|
| ||
|
|
||
Carboxyl Groups (carboxyl + groups)
Selected AbstractsChemInform Abstract: A New Reagent for the Methylation of Carboxyl Groups.CHEMINFORM, Issue 11 2002Bina S. Siddiqui 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] Catalytic effect of dissolved humic acids on the chemical degradation of phenylurea herbicidesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2008Stefano Salvestrini Abstract BACKGROUND: Although biodegradation seems to be the main cause of herbicide degradation, abiotic degradation can also be important for chemicals such as phenylureas, which are subject to catalysed soil reactions. The aim of this work is to investigate the effect of dissolved humic acids (HAs), normally present in natural waters, on the hydrolysis of phenylurea herbicides, and it presents a kinetic model that takes into account the role of adsorption. RESULTS: The linearity of the adsorption isotherms indicates that phenylurea,humic acid interaction can be considered in terms of a repartition-like equilibrium of phenylurea between water and HAs. Kinetic experiments show that the degradation rates of phenylureas increase with HA concentration. CONCLUSION: The kinetic equation adopted adequately describes the experimental data trend, allowing the evaluation of the catalytic effect of HAs on the chemical degradation of phenylureas. Carboxyl groups of HAs seem to play a leading role in the catalysis. The kinetic equation derived in this work could be helpful in predicting the persistence of phenylureas and of related compounds in natural water. Copyright © 2008 Society of Chemical Industry [source] Direct chiral resolution of tartaric acid by ion-pair capillary electrophoresis using an aqueous background electrolyte with (1R,2R)-(,)-1,2-diaminocyclohexane as a chiral counterionELECTROPHORESIS, Issue 15 2003Shuji Kodama Abstract Chiral resolution of native DL -tartaric acid was achieved by ion-pair capillary electrophoresis (CE) using an aqueous-ethanol background electrolyte with (1R,2R)-(,)-1,2-diaminocyclohexane (R -DACH) as a chiral counterion. Factors affecting chiral resolution and migration time of tartaric acid were studied. By increasing the viscosity of the background electrolyte and the ion-pair formation, using organic solvents with a lower relative dielectric constant, resulted in a longer migration time. The optimum conditions for both high resolution and short migration time of tartaric acid were found to be a mixture of 65% v/v ethanol and 35% v/v aqueous solution containing 30 mMR -DACH and 75 mM phosphoric acid (pH 5.1) with an applied voltage of ,30 kV at 25°C, using direct detection at 200 nm. By using this system, the resolution (Rs) of racemic tartaric acid was approximately 1. The electrophoretic patterns of tartaric and malic acids suggest that two carboxyl groups and two hydroxyl groups of tartaric acid are associated with the enantioseparation of tartaric acid by the proposed CE method. [source] Trace metal distribution in soluble organic matter from municipal solid waste compost determined by size-exclusion chromatographyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Arno Kaschl Abstract Municipal solid waste (MSW) composts carry high amounts of trace metals and organic complexing agents that may influence metal bioavailability and mobility after application to soils. In order to assess the degree of organic complexation of trace metals in the solution phase of MSW compost and the relevance of organic ligand type, size exclusion chromatography (SEC) was applied to compost-extracted organic ligands. Adjustment of the elution conditions minimized the interaction with the gel matrix for compost humic substances and dissolved organic matter (DOM) fractions. The SEC was then used to separate the aqueous compost extract into samples with distinct differences in chemical constituents. The highest quantities of Cu, Zn, Ni, Mn, and Cd were found to coelute with the main peak of the SEC elution curve, which, as observed by Fourier-transformed infrared (FTIR) spectroscopy, also had the highest density of carboxyl groups. The ratio of aromatic to aliphatic structures was higher for eluates with low retention times, and cations such as Al, Cr, and Fe were preferably associated with these larger organic molecules. All trace metals in the compost solution phase were bound mostly to DOM rather than forming inorganic complexes. [source] A Fibronectin Peptide-Coupled Biopolymer Nanofibrous Matrix to Speed Up Initial Cellular EventsADVANCED ENGINEERING MATERIALS, Issue 4 2010Ji-Eun Kim Degradable polymer nanofibers produced by electrospinning are attractive for use in cell culture and tissue repair. However, the hydrophobicity and initial poor