Reaction Products (reaction + products)

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Reaction Products

  • chain reaction products
  • maillard reaction products
  • polymerase chain reaction products

  • Selected Abstracts

    Maillard Reaction Products as Encapsulants for Fish Oil Powders

    Mary Ann Augustin
    ABSTRACT The use of Maillard reaction products for encapsulation of fish oil was investigated. Fish oil was emulsified with heated aqueous mixtures comprising a protein source (Na caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrates (glucose, dried glucose syrup, oligosaccharide) and spray-dried for the production of 50% oil powders. The extent of the Maillard reaction was monitored using L*, a*, b* values and absorbance at 465 nm. Encapsulation efficiency was gauged by measurement of solvent-extractable fat and the oxidative stability of the fish oil powder, which was determined by assessment of headspace propanal after storage of powders at 35 °C for 4 wk. Increasing the heat treatment (60 °C to 100 °C for 30 to 90 min) of sodium caseinate-glucose-glucose syrup mixtures increased Maillard browning but did not change their encapsulation efficiency. The encapsulation efficiency of all heated sodium caseinate-glucose-glucose syrup mixtures was high, as indicated by the low solvent-extractable fat in powder (<2% powder, w/w). However, increasing the severity of the heat treatment of the sodium caseinate-glucose-glucose syrup mixtures reduced the susceptibility of the fish oil powder to oxidation. The increased protection afforded to fish oil in powders by increasing the temperature-time treatment of protein-carbohydrate mixtures before emulsification and drying was observed irrespective of the protein (sodium caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrate (glucose, glucose/dried glucose syrup, or oligosaccharide/dried glucose syrup) sources used in the formulation. Maillard reaction products produced by heat treatment of aqueous protein-carbohydrate mixtures were effective for protecting microencapsulated fish oil and other oils (evening primrose oil, milk fat) from oxidation. [source]

    ChemInform Abstract: Synthesis and Structure of Reaction Products Obtained from 1,2-Epoxyperfluorobutane and Bifunctional Nucleophilic Reagents.

    CHEMINFORM, Issue 28 2010
    T. I. Filyakova
    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]

    Nuclear Amination Catalyzed by Fungal Laccases: Reaction Products of p-Hydroquinones and Primary Aromatic Amines.

    CHEMINFORM, Issue 32 2005
    Timo H. J. Niedermeyer
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    Nitro Group Substitution in 2,4,6-Trinitrotoluene under the Action of Arenethiols and Transformations of the Reaction Products.

    CHEMINFORM, Issue 43 2002
    O. V. Serushkina
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]

    ChemInform Abstract: Anticonvulsant Activity of Reaction Products of 5,5-Diphenylhydantoin with Substituted Methylene Bromides.

    CHEMINFORM, Issue 14 2002
    Cyril O. Usifoh
    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]

    Polymerization of linseed oil with phenolic resins

    Gökhan Çayl
    Abstract In this study, linseed oil was directly polymerized with different oil soluble resoles. p- Ethyl (PEP), p-tertiary butyl (PTB), p-tertiary octyl (PTO), and p- phenyl (PPP) phenols were separately reacted with formaldehyde to give linseed oil soluble resoles. These were then reacted with linseed oil to give transparent rubbery polymers. A model reaction was performed with methyl oleate and PTB phenol resole to clarify the reaction mechanism. Reaction products were characterized with 1H-NMR and IR techniques. Spectral examination of the model reaction showed that polymerization reaction proceeded via ene reaction of the quinone methide formed at the end group of the resole with the allylic positions of the fatty ester. Rubbery polymers were obtained with linseed oil using 10 to 40% of the different resoles. Hard, load bearing and tough materials were obtained at 40% phenolic resin loading. Mechanical properties of the materials were characterized by dynamic mechanical analyzer (DMA) and stress,strain tests. The best mechanical and thermal properties were obtained with PEP resole which showed a storage modulus of 350 MPa and a tan , peak at 65°C. Storage moduli of 275, 250, and 30 were obtained for PPP, PTB, and PTO resoles-linseed oil polymers, respectively. At the same phenolic resin loading, elongation at break and swelling ratios in CH2Cl2 increased with the longer alkyl substitution on the resole resins. The highest thermal stability was observed by PEP resole,linseed oil polymer which has a 5% weight loss temperature of 340°C as determined by TGA. The lowest thermal stability was observed for PTB resole-linseed oil polymer at 220°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Penicillin G splitting in a flow-through electro-membrane reactor with the membrane-bound enzyme

