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Sample records for bromosuccinimide

  1. Oxidation of Alcohols by N-bromosuccinimide in Water

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    XIE Min, MIAO Cheng-xia, WANG Shou-feng, SUN Wei J. Mol. Catal. (China) 2012, 26(2), 099-104 A series of alcohols were oxidatized to the correspondinl ketones or aldehydes in high yields by N-bromosuccinimide un-der catalyst-free conditions in water, except for some alcohols bearing donating substituents. However, the oxidation of less ef- fective alcohols could be carried out smoothly with Salen-Co (III) complex as a catalyst in a medium of water and CH2 C12 mixture.

  2. Efficient and selective α-bromination of carbonyl compounds with N-bromosuccinimide under microwave

    KAUST Repository

    Guan, Xiao-Yu

    2014-02-07

    A highly efficient method for the synthesis of α-halocarbonyl compounds has been achieved via selective monobromination of aromatic and aliphatic carbonyl compounds with N-bromosuccinimide catalyzed by p-toluenesulfonic acid under microwave irradiation within 30 min.

  3. Preparation of α-Bromoketones Involving the Reaction of Enol Triethyl Borates with N-Bromosuccinimide

    Directory of Open Access Journals (Sweden)

    Izabella Jastrzebska

    2013-01-01

    Full Text Available The ketones (5α- and 5β-cholestan-3-one and (1S,7aS-1-tert-butoxy-hexahydro-7a-methyl-1H-inden-5-one were efficiently α-monobrominated by treatment of the corresponding enol triethyl borates with N-bromosuccinimide (NBS.

  4. Facile synthesis of bromoallenes via N-bromosuccinimide/CH3SCH3 for the bromination of propargyl alcohols

    Institute of Scientific and Technical Information of China (English)

    Wen Feng Jiang; Xue Song Liu; Xin Du; Jian Wei Wei; Chun Yu Bao

    2012-01-01

    A novel and convenient way has been developed for the preparation of bromoallenes from propargyl alcohols by the reagent combination of N-bromosuccinimide and dimethyl sulfide.Bromoallenes with high regioselectivity were obtained in a convenient method.

  5. N-Bromosuccinimide Catalyzed One-pot and Rapid Synthesis of Acetamidobenzyl Naphthols under Mild and Solvent-free Conditions

    Institute of Scientific and Technical Information of China (English)

    SHATERIAN Hamid Reza; YARAHMADI Hossein; GHASHANG Majid; SAFARI MEHMANDOSTI Moharram

    2008-01-01

    An efficient,facile and expeditious direct protocol for the preparation of acetamidobenzyl naphthols employing a multi-component and one-pot condensation reaction of 2-naphthoi,benzaldehydes,and acetamide in the presence of N-bromosuccinimide(NBS)under thermal and microwave irradiation conditions has been described.The present protocol with NBS catalyst is convincingly superior to the recently reported catalytic methods.

  6. Preparation of Silyl Ethers Using Hexamethyldisilazane in the Presence of N-Bromosuccinimide under Mild and Solvent-Free Conditions

    Institute of Scientific and Technical Information of China (English)

    SHATERIAN Hamid Reza; DOOSTMOHAMMADI Razieh; GHASHANG Majid

    2008-01-01

    A mild,simple,novel and highly efficient method for the rapid protection of various primary,secondary,tertiary aliphatic and aromatic alcohols using hexamethyldisilazane (HMDS) in the presence of N-bromosuccinimide (NBS) as an active,inexpensive,non-toxic and readily available catalyst under solvent-free conditions is described.Trimethylsilyl ethers were prepared in high to excellent yields with short reaction time under mild and almost neutral reaction conditions.

  7. Spectrophotometric determination of some analgesic drugs in pharmaceutical formulations using N-bromosuccinimide as an oxidant

    Directory of Open Access Journals (Sweden)

    Akram M. El-Didamony

    2015-04-01

    Full Text Available New sensitive and rapid spectrophotometric methods for the determination of four analgesic drugs namely, nalbuphine (NALB, naltrexone (NALT, morphine (MORF and tramadol (TRAM in pharmaceutical formulations were developed and optimized. The proposed methods involve the addition of a measured excess of N-bromosuccinimide in acid medium followed by determination of unreacted NBS by reacting with either a fixed amount of methyl orange and measuring the absorbance at 508 nm (Method A, or orange G and measuring the absorbance at 478 nm (Method B. In both methods, the amount of NBS reacted corresponds to the amount of drugs. Under the optimum conditions, Beer’s law limit, molar absorptivity and Sandell’s sensitivity were calculated. The limits of detection and quantification were also reported for both methods. Statistical evaluation of the methods was examined by determining intra-day and inter-day precisions. The methods were successfully applied to the assay of drugs in their pharmaceutical formulations. No interference was observed from common additives and the validity of the methods was tested.

  8. Kinetics of ruthenium(III) catalyzed and uncatalyzed oxidation of monoethanolamine by N-bromosuccinimide

    Science.gov (United States)

    Venkata Nadh, R.; Syama Sundar, B.; Radhakrishnamurti, P. S.

    2016-09-01

    Kinetics of uncatalyzed and ruthenium(III) catalyzed oxidation of monoethanolamine by N-bromosuccinimide (NBS) has been studied in an aqueous acetic acid medium in the presence of sodium acetate and perchloric acid, respectively. In the uncatalyzed oxidation the kinetic orders are: the first order in NBS, a fractional order in the substrate. The rate of the reaction increased with an increase in the sodium acetate concentration and decreased with an increase in the perchloric acid concentration. This indicates that free amine molecules are the reactive species. Addition of halide ions results in a decrease in the kinetic rate, which is noteworthy. Both in absence and presence of a catalyst, a decrease in the dielectric constant of the medium decreases the kinetic rate pointing out that these are dipole—dipole reactions. A relatively higher oxidation state of ruthenium i.e., Ru(V) was found to be the active species in Ru(III) catalyzed reactions. A suitable mechanism consistent with the observations has been proposed and a rate law has been derived to explain the kinetic orders.

  9. Titrimetric and Spectrophotometric Determination of Metaprolol tartrate in Pharmaceuticals Using N-Bromosuccinimide

    Directory of Open Access Journals (Sweden)

    K. Basavaiah

    2007-01-01

    Full Text Available One titrimetric and two spectrophotometric methods are presented for the assay of metaprolol tartrate (MPT in bulk drug and in tablets. The methods employ N-bromosuccinimide (NBS as the oxidimetric reagent and two dyes, methyl orange and indigo carmine as spectrophotometric reagents. In titrimetry, an acidified solution of MPT is treated with a known excess amount of NBS and after a definite time, the unreacted oxidant is determined by iodometric back titration. Spectrophotometry involves adding a measured excess of NBS to MPT in acid medium followed by determination of residual NBS by reacting with a fixed amount of either methyl orange and measuring the absorbance at 520 nm (Method A or indigo carmine and measuring the absorbance at 610 nm (Method B. In all the methods, the amount of NBS reacted corresponds to the amount of MPT. Reaction conditions have been optimized. Titrimetry allows the determination of 1 - 12 mg of MPT and the calculations are based on a 1: 4 (MPT: NBS reaction stoichiometry. In spectrophotometry, the measured absorbance is found to increase linearly with the concentration of MPT serving as basis for quantitation. The systems obey Beer’s law for 0.5 - 4.0 μg mL-1 and 1.25 - 10.0 μg mL-1 for method A and method B, respectively. The apparent absorptivities are calculated to 1.07 × 105 be and 4.22 × 104 L mol cm-1 for method A and method B, respectively. The methods developed were applied to the assay of MPT in commercial tablet formulations, and the results were compared statistically with those of a reference method. The accuracy and reliability of the methods were further ascertained by performing recovery tests via standard-addition method.

  10. Kinetics and Mechanism of Micellar Catalyzed Oxidation of Dextrose by N-Bromosuccinimide in H2SO4 Medium

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    Minu Singh

    2014-01-01

    Full Text Available Kinetics and mechanism of micellar catalyzed N-bromosuccinimide oxidation of dextrose in H2SO4 medium was investigated under pseudo-first-order condition temperature of 40°C. The results of the reactions studied over a wide range of experimental conditions show that NBS shows a first order dependence, fractional order, on dextrose and negative fractional order dependence on sulfuric acid. The determined stoichiometric ratio was 1 : 1 (dextrose : N-bromosuccinimide. The variation of Hg(OAC2 and succinimide (reaction product has insignificant effect on reaction rate. Effects of surfactants, added acrylonitrile, added salts, and solvent composition variation have been studied. The Arrhenius activation energy and other thermodynamic activation parameters are evaluated. The rate law has been derived on the basis of obtained data. A plausible mechanism has been proposed from the results of kinetic studies, reaction stoichiometry, and product analysis. The role of anionic and nonionic micelle was best explained by the Berezin’s model.

  11. Rapid titrimetric and spectrophotometric determination of ofloxacin in pharmaceuticals using N-bromosuccinimide

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    Kanakapura Basavaiah Vinay

    2011-06-01

    Full Text Available One titrimetric and two spectrophotometric methods have been described for the determination of ofloxacin (OFX in bulk drug and in tablets, employing N-Bromosuccinimide as an analytical reagent. The proposed methods involve the addition of a known excess of NBS to OFX in acid medium, followed by determination of unreacted NBS. In titrimetry, the unreacted NBS is determined iodometrically, and in spectrophotometry, unreacted NBS is determined by reacting with a fixed amount of either indigo carmine (Method A or metanil yellow (Method B. In all the methods, the amount of NBS reacted corresponds to the amount of OFX. Titrimetry allows the determination of 1-8 mg of OFX and the calculations are based on a 1:5 (OFX:NBS reaction stoichiometry. In spectrophotometry, Beer's law is obeyed in the concentration ranges 0.5-5.0 µg/mL for method A and 0.3-3.0 µg/mL for method B. The molar absorptivities are calculated to be 5.53x10(4 and 9.24x10(4 L/mol/cm for method A and method B, respectively. The methods developed were applied to the assay of OFX in tablets, and results compared statistically with those of a reference method. The accuracy and reliability of the methods were further ascertained by performing recovery tests via the standard-addition method.Descrevem-se métodos, um titulométrico e dois espectrofotométricos, para a determinação de ofloxacino (OFX na matéria-prima e em comprimidos, empregando a N-bromossuccinimida (NBS como reagente analítico. Os métodos propostos envolvem a adição de excesso conhecido de NBS ao OFX, em meio ácido, seguida de determinação do NBS que não reagiu. Na titulometria, o NBS que não reagiu é determinado iodometricamente e na espectrofotometria, o NBS que não reagiu é determinado pela reação com quantidade fixa de índigo carmim (Método A ou amarelo de metanila (Método B. Em todos os métodos, a quantidade de NBS que reagiu corresponde à quantidade de OFX. A titulometria permite a determina

  12. Sensitive and selective methods for the determination of rizatriptan benzoate in pharmaceuticals using N-bromosuccinimide and two dyes

    Directory of Open Access Journals (Sweden)

    Kudige Nagaraj Prashanth

    2015-05-01

    Full Text Available One titrimetric and two spectrophotometric methods are described for the determination of rizatriptan benzoate (RTB in bulk drugs and in tablets. The methods use N-bromosuccinimide (NBS as an analytical reagent, janus green (JG and calmagite (CMG as auxiliary reagents. All the three methods are indirect in which the unreacted NBS is determined after the reaction between RTB and NBS is judged complete by iodometric back titration (method A or by reacting with a fixed amount of either janus green (method B or calmagite (method C followed by the measurement of absorbance at 620 nm (method B or 540 nm (method C. Titrimetry allows the determination of 1–10 mg of RTB and follows a reaction stoichiometry of 1:3 (RTB:NBS, whereas spectrophotometric methods are applicable over the concentration ranges of 0.5–8.0 μg ml−1 in method B and 1.5–30.0 μg ml−1 in method C. Method B with a calculated molar absorptivity of 3.03 × 104 L mol−1 cm−1 is the second most sensitive spectrophotometric method ever developed for RTB. The quality control/assurance parameters such as limits of detection (LOD, quantification (LOQ and Sandelle’s sensitivity values are also reported for the spectrophotometric method. The accuracy and precision of the methods were studied on intra-day and inter-day basis. No interference was observed from common pharmaceutical adjuvants. Statistical comparison of the results with a reference method showed excellent agreement, and indicates no significant difference in accuracy and precision. The reliability of the methods was further ascertained by recovery studies via standard addition procedures.

