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Solvent Used (solvent + used)
Kinds of Solvent Used Selected AbstractsMaterial Solubility-Photovoltaic Performance Relationship in the Design of Novel Fullerene Derivatives for Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Pavel A. Troshin Abstract The preparation of 27 different derivatives of C60 and C70 fullerenes possessing various aryl (heteroaryl) and/or alkyl groups that are appended to the fullerene cage via a cyclopropane moiety and their use in bulk heterojunction polymer solar cells is reported. It is shown that even slight variations in the molecular structure of a compound can cause a significant change in its physical properties, in particular its solubility in organic solvents. Furthermore, the solubility of a fullerene derivative strongly affects the morphology of its composite with poly(3-hexylthiophene), which is commonly used as active material in bulk heterojunction organic solar cells. As a consequence, the solar cell parameters strongly depend on the structure and the properties of the fullerene-based material. The power conversion efficiencies for solar cells comprising these fullerene derivatives range from negligibly low (0.02%) to considerably high (4.1%) values. The analysis of extensive sets of experimental data reveals a general dependence of all solar cell parameters on the solubility of the fullerene derivative used as acceptor component in the photoactive layer of an organic solar cell. It is concluded that the best material combinations are those where donor and acceptor components are of similar and sufficiently high solubility in the solvent used for the deposition of the active layer. [source] Self-Assembly of m -Diethynylbenzene Macrocycles Containing Exoannular Chiral Side Chains,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2006Y. Tobe Abstract Induced circular dichroism (CD) spectra of the m -diethynylbenzene macrocycles (S)- 2 and (R)- 2 that have exoannular chiral side chains are observed in a methanol/chloroform (8:2) solution, indicating the formation of chiral, helical aggregates in solution. Solid films prepared on the surface of quartz substrates by spin-coating solutions of (S)- 2 also exhibit CD signals that are remarkably dependent on the solvent used for the spin-coating. The relationship between the CD spectra and the morphology of the solid films observed by atomic force microscopy is discussed. [source] Reactions of 2-Unsubstituted 1H -Imidazole 3-Oxides with 2,2-Bis(trifluoromethyl)ethene-1,1-dicarbonitrile: A Stepwise 1,3-Dipolar CycloadditionHELVETICA CHIMICA ACTA, Issue 7 2006Grzegorz Mlosto Abstract The reaction of 1,4,5-trisubstituted 1H -imidazole-3-oxides 1 with 2,2-bis(trifluoromethyl)ethene-1,1-dicarbonitrile (7, BTF) yielded the corresponding 1,3-dihydro-2H -imidazol-2-ones 10 and 2-(1,3-dihydro-2H -imidazol-2-ylidene)malononitriles 11, respectively, depending on the solvent used. In one example, a 1,:,1 complex, 12, of the 1H -imidazole 3-oxide and hexafluoroacetone hydrate was isolated as a second product. The formation of the products is explained by a stepwise 1,3-dipolar cycloaddition and subsequent fragmentation. The structures of 11d and 12 were established by X-ray crystallography. [source] Correlating Nanomorphology with Charge-Transport Anisotropy in Conjugated-Polymer Thin Films,ADVANCED MATERIALS, Issue 29 2009Yi-Fang Huang Anisotropic mobility in spin-coated MEH-PPV films is due to an interfacial layer of several nanometers at the film-substrate interface with a higher electron density assisted by local chain alignment parallel to the substrate. This layer is formed via spin-coating. The strength of this interface effect is dependent on the solvent used. [source] Solvent Effects on the Architecture and Performance of Polymer White-Light-Emitting Diodes with Conjugated Oligoelectrolyte Electron-Transport LayersADVANCED MATERIALS, Issue 5 2009Yunhua Xu Polymer-based white-light-emitting diodes are fabricated using conjugated oligoelec trolytes as effective electron-injection layers. However, the choice of solvent used to deposit the conjugated oligoelectrolyte bears a strong influence on the final composition of the emissive layer. Inclusion of water decreases the contact with hydrophobic underlying coatings, and minimizes the extraction of one of the molecular components required for function. [source] Experimental problems in the application of UV/visible based methods as the quantification tool for the entrapped/released insulin from PLGA carriersJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2009V.L. Lassalle Abstract BACKGROUND: Controlled release of medicaments from biodegradable polymers remains the most convenient way for their sustained release. Although a number of articles have been published, experimental work involving the preparation of polymer-based carriers and release procedures are not described with sufficient level of detail to allow other researchers