    Pavel Hasal
    Abstract Penicillin G (PenG) (0.05 mol dm,3 in phosphate buffer, pH = 8) was hydrolyzed in a continuous flow-through electro-membrane reactor (EMR) with the penicillin G acylase (PGA) (EC immobilized in 10% (w/v) polyacrylamide membrane with an area of 900 mm2, thickness of 1 mm and enzyme activity of 100 U cm,3 and 160 U cm,3, respectively. The PenG was continuously fed to the substrate compartment adjacent to one membrane surface. Reaction products were washed from the membrane by a phosphate buffer solution fed to the product compartment adjacent to the other membrane surface. The mean residence time of both streams was varied from 11.3 min to 45 min. An electric field perpendicular to the membrane surface was imposed on the reactor and the electric current density was varied from 0 to 822 A m,2. Substrate conversion was determined as a function of the mean residence time, of the applied electric current density and of the enzyme activity of the membrane. The conversion increased with increasing residence time. The applied electric current increased substrate conversion by 200% at short residence times and at low enzyme activity of the membrane. Oscillatory reaction regime was evoked by step change of the mean residence time of reactant streams in the reactor. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Composite Multienzyme Amperometric Biosensors for an Improved Detection of Phenolic Compounds

    ELECTROANALYSIS, Issue 22 2003
    B. Serra
    Abstract A biosensor design, in which glucose oxidase and peroxidase are coimmobilized by simple physical inclusion into the bulk of graphite-Teflon pellets, is reported for the detection of phenolic compounds. This design allows the "in situ" generation of the H2O2 needed for the enzyme reaction with the phenolic compounds, which avoids several problems detected in the performance of single peroxidase biosensors as a consequence of the presence of a high H2O2 concentration. So, a much lower surface fouling was found at the GOD-HRP biosensor in comparison with a graphite-Teflon-HRP electrode, suggesting that the controlled generation of H2O2 makes more difficult the formation of polymers from the enzyme reaction products. The construction of trienzyme biosensors, in which GOD, HRP and tyrosinase were coimmobilized into the graphite-Teflon matrix is also reported, and their performance was compared with that of GOD-HRP bienzyme electrodes. The practical applicability of the composite multienzyme amperometric biosensors was evaluated by the estimation of the phenolic compounds content in waste waters from a refinery, and the results were compared with those obtained by using a colorimetric official method based on the reaction with 4-aminoantipyrine. [source]

    Amalgam Electrodes for Electroanalysis

    ELECTROANALYSIS, Issue 8 2003
    Øyvind Mikkelsen
    Abstract Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising. [source]

    "Reverse degradomics", monitoring of proteolytic trimming by multi-CE and confocal detection of fluorescent substrates and reaction products

    ELECTROPHORESIS, Issue 13 2009
    Helene Piccard
    Abstract A platform for profiling of multiple proteolytic activities acting on one specific substrate, based on the use of a 96-channel capillary DNA sequencer with CE-LIF of labeled substrate peptides and reaction products is introduced. The approach consists of synthesis of a substrate peptide of interest, fluorescent labeling of the substrate, either aminoterminally by chemical coupling, or carboxyterminally by transglutaminase reaction, proteolysis by a biological mixture of proteases in the absence or presence of protease inhibitors, multi-channel analysis of substrate and reaction products, and data collection and processing. Intact substrate and reaction products, even when varying by only one amino acid, can be relatively semi-quantified in a high-throughput manner, yielding information on proteases acting in complex biological mixtures and without prepurification. Monitoring, classification and inhibition of multiple proteolytic activities are demonstrated on a model substrate, the aminoterminus of the mouse granulocyte chemotactic protein-2. In view of extensive processing of chemokines into various natural forms with different specific biological activities, and of the fragmentary knowledge of processing proteases, examples of processing by neutrophil degranulate, tumor cell culture fluids and plasma are provided. An example of selection and comparison of inhibitory mAbs illustrates that the platform is suitable for inhibitor screening. Whereas classical degradomics technologies analyze the substrate repertoire of one specific protease, here the complementary concept, namely the study of all proteases acting, in a biological context, on one specific substrate, is developed and tuned to identify key proteases and protease inhibitors for the processing of any biological substrate of interest. [source]