  13. Substrate Directed Regioselective Monobromination of Aralkyl Ketones Using N-Bromosuccinimide Catalysed by Active Aluminium Oxide: α -Bromination versus Ring Bromination.

    Science.gov (United States)

    Mohan, Reddy Bodireddy; Reddy, G Trivikram; Gangi Reddy, N C

    2014-01-01

    Bromination of aralkyl ketones using N-bromosuccinimide in presence of active Al2O3 provided either α -monobrominated products in methanol at reflux or mononuclear brominated products in acetonitrile at reflux temperature with excellent isolated yields depending on the nature of substrate employed. The α -bromination was an exclusive process when aralkyl ketones containing moderate activating/deactivating groups were subjected to bromination under acidic Al2O3 conditions in methanol at reflux while nuclear functionalization was predominant when aralkyl ketones containing high activating groups were utilized for bromination in presence of neutral Al2O3 conditions in acetonitrile at reflux temperature. In addition, easy isolation of products, use of inexpensive catalyst, short reaction time (10-20 min), and safe operational practice are the major benefits in the present protocol.

  14. Green Synthetic Conditions of N-Bromosuccinimide%N-溴代丁二酰亚胺绿色合成工艺条件的探究

    Institute of Scientific and Technical Information of China (English)

    王聪; 王利民; 王芳; 肖孝辉

    2011-01-01

    以溴酸钠、溴化钠、硫酸、丁二酰亚胺为主要原料,研究了N-溴代丁二酰亚胺(NBS)的绿色化合成工艺.优化工艺条件为:原料配比n(溴酸钠):n(溴化钠):n(硫酸):n(丁二酰亚胺)=1:2:1.7:2.6,溶剂水90 mL,反应温度为20~40℃.反应时间为2.5 h,此条件下产品收率87%,有效溴含量为44.3%,纯度98.6%.%N-Bromosuccinimide was prepared by the reaction of sodium bromide, sodium bromide, sulfuric acid and succinimide. The process afforded the product in 87% yield, effective bromine content 44.3%, purity 98.6%[1],under the optimized reaction conditions: molar ratio n( sodium bromide ) :n(sodium bromide ) :n(acid ) :n(succinimide )=1:2:1:7:2.6, water 90 mL, reaction temperature 20~40℃, reaction time 2.5 h.

  15. N-溴代丁二亚酰胺催化制备乙酰化木棉纤维及吸油性能研究%Preparation of Acetylated Kapok Fiber Using N-bromosuccinimide as a Catalyst and Its Oil Sorption Property Investigation

    Institute of Scientific and Technical Information of China (English)

    王锦涛; 王爱勤

    2015-01-01

    以N-溴代丁二亚酰胺(NBS)为催化剂,制备了乙酰化木棉纤维吸油材料.利用红外光谱(FTIR)、扫描电镜(SEM)和X射线光电能谱仪(XPS)对乙酰化前后木棉纤维表面的化学组成和形貌结构进行了表征.考察了NBS浓度、乙酸酐用量、反应温度和反应时间等因素对材料吸油性能的影响.正交试验结果表明,在NBS浓度11.3mmol/L、乙酸酐用量37.5%、反应温度70℃和反应时间1h的条件下,吸油材料有最大的吸油率,对氯仿、甲苯和环己烷的吸油倍率分别可达到82.2 g/g、53.2 g/g和43.8 g/g.

  16. SYNTHESYS OF A FUNCTIONALIZED TETRAHYDROFURAN FRAGMENT THROUGH BROMINATION-CYCLIZATION OF A CONJUGATED DIENE

    Directory of Open Access Journals (Sweden)

    Veaceslav Kulciţki

    2010-06-01

    Full Text Available Conjugate 1,4-addition of N-bromosuccinimide (NBS to a diene system, possessing a suitable oxygen functionality, leads to functionalized tetrahydrofuran derivatives, which can be further derivatized into different synthetic targets.

  17. Rh(0)/Rh(iii) core-shell nanoparticles as heterogeneous catalysts for cyclic carbonate synthesis.

    Science.gov (United States)

    Jung, Younjae; Shin, Taeil; Kim, Kiseong; Byun, Hyeeun; Cho, Sung June; Kim, Hyunwoo; Song, Hyunjoon

    2016-12-22

    Rh(0)/Rh(iii) core-shell nanoparticles were prepared by surface oxidation of Rh nanoparticles with N-bromosuccinimide. They were employed as heterogeneous catalysts for cyclic carbonate synthesis from propylene oxide and CO2, and exhibited high activity and excellent recyclability due to Lewis acidic Rh(iii) species on the shells.

  18. The NBS Reaction: A Simple Explanation for the Predominance of Allylic Substitution over Olefin Addition by Bromine at Low Concentrations.

    Science.gov (United States)

    Wamser, Carl C.; Scott, Lawrence T.

    1985-01-01

    Examines mechanisms related to use of N-bromosuccinimide (NBS) for bromination at an allylic position. Also presents derived rate laws for three possible reactions of molecular bromine with an alkene: (1) free radical substitution; (2) free radical addition; and (3) electrophilic addition. (JN)

  19. On the bromination of the dihydroazulene/vinylheptafulvene photo-/thermoswitch

    DEFF Research Database (Denmark)

    Mazzanti, Virginia; Cacciarini, M.; Broman, Søren Lindbæk;

    2012-01-01

    as of the known 7-bromo-DHA. Results: Radical bromination on two different VHFs by using N-bromosuccinimide/benzoyl peroxide and light, followed by a ring-closure reaction generated the corresponding 3-bromo-DHAs, as confirmed in one case by X-ray crystallography. According to a H-1 NMR spectroscopic study...

  20. A Facile One-Pot Synthesis of α-Bromo-α,β-unsaturated Esters from Alcohols

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    Usama Karama

    2010-05-01

    Full Text Available Treatment ofN-bromosuccinimide (NBS with (carboethoxymethylene triphenylphosphorane (1 in CH2Cl2 followed by the addition of an alcohol in the presence of manganese dioxide under ultrasonic irradiation constitutes a stereoselective one-pot procedure for the preparation of Z-configured α–bromo-α,β-unsaturated esters in good to excellent yield.

  1. カエル舌水受容器に対するトリプトファナーゼおよびヒスチダーゼの作用

    OpenAIRE

    野村, 浩道; 浅沼, 直和

    1993-01-01

    N-bromosuccinimide, which is known to act on histidine and tryptophan residues of polypeptides and proteins, has been shown to inhibit Ca response specifically without inhibiting Na response in the water receptor of the frog. In order to ascertain the involvement of histidine and tryptophan residues in the receptor site responsible for Ca response, effects of histidase, tryptophanase and α-chymotrypsin on Ca and Na responses were examined. Histidase , tryptophanase and α-chymotrypsin inhibite...

  2. Halonium ion mediated synthesis of 2-halomethylene-3-oxoketoxime derivatives from isoxazoline N-oxides.

    Science.gov (United States)

    Raihan, Mustafa J; Rajawinslin, R R; Kavala, Veerababurao; Kuo, Chun-Wei; Kuo, Ting-Shen; He, Chiu-Hui; Huang, Hsiu-Ni; Yao, Ching-Fa

    2013-09-06

    A protocol for the N-bromosuccinimide (NBS)- and trichloroisocyanuric acid (TCCA)-mediated synthesis of novel 2-halomethylene-3-oxoketoximes via one-pot halogenation/oxidation of isoxazoline N-oxide derivatives is described here. The keto functionality of 3-ketoximes was selectively reduced by lithiumaluminum hydride to synthesize an unprecedented type of Baylis-Hillman oxime, which underwent N-O coupling to produce new isoxazoline N-oxide derivative.

  3. Reversible Conformational Changes of PsbO Protein Detected by Terahertz Time-Domain Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    CHEN Hua; CHEN Gui-Ying; LI Shu-Qin; WANG Li

    2009-01-01

    We used a terahertz time-domain spectroscope (THz-TDS) to detect the reversible conformations2 changes of PsbO protein induced by N-bromosuccinimide and Guanidine Hydrochloride.The veracity and sensitivity are confirmed by the fluorescence emission spectra.The results demonstrate that THz-TDS has both advantages and disadvantages in monitoring the denaturation process of proteins,which is important in applying THz-TDS technique to studying biomolecules.

  4. Regioselective aminohalogenation of β-nitrostyrenes using NCS and NBS as nitrogen/halogen sources

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Aminohalogenation reaction of β-nitrostyrenes with N-halosuccinimides(N-chloro and N-bromosuccinimides) has been successfully conducted by using nickel acetate as a catalyst in the presence of potassium carbonate and succinimide as co-additives.The reaction was easily performed at room temperature under nitrogen gas protection to give dihalorinaed haloamino products in good to excellent yields(60%-98%).The structure has been confirmed by X-ray crystal structure analysis.

  5. Spectrophotometric Method for Determination of Meloxicam in Pharmaceutical Formulations Using Nbromosuccinimide as an Oxidant

    Directory of Open Access Journals (Sweden)

    Shlear H. Hasan

    2014-12-01

    Full Text Available A simple, rapid and sensitive spectrophotometric method has been developed for the determination of meloxicam (MX in pure form and in its pharmaceutical preparations. The proposed method involve the addition of a measured excess of N-bromosuccinimide (NBS in acid medium followed by determination of unreacted NBS by reacting with indigo carmine (IC and measuring the absorbance at 610 nm. The optimum reaction conditions and other analytical parameters have been evaluated. Linearity was observed from 0.2-50 μg/ml meloxicam. Statistical analysis of the results and comparison with results by the British Pharmacopoeia method are also reported.

  6. Rapid Kinetics and Relative Reactivity of Some Five Membered Aromatic Heterocycles using Hydrodynamic Voltammetry

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    S. B. Walke

    2015-12-01

    Full Text Available Kinetics of the bromination of imidazole, pyrazole and thiazole by molecular bromine and N-bromosuccinimide has been studied in aqueous medium. Since the reactions are rapid special technique namely, hydrodyanamic voltammetry has been employed to follow the course of the reactions. These reactions follow second order kinetics. The comparative kinetic data determines the reactivity order for these heterocycles towards the bromination using two different brominating reagents. The study justifies the stereochemical principles ascertaining the relative reactivity of these heterocycles quantitatively using kinetics as an investigational tool.

  7. A rapid spectrophotometric assay of some organophosphorus pesticide residues in vegetable samples

    Science.gov (United States)

    Mathew, Sunitha B.; Pillai, Ajai K.; Gupta, Vinay K.

    2007-08-01

    A rapid and sensitive spectrophotometric method for the determination of some organophosphorus insecticides, i.e. malathion, dimethoate and phorate is described. It is based on the oxidation of organophosphorus pesticide with slight excess of N-bromosuccinimide (NBS) and the unconsumed NBS is determined with rhodamine B (lambda max: 550 nm). Beer's law is obeyed in the concentration range 0.108-1.08, 0.056-0.56 and 0.028-0.28 μg mL -1 for malathion, phorate and dimethoate, respectively. The method has been successfully applied for the determination of organophosphorus pesticide residues in various vegetable samples.

  8. 5-Bromo-1H-thieno[2,3-d]imidazole

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    Fen Wang

    2010-08-01

    Full Text Available The crystal structure of the title compound, C5H3BrN2S, shows that bromination of 1H-thieno[2,3-d]imidazole with N-bromosuccinimide in acetonitrile occurs at position 5 of the bicyclic system. The molecule is almost planar, with a mean deviation of 0.015 Å from the least-squares plane through all the non-H atoms. In the crystal, N—H...N hydrogen bonds link the molecules into infinite C(4 chains running along [101].

  9. Synthesis, structural characterization, and benzyl alcohol oxidation activity of mononuclear manganese(II) complex with 2,2'-bipyridine: [Mn(bipy)2(ClO4)2

    OpenAIRE

    KANİ, İbrahim; KURTÇA, Mehmet

    2012-01-01

    A manganese(II) complex of 2,2'-bipyridine (bipy) was synthesized and characterized by X-ray diffraction, IR, and UV-vis spectroscopy. The activity of the complex was tested for oxidation of benzyl alcohols using t-BuOOH as an oxidant in organic solvents and in an organic/water biphasic system (hexane/H2O, toluene/H2O). The effect of solvent, temperature, oxidant, and some additives (KBr, N(C4H9)Br, and N-bromosuccinimide) on the oxidation of benzyl alcohol is reported. The res...