to reproduce the experiments and to compare published results with their own. In this contribution the experimental background of the entrapment and release of insulin from PLGA carriers is described and the problems found at each step related to UV/Visible method used to quantify them are addressed in detail. RESULTS: The quantification of entrapped insulin by UV/visible methods was affected by aggregation. The design of the release experiment influenced the results regarding the entrapment efficiency (EE) and the maximum percentage of released insulin. It was also found that the presence of colloidal polymeric particles, insufficient centrifugation times and the kind of solvent used in the release test might lead to mistakes in the percentage of liberated insulin when UV/visible based methods are employed. CONCLUSIONS: This contribution demonstrates that serious discrepancies in the EE and percentage of released protein may arise if some key experimental factors are not taken into account. Therefore, the analysis presented here tries to point out important aspects of this topic currently not reported, unnoticed or not properly analyzed in the open literature. The results are useful for the entrapment of any protein on any polymeric device using UV/visible based methods to quantify them. Copyright © 2009 Society of Chemical Industry [source] Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (m -THPC) and bacteriochlorin (m -THPBC)JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2001Marc Angotti Abstract The photobleaching of 5,10,15,20-tetrakis(m -hydroxyphenyl)chlorin (temoporfin, m -THPC) and 5,10,15,20-tetrakis(m -hydroxyphenyl)bacteriochlorin (bacteriochlorin, m -THPBC) was studied in ethanol,water (1 : 99, v/v) and in physiological medium (phosphate-buffered saline, PBS) with or without fetal calf serum (FCS). m -THPC solution was irradiated with the laser radiation of 650 nm, whereas m -THPBC solution underwent two consecutive irradiations at 532 and 650 nm. The photoproducts were characterized by UV,visible absorption spectrophotometry and by matrix-assisted laser desorption/ionization (MALDI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS). Independent of the solvent used, the phototransformation of either photosensitizer yielded the formation of 5,10,15,20-tetrakis (m -hydroxyphenyl)porphyrin (m -THPP) through a major dehydrogenation process. Copyright © 2001 John Wiley & Sons, Ltd. [source] Alkylated poly(styrene-divinylbenzene) monolithic columns for ,-HPLC and CEC separation of phenolic acidsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Zdenka Ku, erová Abstract Macroporous poly(styrene-divinylbenzene) monolithic columns were prepared in fused silica capillaries of 100 ,m id by in-situ copolymerization of styrene with divinylbenzene in the presence of propan-1-ol and formamide as the porogen system. The monoliths were subsequently alkylated with linear alkyl C-18 groups via Friedel-Crafts reaction to improve the retention and chromatographic resolution of strongly polar phenolic acids. A new thermally initiated grafting procedure was developed in order to shorten the time of the alkylation process. The grafting procedure was optimized with respect to the reaction temperature, time, the grafting reactant concentration, and the solvent used. The type of solvent and the grafting temperature are the most significant factors affecting the hydrodynamic properties, porosity, and efficiency of the columns. While the equivalent particle diameter of the grafted column increased, the capillary-like flow-through pore diameter decreased in comparison to non-alkylated monoliths. The hydrodynamic permeability of the monolith decreased, but the monolithic column still permitted fast ,-HPLC separations. [source] Potential sources of background contaminants in solid phase extraction and microextractionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2007Robert Stiles Abstract A study to identify the sources of background contamination from SPE, using a C-18 sorbent, and solid-phase microextraction (SPME), using a 70 ,m carbowax/divinylbenzene (CW/DVB) fiber, was carried out. To determine the source of contamination, each material used in the procedure was isolated and examined for their contribution. The solid-phase column components examined were: sorbent material and frits, column housings and each solvent used to elute analytes off the column. The components examined in the SPME procedure were: SPME fiber, SPME vials, water (HPLC grade), and salt (sodium chloride) used to increase the ionic strength. The majority of the background contaminants from SPE were found to be from the SPE sorbent material and frits. The class of contaminants extracted during a blank extraction were phthalates and other plasticizers used during the manufacturing process. All had blank levels corresponding to measured concentrations below 2 ng/mL, except for undecane, which had a concentration of 5.4 ng/mL. The