    Hydrogen peroxide-induced oxidative stress responses in Desulfovibrio vulgaris Hildenborough

    Aifen Zhou
    Summary To understand how sulphate-reducing bacteria respond to oxidative stresses, the responses of Desulfovibrio vulgaris Hildenborough to H2O2 -induced stresses were investigated with transcriptomic, proteomic and genetic approaches. H2O2 and induced chemical species (e.g. polysulfide, ROS) and redox potential shift increased the expressions of the genes involved in detoxification, thioredoxin-dependent reduction system, protein and DNA repair, and decreased those involved in sulfate reduction, lactate oxidation and protein synthesis. A gene coexpression network analysis revealed complicated network interactions among differentially expressed genes, and suggested possible importance of several hypothetical genes in H2O2 stress. Also, most of the genes in PerR and Fur regulons were highly induced, and the abundance of a Fur regulon protein increased. Mutant analysis suggested that PerR and Fur are functionally overlapped in response to stresses induced by H2O2 and reaction products, and the upregulation of thioredoxin-dependent reduction genes was independent of PerR or Fur. It appears that induction of those stress response genes could contribute to the increased resistance of deletion mutants to H2O2 -induced stresses. In addition, a conceptual cellular model of D. vulgaris responses to H2O2 stress was constructed to illustrate that this bacterium may employ a complicated molecular mechanism to defend against the H2O2 -induced stresses. [source]

    Zeolite synthesis employing alkaline waste effluents from the aluminum industry

    A. La Iglesia
    Zeolites 4A, 13X, Y, and HZSM5 have been synthesized from alkaline residues from aluminum finishing plants. These residues could contain concentrations of sodium aluminate and sodium hydroxide between 200 and 300 Kg/m3, and small concentrations of heavy metal cations (Cd, Co, Cr, Cu, Mn, and Zn). These contaminants make handling and disposal of these residues difficult. However, the physicochemical properties of the synthesized zeolites (cation exchange capacity of 3 mmol g,1, specific surface area between 600,900 m2g,1, particle size distribution between 0.5,2 ,m and whiteness of 97%) make them useful as detergents and catalysts. Analysis of the chemical composition of the raw materials and the reaction products demonstrates that the heavy metal cation content in the synthesized zeolites is low enough to allow their industrial use (lower than that of the original residues). Therefore, the production of various types of zeolites for industrial use could be used for the elimination of these residues from the aluminum industry. [source]

    Metalloporphyrin solubility: A trigger for catalyzing reductive dechlorination of tetrachloroethylene

    Ishai Dror
    Abstract Metalloporphyrins are well known for their electron-transfer roles in many natural redox systems. In addition, several metalloporphyrins and related tetrapyrrole macrocycles complexed with various core metals have been shown to catalyze the reductive dechlorination of certain organic compounds, thus demonstrating the potential for using naturally occurring metalloporphyrins to attenuate toxic and persistent chlorinated organic pollutants in the environment. However, despite the great interest in reductive dechlorination reactions and the wide variety of natural and synthetic porphyrins currently available, only soluble porphyrins, which comprise a small fraction of this particular family of organic macrocycles, have been used as electron-transfer shuttles in these reactions. Results from the present study clearly demonstrate that metalloporphyrin solubility is a key factor in their ability to catalyze the reductive dechlorination of tetrachloroethylene and its daughter compounds. Additionally, we show that certain insoluble and nonreactive metalloporphyrins can be activated as catalysts merely by changing solution conditions to bring about their dissolution. Furthermore, once a metalloporphyrin is fully dissolved and activated, tetrachloroethylene transformation proceeds rapidly, giving nonchlorinated and less toxic alkenes as the major reaction products. Results from the present study suggest that if the right environmental conditions exist or can be created, specific metalloporphyrins may provide a solution for cleaning up sites that are contaminated with chlorinated organic pollutants. [source]

    Anion-Dependent Structural Diversity in Silver(I) Complexes of 4-Amino-3,5-diisopropyl-1,2,4-triazole