  10. Chemical modification of L-asparaginase from Cladosporium sp. for improved activity and thermal stability.

    Science.gov (United States)

    Mohan Kumar, N S; Kishore, Vijay; Manonmani, H K

    2014-01-01

    L-Asparaginase (ASNase), an antileukemia enzyme, is facing problems with antigenicity in the blood. Modification of L-asparaginase from Cladosporium sp. was tried to obtain improved stability and improved functionality. In our experiment, modification of the enzyme was tried with bovine serum albumin, ovalbumin by crosslinking using glutaraldehyde, N-bromosuccinimide, and mono-methoxy polyethylene glycol. Modified enzymes were studied for activity, temperature stability, rate constants (kd), and protection to proteolytic digestion. Modification with ovalbumin resulted in improved enzyme activity that was 10-fold higher compared to native enzyme, while modification with bovine serum albumin through glutaraldehyde cross-linking resulted in high stability of L-asparaginase that was 8.5- and 7.62-fold more compared to native enzyme at 28°C and 37°C by the end of 24 hr. These effects were dependent on the quantity of conjugate formed. Modification also markedly prolonged L-asparaginase half-life and serum stability. N-Bromosuccinimide-modified ASNase presented greater stability with prolonged in vitro half-life of 144 hr to proteolytic digestion relative to unmodified enzyme (93 h). The present work could be seen as producing a modified L-asparaginase with improved activity and stability and can be a potential source for developing therapeutic agents for cancer treatment.

  11. A Metal and Base-Free Chemoselective Primary Amination of Boronic Acids Using Cyanamidyl/Arylcyanamidyl Radical as Aminating Species: Synthesis and Mechanistic Studies by Density Functional Theory.

    Science.gov (United States)

    Chatterjee, Nachiketa; Arfeen, Minhajul; Bharatam, Prasad V; Goswami, Avijit

    2016-06-17

    An efficient, metal and base-free, chemoselective synthesis of aryl-, heteroaryl-, and alkyl primary amines from the corresponding boronic acids has been achieved at ambient temperature mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA) and N-bromosuccinimide (NBS) using cyanamidyl/arylcyanamidyl radicals as the aminating species. The primary amine compounds were initially obtained as their corresponding ammonium trifluoroacetate salts which, on treatment with aq NaOH, provide the free amines. Finally, the primary amines were isolated through column chromatography over silica-gel using hexane-EtOAc solvent system as the eluent. The reactions are sufficiently fast, completing within 1 h. Quantum chemical calculations in combination with experimental observations validate that the ipso amination of substituted boronic acids involves the formation of cyanamidyl/arylcyanamidyl radical, followed by regiospecific interaction of its nitrile-N center with boron atom of the boronic acids, leading to chemoselective primary amination.

  12. Toward a formal synthesis of laureatin: unexpected rearrangements involving cyclic ether nucleophiles.

    Science.gov (United States)

    Keshipeddy, Santosh; Martínez, Isamir; Castillo, Bernard F; Morton, Martha D; Howell, Amy R

    2012-09-21

    Laureatin, a metabolite of the red algae Laurencia nipponica, has shown potent activity as a mosquito larvicide. The two previously published syntheses of laureatin involved an initial preparation of the 8-membered cyclic ether, followed by formation of the oxetane ring. Our strategy was the reverse, i.e., to utilize an oxetane as the framework to construct the larger ring. During this work, attempted N-bromosuccinimide (NBS)-mediated cyclization of oxetane alcohol 17, prepared from readily accessible 2-methyleneoxetane 12, yielded epoxytetrahydrofuran 19 rather than the expected laureatin core. Further derivatization of 19 yielded trans fused bis-tetrahydrofuran 32. The synthesis of 19 and 32, as well as structural and stereochemical elucidation studies, are described.

  13. Palladium(II-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

    Directory of Open Access Journals (Sweden)

    Tanveer Mahamadali Shaikh

    2013-08-01

    Full Text Available A series of general and selective Pd(II-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO ligated palladium complex (6 as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.

  14. Ultrasound assisted N-bromosuccinimde catalyzed one pot condensation approach for synthesis of Bis(indolylmethanes from primary alcohols

    Directory of Open Access Journals (Sweden)

    Prakash Chhattise

    2016-07-01

    Full Text Available A simple, efficient protocol for one pot synthesis of bis(indolylmethanes from primary alcohols is investigated with N-bromosuccinimde as a catalyst under ultrasound irradiation. Alcohols can be converted into carbonyl compounds by removal of hydrogen in presence of N-bromosuccinimde as an oxidant and can react in situ with indole to give desired bis(indolylmethanes. In the reported one pot multicomponent condensation reaction N-bromosuccinimde promotes the oxidation of alcohol to aldehyde, facilitating the subsequent condensation with indole to afford bis(indolyl methanes in good to excellent yields. The inexpensiveness and easy handling are some of important feature of N-bromosuccinimde. The by-product N-succinimide can be easily recovered and recycled to N-bromosuccinimide.

  15. Interaction of Rheumatoid Factor with Immobilized ss-DNA

    Institute of Scientific and Technical Information of China (English)

    WANG Lian-yong; LU Jing; YU Yao-ting

    2004-01-01

    Rheumatoid factors(RFs) are the characteristic autoantibodies of rheumatoid arthritis. Recent researches in our laboratory showed that the immobilized single-stranded DNA(ss-DNA) immunoadsorbent can selectively remove RFs from the serum of patients. In the present paper are studied the modification of argininine, tryptophan, lysine residues and carboxyl terminus of IgGRF, which was separated from patients′ serum, with 1,2-cyclohexanedione(CHD), N-bromosuccinimide(NBS), pyridoxal 5′-phosphate(PP) and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide(EDC) respectively, and their effects on the adsorption capacity of the immobilized ss-DNA immunoadsorbent for IgGRF. After the specific modification, the corresponding adsorption capacities of the adsorbents were changed from 48%, 46%, 44% and 54% to 84%, 14%, 21% and 81%, respectively. These results indicate that the electrostatic or ionic-bonding is essential for the interaction between ss-DNA and IgGRF.

  16. Chemical modification of amino acid residues in glycerinated Vorticella stalk and Ca(2+)-induced contractility.

    Science.gov (United States)

    Kono, R; Ochiai, T; Asai, H

    1997-01-01

    The glycerinated stalk of the peritrich ciliate Vorticella, was treated with various reagents to chemically modify the amino acid residues. The influences of these modifcations on spasmoneme contractility were investigated. First, it was confirmed that the spasmoneme contraction is not inhibited by alteration of SH groups. It was also demonstrated that chemical modification of methionine and tryptophan residues abolishes spasmoneme contractility. The reagents used for chemical modification were N-bromosuccinimide (NBS), chloramine T, and 2-hydroxy-5-nitrobenzyl bromide (HNBB), which abolished spasmoneme contractility at concentrations of 40-50 microM, 200-300 microM, and 4 mM, respectively. These results suggest that, along with Ca2+ binding proteins, there are other as yet to be identified proteins involved in contractility.

  17. trans-4-(2-Amino-5-bromo-6-methylpyrimidin-4-ylamino-1-methylcyclohexanol

    Directory of Open Access Journals (Sweden)

    Jacqui E. Hoffman

    2009-10-01

    Full Text Available The title compound, C12H19BrN4O, represents the minor component of the two products obtained in a series of transformations involving the Grignard reaction of tert-butoxycarbonyl-protected 4-aminocyclohexanone with MeMgBr, and subsequent interaction of the obtained amino-substituted cyclohexanol with 4-chloro-6-methylpyrimidin-2-amine followed by bromination with N-bromosuccinimide. The X-ray structure showed that this product represents a trans isomer with respect to the amino and hydroxy substituents in the cyclohexyl ring; the dihedral angle between the aminopyrimidine plane and the (noncrystallographic mirror plane of the substituted cyclohexyl fragment is 33.6 (3°. Only two of the four potentially `active' H atoms participate in intermolecular N—H...O and O—H...N hydrogen bonds, linking the molecules into layers parallel to the (10overline{1} plane.

  18. Chemical Modification and Fluorescence Spectrum of Tryptophan Residues in Pullulanase

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Tryptophan(Trp) residues in a pullulanase were modified by N-bromosuccinimide(NBS). The results of the Spande method indicate that there are 18 Trp residues in the pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are nonessential residues which show the fastest reaction rate according to the Zou′s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are the slowest in the reaction rate or non-reactive residues for the reaction. The fluorescence and circular dichroism(CD) spectra of the pullulanase have been changed after the reaction with NBS. Potassium iodide(KI) and acrylamide also have remarkable influences on the fluorescence spectra of the pullulanase.

  19. Chemical Modification of Tryptophan Residues in Superoxide Dismutase from Camellia Pollen and Its Fluorescence Spectrum

    Institute of Scientific and Technical Information of China (English)

    HE Xiao-hong; WU Min; LI Shan-yu; CHU Yu-zhuo; CHEN Jia; LIU Lan-ying

    2005-01-01

    The amino acid composition of the superoxide dismutase(SOD) from camellia pollen was measured and the tryptophan(Trp) residues were modified by using N-bromosuccinimide(NBS). The results show that there are 21 Trp residues in an SOD molecule and seven of which are located on the surface of the enzyme. By researching the fluorescence spectra of the native SOD and the modified SOD, we have found that the emission wavelength of Trp is at 335 nm and the fluorescence intensity will decrease when the enzyme is modified. The results also show that potassium iodide(KI) can significantly quench the fluorescence of the native SOD, but it has a less pronounced effect on the modified enzyme. Glycerin as a surface activation reagent can stabilize the fluorescence of the modified enzyme.

  20. Tryptic digestion of the human erythrocyte glucose transporter: effects on ligand binding and tryptophan fluorescence.

    Science.gov (United States)

    May, J M; Qu, Z C; Beechem, J M

    1993-09-21

    The conformation of the human erythrocyte glucose transport protein has been shown to determine its susceptibility to enzymatic cleavage on a large cytoplasmic loop. We took the converse approach and investigated the effects of tryptic digestion on the conformational structure of this protein. Exhaustive tryptic digestion of protein-depleted erythrocyte ghosts decreased the affinity of the residual transporter for cytochalasin B by 3-fold but did not affect the total number of binding sites. Tryptic digestion also increased the affinity of the residual transporter for D-glucose and inward-binding sugar phenyl beta-D-glucopyranoside but decreased that for the outward-binding 4,6-O-ethylidene glucose. These results suggest that tryptic cleavage stabilized the remaining transporter in an inward-facing conformation, but one with decreased affinity for cytochalasin B. The steady-state fluorescence emission scan of the purified reconstituted glucose transport protein was unaffected by tryptic digestion. Addition of increasing concentrations of potassium iodide resulted in linear Stern-Volmer plots, which were also unaffected by prior tryptic digestion. The tryptophan oxidant N-bromosuccinimide was investigated to provide a more sensitive measure of tryptophan environment. This agent irreversibly inhibited 3-O-methylglucose transport in intact erythrocytes and cytochalasin B binding in protein-depleted ghosts, with a half-maximal effect observed for each activity at about 0.3-0.4 nM. Treatment of purified glucose transport protein with N-bromosuccinimide resulted in a time-dependent quench of tryptophan fluorescence, which was resolved into two components by nonlinear regression using global analysis. Tryptic digestion retarded the rate of oxidation of the more slowly reacting class of tryptophans. (ABSTRACT TRUNCATED AT 250 WORDS)

  1. [Purification and properties of two chloridazondihydrodiol dehydrogenases from chloridazon degrading bacteria].

    Science.gov (United States)

    Eberspächer, J; Lingens, F

    1978-10-01

    A cell-free extract of Chloridazon-degrading soil bacteria catalyzes the conversion of the dihydrodiol derivative of chloridazon to the corresponding catechol derivative. NAD is required as hydrogen acceptor. Chromatography of the crude extract on DEAE-cellulose results in the elution of two different enzymes (enzyme A and enzyme B, respectively) with the same catalytic capacity. Both enzymes were purified to homogeneity in disc-gel electrophoresis and their properties were compared. The molecular weight was found to be 220 000 for both enzymes. Dodecyl sulphate polyacrylamide gel electrophoresis indicated subunits of molecular weight 50 000 in both cases. The synthesis of the enzymes does not seem to be under inductive control. The two dehydrogenases differ in heat-stability, pH-optimum, Km-values for the substrate and in their sensitivity to inhibitors. Enzyme A shows relatively high heat lability, a pH-optimum at pH 9.5, and a Km-value of 0.25 mM for the dihydrodiol derivative of chloridazon. The catalytic activity of enzyme A is not influenced by p-chloromercuribenzoate or by N-bromosuccinimide. In contrast enzyme B is relatively stable at high temperatures, showing a pH-optimum of 7.0, and a Km for the dihydrodiol derivative of chloridazon of 1.0 mM. Enzyme B can be completely inhibited by even small amounts of p-chloromercuribenzoate and by N-bromosuccinimide. Striking differences were found in the substrate specificities of the two dehydrogenases. Whereas enzyme A exhibits a high specificity towards dihydrodiols derived from aromates of the chloridazon or phenazon type, enzyme B is much less specific and is also able to convert the dihydrodiols of benzene, toluene or chlorobenzene into the corresponding catechols. Both enzymes are competitively inhibited by the reaction product, the catechol of chloridazon. Other catechols differed in their inhibitory effect on the two dehydrogenases. These differences are correlated with the different substrate

  2. Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

    Science.gov (United States)

    Weiber, E Annika; Jannasch, Patric

    2014-09-01

    A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells.