most prevalent contaminants in the SPME blank procedure are 1,9-nonanediol, a mixture of phthalates and highly bis- substituted phenols. All the concentrations were below 2 ng/mL, with the exception of bis (2-ethylhexyl) phthalate, which had concentrations ranging from 5 to 20 ng/mL. [source] Effect of Solvents on Living Polymerization of Propylene with [t -BuNSiMe2Flu]TiMe2 -MMAO Catalyst SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2004Kei Nishii Abstract Summary: Batchwise polymerization of propylene was conducted at 0,°C in heptane using [tert -BuNSiMe2Flu]TiMe2 (1) combined with dried methylaluminoxane (MAO) and dried modified methylaluminoxane (MMAO), which were prepared from the toluene solutions of MAO and MMAO by removing the solvent and the free trialkylaluminium. The dried MMAO system quantitatively gave the polymer with higher molecular weight and narrower molecular weight distribution (MWD), ca. 1.3, compared with the dried MAO system. In addition, the polymerization with dried MMAO in toluene, chlorobenzene (CB) and ortho -dichlorobenzene (o -DCB), as solvent, also produced polymers quantitatively with MWD of ca. 1.1,1.3. The number-average molecular weight () of the polymers, obtained with these systems, increased linearly against the polymer yield, while the narrow MWD was retained and the number of polymer chains was almost constant. The results of post-polymerization in heptane and o -DCB proved that the living polymerization proceeded irrespective of the solvent used. The semi-batch polymerizations under an atmospheric pressure of propylene indicated that the propagation rate was more than 10 times higher in o -DCB than in heptane. The 13C NMR analysis of the polymers indicated that the syndiotacticity also depended on the polarity of the solvent and increased in the following order: CB,,,o -DCB,<,toluene,<,heptane. A plausible scheme for the interaction between active species and solvents. [source] A Novel Synthetic Procedure for Stereoblock Poly(propylene) with a Living Polymerization System,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2004Kei Nishii Abstract Summary: Propylene polymerization was conducted at 0,°C in heptane or chlorobenzene (CB) by an ansa -fluorenylamidodimethyltitanium complex combined with dried, modified methylaluminoxane that had been treated by dilution with heptane and successively repeatedly vacuum dried to remove any free trialkylaluminiums. The post-polymerizations testified that the living polymerization proceeded irrespective of the solvent used. The heptane system gave the syndiotactic poly(propylene)s (PPs), whereas the CB system gave almost atactic PPs. After the first polymerization in heptane had been completed, the same amounts of propylene and CB were added for the second polymerization. This procedure gave the syndiotactic-atactic stereoblock PP with narrow molecular-weight distributions. Structure of the ansa -fluorenylamidodimethyltitanium complex and its application to the synthesis of syndiotactic-atactic stereoblock poly(propylene)s reported here. [source] Photobleaching of Hypocrellin B and its Butylamino-substituted Derivative in SolutionsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2001Shangjie Xu ABSTRACT The photobleaching of hypocrellin B (HB) and its derivative butylamino-substituted hypocrellin B (BAHB), both of which are potent sensitizers for photodynamic therapy (PDT), were investigated by studies of absorption spectra and quenching experiments and by the determination of photoproducts. Control experiments indicated that the sensitizer, oxygen and light were essential for the photobleaching of HB and BAHB, which suggested that it was a photodynamic process, e.g. the photobleaching processes of both HB and BAHB were mainly self-sensitized photooxidations. The illumination of HB with visible light in oxygenated nonpolar solvents generated singlet oxygen efficiently [,(1O2) = 0.76] which in turn attacked the sensitizer HB with the subsequent formation of an endoperoxide product. The endoperoxide of HB is unstable at room temperature and undergoes loss of singlet oxygen with regeneration of the parent HB. The singlet oxygen released from the endoperoxide of HB was detected with chemical trapping experiments. The quenching experiments indicated that in increasingly polar solvents the superoxide anion mechanism (type I) as well as the singlet oxygen mechanism (type II) contributed to the photobleaching of HB. The introduction of the electron-donating butylamino group not only enhanced the yield of the superoxide anion generation but also altered the position of attack in the BAHB molecule by the activated oxygen species. No endoperoxide product was observed, and no singlet oxygen released from the photobleaching process of BAHB was detected. The photobleaching process of BAHB was more complex. Both the singlet oxygen and superoxide anion mechanism played important roles in the photobleaching of BAHB in all organic solvent