    Guang Yang
    Abstract Reactions of silver salts with 4-amino-3,5-diisopropyl-1,2,4-triazole (L) afford dinuclear complex [Ag2L2(NO3)2(CH3CN)], triangular complex [Ag3L3](CF3SO3)3, and cyclic tetranuclear complexes [Ag4L6](BF4)4 and [Ag4L6](ClO4)4. On the basis of the X-ray analyses, anions are found to play an important role in determining the structures. Through coordination/noncoordination, anions can impart their influence on the coordination geometry of Ag atoms and the angles of N,Ag,N, which seems to be the main factor controlling the nuclearity of the reaction products in this system. 1H NMR and MS measurements suggest that these complexes probably retain their structural integrities in CH3CN solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Volatile compounds of original African black and white shea butter from Tchad and Cameroon

    Sabine Krist
    Abstract Shea butter is used as an edible vegetable fat in many African countries. It can be utilized as a substitute or complete replacement for cocoa butter in various applications and plays an important role in traditional African medicinal practice. Although detection of volatile compounds by solid-phase micro-extraction gas-chromatography mass-spectroscopy (SPME-GC-MS) is a very reliable and reproducible technique, which can be used as an important part of authenticity checking, production monitoring and contamination detection, no published data about volatile compounds of shea butter are available so far. In this investigation, the characteristic volatiles in the headspace of original African shea butter samples were identified by using SPME-capillary-GC coupled to a mass selective detector. Almost 100,different volatile components were identified, e.g. fatty acids, saturated and unsaturated aldehydes and ketones, terpenes, and typical Maillard reaction products such as methylfuranes and pyrazines. Furthermore, the samples have been olfactorily evaluated by a panel of professional flavorists and trained analytical chemists. It can be stated that variations in processing conditions of shea butter result in considerable differences in the composition of headspace volatiles, detected by SPME-GC-MS and human olfaction. [source]

    Characterization of porcine dentin sialoprotein (DSP) and dentin sialophosphoprotein (DSPP) cDNA clones

    Yasuo Yamakoshi
    Dentin sialophosphoprotein (DSPP) is a chimeric glycoprotein with dentin sialoprotein (DSP) on its N -terminus and dentin phosphoprotein (DPP) on its C -terminus. We have constructed and screened a unidirectional cDNA library derived from the pulp organ of developing pig teeth, and isolated cDNA clones encoding DSP-only, as well as two DSPP clones with alternative sequences in their 3, coding regions. The DSP-only transcript has an open reading frame of 386 codons, and is generated through the use of a polyadenylation signal within intron 4, immediately following the DSP coding region. the use of this polyadenylation signal deletes the DPP coding region and places a TGA translation termination signal as the fourth codon following the exon 4-encoded segment. The DSPP cDNAs contain open reading frames of 593 and 600 codons. Northern blots hybridized to radiolabeled DSP probes showed bands at 1.4, 2.5, 4.4, and 4.8 kb. Cloning and characterization of reverse transcriptase polymerase chain reaction products confirmed the existence of mRNA encoding pDSP386, pDSPP593, and pDSPP600in vivo, but also suggested that DNA sequence redundancies in the DSPP coding region make it prone to cloning artifacts. [source]

    Nucleophilic Reactivities of Pyrroles,

    Tobias A. Nigst
    Abstract The second-order rate constants of the reactions of alkyl-substituted pyrroles with a series of benzhydrylium ions were determined in acetonitrile, and the reaction products were fully characterized by NMR spectroscopy and mass spectrometry. The formation of the , adducts is the rate-limiting step of these reactions. Because the second-order rate constants correlate linearly with the electrophilicity parameters of the benzhydrylium ions, the determination of the nucleophilicity parameters N and s according to the linear free energy relationship log k2 (20 °C) = s(N + E) was achieved. With these findings, a direct comparison of the nucleophilic reactivities of these ,-excessive heterocycles with other nucleophiles became possible, and the pyrroles were integrated into the comprehensive scale of nucleophilicity, covering a range of 8,9 orders of magnitude from N -(triisopropylsilyl)pyrrole (N = 3.12), the weakest nucleophile of this series, to kryptopyrrole (3-ethyl-2,4-dimethylpyrrole, N = 11.63). Thus, highly reactive pyrroles show similar nucleophilic reactivities as enamines, whereas those of less-reactive pyrroles are comparable to allylsilanes or indoles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Alternative Mechanistic Paths in the Hetero-Diels,Alder Reaction of ,-Oxothiones: A Theoretical Study