  3. Acetylation of oil palm empty fruit bunch fiber as an adsorbent for removal of crude oil.

    Science.gov (United States)

    Asadpour, Robabeh; Sapari, Nasiman B; Isa, Mohamed Hasnain; Kakooei, Saeid

    2016-06-01

    Removal of oil spillage from the environment is a global concern. Various methods, including the use of fibers as sorbents, have been developed for oil spill control. Oil palm empty fruit bunch (OPEFB) fiber is a plant biomass that may be acetylated by acetic anhydride using N-bromosuccinimide (NBS) as a catalyst; here, the extent of acetylation may be calculated in terms of weight percent gain (WPG). The modified fiber was used to remove Tapis and Arabian crude oils. The optimum time, temperature, and catalyst concentration were 4 h, 120 °C, and 3 %, respectively, and these parameters could achieve an 11.49 % increase in WPG. The optimized parameters improved the adsorption capacity of OPEFB fibers for crude oil removal. The acetylated OPEFB fibers were characterized by using Fourier transform infrared spectroscopy and field emission scanning electron microscopy to observe the functional groups available and morphology. Kinetic and isotherm studies were conducted using different contact times and oil/water ratios. The rate of oil sorption onto the OPEFB fibers can be adequately described by the pseudo-second-order equation. Adsorption studies revealed that adsorption of crude oil on treated OPEFB fiber could be best described by the Langmuir isotherm model.

  4. A novel thermophilic endoglucanase from a mesophilic fungus Fusarium oxysporum

    Institute of Scientific and Technical Information of China (English)

    LIU Shuyan; DUAN Xinyuan; LU Xuemei; GAO Peiji

    2006-01-01

    A novel thermophilic endoglucanase (EGt) was extracted from a mesophilic fungus (Fusarium oxysporum L19). We invoked conventional kinetic enzyme reactions using the sodium salt of carboxymethyl cellulose (CMC-Na) as substrate. EGt displayed optimal activity at 75℃ when kept running 30 min in the temperature range of 30―85℃. Thermal stability curve measured at 70℃ suggested that its half-life time is 15.1 min. The activity was enhanced in the presence of Co2+ or Mg2+ but inhibited by Pb2+ and Fe3+. Moreover, N-bromosuccinimide (NBS) modification resulted in a complete loss of EGt activity, suggesting that tryptophan residues 5 be involved in the enzyme active site. Amino acid composition analysis demonstrated that EGt contains more proline residues. EGt lacks activity towards p-nitrophenyl cellobiose (pNPC). The N-terminal amino acid sequence of EGt is SYRVPAANGFPNP- DASQEKQ, and the gene of EGt was sequenced and analyzed. Extensive sequence alignments failed to show any homology between EGt and any known endoglucanases. This is the first report addressing the thermal adaptation of a cellulolytic enzyme from the mesophilic fungus F. oxysporum. 5be the expression of multiple isoenzyme in an organism helps it adapt to complex living environments.

  5. Preparation, purification and primary bioevaluation of radioiodinated ofloxacin. An imaging agent

    Energy Technology Data Exchange (ETDEWEB)

    Kandil, Shaban; Seddik, Usama; Hussien, Hiba; Shaltot, Mohamed [Atomic Energy Authority, Cairo (Egypt). Cyclotron Project; El-Tabl, Abdou [Monofia Univ. (Egypt). Faculty of Science

    2015-07-01

    The broad-spectrum antibiotic agents have been demonstrated as promising diagnostic tools for early detection of infectious lesions. We set out ofloxacin (Oflo), a second-generation fluoroquinolone, for the radioiodination process. In particular, this was carried out with {sup 125}I via an electrophilic substitution reaction. The radiochemical yield was influenced by different factors; drug concentration, different oxidizing agents, e.g. chloramine-T, iodogen and n-bromosuccinimide, pH of medium, reaction time, temperature and different organic media. These parameters were studied to optimize the best conditions for labeling with ofloxacin. We found that radiolabeling in ethanol medium showed a 70% radiochemical yield of {sup 125}I-ofloxacin. The radioiodination was determined by means of TLC and HPLC. The cold labeled Oflo ({sup 127}I-Oflo) was prepared and controlled by HPLC. The cold labeled Oflo was also confirmed by NMR and MS techniques. Furthermore, biodistribution studies for labeled {sup 125}I-Oflo were examined in two independent groups (3 mice in each one); control and E. Coli-injected (inflamed). The radiotracer showed a good localization in muscle of thigh for inflamed group as compared to control. In conclusion, ofloxacine might be a promising target as an anti-inflammatory imaging agent.

  6. Structural and biochemical features of acidic α-amylase of Bacillus acidicola.

    Science.gov (United States)

    Sharma, Archana; Satyanarayana, T

    2013-10-01

    The investigation is aimed at understanding structure-function aspect of α-amylase of an acidophilic bacterium Bacillus acidicola (BAamy), which is Ca(2+)-independent and active at acidic pH of native starch, and thus, suits better in starch saccharification process. The CD spectroscopic data analysis revealed that the enzyme has 30% α-helices, 14.2% β-sheets, and 55.8% random coils at 60 °C and pH 4.0. Using Bacillus stearothermophilus α-amylase (BStA) as the template, 3-D structure of rBAamy has been proposed. A complete loss in α-amylase activity was recorded when the amino acid residues (D231, E261 and D328) were substituted that confirmed their role in catalysis. The CD studies indicated a decrease in the α-helices content below and beyond the optimum pH and temperature that suggests a critical role of α-helix in maintaining the structural conformation of the enzyme. Fluorescence-quenching by N-bromosuccinimide (NBS) suggested the role of tryptophan in maintaining structural integrity of α-amylase and that by acrylamide indicated interaction by simple collision process.

  7. Reductive spectrophotometry of divalent tin sensitization on soda lime glass

    Science.gov (United States)

    Bejugam, Vinith; Wei, Xingfei; Roper, D. Keith

    2016-07-01

    Rapid and facile evaluation of tin (II) sensitization could lead to improved understanding of metal deposition in electroless (EL) plating. This report used a balanced redox reaction between 3,3‧,5,5‧-tetramethylbenzidine dihydrochloride (TMB-HCL) and N-bromosuccinimide (NBS) to evaluate effects of sensitization conditions (i.e., sensitization time, analyte concentration, aqueous immersion, and acid content) on the accumulated mass of surface-associated divalent tin ion. The accumulated mass of tin (II) increased as the sensitization time increased up to 30 s in proportion to aqueous tin (II) chloride concentrations between 2.6 and 26 mM at a trifluoroacetic acid (TFA) content of 68 mM. The average mass peaked at 7.3 nanomoles (nmol) per cm2 after a 5 s aqueous immersion post-sensitization, and then decreased with increasing aqueous immersion post-sensitization. The total average tin (II) + tin (IV) accumulated on soda lime glass measured by inductively coupled plasma optical emission spectrometry (ICP-OES) was 17% higher at 30 s sensitization, suggesting a fraction of the tin (II) present may have oxidized to tin (IV). These results indicated that in situ spectrophotometric evaluation of tin (II) could support development of EL plating for electronics, catalysis, and solar cells.

  8. Spectral analyses on tryptophan environment in phycoerythrocyanin isomerase/lyase of Mastigocladus laminosus%层理鞭枝藻藻红蓝蛋白裂合异构酶色氨酸环境的光谱探测

    Institute of Scientific and Technical Information of China (English)

    周明; 武栋

    2007-01-01

    应用N-溴化琥珀酰亚胺(N-bromosuccinimide)研究了层理鞭枝藻藻红蓝蛋白裂合异构酶(PecE、PecF)色氨酸的化学修饰,用紫外吸收光谱、圆二色光谱和荧光光谱探测了色氨酸化学修饰过程中蛋白质结构微观环境,发现PecE和PecF的色氨酸都处在疏水区域或带负电荷区域,PecE的色氨酸残基更靠近分子表面.由于色氨酸是藻红蓝蛋白裂合异构酶的必需氨基酸,这些分析加深了解了色氨酸在藻红蓝蛋白裂合异构酶催化过程中的作用.

  9. Characteristics and Applicability of Phytase of the Yeast Pichia anomala in Synthesizing Haloperoxidase.

    Science.gov (United States)

    Joshi, Swati; Satyanarayana, Tulasi

    2015-07-01

    The phytase of the yeast Pichia anomala is a histidine acid phosphatase based on signature sequences and catalytic amino acids identified by site-directed mutagenesis. Among modulators, N-bromosuccinimide and butanedione inhibit phytase, while Ca(2+) and Ni(2+) stimulate slightly. Vanadate exhibits competitive inhibition of phytase, making it bifunctional to act as haloperoxidase. Molecular docking supports vanadate to share its binding site with phytate. The T 1/2, activation energy (E a ), temperature quotient (Q 10), activation energy of thermal inactivation (Ed), and enthalpy (ΔH d (0) ) of the enzyme are 4.0 min (80 °C), 27.72 kJ mol(-1), 2.1, 410.62 kJ mol(-1), and ∼407.8 kJ mol(-1) (65-80 °C), respectively. The free energy of the process (ΔG d (o) ) increases from 49.56 to 71.58 kJ mol(-1) with rise in temperature, while entropy of inactivation (ΔS d (0) ) remains constant at ∼1.36 kJ mol(-1) K(-1). The supplementation of whole wheat dough with rPPHY resulted in 72.5 % reduction in phytic acid content of bread. These characteristics confirm that the phytase has adequate thermostability for its applicability as a food and feed additive.

  10. Synthesis of Phenolic Compounds by Trapping Arynes with a Hydroxy Surrogate

    Directory of Open Access Journals (Sweden)

    Rajdip Karmakar

    2015-08-01

    Full Text Available Trapping of arynes with various nucleophiles provides a range of heteroatom-functionalized arene derivatives, but the corresponding reaction with water does not provide phenol derivatives. Silver trifluroacetate (AgO2CCF3 can nicely solve this problem. It was found that in typical organic solvent, AgO2CCF3 readily reacts with arynes to generate trifluoroacetoxy organosilver arene intermediate, which, upon treating with silica gel, provides phenolic products. This protocol can be extended to the synthesis of α-halofunctionalized phenol derivatives by simply adding NBS (N-bromosuccinimides or NIS (N-iodosuccinimides to the reaction along with silver trifluroacetate, which provided α-bromo or α-iodophenol derivatives in good yield. However, the similar reactions with NCS (N-chlorosuccinimides afforded only the protonated product instead of the expected α-chlorophenols derivatives. Interestingly, substrates containing silyl substituents on 1,3-diynes resulted in α-halotrifluoroacetates rather than their hydrolyzed product. Additionally, trapping the same arynes with other oxygen-based nucleophiles containing silver counter cation, along with NXS (N-halosuccinimides, generated α-halooxyfunctionalized products.

  11. Properties and cDNA cloning of an antihemorrhagic factor (HSF) purified from the serum of Trimeresurus flavoviridis.

    Science.gov (United States)

    Deshimaru, Masanobu; Tanaka, Chie; Fujino, Kazuya; Aoki, Narumi; Terada, Shigeyuki; Hattori, Shosaku; Ohno, Motonori

    2005-12-15

    Habu serum factor (HSF) is a metalloproteinase inhibitor that is isolated from the serum of habu snake (Trimeresurus flavoviridis), and it can suppress snake venom-induced hemorrhage. In the present study, the inhibitory property and fundamental structure of HSF were analyzed in detail. HSF inhibited all the hemorrhagic and most of the non-hemorrhagic metalloproteinases tested from the venoms of T. flavoviridis and Gloydius halys brevicaudus. HSF was extremely stable in a broad range of temperature and pH, and the treatments with a temperature of 100 degrees C or pH ranging from 1 to 13 barely affects its reactivity against G. halys brevicaudus H6 protease. Gel filtration chromatography revealed that HSF binds to the H6 protease with a 1:1 molar ratio. A secondary structure profile of HSF that was monitored by circular dichroism spectrum remained unvaried up to 2 M urea. The activity of HSF was stoichiometrically abolished by chemical modification with 2,4,6-trinitrobenzene sulfonic acid and N-bromosuccinimide; this indicates that Lys and Trp residues in its sequence play a role in the inhibitory mechanism. In this study, the amino acid sequence of HSF that was obtained by cDNA cloning was identical to that reported previously, except for five substitutions. We concluded that these discrepancies reflect a difference in the places of capture of the snake specimens.