used here, even in aerobic nonpolar solvents such as CHCl3. [source] Assessment of acetone as an alternative to acetonitrile in peptide analysis by liquid chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2009Ria Fritz Acetonitrile as a solvent used in liquid chromatography/mass spectrometry (LC/MS) of peptides and proteins is a relatively toxic solvent (LD50 oral; rat; 2,460,mg/kg) compared to alternatives like methanol (LD50 oral; rat; 5,628,mg/kg) and acetone (LD50 oral; rat; 5,800,mg/kg). Strategies to minimize its consumption in LC are either to reduce the inner diameter of the column or replace acetonitrile with a suitable alternative. Methanol is often recommended to replace acetonitrile in peptide analysis. In this study however, the main focus lies on another alternative solvent for LC/MS of peptides; acetone. A number of model proteins were tryptically digested and the peptide solutions were analyzed on a linear trap quadrupole (LTQ) mass spectrometer. The performances of acetonitrile, methanol and acetone were compared according to the quality of the chromatograms obtained and identification of the peptides using the BioWorksÔ software developed by Thermo Scientific. In accordance to the elutropic series, acetone was found to significantly reduce the retention times of peptides separated by C18 column material with regard to acetonitrile while methanol led to increased retention times. Acetone was the superior solvent to methanol for most of the tested model proteins reaching similar sequence coverage and numbers of identified peptides as acetonitrile. We therefore propose acetone as an alternative to acetonitrile in LC/MS of peptides. Copyright © 2009 John Wiley & Sons, Ltd. [source] Porous polymer monolith for surface-enhanced laser desorption/ionization time-of-flight mass spectrometry of small moleculesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004Dominic S. Peterson Porous poly(butyl methacrylate- co -ethylene dimethacrylate), poly(benzyl methacrylate- co -ethylene dimethacrylate), and poly(styrene- co -divinylbenzene) monoliths have been prepared on the top of standard sample plates used for matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and the modified plates were used for laser desorption/ionization mass spectrometry (LDI-MS). The hydrophobic porous surface of these monoliths enables the transfer of sufficient energy to the analyte to induce desorption and ionization prior to TOFMS analysis. Both UV and thermally initiated polymerization using a mask or circular openings in a thin gasket have been used to define spot locations matching those of the MALDI plates. The desorption/ionization ability of the monolithic materials depends on the applied laser power, the solvent used for sample preparation, and the pore size of the monoliths. The monolithic matrices are very stable and can be used even after long storage times in a typical laboratory environment without observing any deterioration of their properties. The performance of the monolithic material is demonstrated with the mass analysis of several small molecules including drugs, explosives, and acid labile compounds. The macroporous spots also enable the archiving of samples. Copyright © 2004 John Wiley & Sons, Ltd. [source] Improved chromatographic fingerprints for facile differentiation of two Ganoderma spp.BIOMEDICAL CHROMATOGRAPHY, Issue 3 2009Chun-Mei Fu Abstract This paper addresses a comprehensive and comparative study of six phytochemical extraction methods for triterpenes from the fruiting body of Ganoderma spp. Quantitative analysis of extracts was performed by HPLC with photodiode array detection. In general, pressurized liquid extraction and microwave-assisted extraction under optimized conditions produce better yields, and the former also significantly reduces the total time of extraction and manipulation of a sample, as well as the amount of solvent used in comparison with conventional soxhlet, reflux, ultrasonic, and methanol,CO2 supercritical fluid extractions. Based on the improved extraction protocol, the fingerprinting profiles for two species of Lingzhi were established using the consistent chromatographic features of 12 authentic samples. Eleven common peaks of ganoderic/ganoderenic acids were identified using LC-ESI-MS-MS. These specific triterpene groups were adopted as chemical markers for Lingzhi. Using chemometric analysis, the developed fingerprinting was successfully applied to differentiate between the two species under the Ganoderma genus and is applicable as a method for quality evaluation of this valuable medicinal fungus and its related proprietary products. Copyright © 2008 John Wiley & Sons, Ltd. [source] Inhibition of fatty acid amide hydrolase by kaempferol and related naturally occurring flavonoidsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2008L Thors Background and purpose: Recent studies have demonstrated that the naturally occurring isoflavone compounds genistein and