cell adhesion of synthetic polymers have limited their use in tissue regeneration. Herein, the surface of a poly(lactide-co-caprolactone) Arg-Gly-Asp sequence of nanofiber was tailored with a fibronectin peptide (FN10), which was designed to retain the central cell-binding domain. The electrospun nanofibers are first treated with an alkaline solution to reveal the carboxyl groups on the surface, which is followed by coupling with an FN10 solution in conjunction with a carbodiimide-based agent. Peptide coupling occurs effectively with saturation within 1,h, and the coupled peptide maintains its stability for several days. The peptide-coupled nanofibers show significant improvements in initial cell adhesion and spreading compared with the untreated one, confirming the role of the FN10 peptide in the initial cell events. This methodology may be useful in tailoring the surface of polymeric nanofibers with biomolecules targeted for specific tissue responses. [source] Synthesis of Carboxyl-Tethered Symmetric Conjugated Polyenes as Fluorescent Transmembrane Probes of Lipid BilayersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2003Ernesto Quesada Abstract The synthesis of a new series of fluorescent transmembrane probes in which two hydrophilic methyl ester or carboxyl groups are connected by a polymethylene chain, with four, five or six conjugated double bonds in a central position, is reported. The length of the linear structures was designed to match the width of typical lipid bilayers. These bolaamphiphilic compounds result, with overall yields higher than 80%, from an easy PdII -catalyzed double cross-coupling between terminal acetylene esters and conjugated 1,,-dihalopolyenes, followed by selective triple bond partial reduction with activated zinc, and iodine isomerization to the all-(E) isomer. An alternative approach, based on a Stille double cross-coupling between the appropriate all-(E)-,-halopolyenes and (E)-bis(tributylstannyl)ethene, yielded mixtures that could not be resolved by standard chromatographic methods due to the presence of other simultaneous coupling reactions, which are also discussed in detail. Nevertheless, the Stille method can be of utility for the obtention of carbonyl-polyene conjugated analogs. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Identification of domains on the extrinsic 23 kDa protein possibly involved in electrostatic interaction with the extrinsic 33 kDa protein in spinach photosystem IIFEBS JOURNAL, Issue 5 2004Akihiko Tohri To elucidate the domains on the extrinsic 23 kDa protein involved in electrostatic interaction with the extrinsic 33 kDa protein in spinach photosystem II, we modified amino or carboxyl groups of the 23 kDa protein to uncharged methyl ester groups with N -succinimidyl propionate or glycine methyl ester in the presence of a water-soluble carbodiimide, respectively. The N -succinimidyl propionate-modified 23 kDa protein did not bind to the 33 kDa protein associated with PSII membranes, whereas the glycine methyl ester-modified 23 kDa protein completely bound. This indicates that positive charges on the 23 kDa protein are important for electrostatic interaction with the 33 kDa protein associated with the PSII membranes. Mapping of the N -succinimidyl propionate-modified sites of the 23 kDa protein was performed using Staphylococcus V8 protease digestion of the modified protein followed by determination of the mass of the resultant peptide fragments with MALDI-TOF MS. The results showed that six domains (Lys11,Lys14, Lys27,Lys38, Lys40, Lys90,Lys96, Lys143,Lys152, Lys166,Lys174) were modified with N -succinimidyl propionate. In these domains, Lys11, Lys13, Lys33, Lys38, Lys143, Lys166, Lys170 and Lys174 were wholly conserved in the 23 kDa protein from 12 species of higher plants. These positively charged lysyl residues on the 23 kDa protein may be involved in electrostatic interactions with the negatively charged carboxyl groups on the 33 kDa protein, the latter has been suggested to be important for the 23 kDa binding [Bricker, T.M. & Frankel, L.K. (2003) Biochemistry42, 2056,2061]. [source] Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmasJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Chunxia Wang Abstract The effect of atmospheric pressure plasma treatment on wettability and dyeability of nylon 6 fibers is investigated. The plasma treatments resulted in an average of 10°,20° decrease in the advancing contact angle and 20°,30° decrease in the receding contact angle. An increased dye diffusion rate of nylon 6 fibers was observed using laser scanning confocal microscope (LSCM). Scanning electron microscope confirmed that the fiber surfaces were roughened, and X-ray photoelectron spectroscopy showed that the polar groups on the fiber surfaces increased after the plasma treatments. As the plasma treatment time increased, a greater degree of etching was achieved and more polar groups such as hydroxyl and carboxyl groups produced on the surfaces of the nylon 6 fibers, leading to a better wettability and thus a better dyeability of the fiber. This study proved that LSCM may be effectively used in detecting the change of dye diffusion rate in nylon fibers treated with plasmas and the mounting medium should have a close refractive index as the fiber to avoid distortion of the fiber cross section image. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Poly(1,3-propylene glycol-hexanedioic acid) grafted hydroxyl multiwall carbon nanotubesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Qing-Jie Meng Abstract Poly(1,3-propylene glycol-hexanedioic acid) grafted hydroxyl multiwall carbon nanotube (PHHCNT) was fabricated in the presence of butyl titanate using 1,3-propylene glycol, hexanedioic acid, and hydroxyl multiwall carbon nanotubes as reactants. The hydroxyl groups at carbon nanotubes reacted with hexanedioic acid and a small amount of carboxyl groups reacted with 1,3-propylene glycol, resulting in the PGHA grafted on the carbon nanotubes. The carbon nanotubes surrounded by the PGHA chains with an average thickness of , 2 nm. The polycondensation reactions can be controlled by the feed contents of HCNTs and the catalyst concentration in the reactants. The content of HCNTs in PHHCNT rises with an increase of the feed contents of HCNTs. In addition, the content of HCNTs in PHHCNT is higher than the feed contents of HCNTs in the reactants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Functional finishing by using atmospheric pressure plasma: Grafting of PET nonwoven fabricJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Younsook Shin Abstract Poly (ethylene terephtalate) (PET) nonwoven fabric was treated with He/O2 plasma to produce peroxides and grafted with acrylic acid (AA) for introducing carboxyl groups onto PET surface. The graft yield increased with AA concentration from 1.5M to 2.5M, and then decreased with further increase in AA concentration. Graft yield increased with sodium pyrosulfite (SPS) concentration from 0.005M to 0.02M, and then decreased with further increase of SPS concentration. X-ray photoelectron spectroscopy results indicated that both of plasma treatment and AA grafting increased oxygen content and decreased carbon content on the PET nonwoven fabric surface. The grafted PET nonwoven fabric showed increase in moisture regain and dye uptake. And drastic increase in wettability was observed after grafting. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3655,3659, 2007 [source] Polyelectrolyte complex hydrogel composed of chitosan and poly(,-glutamic acid) for biological application: Preparation, physical properties, and cytocompatibilityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Hahk-Soo Kang Abstract Polyelectrolyte complex (PEC) hydrogels composed of chitosan as a cationic polyelectrolyte and poly (,-glutamic acid) (,-PGA) as an anionic polyelectrolyte were prepared from PEC dispersions based on a chitosan solution to which different amounts of ,-PGA solutions were added to charge equivalency. The chemical structures of the PEC hydrogels were investigated by Fourier transform infrared spectroscopy. The physical properties, fixed charge concentration, crystallinity, mechanical properties, micromorphology, and swelling properties of the PEC hydrogels were also investigated. The total fixed charge concentration of the PEC hydrogels varied as a function of pH on the pK intervals between chitosan (pK = 6.5) and ,-PGA (pK = 2.27). The isoelectric points (IEP) were shifted to a lower pH with a higher weight ratio of ,-PGA to chitosan. The elastic modulus was decreased with the weight ratio increasing from 0 : 1 to 1 : 1 (,-PGA/chitosan) by ionic crosslinking between the amino groups of chitosan and the carboxyl groups of ,-PGA. The results of the swelling study showed that the swelling properties of PEC hydrogels were more affected by the change in the elastic restoring force than by the change in the fixed charge concentration depending on the pH. Also, the cytotoxicity of the PEC hydrogels was investigated using normal human dermal fibroblast (NHDF) cell lines, and the results showed the PEC hydrogels were not toxic. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:386,394, 2007 [source] Effect of Soluble Soybean Protein Hydrolysate-Calcium Complexes on Calcium Uptake by Caco-2 CellsJOURNAL OF FOOD SCIENCE, Issue 7 2008Y. Lv ABSTRACT:, Soybean protein hydrolysates (SPHs) bind with calcium, forming soluble SPH-calcium complexes via the carboxyl groups of glutamic and aspartic acid residues. However, their effect on calcium uptake is still unclear. In this study, Caco-2 cells were used to estimate the effect of SPH-calcium complexes with different molecular weights on calcium uptake in vitro. The changes in intracellular calcium ion concentration were measured by Fura-2 loading and expressed in fluorescence intensity. SPH-calcium complexes could promote calcium uptake. Improved fluorescence intensity was significantly different in SPH-calcium complexes (10 to 30 kDa), SPH-calcium complexes (3 to 10 kDa), and SPH-calcium complexes (1 to 3 kDa). The maximum levels of relative fluorescence intensity (18.3) occurred with SPH-calcium complexes (10 to 30 kDa). The effect of SPH-calcium complexes (10 to 30 kDa) on Ca2+ increase was determined to be concentration dependent in the range of 0.5 to 4 mg/mL. Our results indicate that soybean protein itself might be responsible for promoting calcium absorption. [source] Biotransformation of 4-Hydroxybenzen Derivatives by Hairy Root Cultures of Polygonum multiflorum Thunb.JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 2 2007Chun-Yan Yan Abstract The biotransformation of four 4-hydroxybenzen derivatives (1,4-benzenediol (compound 1), 4-hydroxybenzaldehyde (compound 2), 4-hydroxybenzyl alcohol (compound 3) and 4-hydroxybenzoic acid (compound 4)) by the hairy root cultures of Polygonum multiflorum Thunb. as a new biocatalyst was investigated. It was found that the substrates were transformed to their corresponding glucosides, 4-hydroxyphenyl ,- D -glucopyranoside (arbutin, compound 1a), 4-hydroxymethylphenyl ,- D -glucopyranoside (gastrodin, compounds 2a, 3a) and 4-carboxyphenyl ,- D -glucopyranoside (compound 4a), respectively. In the meantime, the hairy roots of P. multiflorum were able to stereoselectively and regioselectively glucosylate phenolic hydroxyl groups of compounds 1,4, but the cultures could not glucosylate the aldehyde group of compound 2 or the benzylic hydroxyl group of compound 3, and no glucosyl esterification of carboxyl groups of compound 4 was detected. On the other hand, the result also showed that the hairy roots of P. multiflorum were able to reduce the 4-hydroxybenzaldehyde to its corresponding alcohol. This is the first report that substrate 4 has been converted into its ,- D -glucopyranoside by a plant biotransformation system. [source] Comparative evaluation of 99mTc-ethylene bis-l-cysteine and 99mTc-ethylene bis-l-,-homocysteine during reversed phase HPLC analysis and electrophoresis at various pH conditionsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2001K.O. Mang'era Ethylene bis- L -,-homocysteine (L,L -EH) differs from ethylene bis- L -cysteine (L,L -EC) in having an extra methylene group between each pair of amine and carboxyl groups. The objective of this study was to determine the effect of the extra methylene groups on the characteristics of the complex of these compounds with technetium-99m during analysis by reversed phase HPLC and by electrophoresis at various pH values. Up to pH 5.5, 99mTc- L,L -EH exhibits a substantially longer retention time during reversed phase HPLC than 99mTc- L,L -EC, suggesting a more lipophilic character for 99mTc- L,L -EH under these conditions. On the other hand, 99mTc- L,L -EH clearly possesses a higher negative charge in the pH range 3-6.5 as shown by the markedly greater migration towards the anode in electrophoresis experiments. A rational explanation for these seemingly opposing observations can not yet be offered. Copyright © 2001 John Wiley & Sons, Ltd. [source] Novel Polysaccharide-derived hydrogel prevents perineural adhesions in a rat model of sciatic nerve adhesionJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2010Michiro Yamamoto Abstract We investigated the effects of a novel carboxymethylcellulose (CMC)-derived hydrogel, in which phosphatidylethanolamine (PE) was introduced into the carboxyl groups of CMC, for preventing perineural adhesion after extensive internal neurolysis of rat sciatic nerve. Sciatic nerves were randomly assigned to one of the following groups: the Control group, operated but no treatment; the HA group, operated and treated with 1% hyaluronan; the CMC,PE(L) group, operated and treated with low-viscosity CMC,PE hydrogel; and the CMC,PE(H) group, operated and treated with high-viscosity CMC,PE hydrogel. Perineural adhesions were evaluated at 6 weeks. Nerves were also subjected to biomechanical testing to assess ultimate breaking strength. Electrophysiological and wet muscle weight measurements were performed. Breaking strengths were significantly lower for the CMC,PE(L) group than for the Control and HA groups. Latency was significantly longer for the Control group than for the CMC,PE(L) group at 20 days. The mean percentage of wet muscle weight to body weight was significantly lower for the Control group than for the CMC,PE(L) group at 6 weeks. Low-viscosity CMC,PE hydrogel appears to prevent perineural adhesions and allow early restoration of nerve function. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:284,288, 2010 [source] Water-resistant conducting hybrids from electrostatic interactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2007Jing Luo Abstract Conductive hybrids were prepared in a water/ethanol solution via the sol,gel process from an inorganic sol containing carboxyl groups and water-borne conductive polyaniline (cPANI). The inorganic sol was prepared by the hydrolysis and condensation of methyltriethoxysilane with the condensed product of maleic anhydride and aminopropyltriethoxysilane as a catalyst, for which the carboxyl counterion along the cPANI backbone acted as an electrostatic-interaction moiety. The existence of this electrostatic interaction could improve the compatibility of the two components and contribute to the homogeneous dispersion of cPANI in the silica phase. The electrostatic-interaction hybrids displayed a conductivity percolation threshold as low as 1.1 wt % polyaniline in an emeraldine base, showing 2 orders of magnitude higher electrical conductivity than that without electrostatic interactions. The electrostatic-interaction hybrids also showed good water resistance; the electrical conductivity with a cPANI loading of 16 wt % underwent a slight change after 14 days of soaking in water. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1424,1431, 2007 [source] Synthesis and characterization of multiblock copolymers based on L -lactic acid, citric acid, and poly(ethylene glycol)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2003Fanglian Yao Abstract Because poly(L -lactic acid) (PLLA) is a biodegradable polyester with low immunogenicity and good biocompatibility, it is used as a biomaterial. However, hydrophobic PLLA does not have any reactive groups. Thus, its application is limited. To increase the hydrophilicity of PLLA and accelerate its degradation rate, functionalized pendant groups and blocks were introduced through copolymerization with citric acid and poly(ethylene glycol) (PEG), respectively. This article describes the synthesis and characterization of poly(L -lactic- co -citric acid) (PLCA)-PLLA and PLCA-PEG multiblock copolymers. The results indicated that the hydrolysis rate was enhanced, and the hydrophilicity was improved because of the incorporation of carboxyl groups in PLCA-PLLA. The joining of the PEG block led to improved hydrophilicity of PLCA, and the degradation rate of PLCA-PEG accelerated as compared with that of PLCA-PLLA. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2073,2081, 2003 [source] Monitoring oxidation of multiwalled carbon nanotubes by Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2007Sebastian Osswald Abstract Multiwalled carbon nanotubes (MWCNTs) were oxidized in air and acids while varying the treatment time and/or temperature. The goal of this approach was to create the highest density of carboxyl groups with moderate sample loss, which is necessary for nanocomposite applications. In situ Raman experiments allowed real-time observation of the structural changes in MWCNTs upon oxidation. The ratio of the Raman intensities of the D and G bands was used to estimate the concentration of defects. It was found that while an oxidation for 6 h in H2SO4/HNO3 provided the strongest effect, a ,flash oxidation' in air (15 min at 550 °C) also leads to an efficient functionalization in a cost-effective and environmentally friendly way. Transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis and electrophoretic mobility analysis were used to study the oxidized nanotubes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of an antibody pharmaceutical, tocilizumab, by capillary electrophoresis using a carboxylated capillaryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5 2008Atsushi Taga Abstract Antibody pharmaceuticals are becoming more and more prevalent due to their excellent effectiveness in clinical medications, and are expected to allow tailor-made medical treatment for rheumatic diseases, immunosuppression in cardiac transplantation, and cancer. Antibody-type pharmaceuticals of immunoglobulin G (IgG) commonly have N -glycosylated carbohydrate chains attached to heavy chains. The carbohydrate chains play important roles in the effectiveness of antibodies. Therefore evaluation of a glycosylated species is important in the first step