  12. Indirect flow-injection spectrophotometric determination of meloxicam, tenoxicam and piroxicam in pharmaceutical formulations.

    Science.gov (United States)

    Al-Momani, Idrees F

    2006-12-01

    A simple and sensitive indirect spectrophotometric method for the assay of meloxicam (MX), tenoxicam (TX) and piroxicam (PX) in pure and in pharmaceutical formulations by flow injection analysis (FIA) has been proposed. The method is based on the oxidation of these drugs by a known excess of N-bromosuccinimide (NBS) in an acidic medium, followed by a reaction of excess oxidant with chloranilic acid (CAA) to bleach its purple color. The absorbance values increased linearly with increasing concentrations of the drugs. Variables, such as the acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The system obeyed Beer's low over concentration ranges of 10 - 160, 20 - 200 and 10 - 160 microg/ml for MX, TX and PX, respectively. The common excipients and additives did not interfere with their determinations. The method was successfully applied to the determinations of MX, TX and PX in various pharmaceutical preparations. The results obtained by the proposed method were found to be in good agreement with those found by the official HPLC methods.

  13. Nitroxide mediated and atom transfer radical graft polymerization of atactic polymers onto syndiotactic polystyrene

    Directory of Open Access Journals (Sweden)

    M. Abbasian

    2012-06-01

    Full Text Available 'Living' radical graft polymerization was employed to prepare graft copolymers with nitroxide-mediated arylated syndiotactic polystyrene as the backbone and polystyrene (PS, poly(p-methylstyrene (PMS and poly(methylmethacrylate (PMMA as branches. A two-stage process has been developed to synthesize the macroinitiator. First, syndiotactic polystyrene (sPS was modified by the Friedel-Crafts reaction to introduce chlorine; second, the chlorine groups were converted to nitroxide mediated groups by coupling with 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH. The resulting macroinitiator (sPS-TEMPO for 'living' free radical polymerization was then heated in the presence of styrene and p-methylstyrene to form graft and block copolymers. We used the obtained copolymer and N-bromosuccinimide as brominating agent to achieve polymers with bromine groups. This brominated copolymer was used as a macroinitiator for polymerizing methyl methacrylate in the presence of the CuBr/bpy catalyst system. The formation of the graft and block copolymers was confirmed by DSC, ¹H NMR and FTIR spectroscopy. This approach using macroinitiators is an effective method for the preparation of new materials.

  14. Nitroxide mediated and atom transfer radical graft polymerization of atactic polymers onto syndiotactic polystyrene

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, M. [Department of Basic Science, Payame Noor University, Tehran (Iran, Islamic Republic of); Shoja, S. Esmaeily [Lab. of Materials, Faculty of Engineering, Islamic Azad University, Bonab (Iran, Islamic Republic of)

    2012-04-15

    'Living' radical graft polymerization was employed to prepare graft copolymers with nitroxide mediated arylated syndiotactic polystyrene as the backbone and polystyrene (PS), poly(p-methylstyrene) (PMS) and poly(methylmethacrylate) (PMMA) as branches. A two-stage process has been developed to synthesize the macroinitiator. First, syndiotactic polystyrene (sPS) was modified by the Friedel-Crafts reaction to introduce chlorine; second, the chlorine groups were converted to nitroxide mediated groups by coupling with 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH). The resulting macroinitiator (sPSTEMPO) for 'living' free radical polymerization was then heated in the presence of styrene and pmethylstyrene to form graft and block copolymers. We used the obtained copolymer and N-bromosuccinimide as brominating agent to achieve polymers with bromine groups. This brominated copolymer was used as a macroinitiator for polymerizing methyl methacrylate in the presence of the CuBr/bpy catalyst system. The formation of the graft and block copolymers was confirmed by DSC, {sup 1}H NMR and FTIR spectroscopy. This approach using macroinitiators is an effective method for the preparation of new materials. (author)

  15. Dehydration of Carbohydrates to 5-Hydroxymethylfurfural in Ionic Liquids Catalyzed by Hexachlorotriphosphazene

    Institute of Scientific and Technical Information of China (English)

    宋金良; 张斌斌; 史敬华; 马珺; 杨冠英; 韩布兴

    2012-01-01

    Development of efficient catalysts for the dehydration of carbohydrates to produce 5-hydroxymethylfurfural (HMF) is a very attractive topic. In this work, dehydration of fructose catalyzed by three organic molecules, includ- ing hexachlorotriphosphazene (N3P3CI6), trichloromelamine (C3N6H3CI3) and N-bromosuccinimide (NBS), was studied in ionic liquids. It was discovered that the three organic molecules had high activity in accelerating the de- hydration of fructose and N3P3C16 was the most efficient catalyst among them. The effects of amount of catalysts, temperature, solvents, reaction time, and substrate/solvent weight ratio on the reaction were investigated using N3P3C16 as the catalyst and 1-butyl-3-methylimidazolium chloride ([Bmim]C1) as the solvent. It was demonstrated that the N3P3C16/[Bmim]CI catalytic system was very effective for catalyzing the reaction. The yield of HMF could reach 92.8% in 20 rain at the optimized conditions and the N3P3C16/[Bmim]C1 system could be reused. Further study indicated that the N3P3C16/[Bmim]CI system was also effective for the dehydration of sucrose and inulin and satisfactory yield could be obtained at suitable conditions.

  16. Sensitive spectrophotometric methods for determination of some organophosphorus pesticides in vegetable samples

    Directory of Open Access Journals (Sweden)

    MAGDA A. AKL

    2010-03-01

    Full Text Available Three rapid, simple, reproducible and sensitive spectrophotometric methods (A, B and C are described for the determination of two organophosphorus pesticides, (malathion and dimethoate in formulations and vegetable samples. The methods A and B involve the addition of an excess of Ce4+ into sulphuric acid medium and the determination of the unreacted oxidant by decreasing the red color of chromotrope 2R (C2R at a suitable lmax = 528 nm for method A, or a decrease in the orange pink color of rhodamine 6G (Rh6G at a suitable lmax = = 525 nm. The method C is based on the oxidation of malathion or dimethoate with the slight excess of N-bromosuccinimide (NBS and the determination of unreacted oxidant by reacting it with amaranth dye (AM in hydrochloric acid medium at a suitable lmax = 520 nm. A regression analysis of Beer-Lambert plots showed a good correlation in the concentration range of 0.1-4.2 μg mL−1. The apparent molar absorptivity, Sandell sensitivity, the detection and quantification limits were calculated. For more accurate analysis, Ringbom optimum concentration ranges are 0.25-4.0 μg mL−1. The developed methods were successfully applied to the determination of malathion, and dimethoate in their formulations and environmental vegetable samples.

  17. Functional and fluorescence analyses of tryptophan residues in H+-pyrophosphatase of Clostridium tetani.

    Science.gov (United States)

    Chen, Yen-Wei; Lee, Ching-Hung; Huang, Yun-Tzu; Pan, Yih-Jiuan; Lin, Shih-Ming; Lo, Yueh-Yu; Lee, Chien-Hsien; Huang, Lin-Kun; Huang, Yu-Fen; Hsu, Yu-Di; Pan, Rong-Long

    2014-04-01

    Homodimeric proton-translocating pyrophosphatase (H+-PPase; EC 3.6.1.1) maintains the cytoplasmic pH homeostasis of many bacteria and higher plants by coupling pyrophosphate (PPi) hydrolysis and proton translocation. H+-PPase accommodates several essential motifs involved in the catalytic mechanism, including the PPi binding motif and Acidic I and II motifs. In this study, 3 intrinsic tryptophan residues, Trp-75, Trp-365, and Trp-602, in H+-PPase from Clostridium tetani were used as internal probes to monitor the local conformational state of the periplasm domain, transmembrane region, and cytoplasmic domain, respectively. Upon binding of the substrate analog Mg-imidodiphosphate (Mg-IDP), local structural changes prevented the modification of tryptophan residues by N-bromosuccinimide (NBS), especially at Trp-602. Following Mg-Pi binding, Trp-75 and Trp-365, but not Trp-602, were slightly protected from structural modifications by NBS. These results reveal the conformation of H+-PPase is distinct in the presence of different ligands. Moreover, analyses of the Stern-Volmer relationship and steady-state fluorescence anisotropy also indicate that the local structure around Trp-602 is more exposed to solvent and varied under different environments. In addition, Trp-602 was identified to be a crucial residue in the H+-PPase that may potentially be involved in stabilizing the structure of the catalytic region by site-directed mutagenesis analysis.

  18. 特异性溶瘤重组腺病毒KH901的碘标记方法及其生物学分布%Iodination Conditions of KH901, a Tumor-specific Oncolytic Recombinant Adenovirus, and Its ~(125)I-labeled Compounds Biodistribution in Animals

    Institute of Scientific and Technical Information of China (English)

    米彦霞; 李云春; 龙亚红; 解朋

    2009-01-01

    研究一种~(125)I直接标记特异性溶瘤重组腺病毒KH901的简便高效的方法,以及评价~(125)I-KH901的体内生物学行为.采用N-溴代琥珀酰亚胺(NBS)方法对KH901进行标记,确定最佳标记条件;用凝胶过滤层析法对标记物进行分离纯化,纸层析法测定放化纯度.对~(125)I-KH901进行正常小鼠体内生物学分布检测.结果显示,~(125)I-KH901的放化纯达到95%以上,标记率可达到78%;正常小鼠尾静脉注射~(125)I-KH901后体内分布显示肝脏中放射性浓集度最高,24 h检测肝脏仍有较多放射性滞留,可达13.34 %ID/g,标记物在肾脏的摄取也较高,为8.06% ID/g. 因此, N-溴代琥珀酰亚胺(NBS)方法是一种步骤简便、标记率高的比较理想的碘标记病毒方法,~(125)I-KH901主要分布在肝脏和肾脏.%In this research was developed high efficiency method using ~(125)I for directly labeling KH901,a tumor-specific oncolytic recombinant adenovirus,biodistribution of ~(125)I-labeled compound in normal mice was investigated. ~(125)I-KH901 was prepared by N-bromosuccinimide labeling method to find the optimal ratio of labeling response. The compounds were isolated and purified by Sephadex-G10 agarose and the radiochemical purity of compounds was analyzed by paper chromatography. The radioactivity biodistribution in mice was measured at different times after caudal vein injection with 0.1ml ~(125)I-KH901. The labeling yield of ~(125)I-KH901 was 78% and the radiochemical purity was 95% after purification by Sephadex-G10 agarose. Biodistribution revealed that the uptake of ~(125)I-KH901 in liver was higher than in other organs at all time points of the experiment. ~(125)I-KH901 was mainly concentrated in liver,kidneys,spleen and lung. It can be seen that N-bromosuccinimide labeling method is an optimal method with simple steps and high labeling yield in labeling KH901 with ~(125)I. ~(125)I-KH901 has a biodistribution trait which is an advantage to treating liver

  19. Characterization of endo-β-mannanase from Enterobacter ludwigii MY271 and application in pulp industry.

    Science.gov (United States)

    Yang, Miao; Cai, Jun; Wang, Changgao; Du, Xin; Lin, Jianguo

    2017-01-01

    β-Mannanases are the second most important enzymes for the hydrolysis of hemicelluloses. An endo-β-mannanase from Enterobacter ludwigii MY271 was purified at 11.7 ± 0.2-fold to homogeneity with a final recovery of 15.2 ± 0.2 %. Using purified β-mannanase protein and SDS-PAGE, the molecular mass was found to be 43.16 kDa. The optimal pH and temperature of the enzyme was found to be 7.0 and 55 °C, respectively. The β-mannanase activity was stable over a broad pH range of pH 2.0-10.0. In addition, the purified enzyme was highly activated by several metal ions and chemical reagents, such as Mg(2+), L-cysteine, glutathione (GSH) and β-mercaptoethanol. Whereas the enzyme was strongly inhibited by Hg(2+), Cu(2+), N-bromosuccinimide (NBS), 1-ethyl-3-(3-dimethyl-amino-propyl)-carbodiimide (EDC), phenylmethanesulfonyl fluoride (PMSF), and sodium dodecyl sulfate (SDS). The β-mannanase was highly active towards glucomannan, and showed endo-activity by producing a mixture of oligosaccharides. Moreover, the enzyme displayed a classical endo-type mode on mannooligosaccharides. The β-mannanase coupled with xylanase significantly improved the brightness of kraft pulp, whereas it has no remarkable effect on the tensile strength of the pulp. Our functional studies of the purified β-mannanase indicate that the enzyme is beneficial to industrial applications, in particular, biotechnological processes, such as food, feed and pulp industry.