    Laura Legnani
    Abstract DFT calculations at the B3LYP/6-311+G(d,p) level for the C, H, and O atoms and at the 6-311+G(2df,p) level for the S atom were used to study the hetero-Diels,Alder reactions between several ,-oxothiones and ethylene or methyl vinyl ether (MVE). All the transition states and the intermediates along the reaction pathways, as well as the reaction products, were located. The reactions with ethylene are all concerted though asynchronous whereas in the reactions with MVE the electron-releasing character of the methoxy substituent lowers the energy barriers and enhances the asynchronicity and the charge transfer process to such an extent that the reaction may become unconcerted and exhibit a two-step mechanism with a zwitterionic intermediate derived from nucleophilic attack of electron-rich MVE to the sulfur atom of the strongly electrophilically activated ,-oxothiones. The reactions are also favored by the conjugation of the newly formed C=C bond. Moreover, the geometric features of the diene exert a nonnegligible role, as dienes that are planar or almost planar in their ground state show a lower energy barrier. Thus, both geometric and electronic features of the dienes as well as of the dienophiles play a significant role in the easiness of the reactions and in their mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Identification of substrates for transglutaminase in Physarum polycephalum, an acellular slime mold, upon cellular mechanical damage

    FEBS JOURNAL, Issue 11 2007
    Fumitaka Wada
    Transglutaminases are Ca2+ -dependent enzymes that post-translationally modify proteins by crosslinking or polyamination at specific polypeptide-bound glutamine residues. Physarum polycephalum, an acellular slime mold, is the evolutionarily lowest organism expressing a transglutimase whose primary structure is similar to that of mammalian transglutimases. We observed transglutimase reaction products at injured sites in Physarum macroplasmodia upon mechanical damage. With use of a biotin-labeled primary amine, three major proteins constituting possible transglutimase substrates were affinity-purified from the damaged slime mold. The purified proteins were Physarum actin, a 40 kDa Ca2+ -binding protein with four EF-hand motifs (CBP40), and a novel 33 kDa protein highly homologous to the eukaryotic adenine nucleotide translocator, which is expressed in mitochondria. Immunochemical analysis of extracts from the damaged macroplasmodia indicated that CBP40 is partly dimerized, whereas the other proteins migrated as monomers on SDS/PAGE. Of the three proteins, CBP40 accumulated most significantly around injured areas, as observed by immunofluoresence. These results suggested that transglutimase reactions function in the response to mechanical injury. [source]

    Properties of pyranose dehydrogenase purified from the litter-degrading fungus Agaricus xanthoderma

    FEBS JOURNAL, Issue 3 2007
    Magdalena Kujawa
    We purified an extracellular pyranose dehydrogenase (PDH) from the basidiomycete fungus Agaricus xanthoderma using ammonium sulfate fractionation and ion-exchange and hydrophobic interaction chromatography. The native enzyme is a monomeric glycoprotein (5% carbohydrate) containing a covalently bound FAD as its prosthetic group. The PDH polypeptide consists of 575 amino acids and has a molecular mass of 65 400 Da as determined by MALDI MS. On the basis of the primary structure of the mature protein, PDH is a member of the glucose,methanol,choline oxidoreductase family. We constructed a homology model of PDH using the 3D structure of glucose oxidase from Aspergillus niger as a template. This model suggests a novel type of bi-covalent flavinylation in PDH, 9- S -cysteinyl, 8-,- N3-histidyl FAD. The enzyme exhibits a broad sugar substrate tolerance, oxidizing structurally different aldopyranoses including monosaccharides and oligosaccharides as well as glycosides. Its preferred electron donor substrates are d -glucose, d -galactose, l -arabinose, and d -xylose. As shown by in situ NMR analysis, d -glucose and d -galactose are both oxidized at positions C2 and C3, yielding the corresponding didehydroaldoses (diketoaldoses) as the final reaction products. PDH shows no detectable activity with oxygen, and its reactivity towards electron acceptors is rather limited, reducing various substituted benzoquinones and complexed metal ions. The azino-bis-(3-ethylbenzthiazolin-6-sulfonic acid) cation radical and the ferricenium ion are the best electron acceptors, as judged by the catalytic efficiencies (kcat/Km). The enzyme may play a role in lignocellulose degradation. [source]