of quality control of antibody pharmaceuticals. In the present work, we examined capillary electrophoresis with a newly developed, chemically modified capillary, the inner surface of which is modified with carboxyl groups, for evaluation of IgG molecular species which have carbohydrate chains; tocilizumab was used as a model. The analytical system developed in the present study is useful for determining the content of non-glycosylated peptides. In the analysis of tocilizumab, the ratio of non-glycosylated peptide was estimated to be 1.23% with a relative standard deviation of 3.05%. The method affords high reproducibility with simple operation, and analysis can be completed within 6 min. [source] Ion-Exchange Loading of Yttrium Acetate as a Sintering Aid on Aluminum Nitride Powder via Aqueous ProcessingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000Yasuhiro Shimizu A novel fabrication process of AlN ceramics via aqueous colloidal processing and pressureless sintering has been presented. The chemical stability of AlN powder in water was improved by the surface chemical modification with sebacic acid, while maintaining a hydrophilic surface. The treatment of the sebacic acid-modified powder with yttrium acetate tetrahydrate resulted in strong immobilization of Y3+ ions, as a sintering aid, at a highly dispersive level on the AlN powder surface through ion exchange with the free carboxyl groups of the sebacic acid molecules attached to the AlN surface. By selecting slip compositions for a well-deflocculated condition and firing conditions to burn out organic components in the slip cast compacts, a thermal conductivity of about 250 W/(m·K) could be attained by the pressureless sintering at 1900°C for 5 h. [source] Emulsifying properties of gelatin conjugated to pectin under alkaline conditionsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2005Nickolaos G Diftis Abstract Gelatin,pectin mixed solution incubated under mild alkaline conditions for a period of 4 h exhibited an improvement of emulsion stability in terms of both droplet coalescence and serum separation. Application of SDS,PAGE provided evidence for gelatin,pectin hybrid formation possibly due to amide bonds between the lysine group residues of protein and the esterified carboxyl groups of the polysaccharide. The superior stabilizing properties of the heat-treated protein,polysaccharide conjugate is attributed to the enhancement of the repulsive steric forces operating between emulsion oil droplets, as a result of conjugate adsorption through their protein moiety. Copyright © 2004 Society of Chemical Industry [source] Formation of Poly(propylene)-Based Biocomposite Films and Their Use in the Attachment of Methylene BlueMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Jesica A. Cavallo Abstract Biocomposite PP -g- PAAc-CS films based on PP were generated and utilized as support of methylene blue, a thiazidic dye. Using a photograft polymerization of acrylic acid, the PP film was functionalized with carboxyl groups (PP -g- PAAc), which attached chitosan by electrostatic bond. A longer poly(acrylic acid) chain or a higher CS immobilization temperature led to a higher chain interpenetration and crosslinking reaction. Immobilized MB confirmed to possess redox activity from its reaction with ascorbic acid, where the dye decomposition rate () increases together with the chain interpenetration, then decreasing with the increase in the crosslinking degree. [source] Modeling of Semibatch Esterification Process for Poly(ethylene terephthalate) SynthesisMACROMOLECULAR REACTION ENGINEERING, Issue 4 2007Himanshu Patel Abstract The esterification kinetics of terephthalic acid (TPA) and ethylene glycol (EG) in poly(ethylene terephthalate) (PET) synthesis were studied using a semibatch reactor. Rate constants were optimized by data fitting with the oligomeric chain length, the fraction of carboxyl groups in the terminal groups (,) and the water generation curve for different EG/TPA feed ratios. The influence of the TPA particle size distribution on the solid-liquid mass transfer rate and on acid conversion (,) was investigated. It was observed that conversion became more sensitive towards TPA particle size as the EG/TPA feed ratio was lowered. It is advantageous to use the model based on TPA particle size for mass transfer limited esterification reactors. The effect of the monomer feed ratio on conversion, chain length and system heterogeneity can be predicted with this model. [source] Synthesis, characterization and properties of polycarbonate containing carboxyl side groupsMACROMOLECULAR SYMPOSIA, Issue 1 2003Ruifeng Zhang Abstract Diphenolic Acid, DPA [bis(4-hydroxyphenyl)pentanoic acid] can be made