daidzein inhibit the hydrolysis of anandamide by fatty acid amide hydrolase (FAAH) in the low micromolar concentration range. The purpose of the present study was to determine whether this property is shared by flavonoids. Experimental approach: The hydrolysis of anandamide in homogenates and intact cells was measured using the substrate labelled in the ethanolamine part of the molecule. Key results: Twenty compounds were tested. Among the commonly occurring flavonoids, kaempferol was the most potent, inhibiting FAAH in a competitive manner with a Ki value of 5 ,M. Among flavonoids with a more restricted distribution in nature, the two most active toward FAAH were 7-hydroxyflavone (IC50 value of 0.5,1 ,M depending on the solvent used) and 3,7-dihydroxyflavone (IC50 value 2.2 ,M). All three compounds reduced the FAAH-dependent uptake of anandamide and its metabolism by intact RBL2H3 basophilic leukaemia cells. Conclusions and implications: Inhibition of FAAH is an additional in vitro biochemical property of flavonoids. Kaempferol, 7-hydroxyflavone and 3,7-dihydroxyflavone may be useful as templates for the synthesis of novel compounds, which target several systems that are involved in the control of inflammation and cancer. British Journal of Pharmacology (2008) 155, 244,252; doi:10.1038/bjp.2008.237; published online 16 June 2008 [source] Progress in the Field of Electrospinning for Tissue Engineering ApplicationsADVANCED MATERIALS, Issue 32-33 2009Seema Agarwal Abstract Electrospinning is an extremely promising method for the preparation of tissue engineering (TE) scaffolds. This technique provides nonwovens resembling in their fibrillar structures those of the extracellular matrix (ECM), and offering large surface areas, ease of functionalization for various purposes, and controllable mechanical properties. The recent developments toward large-scale productions combined with the simplicity of the process render this technique very attractive. Progress concerning the use of electrospinning for TE applications has advanced impressively. Different groups have tackled the problem of electrospinning for TE applications from different angles. Nowadays, electrospinning of the majority of biodegradable and biocompatible polymers, either synthetic or natural, for TE applications is straightforward. Different issues, such as cell penetration, incorporation of growth and differentiating factors, toxicity of solvents used, productivity, functional gradient, etc. are main points of current considerations. The progress in the use of electrospinning for TE applications is highlighted in this article with focus on major problems encountered and on various solutions available until now. [source] Micelle-catalyzed reaction of ninhydrin with DL -valine in the absence and presence of organic solventsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2006Kabir-ud-Din Kinetics of the DL -valine-ninhydrin reaction has been studied spectrophotometrically under varying conditions of [CTAB], [ninhydrin], [DL -valine], pH, temperature, and %(v/v) organic solvents (solvents used: 1-propanol, methylcellosolve, acetonitrile, and dimethyl sulfoxide). Addition of CTAB and increase in the proportion of organic solvents, both showed catalyzing effect on the reaction. The effect of simultaneous presence of CTAB and DMSO in the reaction mixture has also been seen. The rate profiles obtained for solutions containing from 10% to 70% DMSO exhibited clear maxima that shifted progressively to higher concentrations of CTAB. The experimental results are explained in terms of specific solvent effects and the formation of stoichiometric hydrate DMSO · 2H2O and the inhibitory effect of DMSO on micelle formation. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 634,642, 2006 [source] A Convenient and Efficient Rhenium-Catalyzed Hydrosilylation of Ketones and AldehydesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Hailin Dong Abstract The easily available rhenium(I) complex [Re(CH3CN)3Br2(NO)] catalyzes the homogeneous hydrosilylation of a great variety of organic carbonyl compounds (ketones and aldehydes). The reaction is quite sensitive to the solvent applied. Chlorobenzene was found to be superior over all the other solvents used. Various aliphatic and aromatic silanes were tested. Excellent yields were achieved at 85,°C in chlorobenzene using triethylsilane, the reaction affording TOF values of up to 495,h,1. A possible reaction mechanism for the hydrosilylation is presented. [source] Use of ionic liquids as ,green' solvents for extractionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2005Hua Zhao Abstract This review summarizes recent applications of ionic liquids (ILs) as ,green' solvents in extractions of a variety of substances, including metal ions, organic and bio-molecules, organosulfur from fuels, and gases. ILs could also be used along with another ,green' technology, supercritical fluid extraction (SFE), for a more effective