    Inactivation of Aeromonas hydrophila metallo-,-lactamase by cephamycins and moxalactam

    FEBS JOURNAL, Issue 13 2001
    Astrid Zervosen
    Incubation of moxalactam and cefoxitin with the Aeromonas hydrophila metallo-,-lactamase CphA leads to enzyme-catalyzed hydrolysis of both compounds and to irreversible inactivation of the enzyme by the reaction products. As shown by electrospray mass spectrometry, the inactivation of CphA by cefoxitin and moxalactam is accompanied by the formation of stable adducts with mass increases of 445 and 111 Da, respectively. The single thiol group of the inactivated enzyme is no longer titrable, and dithiothreitol treatment of the complexes partially restores the catalytic activity. The mechanism of inactivation by moxalactam was studied in detail. Hydrolysis of moxalactam is followed by elimination of the 3, leaving group (5-mercapto-1-methyltetrazole), which forms a disulfide bond with the cysteine residue of CphA located in the active site. Interestingly, this reaction is catalyzed by cacodylate. [source]

    Purification and structure of the major product obtained by reaction of NADPH and NMNH with the myeloperoxidase/hydrogen peroxide/chloride system

    FEBS JOURNAL, Issue 10 2001
    Françoise Auchère
    The first spectrophotometric study of the reaction of the myeloperoxidase/H2O2/Cl, system with NADPH and NMNH showed that the reaction products were not the corresponding oxidized nucleotides and that modifications would take place on the nicotinamide part of the molecule [Auchère, F. & Capeillère-Blandin, C. (1999) Biochem. J. 343, 603,613]. In this report, in order to obtain more precise information on the structural modifications and mechanism of the reaction, we focus on the purification and isolation of products derived from NADPH and NMNH by RP-HPLC. Electrospray ionization mass spectra indicated that the relative height of the peaks reflected that of the natural isotopic abundance of 35Cl and 37Cl, providing evidence that the products derived from NADPH and NMNH were monochlorinated. Moreover, calculated masses revealed the 1 : 1 addition of HOCl to the molecule. Various 1D and 2D NMR experiments provided data for the assignments of the chemical shifts of protons and carbons and the coupling constants of the protons of the chlorinated nucleotides. Further NOESY experiments allowed the characterization of the spatial structure of the chlorinated product and showed that trans HOCl addition occurred at the C5=C6 carbon double bond of the nicotinamide ring, leading to a chlorohydrin. [source]

    Portable Size DMFC-Stack

    FUEL CELLS, Issue 3 2004
    A. Oedegaard
    Abstract A small, low temperature, direct methanol fuel cell stack for portable applications has been developed. Several flow field designs were investigated with respect to stable operation and high performance. Due to carbon dioxide and water production on the anode and cathode, respectively, methanol and oxygen access to the electrodes is hindered. During single cell operation the effect of both carbon dioxide evolution and water production on the current output was observed. The difference between parallel and serial feeding of both fuel and oxidant to the DMFC stack was also investigated. It was found that it is very important to remove reaction products from the active cell surface in order to ensure stable stack operation at low temperatures. The maximal power realised with the 12-cell direct methanol fuel cell stack was 30 W. [source]

    Human Werner helicase interacting protein 1 (WRNIP1) functions as a novel modulator for DNA polymerase ,

    GENES TO CELLS, Issue 1 2005
    Toshiki Tsurimoto
    Human WRNIP1, a Werner DNA helicase interacting protein 1, was expressed in insect cells and E. coli. The purified protein behaved as a homo-oligomeric complex with a native molecular mass indicative of an octamer, and the complex copurified with an ATPase activity that was stimulated by double-stranded DNA ends. As suggested by genetic studies of budding yeast WRNIP1/Mgs1, the purified human WRNIP1 complex interacted physically with human DNA polymerase , (pol ,), stimulating its DNA synthesis activity more than fivefold in the presence or absence of proliferating cell nuclear antigen. Analysis of reaction products demonstrated the stimulation to be partly due to an increased processivity of pol , but more importantly to an increase in its initiation frequency. Addition of ATP to reactions partially suppressed stimulation by WRNIP1. Furthermore, a mutant WRNIP1 lacking ATPase activity could stimulate pol , normally but was insensitive to suppression by ATP. These results indicate that WRNIP1 functions as a modulator for initiation or restart events during pol ,-mediated DNA synthesis and that its ATPase activity is utilized to sense DNA ends and to regulate the extent of stimulation. [source]