from cellulose-rich waste. The t-butyl ester was converted to homo- and copolycar- bonates (with bis-phenol-A, BPA). Deblocking the ester yielded polycarbonates with pendent carboxyl groups that exhibit all the properties of polyelectrolytes and retain solubility in aqueous base without degradation for long periods. [source] Application of 31P NMR spectroscopy and chemical derivatization for metabolite profiling of lipophilic compounds in human serumMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2009M. Aruni DeSilva Abstract New methods for obtaining metabolic fingerprints of biological samples with improved resolution and sensitivity are highly sought for early disease detection, studies of human health and pathophysiology, and for better understanding systems biology. Considering the complexity of biological samples, interest in biochemical class selection through the use of chemoselective probes for improved resolution and quantitation is increasing. Considering the role of lipids in the pathogenesis of a number of diseases, in this study fingerprinting of lipid metabolites was achieved by 31P labeling using the derivatizing agent 2-chloro-4,4,5,5-tetramethyldioxaphospholane. Lipids containing hydroxyl, aldehyde and carboxyl groups were selectively tagged with 31P and then detected with good resolution using 31P NMR by exploiting the 100% natural abundance and wide chemical shift range of 31P. After standardizing the reaction conditions using representative compounds, the derivatization approach was used to profile lipids in human serum. The results show that the 31P derivatization approach is simple, reproducible and highly quantitative, and has the potential to profile a number of important lipids in complex biological samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] 31P NMR spectroscopy in the quality control and authentication of extra-virgin olive oil: A review of recent progressMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2007Photis Dais Abstract This review is a brief account on the application of a novel methodology to the quality control and authentication of extra-virgin olive oil. This methodology is based on the derivatization of the labile hydrogens of functional groups, such as hydroxyl and carboxyl groups, of olive oil constituents with the phosphorus reagent 2-chloro-4,4,5,5-tetramethyldioxaphospholane, and the use of the 31P chemical shifts to identify the phosphitylated compounds. Various experimental aspects such as pertinent instrumentation, sample preparation, acquisition parameters and properties of the phosphorus reagent are reviewed. The strategy to assign the 31P signals of the phosphitylated model compounds and olive oil constituents by employing 1D and 2D NMR experiments is presented. Finally, the capability of this technique to assess the quality and the genuineness of extra-virgin olive oil and to detect fraud is discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Experimental and theoretical NMR study of selected oxocarboxylic acid oximesMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2004Kamilla Malek Abstract 1H and 13C NMR spectra of the oxocarboxylic acid oximes 2-hydroxyiminopropanoic acid (1), 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (2) and 2-cyano-2-(hydroxyimino)acetic acid (3) were measured in DMSO- d6, D2O and acetone- d6 solutions. The data indicate the presence of hydrogen bonding in 1 and 2 and a strong electron-withdrawing effect due to the cyano group in 3. The effect of intra- and intermolecular hydrogen bonding on the hydrogen and carbon chemical shifts in these molecules was studied theoretically. Total energy calculations of the stability of various hydrogen-bonded species, in addition to equilibrium parameters and chemical shifts, were calculated using ab initio methods (RHF, MP2) and density functional theory (B3LYP), implemented in the Gaussian 98 software package. The gauge-including atomic orbital (GIAO) method was used to predict magnetic shielding constants. Chemical shift calculations for the most stable species agree fairly well with the observed data, especially for the hydroxyl protons. Substituents adjacent to the ,-carbon show some influence of the oximic and carboxyl groups on the 13C chemical shifts, as expected for groups with different polar and anisotropic character. Copyright © 2003 John Wiley & Sons, Ltd. [source] Dry Grinding of Mefenamic Acid Particles for Enhancement of its Water Dissolution RatePARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2007Tomohiro Iwasaki Abstract This paper details an investigation into the enhancement of the water dissolution rate of mefenamic acid (MA) by means of a dry grinding treatment. The physico-chemical