  20. Purification, enzymatic properties, and active site environment of a novel manganese(III)-containing acid phosphatase.

    Science.gov (United States)

    Sugiura, Y; Kawabe, H; Tanaka, H; Fujimoto, S; Ohara, A

    1981-10-25

    A new manganese-containing acid phosphatase has been isolated and crystallized from sweet potato tubers. The pure enzyme contains one atom of manganese per Mr = 110,000 polypeptide and shows phosphatase activity toward various phosphate substrates. The pH optimum of the enzyme was 5.8 and the enzyme activity was inhibited by Cu2+, Zn2+, Hg2+, AsO43-, and MoO42-. This stable metalloenzyme is red-violet in color with an intense absorption band at 515 nm (epsilon - 2460). Our electronic, circular dichroism, and electron spin resonance findings strongly indicate that the Mn-valence state of the native enzyme is trivalent. When the Mn-enzyme is excited by the 5145 A line of Ar+ laser, prominent Raman lines at 1230, 1298, 1508, and 1620 cm-1 were detected. This Raman spectrum can probably be interpreted in terms of internal vibration of a coordinated tyrosine phenolate anion. The tryptophan-modified enzyme showed a positive Raman band at 370 cm-1, which is preferentially assigned to a Mn(III)-S streching mode. The modification of the Mn-enzyme by N-bromosuccinimide led to a large decrease in the fluorescence intensity of 335 nm which was dominated by its tryptophan residues within a considerable hydrophobic environment. The acid phosphatase activity was significantly decreased by the tryptophan modification. With respect to the active site donor sets, the Mn(III)-containing acid phosphatase is distinctly different from the Zn(II)-containing alkaline phosphatase. Of interest is also the appreciable similarity of some enzymatic and spectroscopic properties between the present enzyme and uteroferrin.

  1. Characterization of Pullulanase Type II from Bacillus cereus H1.5

    Directory of Open Access Journals (Sweden)

    Hii Siew Ling

    2009-01-01

    Full Text Available Problem statement: Pullulanase is one of the important enzymes in starch industry. Search for the pullulanase with distinct features, possibly from easily grown bacterium, is of interest for industrial applications Approach: The extracellular pullulanase produced by Bacillus cereus HI.5 was purified by chromatographic method of DEAE-Sepharose, followed by Superdex gel filtration. The enzyme was characterized in terms of the optimal pH and temperature for activity as well as substrate specificity. Results: The enzyme showed optimal activity at 55°C and pH 6.0. The thermostability and the thermoactivity of the enzyme were increased considerably in the presence of Ca2+. In the present of 2 mM Ca2+, the enzyme had half-life duration of more than 2 h at 50°C. Almost all metal ions had a strong inhibitory effect, except Ca2+ and Mn2+. The Ca2+ had a very strong stimulating effect on the enzyme, increasing its activity by 170%. The enzyme was activated by 2-mercaptoethanol and dithiothreitol, where as N-bromosuccinimide and Schardinger dextrins were inhibitors, suggesting that tryptophan and thiol residues may be important for the activity. The apparent Km and Vmax value for pullulan was 1.1 mg mL-1 and 0.275 µmol min-1, respectively. A relative substrate specificity for hydrolysis of pullulan, amylopectin and soluble starch by this pullulanase was 100, 28.5 and 20.4%, respectively. Conclusion: The enzyme was able to attack specifically the α-1,6 linkages in pullulan to generate maltotriose as the major end product, as well as the α-1,4 linkages in amylopectin and soluble starch leading to the formation of a mixture of maltose and glucose and therefore be classified as a type II pullulanase or an amylopullulanase.

  2. 2-(取代哌嗪-1-甲基)-3-喹啉甲酸乙酯及其衍生物的合成、表征及晶体结构%Synthesis, Characterization and Single Crystal Structure of Ethyl 2-(Substituted-piperazin-1-ylmethyl)-quinoline-3-carboxylate Derivatives

    Institute of Scientific and Technical Information of China (English)

    吴利欢; 杨定乔

    2009-01-01

    以邻硝基苯甲醛为起始原料,经还原、Friedlander缩合反应合成2-甲基-3-喹啉甲酸乙酯(2),2经N-溴代丁二酰亚胺(NBS)溴代得到化合物3,3再与N-取代哌嗪5a~5p发生SN2亲核取代反应,合成一系列2-(取代哌嗪-1-甲基)-3-喹啉甲酸乙酯及其衍生物6a~6p.它们的结构通过元素分析,IR,1H NMR,13C NMR和MS进行了鉴定和表征,并用X射线衍射法测定了化合物6n的晶体结构.%2-Methyl-quinoline-3-carboxylic acid ethyl ester (2) was prepared by reduction of o-nitrobenzaldehydebe and Friedlander condensation with o-aminobenzaldehyde, followed by bromination with N-bromosuccinimide (NBS) to give compound 3. The SN2 reaction of compound 3 with N-substitutedpiperazine 5a~5p yielded a series of ethyl 2-(substituted-piperazin-1-ylmethyl)-quinoline-3-carboxylate derivatives 6a~6p. The structures of the title compounds 6a~6p were characterized by elemental analysis, IR,1H NMR, 13C NMR and MS techniques. The compound 6n was confirmed by X-ray single crystal diffraction analysis.

  3. Spectrophotometric and potentiometric determination of piroxicam and tenoxicam in pharmaceutical preparations.

    Science.gov (United States)

    El-Ries, Mohamed A; Mohamed, Gehad; Khalil, Shaeban; El-Shall, Manal

    2003-01-01

    Two simple and accurate methods are described for the determination of piroxicam and tenoxicam in their pharmaceutical preparations. The spectrophotometric method involves the oxidation of these drugs with potassium iodate in acid medium with the liberation of iodine and subsequent extraction with cyclohexane followed by measuring the absorbance at lambda=522 nm. Beer's law is obeyed in the concentration range of 0.05-1.1 and 0.05-0.6 mg x ml(-1) for piroxicam and tenoxicam, respectively. The apparent molar absorptivities of the resulting coloured products are found to be 2.7 x 10(3) and 2.5 x 10(3) l mol(-1) x cm(-1), whereas Sandell sensitivities are 0.012 and 0.013 g x cm(-2) for piroxicam and tenoxicam, respectively. The potentiometric method involves the direct titration of both drugs with N-bromosuccinimide in acid medium and the end point is determined potentiometrically using platinum indicator electrode. Piroxicam and tenoxicam can be determined quantitatively in the concentration range of 0.33-3.37 and 0.33-4.08 mg x ml(-1) for tenoxicam and piroxicam, respectively. The standard deviation and relative standard deviation values are found to be ranged from 0.05-0.07 and 0.37-0.98% and 0.025-0.078 and 0.25-1.2% for tenoxicam and piroxicam, respectively. The two methods are accurate within +/-1.0%. Optimum conditions affecting both methods are studied. The proposed methods are applied for the determination of the drugs in pure form and in commercial pharmaceutical preparations.

  4. Synthesis of Graft Copolymer of Natural Rubber by ATRP Ⅲ.Preparation of NR-g-PMMA%采用ATRP合成天然橡胶接枝共聚物——Ⅲ.NR-g-PMMA的制备

    Institute of Scientific and Technical Information of China (English)

    赵伟; 廖建和; 廖禄生; 杨耀华; 黄仙红; 陈永平

    2012-01-01

    An atom transfer radical polymerization(ATRP) macroinitiator, bromo-(natural rubber) [NR-Br(l) ], was synthesized by the reaction of natural rubber (NR) with N-bromosuccinimide. A novel graft copolymer, (natural rubber)-g-poly( methyl methacrylate) [NR-g-PMMA(2) ] , was prepared from methyl methacrylate (MMA) using 1 as a macroinitiator and CuBr/PMDTA as the catalyst by ATRP. The structures were characterized by !H NMR and IR. The results of preliminary study of graft copolymerization dynamics showed that the reaction of NR with NBS at high temperature easily occurred addition and cyclization, 1 prepared at room temperature exhibited higher initiating activity, and the graft copolymerization accorded with first-order kinetic reaction because the molecular weight of 2 increaseed as MMA monomer conversion increases.%N-溴代丁二酰亚胺与天然橡胶(NR)反应合成了大分子引发剂——溴代天然橡胶[NR-Br(1)].通过原子转移自由基聚合(ATRP),以CuBr/PMDTA为催化体系,1引发甲基丙烯酸甲酯(MMA)接枝共聚制得新型天然橡胶-g-聚甲基丙烯酸甲酯[NR-g-PMMA(2)],其结构经1H NMR和IR表征.初步聚合反应动力学研究结果表明,NBS与NR在高温下反应容易伴随双键加成和环化反应,于室温反应所得1具有较高的引发活性;接枝聚合符合一级动力学反应,即2的分子量随MMA单体转化率的提高而增加.

  5. 2-氟-5-溴硝基苯的合成%Synthesis of 2-Fluoro-5-bromonitrobenzene

    Institute of Scientific and Technical Information of China (English)

    丁明杰; 董燕敏; 牛纪胜; 陈兴权

    2012-01-01

    采用冰醋酸作为溶剂,以邻氟硝基苯为原料,N-溴代丁二酰亚胺(NBS)为溴代试剂,合成了2-氟-5-溴硝基苯.所得目标产物通过GC-MS定性、GC定量检测.结果表明,最佳反应条件为:n(邻氟硝基苯)∶n(NBS)=1∶1.05,以冰醋酸作溶剂,反应温度10℃,反应时间2h,在该条件下2-氟-5-溴硝基苯的收率为98.6%,原料转化率100%.该反应条件温和,易于控制,重复性好.%2-Fluoro-5-bromonitrobenzene was prepared from 2-fluoronitrobenzene, using acetic acid (CH3COOH),instead of sulfuric acid or boron trifluoride,as solvent, and N-bromosuccinimide( NBS) as bromide reagent. The reaction conditions were mild and easy to control. The qualitative analysis of the target product was carried out by means of GC-MS and the quantification was carried out by means of GC. The best yield ( 98. 6% ) of 2-fluoro-5-bromonitrobenzene and conversion ( 100% ) of 2-fluoronitrobenzene were obtained under optimized conditions that n(2-fluoronitrobenzene) :n( NBS) = 1 :1. 05 ,the reaction temperature was 10 ℃ and the reaction time was 2 h. The repeat experiments show that the technology had a good repeatability under the above optimum conditions.

  6. Synthesis of novel 6-bromo-8-(tert-butyl)-5H-[1,2,4] triazino[5,6-b] indole-3-thiols%6-溴-8-叔丁基-5H-[1,2,4]三嗪并[5,6-b]吲哚-3-硫醇类化合物的合成

    Institute of Scientific and Technical Information of China (English)

    符鑫博; 白仁青卓玛; 赵勋章; 李阳

    2016-01-01

    5-叔丁基靛红(1)与N-溴代丁二酰亚胺(NBS)在环境友好的聚乙二醇-400(PEG-400)为溶剂的条件下进行溴代反应,生成5-叔丁基-7-溴靛红(2a)。随后,其在NaH为碱、DMF为溶剂的条件下发生烷基化反应,生成N-烃基取代的5-叔丁基-7-溴靛红2b-f。化合物2a-f与硫代氨基脲(3)反应得到一系列结构新颖的6-溴-8-叔丁基-5H-[1,2,4]三嗪并[5,6-b]吲哚-3-硫醇衍生物4a-f。%The synthesis of a series of structural newly 6-bromo-8-(tert-butyl)-5H-[1,2,4]triazino[5,6-b]indole-3-thiol deriva-tives 4a-f had been achieved via the condensation reaction of 7-bromo-5-tert-butylisatins 2a-f with thiosemicarbazide(3). The sub-strate 2a was prepared through the bromination reaction of 5-tert-butylisatin(1)with N-bromosuccinimide(NBS)using eco-friendly PEG-400 as solvent,which was further alkylated in DMF in the presence of NaH to give the corresponding substrates 2b-f.