separation of products from ILs. In addition to their environmentally-benign feature, ILs have other favorable properties over organic solvents used for extraction, such as adjustable hydrophobicity, polarity and selectivity. Copyright © 2005 Society of Chemical Industry [source] Atom transfer radical polymerization of n -butyl acrylate catalyzed by CuBr/N -(n -hexyl)-2-pyridylmethanimineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Huiqi Zhang Abstract The homogeneous atom transfer radical polymerization (ATRP) of n -butyl acrylate with CuBr/N -(n -hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N -dimethylformamide, and 1-butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index , 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self-regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n -butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N -(n -hexyl)-2-pyridylmethanimine-based system was proven to be applicable to living block copolymerization and living random copolymerization of n -butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549,3561, 2002 [source] Spectroscopic study of the penetration depth of grafted polystyrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) substrates.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2002Abstract This study concerns the radiation grafting of styrene onto poly(tetrafluoroethylene- co -perfluoropropylvinylether) (PFA) substrates and the penetration depth of the graft. Grafting was obtained by the simultaneous irradiation method, and the spectroscopic analysis was made with the micro-Raman technique. Effects of grafting conditions such as the type of solvent, dose rate, and irradiation dose on the grafting yield were investigated. Of the different solvents used, the most efficient in terms of increasing grafting yield were dichloromethane, benzene, and methanol, respectively. A mixture of methanol and dichloromethane used as a solvent for styrene achieved a higher degree of grafting and concentration of grafted polystyrene onto the surface of PFA substrates than solutions of the monomer in the separate solvents. The degree of grafting increased with increasing radiation dose up to 500 kGy, stabilizing above this dose. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield was accompanied by a proportional increase in the penetration depth of the grafts into the substrate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3191,3199, 2002 [source] Supported liquid membranes in hollow fiber liquid-phase microextraction (LPME) , Practical considerations in the three-phase modeJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2007Kari Folde Bårdstu Abstract In this work, three-phase liquid-phase microextraction (LPME) based on a supported liquid membrane (SLM) sustained in the wall of a hollow fiber was investigated with special focus on optimization of the experimental procedures in terms of recovery and repeatability. Recovery data for doxepin, amitriptyline, clomipramine, and mianserin were in the range of 67.8,79.8%. Within-day repeatability data for the four basic drugs were in the range of 4.1,7.7%. No single factor was found to be responsible for these variations, and the variability was caused by several factors related to the LPME extractions as well as to the final HPLC determination. Although the volume of the SLM varied within 0.4,3.1% RSD depending on the preparation procedure, and the volume of the acceptor solution varied within 4.8% RSD, both recoveries and repeatability were found to be relative insensitive to these variations. Thus, the handling of microliters of liquid in LPME was not a very critical factor, and the preparation of the SLM was accomplished in several different ways with comparable performance. Reuse of hollow fibers was found to suffer from matrix effects due to built-up of analytes in the SLM, whereas washing of the hollow fibers in acetone was beneficial in terms of recovery, especially for the extraction of the most hydrophobic substances. Several of the organic solvents used in the literature as SLM suffered from poor long-term stability, but silicone oil AR 20 (polyphenyl-methylsiloxane), 2-nitrophenyl octyl ether (NPOE), and dodecyl acetate (DDA) all extracted with unaltered performance even after 60 days of storage at room temperature. [source] Synthesis and Characterization of Highly Dispersed Antimony-Doped Stannic Hydroxide Nanoparticles: Effects of the Azeotropic Solvents to Remove Water on the Properties and Microstructures of the NanoparticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Fen Yang Highly dispersed antimony (Sb)-doped stannic hydroxide nanoparticles have been successfully prepared using the solution chemistry method. The properties and microstructures of the nanoparticles are investigated in detail by means of infrared, transmission electron microscope, X-ray diffractometer, and Brunauer-Emmett-Teller nitrogen surface area measurements. The results indicate that