properties of the ground MA particles were analyzed by measurements of specific surface area, powder X-ray diffraction patterns, differential scanning calorimetry thermograms and infrared spectra, and the effects of the change in the physico-chemical properties (especially, crystalline structure) on the dissolution rate were studied. The polymorphic transition from Form I (original) to II and the change of the molecular structure of MA did not occur in the grinding treatments. However, the specific surface area of the MA particles increased, and the crystallinity decreased (i.e., the amorphization level increased) as the grinding progressed. Hydrogen bonds formed between the carboxyl groups of the opposed asymmetric MA molecules were broken gradually after the grinding limit was attained in the grinding system, resulting in an effective improvement of the initial dissolution rate. [source] Cationic Dye,sensitized Degradation of Sodium Hyaluronate Through Photoinduced Electron Transfer in the Upper Excited State,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2001Masanobu Kojima ABSTRACT The formation of ground-state complexes of methylene blue (MB) and thionine (TN) with sodium hyaluronate (NaHA) was clearly observed by means of absorption spectra in aqueous solution. Irradiation of the complexes using 313 nm light caused significant degradation of NaHA under oxygen and argon. However, the use of visible light over 400 nm, which gives the lowest excited singlet state of the cationic dyes, caused no degradation. MB and TN were more efficient sensitizers for the degradation of NaHA than rose bengal (RB), although RB is a more efficient singlet oxygen (1O2) sensitizer than the cationic dyes. Under similar conditions the polysaccharides with carboxyl groups, such as alginic acid and polygalacturonic acid, also photodecomposed. However, the polysaccharides without carboxyl groups, such as pullulan and methyl cellulose, did not. The irradiation of the polysaccharides in the presence of powdered titanium dioxide as a photocatalyst to generate the hydroxyl radical (·OH) in aerated aqueous solution caused the fragmentation of all the polymers. It was confirmed that methyl viologen, an electron-accepting sensitizer, formed a charge-transfer complex with NaHA, the irradiation of which caused the efficient degradation of NaHA. In the presence of ,- and ,-cyclodextrins the MB- and TN-sensitized photodegradation of NaHA was markedly suppressed. This was probably due to the formation of the inclusion complexes comprising the cationic dyes and the cyclodextrins. On the basis of the results obtained we propose that the cationic dye,sensitized degradation of NaHA involves a photoinduced electron-transfer process between the upper excited dyes and the ground-state NaHA and that ·OH and 1O2 do not participate in the degradation. [source] Reactive compatibilization of biodegradable poly(lactic acid)/poly(,-caprolactone) blends with reactive processing agentsPOLYMER ENGINEERING & SCIENCE, Issue 7 2008Masaki Harada Poly(lactic acid) (PLA) blended with poly(,-caprolactone) (PCL) was prepared with various reactive processing agents. Four isocyanates-lysine triisocyanate (LTI); lysine diisocyanate (LDI); 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione (Duranate TPA-100); 1,3,5-tris(6-isocyanatohexyl)biuret (Duranate 24A-100)-and an industrial epoxide-trimethylolpropane triglycidyl ether (Epiclon 725)-were used as reactive processing agents. PLA/PCL blended in the presence of LTI had the highest torque in a mixer test. The test specimens were prepared by injection molding. The mechanical properties, thermal properties, molecular weight, melt viscosity, phase behavior, and morphology were investigated using tensile strength, impact strength, differential scanning calorimetry, melt mass-flow rate measurements, capillary rheometery, gel permeation chromatography, laser scanning confocal microscopy (LSCM), and visco-elasticity atomic force microscopy (VE-AFM). The impact strength increased considerably at 20 wt% PCL. The nominal tensile strain of PLA/PCL blended with LTI increased by 270%. The MFR values of PLA/PCL blends decreased with increasing LTI. Similar results were observed for shear viscosity. LSCM measurements showed that the diameters of PCL were dispersed about 0.4 ,m in the presence of LTI. VE-AFM showed that spherical particles with diameters of 50 nm were PCL-rich domain. These results indicate that isocyanate groups of LTI react with both terminal hydroxyl or carboxyl groups of polymers, and the compatibility of PLA/PCL blends improves with LTI by reactive processing. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] | ||||||||||||||||||||||||||||||||||