    Photochemical Reactions of Regioisomeric 2,2-Dimethyl-5,5-diphenyl- and 5,5-Dimethyl-2,2-diphenyl-Substituted Diazo Ketones of a Tetrahydrofuran Series

    Abstract The principal direction of conventional photolysis of the regioisomeric 2,2-dimethyl-5,5-diphenyl- and 5,5-dimethyl-2,2-diphenyl-substituted 4-diazodihydrofuran-3(2H)-ones 1a and 1b, respectively, is the Wolff rearrangement, while other photochemical processes, which are giving rise to the formation of CH-insertion, 1,2-alkyl- or -aryl-shifts, as well as H-atom-abstraction products occur to a much lower degree (Schemes,2 and 3). The ratio of similar reaction products from both regioisomers 1a and 1b is essentially independent of their structure, and a substantial effect of the relative position of the Ph and diazo group to each other on the yield of CH-insertion products does not occur. Based on stereochemical considerations, the Wolff rearrangement of diazodihydrofuran-3(2H)-ones apparently proceeds in a concerted manner, whereas the appearance in the reaction mixture of 1,2-shift and H-atom-abstraction products points to the parallel generation during photolysis of singlet and triplet carbenes (Schemes,4 and 5). [source]

    Efficient method of cyclic imides synthesis under ozone influence by the example of ,-caprolactam oxidation reaction

    Olga Alekseeva
    The process of ,-caprolactam oxidation by ozone in a CCl4 solution was investigated. Stoichiometric coefficient (1:1) and the mechanism of oxidation were identified. The composition and structure of the ozonolysis reaction products and the ozone attack on the caprolactam molecule were determined by IR and 1H NMR spectroscopy methods, as well as using thin-layer chromatography. It was found that the ozonolysis reaction is rather selective. The main reaction product,azepane-2,7-dione (Scharf et al., Angew Makromol Chem 1979, 79, 193),was formed with a yield of more than 90% and can be used as an intermediate during the production of commercially important antibiotics. Kinetics of the reaction obeyed the bimolecular law, the effective rate constant of the reaction in the CCl4 solution is equal to kr = 22.7 l/(mol s). The method of fast conversion of lactame to cycloimide under the ozone influence is reported. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:661,666, 2008; Published online in Wiley InterScience ( DOI 10.1002/hc.20492 [source]

    Development of odorless organosulfur reagents and asymmetric reaction using odorless thiols

    Manabu Node
    Odorless organosulfur reagents were developed by increasing their molecular weights to suppress volatility. 1-Dodecanethiol (4), dodecyl methyl sulfide (5), p -heptylphenylmethanethiol (6), p -dodecylbenzenethiol (7), p -heptylbenzenethiol (8), 2-dodecyl-1,3-propanedithiol (11), p -octyloxyphenyl-methanethiol (18b), and p -octyloxybenzenethiol (19) are typical examples of the odorless thiols and sulfides. 6-Morpholinohexyl thiol (15), methyl 6-morpholinohexyl sulfide (16), and methyl 6-morpholinohexyl sulfoxide (17) were also developed as separable reagents from reaction products by facile acid-base extraction. In addition, p -tetramethylsilylphenylmethanethiol (18) and p -tetramethylsilylbenzenethiol (14) were synthesized as the odorless synthetic substitutes of benzyl mercaptan and benzenethiol, respectively. In a similar way, silylated diphenyl disulfide (26) and diselenide (27) were prepared as odorless disulfide and diselenide. Moreover, 10-sulfanylisoborneol (1) was found to be an excellent chiral odorless substitute of hydrogen sulfide in Michael addition. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:572,583, 2007; Published online in Wiley InterScience ( DOI 10.1002/hc.20348 [source]