  7. 2,4-Diaminothieno[2,3-d]pyrimidine lipophilic antifolates as inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase.

    Science.gov (United States)

    Rosowsky, A; Papoulis, A T; Queener, S F

    1997-10-24

    Ten previously unreported 2,4-diaminothieno[2,3-d]pyrimidine lipophilic dihydrofolate reductase inhibitors were synthesized as potential inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase. Pivaloylation of 2,4-diamino-5-methylthieno[2,3-d]pyrimidine followed by dibromination with N-bromosuccinimide in the presence of benzoyl peroxide gave 2,4-bis(pivaloylamino)-6-bromo-5-(bromomethyl)thieno[2,3-d]pyrimid ine, which after condensation with substituted anilines or N-methylanilines and deprotection with base yielded 2,4-diamino-6-bromo-5-[(substituted anilino)methyl]thieno[2,3-d]pyrimidines. Removal of the 6-bromo substituent was accomplished with sodium borohydride and palladium chloride. The reaction yields were generally good to excellent. The products were tested as inhibitors of dihydrofolate reductase (DHFR) from P. carinii, T. gondii, and rat liver. Although the IC50 could not be reached for the 6-unsubstituted compounds because of their extremely poor solubility, three of the five 6-bromo derivatives were soluble enough to allow the IC50 to be determined against all three enzymes. 2,4-Diamino-5-[3,5-dichloro-4-(1-pyrrolo)anilino]methyl]- 6-bromothieno[2,3-d]pyrimidine was the most active of the 6-bromo derivatives, with an IC50 of 7.5 microM against P. carinii DHFR, but showed no selectivity for either P. carinii or T. gondii DHFR relative to the enzyme from rat liver.

  8. Partial characterization of low density lipoprotein preparations isolated from fresh and frozen plasma after radiolabeling by seven different methods

    Energy Technology Data Exchange (ETDEWEB)

    Atsma, D.E.; Kempen, H.J.; Nieuwenhuizen, W.; van ' t Hooft, F.M.; Pauwels, E.K. (Gaubius Institute TNO, Leiden (Netherlands))

    1991-01-01

    Four {sup 99m}Tc and three {sup 123}I labeling methods were evaluated for their suitability to label low density lipoproteins (LDL) for the purpose of scintigraphic biodistribution studies. For {sup 99m}Tc these methods were: direct incorporation in LDL of {sup 99m}TcO4- using sodium dithionite (dithionite method); a method using first N,N-dimethylformamide to prepare a {sup 99m}Tc-complex reacting with LDL in a subsequent step (DMF method); a technique in which {sup 99m}TcO4- is first coupled to a diamide dithiolate derivative of pentanoic acid by reduction with dithionite, followed by coupling of this ligand to LDL (N2S2 method); and a method using sodium borohydride and stannous chloride as reducing agents (borohydride method). The iodination techniques were based on oxidation of I(-)----I+, using iodine monochloride (ICl method), 1,3,4,6-tetrachloro-3,6-diphenylglycoluril (Iodogen method), and N-bromosuccinimide (NBS method) as oxidants. We studied labeling yields, modification of LDL caused by the labeling procedures using agarose-gel electrophoresis, and radiochemical stability of the labeled LDL complex upon incubation in plasma at 37 degrees C for 15 h. We used Sepharose CL6B chromatography to separate LDL from other plasma proteins. We also examined whether LDL isolated from frozen plasma (Pool-LDL) gave results similar to LDL obtained from freshly prepared plasma (Fresh-LDL). Pool-LDL radiolabeled by the dithionite, DMF, NBS, and Iodogen methods lost its label upon incubation with plasma. This also happened with Fresh-LDL when the DMF, NBS and Iodogen methods were used. Upon agarose-gel electrophoresis, no modification of LDL was observed with all methods when the radionuclide/LDL ratio was kept low.

  9. Purification and biochemical characterization of an extracellular lipase produced by a new strain of Rhizopus sp. Purificação e caracterização bioquímica de lipase extracelular produzida por uma nova linhagem de Rhizopus sp.

    Directory of Open Access Journals (Sweden)

    Maria Gabriela Bello Koblitz

    2006-06-01

    Full Text Available The present study had as a goal to purify and characterize the lipolytic fraction secreted by a strain of Rhizopus sp. Only 3 steps of purification were necessary to achieve SDS-PAGE homogeneity. One band with 37.5 KDa molecular mass and with 1446 U/mg specific activity was obtained. The purified fraction presented 2 lipase isoforms; both showed optimum activity at 50ºC, and were stable between 6.5 and 7.5 pH values and at temperatures below 50ºC and also kept their activity in hexane. The lipase was inactivated by Hg+2 and by n-bromosuccinimide and activated by Na+.O presente trabalho teve por objetivo purificar e caracterizar a fração lipolítica secretada por uma linhagem de Rhizopus sp. Apenas 3 etapas de purificação foram necessárias para alcançar homogeneidade em eletroforese de proteína desnaturada. Uma única banda com massa molecular de 37,5 KDa e atividade específica de 1446U/mg foi obtida. A fração purificada apresentou 2 isoformas de lipase, ambas com temperatura ótima de atividade igual a 50ºC, mantiveram-se estáveis entre valores de pH entre 6,5 e 7,5 e a temperaturas inferiores a 50ºC e mantiveram sua atividade na presença de hexano. A fração lipolítica foi inativada por Hg+ e por n-bromosuccinimida e ativada por Na+.

  10. Biophysical and biochemical characterization of a hyperthermostable and Ca2+ -independent alpha-Amylase of an extreme thermophile Geobacillus thermoleovorans.

    Science.gov (United States)

    Uma Maheswar Rao, J L; Satyanarayana, T

    2008-08-01

    alpha-Amylases reported from various microbial sources have been shown to be moderately thermostable and Ca2+ dependent. The bacterial strain used in this investigation is an extremely thermophilic bacterium Geobacillus thermoleovorans that produces a novel alpha-amylase (26 kDa; alpha-amylase gt), which is hyperthermostable (Topt 100 degrees C) and does not require Ca2+ for its activity/stability. These special features of alpha-amylase gt make it applicable in starch saccharification process. The structural aspects of alpha-amylase gt are, therefore, of significant interest to understand its structure-function relationship. The circular dichroism spectroscopic data revealed the native alpha-amylase gt to contain 25% alpha-helix, 21% beta-sheet, and 54% random coils. The addition of urea, at high concentration (8 M), appeared to expose the buried Trp residues of the native alpha-amylase gt to the aqueous environment and thus showed low fluorophore. Fluorescence-quenching experiments using KI, CsCl, N-bromosuccinimide, and acrylamide revealed interesting features of the tryptophan microenvironment. Analysis of Ksv and fa values of KI, CsCl, and acrylamide suggested the overall Trp microenvironment in alpha-amylase to be slightly electropositive. Fluorescence-quenching studies with acrylamide revealed the occurrence of both collisional as well as static quenching processes. There was no change in the alpha-helix content or the enzyme activity with an increase in temperature (60-100 degrees C) that suggested a critical role of the alpha-helix content in maintaining the catalytic activity.

  11. 具有叶绿素-a基本骨架的20-meso-位取代二氢卟吩衍生物的合成%Synthesis of 20-meso-Substituted Chlorins with the Basic Skeleton of Chlorophyll-a

    Institute of Scientific and Technical Information of China (English)

    王鲁敏; 王振; 杨泽; 金英学; 王进军

    2012-01-01

    以脱镁叶绿酸-a甲酯(MPa)为起始原料,分别与氯化、溴化和硫酸重氮苯进行偶联反应,其主要产物为20-卤素取代或者亚硝基取代的二氢卟吩,仅以微量产率的得到期待的产物.焦脱镁叶绿酸的锌配合物与3-N,N-二甲胺基丙烯醛的Vilsmeier反应生成20-甲酰乙烯基焦脱镁叶绿酸.焦脱镁叶绿酸-d与N-溴代丁二酰亚胺(NBS)的溴代反应生成单一的20-溴代产物,再经Wittig反应恢复乙烯基而得到20-溴代焦脱镁叶绿酸-a甲酯.其它叶绿素降解产物的亲电取代反应均以较好的产率得到生成的20-meso-位取代的二氢卟吩衍生物.首次报道的具有叶绿素基本碳架的二氢卟吩衍生物的化学结构均经UV,IR,1H NMR及元素分析得以证实.%Methyl pheophorbide-a (MPa) was used as starting material. The coupling reaction of MPa with diazobenzene hydrochloride, hydrobromide and sulfate was carried out to give traces of expected product, while major products were 20-halogenated and nitroso-substituted chlorins. Zinc methyl pyropheophorbide-a reacted with 3-N-dimethylacrolein to give Vilsmeier product. The bromination of pyropheophorbide-d with N-bromosuccinimide (NBS) formed single 20-brominated product, the vinyl group of which was resumed by Wittig reaction to give 20-bromopyropheophorbide-a The electrophilic substitution of other chlorphyllous degradation products afforded corresponding 20-meso-substituted chlorin derivatives in better yields, respectively. The structures of all the new chlorins with basic skeleton of chlorophyll were characterized by UV, IR, 1H NMR spectra and elemental analysis.

  12. Purification and kinetics of a raw starch-hydrolyzing, thermostable, and neutral glucoamylase of the thermophilic mold Thermomucor indicae-seudaticae.

    Science.gov (United States)

    Kumar, Sanjeev; Satyanarayana, T

    2003-01-01

    The purified glucoamylase of the thermophilic mold Thermomucor indicae-seudaticaehad a molecular mass of 42 kDa with a pI of 8.2. It is a glycoprotein with 9-10.5% carbohydrate content, which acted optimally at 60 degrees C and pH 7.0, with a t(1/2) of 12 h at 60 degrees C and 7 h at 80 degrees C. Its experimental activation energy was 43 KJ mol(-1) with temperature quotient (Q(10)) of 1.35, while the values predicted by response surface methodology (RSM) were 43 KJ mol(-1) and 1.28, respectively. The enzyme hydrolyzed soluble starch at 50 degrees C (K(m) 0.50 mg mL(-1) and V(max) 109 micromol mg(-1) protein min(-1)) and at 60 degrees C (K(m) 0.40 and V(max) 143 micromol mg(-1) protein min(-1)). The experimental K(m) and V(max) values are in agreement with the predicted values at 50 degrees C (K(m) 0.45 mg mL(-1) and V(max) 111.11 micromol mg(-1) protein min(-1)) and at 60 degrees C (K(m) 0.36 mg mL(-1)and V(max) 142.85 micromol mg(-1) protein min(-1)). An Arrhenius plot indicated thermal activation up to 60 degrees C, and thereafter, inactivation. The enzyme was strongly stimulated by Co(2+), Fe(2+), Ag(2+), and Ca(2+), slightly stimulated by Cu(2+) and Mg(2+), and inhibited by Hg(2+), Zn(2+), Ni(2+), and Mn(2+). Among additives, dextran and trehalose slightly enhanced the activity. Glucoamylase activity was inhibited by EDTA, beta-mercaptoethanol, dithiothreitol, and n-bromosuccinimide, and n-ethylmaleimide inhibited its activity completely. This suggested the involvement of tryptophan and cysteine in catalytic activity and the critical role of disulfide linkages in maintaining the conformation of the enzyme. The enzyme hydrolyzed around 82% of soluble starch and 65% of raw starch (K(m) 2.4 mg mL(-1), V(max) 50 micromol mg(-1) protein min(-1)), and it was remarkably insensitive to glucose, suggesting its applicability in starch saccharification.