the properties and microstructures of the nanoparticles strongly depend on the azeotropic solvents used to remove water at the drying stage. Various azeotropic solvents are screened to investigate their effects on the size and dispersivity of dried Sb-doped stannic hydroxide. Three empirical rules are drawn for selecting an effective azeotropic solvent: (1) the solvent molecule should contain at least one atom such as oxygen as the hydrogen (H)-bond acceptor to form H bonds with the surface ,OH (acting as an H-bond donor) of polymer particle; (2) the H-bond acceptor should locate in the middle of the alkane chain rather than on the terminal so that the alkane chain can stretch out and cover more surface area, improving the dispersivity of the dried product; and (3) the solvent should have a higher boiling point (,140°C) to reduce the time of azeotropic distillation for removing water and maintain a lower residual amount of azeotropic agent. Based on the empirical rules, it is discovered that iso-amyl acetate is the most effective azeotropic solvent. [source] Electrostatic Assembly of Poly(ethylene glycol) NanotubesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2010Woo-Sik Jang Abstract Poly(ethylene glycol) (PEG)-based films, nanotubes, and nanotube arrays were successfully made using layer-by-layer (LbL) assembly ion-containing PEO derivatives on porous templates and planar substrates. PEG nanotubes are challenging to produce because PEG dissolves into solutions and solvents used during nanotube processing, but our techniques circumvent the issue. Nanotube dimensions were verified using microscopy and the average observed diameter was 155,nm. The PEG-based structures showed remarkable stability in water, salt water, and sodium hydroxide solution. [source] Secondary conformation of short lysine- and leucine-rich peptides assessed by optical spectroscopies: Effect of chain length, concentration, solvent, and timeBIOPOLYMERS, Issue 1 2006Belén Hernández Abstract Solution secondary structures of three synthetic cationic peptides, currently used in antisense oligonucleotide delivery into living cells, have been analyzed by means of circular dichroism (CD) and Raman scattering in different buffers as a function of concentration and time. All three peptides are of minimalist conception, i.e., formed by only two types of amino acids (leucine: L and lysine: K). Two of these peptides contain 15 aminoacids: Nter - KLLKLLLKLLLKLLK (L10K5), Nter -KLKLKLKLKLKLKLK (L7K8), and the third one has only 9 residues: Nter -KLKLKLKLK (L4K5). The conformational behavior of the 15-mers in pure water differs considerably one from another. Although both of them are initially disordered in the 50,350 ,M range, L10K5 gradually undergoes a disordered to , -helix transition for molecular concentrations above 100 ,M. In all other solvents used, L10K5 adopts a stable , -helical conformation. In methanol and methanol/Tris mixture, nonnative , -helices can be induced in both KL-alternating peptides, i.e., L7K8 and L4K5. However, in major cases and with a time delay depending on peptide concentration, , -like structures can be gradually formed in both solutions. In PBS and methanol/PBS mixture, the tendency for L7K8 and L4K5 is to form structures belonging to , -family. A discussion has been undertaken on the effect of counterions as well as their nature in the stabilization of ordered structures in both KL-alternating peptides. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 8,19, 2006 This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Effect of solvent concentration on the extraction kinetics and diffusivity of Cyclosporin A in the fungus Tolypocladium inflatumBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2007May Ly Abstract The kinetics of solid-liquid extraction and extraction yields of the immunosuppressant drug Cyclosporin A (CyA) from the mycelia of Tolypocladium inflatum were examined in this study. A 2 L stirred, baffled vessel was used to extract CyA from wet mycelia mass. Three different organic solvents were used, namely, methanol, acetone, and isopropanol at different concentrations in aqueous mixtures at room temperature. It was found that the best solvent was acetone at 50% v/v concentration achieving 100% extraction of CyA from the mycelia of T. inflatum. Although acetone proved to be the better solvent for CyA extraction, further studies were performed using methanol. A linear relationship was found between extraction yield of CyA and methanol concentration with 100% CyA extraction at 90% v/v methanol. The partition coefficients of CyA between the solid mycelia phase and the aqueous solvent phase were found to decrease exponentially with increasing methanol concentration. A liquid extraction model was developed based on the diffusion equation to correlate the kinetic data of CyA extraction from the solid mycelia of T. inflatum. Non-linear regression analysis of experimental data was used with the diffusion equation in order to calculate the effective diffusivities of CyA in the mycelia of T. inflatum. For all three organic solvents used, the effective diffusivities of CyA were found to be between 4.41,×,10,15 and 6.18,×,10,14 m2/s. This is the first time CyA effective diffusivities in T. inflatum are reported in the literature. Biotechnol. Bioeng. 