    Syntheses of optically active 2-(2-benzothiazolylimino)-heterazolidines

    Alejandro Cruz
    The syntheses of compounds 4R, 5R-2-[2-benzothiazolylimino]-3-hydro-4-methyl-5-phenylthiazolidine (5a), 4S,5S-2-[2-benzothiazolylimino]-3,4-dimethyl-5-phenylthiazolidine (5b), 4R,5S-[2-benzothiazolylimino]-3-hydro-4-methyl-5-phenyloxazolidine (5c), 4R,5S-2-[2-benzothiazolyl-imino]-3,4-dimethyl-5-phenyloxazolidine (5d), and 4R,5S-2-[2-benzothiazolylimino]-1,3,4-trimethyl-5-phenylimidazolidine (5e) are reported. The stereochemistry of the reaction products and the X-ray diffraction analyses of compounds 5a,d are discussed. Compounds 5a,d present planar structures. We have found short distances between the thiazolidine S1 atom and the benzothiazole N9 atom for 5a and 5b (2.782 and 2.824 Å, respectively) and the distance between the oxazolidine O1 and the benzothiazole S7 for 5d (2.721 Å). These distances are shorter than the sum of the van der Waals radii. These distances, together with the coplanarity of the heterocycles, seem to indicate the existence of a weak coordination bonding from sp2 oxygen or nitrogen atoms towards the sulfur atom. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:586,593, 2001 [source]

    ,-Ionone reactions with the nitrate radical: Rate constant and gas-phase products

    Joel C. Harrison
    The bimolecular rate constant of k (9.4 ± 2.4 × 10,12 cm3 molecule,1 s,1 was measured using the relative rate technique for the reaction of the nitrate radical (NO3,) with 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3-buten-2-one (,-ionone) at (297 ± 3) K and 1 atmosphere total pressure. In addition, the products of ,-ionone + NO3, reaction were also investigated. The identified reaction products were glyoxal (HC(O)C(O)H), and methylglyoxal (CH3C(O)C(O)H). Derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and N,O-bis(trimethylsilyl)trifluoroacetamide were used to propose the other major reaction products: 3-oxobutane-1,2-diyl nitrate, 2,6,6-trimethylcyclohex-1-ene-carbaldehyde, 2-oxo-1-(2,6,6-trimethylcyclohex-1-en-1-yl)ethyl nitrate, pentane-2,4-dione, 3-oxo-1-(2,6,6-trimethylcyclohex-1-en-1-yl)butane-1,2-diyl dinitrate, 3,3-dimethylcyclohexane-1,2-dione, and 4-oxopent-2-enal. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible ,-ionone + NO3, reaction mechanisms based on previously published volatile organic compound + NO3, gas-phase mechanisms. The additional gas-phase products 5-acetyl-2-ethylidene-3-methylcyclopentyl nitrate, 1-(1-hydroxy-7,7-dimethyl-2,3,4,5,6,7-hexahydro-1 H-inden-2-yl)ethanone, 1-(1-hydroxy-3a,7-dimethyl-2,3,3a,4,5,6,-hexahydro-1 H-inden-2-yl)ethanone, and 5-acetyl-2-ethylidene-3-methylcyclopentanone are proposed to be the result of cyclization through a reaction intermediate. © 2009 Wiley Periodicals, Inc., Int J Chem Kinet 41: 629,641, 2009 [source]

    Synthesis, thermal reactivity, and kinetics of stabilized phosphorus ylides, part 2: [(Arylcarbamoyl)(cyano)methylene]triphenylphosphoranes and their thiocarbamoyl analogues

    R. Alan Aitken
    A series of five cyano(arylcarbamoyl) phosphorus ylides 2 and five cyano(arylthiocarbamoyl) phosphorus ylides 3 are prepared and fully characterized. Pyrolytic reaction products of a representative example of each type obtained by flash vacuum pyrolysis technique show that they undergo thermal extrusion of Ph3PO or Ph3PS. Kinetic study of the gas-phase pyrolysis of each ylide by static method shows that these reactions are unimolecular and first order with no significant substituent effect, but the thiocarbamoyl ylides 3 react 40,65 times more rapidly than their carbamoyl analogues 2. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 496,502, 2006 [source]