  13. Purification and properties of detergent-compatible extracellular alkaline protease from Scopulariopsis spp.

    Science.gov (United States)

    Niyonzima, Francois Niyongabo; More, Sunil

    2014-10-03

    A fungal alkaline protease of Scopulariopsis spp. was purified to homogeneity with a recovery of 32.2% and 138.1 U/mg specific activity on lectin-agarose column. The apparent molecular mass was 15 ± 1 kD by sodium dodecyl sulfate polyacryalamide gel electrophoresis (SDS-PAGE). It was a homogenous monomeric glycoprotein as shown by a single band and confirmed by native PAGE and gelatin zymography. The enzyme was active and stable over pH range 8.0-12.0 with optimum activity at pH 9.0. The maximum activity was recorded at 50°C and remained unaltered at 50°C for 24 hr. The enzyme was stimulated by Co(2+) and Mn(2+) at 10 mM but was unaffected by Ba(2+), Mg(2+), Cu(2+), Na(+), K(+), and Fe(2+). Ca(2+) and Fe(3+) moderately reduced the activity (∼18%); however, a reduction of about 40% was seen for Zn(2+) and Hg(2+). The enzyme activity was completely inhibited by 5 mM phenylmethylsulfonyl fluoride (PMSF) and partially by N-bromosuccinimide (NBS) and tocylchloride methylketone (TLCK). The serine, tryptophan, and histidine may therefore be at or near the active site of the enzyme. The protease was more active against gelatin compared to casein, fibrinogen, egg albumin, and bovine serum albumin (BSA). With casein as substrate, Km and Vmax were 4.3 mg/mL and 15.9 U/mL, respectively. An activation was observed with sodium dodecyl sulfate (SDS), Tween-80, and Triton X-100 at 2% (v/v); however, H2O2 and NaClO did not affect the protease activity. Storage stability was better for all the temperatures tested (-20, 4, and 28 ± 2°C) with a retention of more than 85% of initial activity after 40 days. The protease retained more than 50% activity after 24 hr of incubation at 28, 60, and 90°C in the presence (0.7%, w/v) of commercial enzymatic and nonenzymatic detergents. The Super Wheel-enzyme solution was able to completely remove blood staining, differing from the detergent solution alone. The stability at alkaline pH and high temperatures, broad substrate specificity

  14. Development and validation of a rapid stability indicating HPLC-method using monolithic stationary phase and two spectrophotometric methods for determination of antihistaminic acrivastine in capsules

    Science.gov (United States)

    Gouda, Ayman A.; Hashem, Hisham; Jira, Thomas

    2014-09-01

    Simple, rapid and accurate high performance liquid chromatographic (HPLC) and spectrophotometric methods are described for determination of antihistaminic acrivastine in capsules. The first method (method A) is based on accurate, sensitive and stability indicating chromatographic separation method. Chromolith® Performance RP-18e column, a relatively new packing material consisting of monolithic rods of highly porous silica, was used as stationary phase applying isocratic binary mobile phase of ACN and 25 mM NaH2PO4 pH 4.0 in the ratio of 22.5:77.5 at flow rate of 5.0 mL/min and 40 °C. A diode array detector was used at 254 nm for detection. The elution time of acrivastine was found to be 2.080 ± 0.032. The second and third methods (methods B and C) are based on the oxidation of acrivastine with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilic acid (λmax: 520 nm) or amaranth dye (λmax: 530 nm). The reacted oxidant corresponds to the drug content. Beer’s law is obeyed over the concentration range 1.563-50, 2.0-20 and 1.0-10 μg mL-1 for methods A, B and C, respectively. The limits of detection and quantitation were 0.40, 0.292 and 0.113 μg mL-1 and 0.782, 0.973 and 0.376 μg mL-1 for methods A, B and C, respectively. The HPLC method was validated for system suitability, linearity, precision, limits of detection and quantitation, specificity, stability and robustness. Stability tests were done through exposure of the analyte solution for four different stress conditions and the results indicate no interference of degradants with HPLC-method. The proposed methods was favorably applied for determination of acrivastine in capsules formulation. Statistical comparison of the obtained results from the analysis of the studied drug to those of the reported method using t- and F-tests showed no significant difference between them.

  15. 一种含氧供电基团的染料合成及其光伏性能%Synthesis of a New Organic Dye Containing Alkoxy Group as Donor for Dye-Sensitized Solar Cells

    Institute of Scientific and Technical Information of China (English)

    孙思远; 徐英军; 梁茂; 孙喆; 薛松

    2011-01-01

    以对溴苯酚为原料,经碘丁烷的烷基化后,与硼酸三甲酯反应生成对丁氧基苯硼酸.环戊二噻吩经N-溴代丁二酰亚胺(NBS)的溴化和Vilsmeier-Haack反应,再与对丁氧基苯硼酸偶联、氰基乙酸缩合,生成目标化合物环戊二噻吩基光敏染料(L1).该化合物是一种以含氧基团为给体,环戊二噻吩作为共轭桥的有机染料,将其制备成有机染料敏化太阳能电池,在AM 1.5,100 mW/cm2的光强下,电池的单色光的光电转换效率(IPCE)值达到62%,开路电压(Voc)为535mV,短路电流密度(Jsc)为6.4mA·cm-2,填充因子(FF)为0.60,总光电转换效率为2.1%.%A new organic dye (named L1) containing butoxy group as donor was designed and synthesized.Treatment of 4-bromophenol with n-BuI and B(OCH3)3 gave the boronic acid.The intermediate aldehyde was prepared from bis-thiophene via bromonation reaction with N-bromosuccinimide (NBS) and Vilsmeier-Haack reaction.The dye was synthesized from the Suzuki coupling reaction of the boronic acid with the aldehyde, followed by Knoevenagel condensation reaction with cyanoacetic acid.The dye was applied to nanocrystalline TiO2 dye-sensitized solar cells through standard operations.For a typical device the maximal monochromatic incident photon-to-current conversion efficiency (IPCE) can reach 62%, with a short-circuit photocurrent density (JSC) 6.4 mA·cm-2, an open-circuit photovoltage (VOC) 535 mV, and fill factor (FF) 0.60, which corresponds to an overall conversion efficiency of 2.1%.

  16. Radioiodine Labeled L-Tyrosine SPECT Scintigraphy in E.coli Focus Infection of Mouse%放射性碘标记L-酪氨酸对小鼠大肠杆菌感染灶的SPECT显像

    Institute of Scientific and Technical Information of China (English)

    唐恭顺; 俞英; 潘明志

    2012-01-01

    The aim of this study was to assess the role of 131 I-L-tyrosine for diagnosing E. coli infection and differentiating the infection from the inflammary lesion in mice. The L-tyrosine was labeled with 12SI by N-bromosuccinimide. The binding rates of 125 I-L-tyrosine with E. coli were tested by culturing E. coli with 125 I-L-tyrosine in poor nitrogen yeast medium and in rich nitrogen LB medium separately. The bio-distribution of 125 I-L-tyrosine and the 131 I-L-tyrosine SPECT scintigraphy in E. coli infection of mice were studied separately. The results revealed that the label rate of 125 I-L-tyrosine was more than 99%. The percentage of 12S I-L-tyrosine binding with E. coli was 2. 78 % in yeast medium, and was 0. 85% in LB medium. The distribution peak of 125-L-tyrosine in E, coli focal infection of mice was in the range between 45 and 60min. The infection/normal muscle ratio was 2. 46 after 60 minutes. The SPECT scintigraphy demonstrated an accumulation of the 131 I-L-tyrosine in the E. coli focal infection during the 45-60 minutes. The infection/normal muscle ratio of the 131 I-L-tyrosine radioactivity was 2. 51 in infectious mouse. However, the SPECT scintigraphy also demonstrated an accumulation of the 131 I-L-tyrosine in the inflammatory lesion during the 45-60 minutes. The lesion/normal muscle ratio of the 131 I-L-tyrosine radioactivity was 2. 29 in inflammatory mouse at 60 mins. Thus, the 131 I-L-tyrosine SPECT scintigraphy could diagnose the E. coli infection, but it can not be used for differentiating the bacteria infection and the inflammatory lesion in mice. Our study revealed that the m I-L-tyrosine would play a potential role in diagnosing the inflammatory lesion in human beings.%本文评价131I-L-酪氨酸能否诊断大肠杆菌感染灶和鉴别细菌感染与无菌性炎症.采用N-嗅代丁二酰亚胺法标记125I-L-酪氨酸,研究125I-L-酪氨酸与大肠杆菌的体外结合,在大肠杆菌肌肉感染模型小鼠的体内分

  17. “一锅法”合成2-氨基-N,3-二甲基-5-卤代苯甲酰胺%One-Pot Synthesis of 2-Amino-5-halogenated-N,3-dimethylben-zamides

    Institute of Scientific and Technical Information of China (English)

    秦伟艳; 刘波; 由君; 马静; 李香; 吕程程

    2012-01-01

    报道了从3-甲基-2-氨基苯甲酸出发一锅三步合成2-氨基-N,3-二甲基-5-卤代苯甲酰胺的方法.3-甲基-2-氨基苯甲酸(1)与固体光气反应生成中间体8-甲基-2H-3,1-苯并噁嗪-2,4(1H)-二酮(2),化合物2与甲胺水溶液发生胺解反应生成2-氨基-N,3-二甲基苯甲酰胺(3),3再与氯代丁二酰亚胺(NCS)、溴代丁二酰亚胺(NBS)或碘代丁二酰亚胺(NIS)发生芳香亲电取代反应生成目标产物2-氨基-N,3-二甲基-5-卤代苯甲酰胺(4~6).整个反应过程不需分离中间产品,最终产物经减压浓缩除去有机溶剂后,直接从水中析出针状晶体,总收率达到87%~94%,较文献报道的分步法收率提高30%以上.该方法工艺操作简单、反应条件温和、反应时间短、收率高,是一条环境友好的绿色合成路线.%The synthetic method of 2-amino-5-halogenated-N,3-dimethylbenzamides is reported from 2-amino-3-methylbenzoic acid by three steps in one pot. Firstly, 8-methyl-2H-3,l-benzoxazine-2,4(1H)-dione (2) was synthesized by using 2-amino-3-methylbenzoic acid (1) and bis(trichloromethyl) carbonate. Secondly, 2-amino-N,3-dimethyl-benzamide (3) was prepared through the aminolysis of compounds 2 and aqueous methylamine. Lastly the target products 2-amino-5-halogenated- N,3-dimethylbenzamides (4 ~ 6) were obtained by using 3 and N-chlorosuccinimide (NCS), iV-bromosuccinimide (NBS) or iV-iodosuccinimide (NIS) through electrophilic aromatic substitution. This whole process does not need to separate the middle products, and the needlelike crystals of the target product can be directly separated from water after evaporating the organic solvent under reduced pressure. The overall yield was 87%~94%, at least 30% higher than using the substep methods which reported by early literatures. This method gets the advantages of simple work-up procedure, milder conditions, shorter reaction time, higher yield and environ-mental friendliness, which is a green synthetic route.

  18. Production and characterization of an enzyme complex from a new strain of Clostridium thermocellum with emphasis on its xylanase activity Produção e caracterização de um complexo enzimático de uma nova linhagem de Clostridium thermocellum com enfase em sua atividade de xilanase

    Directory of Open Access Journals (Sweden)

    Werner Bessa Vieira

    2007-06-01

    Full Text Available A new bacterial strain (ISO II was isolated from manure cow and identified as phylogenetically close to the thermophilic cellulolytic bacterium Clostridium thermocellum. The new strain produced extracellular xylanase, pectinase, mannanase and cellulase activities when grown in liquid culture medium containing banana stem as carbon source. The enzyme production profile after growth on banana stem showed that xylanase and cellulase activities were detected in different incubation periods. An enzyme complex containing xylanase, cellulase and mannanase activities was isolated from culture supernatant samples of strainISO II. The complex was partially purified by ultrafiltration and gel filtration chromatography on Sephacryl S-300. Zymogram analysis after SDS-PAGE presented at least 05 subunits with xylanase activity. The enzyme showed single protein and xylanase activity bands after electrophoresis under non-denaturing conditions. The hydrolysis of xylan was optimal at temperature range of 55-75ºC and pH 6.0. Xylanase activity was quite stable at 65ºC, retaining 80% of its original activity after 12 h incubation. The apparent Km values, using insoluble and soluble arabinoxylans as substrates, were 1.54 and 11.53 mg/mL, respectively. Xylanase was activated by dithiothreitol, L-tryptophan and L-cysteine and strongly inhibited by N-bromosuccinimide and CoCl2. The characterization of mannanase showed Km and temperature optimum of 0.846 mg/mL and 65ºC, respectively and pH 8.0. By contrast to xylanase, it was less stable at 65ºC with half-life of 2.5 h and inhibited by dithiothreitol and Ca2+.Uma nova linhagem de bactéria (ISO II foi isolada de esterco bovino e identificada como filogeneticamente próxima à bactéria termofílica Clostridium thermocellum. A nova linhagem produziu atividades de xilanase, mananase, pectinase e celulase quando cultivada em meio de cultura líquido contendo engaço de bananeira como fonte de carbono. O perfil de produ