BMS-204352 in dogs following a single intravenous dose administration. In conclusion, the assay is accurate, precise, specific, sensitive and reproducible for the pharmacokinetic analysis of BMS-204532 in dog plasma. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Microbial bio-production of a recombinant stimuli-responsive biosurfactant

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009
W. Kaar
Abstract Biosurfactants have been the subject of recent interest as sustainable alternatives to petroleum-derived compounds in areas ranging from soil remediation to personal and health care. The production of naturally occurring biosurfactants depends on the presence of complex feed sources during microbial growth and requires multicomponent enzymes for synthesis within the cells. Conversely, designed peptide surfactants can be produced recombinantly in microbial systems, enabling the generation of improved variants by simple genetic manipulation. However, inefficient downstream processing is still an obstacle for the biological production of small peptides. We present the production of the peptide biosurfactant GAM1 in recombinant E. coli. Expression was performed in fusion to maltose binding protein using chemically defined minimal medium, followed by a single-step affinity capture and enzymatic cleavage using tobacco etch virus protease. Different approaches to the isolation of peptide after cleavage were investigated, with special emphasis on rapid and simple procedures. Solvent-, acid-, and heat-mediated precipitation of impurities were successfully applied as alternatives to post-cleavage chromatographic peptide purification, and gave peptide purities exceeding 90%. Acid precipitation was the method of choice, due to its simplicity and the high purification factor and recovery rate achieved here. The functionality of the bio-produced peptide was tested to ensure that the resulting peptide biosurfactant was both surface active and able to be triggered to switch between foam-stabilizing and foam-destabilizing states. Biotechnol. Bioeng. 2009;102: 176,187. © 2008 Wiley Periodicals, Inc. [source]

Effects of Composition, Solvent, and Salt Particles on the Physicochemical Properties of Polyglycolide/Poly(lactide- co -glycolide) Scaffolds

BIOTECHNOLOGY PROGRESS, Issue 6 2006
Yung-Chih Kuo
Polyglycolide (PGA)/poly(lactide- co -glycolide) (PLGA) scaffolds were fabricated by a solvent casting/particulate leaching method using hexafluoroisopropanol (HFIP) or acetone for material dissolution and NaCl particles as porogen. The results revealed that the mechanical strength increased as the PGA percentage in a HFIP-processed scaffold increased. Chemical ingredients did not substantially affect the mechanical strength of acetone-processed scaffolds. Large NaCl particles led to weak mechanical strength, low porosity, and small specific surface area. For a fixed composition, PGA crystals in a HFIP-processed scaffold were smaller than those in an acetone-processed scaffold. High PGA fractions yielded partly fused PGA/PLGA scaffolds. A faster degradation rate of a scaffold could result from a higher PGA percentage, smaller NaCl particles, or the existence of chondrocytes. The combination of PGA and PLGA, which compensated each other for bioactivity, would be beneficial to cartilage regeneration. [source]

Acceleration of Short Helical Peptide Conformational Dynamics by Trifluoroethanol in an Organic Solvent

CHEMBIOCHEM, Issue 7 2005
Matthew Kubasik Prof.
Solvent dependency. The influence of the cosolvent trifluorethanol on the rate of enantiomerization of an octameric peptide (see figure) in CD2Cl2 solution is described. Kinetic data have been taken over a range of temperatures, thus allowing for a discussion of the enthalpic and entropic origins of the catalytic effect. [source]

ChemInform Abstract: Au/Ag-Cocatalyzed Aldoximes to Amides Rearrangement under Solvent- and Acid-Free Conditions.

CHEMINFORM, Issue 24 2010
Ruben S. Ramon
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]