2007;96: 67,79. © 2006 Wiley Periodicals, Inc. [source] Role of Arginine in Protein Refolding, Solubilization, and PurificationBIOTECHNOLOGY PROGRESS, Issue 5 2004Kouhei Tsumoto Recombinant proteins are often expressed in the form of insoluble inclusion bodies in bacteria. To facilitate refolding of recombinant proteins obtained from inclusion bodies, 0.1 to 1 M arginine is customarily included in solvents used for refolding the proteins by dialysis or dilution. In addition, arginine at higher concentrations, e.g., 0.5,2 M, can be used to extract active, folded proteins from insoluble pellets obtained after lysing Escherichia coli cells. Moreover, arginine increases the yield of proteins secreted to the periplasm, enhances elution of antibodies from Protein-A columns, and stabilizes proteins during storage. All these arginine effects are apparently due to suppression of protein aggregation. Little is known, however, about the mechanism. Various effects of solvent additives on proteins have been attributed to their preferential interaction with the protein, effects on surface tension, or effects on amino acid solubility. The suppression of protein aggregation by arginine cannot be readily explained by either surface tension effects or preferential interactions. In this review we show that interactions between the guanidinium group of arginine and tryptophan side chains may be responsible for suppression of protein aggregation by arginine. [source] Tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene: a new resin support for solid-phase peptide synthesisCHEMICAL BIOLOGY & DRUG DESIGN, Issue 1 2003P.G. Sasikumar Abstract: A highly flexible, mechanically and chemically stable copolymer, tri(propylene glycol) glycerolate diacrylate cross-linked polystyrene (PS-TRPGGDA), was synthesized by the suspension polymerization and employed as a solid support for peptide synthesis. The beaded polymer support containing secondary hydroxyl functional groups in the cross-linker was used as the growth site for peptide synthesis. The procedure is unique and cost-effective in that it avoids the initial functionalization steps required for most of the styrene-based polymer supports. The resin was characterized by 13C-CP-MAS NMR spectroscopy and the morphologic features of the resin were investigated using scanning electron microscopy. Swelling studies conducted on the new support revealed that the PS-TRPGGDA resin undergoes more effective swelling and solvation than PS-DVB resin in all solvents used in peptide synthesis. The efficiency of the new support was demonstrated by synthesizing a ,difficult' sequence Ala-Arg-(Ala)6 -Lys and comparing it with commercially available Merrifield and Sheppard resins. The synthetic efficiency was further demonstrated by the synthesis of a 24-residue NR 2A peptide substrate of calcium/calmodulin-binding peptide. The high yield and purity of the peptide synthesized on the novel support indicates the positive role of the flexible and hydrophilic cross-linking agent in the solid support. [source] Electronic Energy Levels in all- trans Long Linear Polyenes: The Case of the 3,20-Di(tert -butyl)-2,2,21,21-tetramethyl-all- trans -3,5,7,9,11,13,15,17,19-docosanonaen (ttbp9) Conforming to Kasha's RuleCHEMISTRY - A EUROPEAN JOURNAL, Issue 13 2005Javier Catalán Prof. Dr. Abstract The absorption, fluorescence and fluorescence excitation spectra for 3,20-di(tert -butyl)-2,2,21,21-tetramethyl-all- trans -3,5,7,9,11,13,15,17,19-docosanonaen (ttbP9) in dilute solutions of 2-methylbutane were recorded at temperatures over the range 120,280 K. The high photostability of this nonaene allows us to assert that it exhibits a single fluorescence and that this can be unequivocally assigned to emission from its 11Bu excited state, it being the first excited electronic state. Available photophysical data for this polyene and the wealth of information reported for shorter all- trans polyenes allow us to conclude that if the first excited electronic state for the chromophore possessed 21Ag symmetry, then the energy of such a state might have been so close to that of the 11Bu state that: 1) the radiationless internal conversion mechanism would preclude the observation of the emission from the 11Bu state reported in this work and 2) the 21Ag state reached through internal conversion would be vibrationally coupled to 11Bu and would facilitate the detection of the emission from 21Ag, which was not observed in any of the solvents used in this work. The spectroscopic and photochemical implications of these findings for other polyenes are discussed. [source] | ||||||||||||||||||||||||||||