Sample records for bromosuccinimide

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

    KAUST Repository

    Guan, Xiao-Yu


    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.

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

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    Xiao-Yu Guan


    Full Text Available 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. An Efficient Method for the N-Bromosuccinimide Catalyzed Synthesis of Indolyl-Nitroalkanes

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    Ching-Fa Yao


    Full Text Available An efficient and practical method for the synthesis of indolyl-nitroalkane derivatives catalyzed by N-bromosuccinimide is described. The generality of this method was demonstrated by synthesizing an array of diverse 3-substituted indole derivatives by the reaction of different β-nitrostyrenes with various substituted indoles. Simple reaction conditions accompanied by good yields of indolyl-nitroalkanes are the merits of this methodology.

  4. Spectrophotometric Determination of Ceftiofur Hydrochloride Using N-Bromosuccinimide and p-Dimethylaminobenzaldehyde

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    V. Annapurna


    Full Text Available Simple, accurate and reproducible UV-Visible spectrophotometric methods were established for the assay of ceftiofur based on the formation of oxidation and condensation products. Method A involves the oxidation of the ceftiofur (CEFT with N-bromosuccinimide (NBS and determination of the unconsumed NBS with p-N-methylaminophenol (PMAP-sulfanilamide (SA (PMAP-SA reagent. Method B includes the determination of unreacted NBS using a known excess of celestine blue (CB and measuring the remaining dye. Condensation of p-dimethylaminobenzaldehyde (PDAB with the drug was the basis of method C. Determination of CEFT in bulk form and in pharmaceutical formulations was also incorporated.

  5. Utility of N-bromosuccinimide for the titrimetric and spectrophotometric determination of famotidine in pharmaceutical formulations. (United States)

    Zenita, O; Basavaiah, K


    Two titrimetric and two spectrophotometric methods are described for the assay of famotidine (FMT) in tablets using N-bromosuccinimide (NBS). The first titrimetric method is direct in which FMT is titrated directly with NBS in HCl medium using methyl orange as indicator (method A). The remaining three methods are indirect in which the unreacted NBS is determined after the complete reaction between FMT and NBS by iodometric back titration (method B) or by reacting with a fixed amount of either indigo carmine (method C) or neutral red (method D). The method A and method B are applicable over the range of 2-9 mg and 1-7 mg, respectively. In spectrophotometric methods, Beer's law is obeyed over the concentration ranges of 0.75-6.0 μg mL(-1) (method C) and 0.3-3.0 μg mL(-1) (method D). The applicability of the developed methods was demonstrated by the determination of FMT in pure drug as well as in tablets.

  6. Flow-injection chemiluminescence determination of diazepam by oxidation with N-bromosuccinimide. (United States)

    Han, Suqin; Jia, Shize; Guo, Liang


    A rapid and sensitive flow-injection chemiluminescence (FI-CL) method is described for the determination of diazepam based on its reaction with N-bromosuccinimide (NBS) in alkaline medium in the presence of dichlorofluorescein (DCF) as an effective energy-transfer agent. Under optimum conditions, the proposed method allowed the measurement of diazepam over the range of 2.0 × 10(-6) to 2.0 × 10(-4) mol/L with a detection limit of 5.0 × 10(-7) mol/L. The relative standard deviation for 11 parallel measurements of 2.0 × 10(-5) mol/L diazepam was 2.1%. The method was applied satisfactorily for the determination of diazepam in pharmaceutical preparations, and the results agree well with those obtained by spectrophotometry. The use of the proposed system for the determination of diazepam in urine and plasma samples was also tested. The possible mechanism of the chemiluminescence reaction is discussed briefly. Copyright © 2012 John Wiley & Sons, Ltd.

  7. Utility of N-Bromosuccinimide for the Titrimetric and Spectrophotometric Determination of Famotidine in Pharmaceutical Formulations

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    O. Zenita


    Full Text Available Two titrimetric and two spectrophotometric methods are described for the assay of famotidine (FMT in tablets using N-bromosuccinimide (NBS. The first titrimetric method is direct in which FMT is titrated directly with NBS in HCl medium using methyl orange as indicator (method A. The remaining three methods are indirect in which the unreacted NBS is determined after the complete reaction between FMT and NBS by iodometric back titration (method B or by reacting with a fixed amount of either indigo carmine (method C or neutral red (method D. The method A and method B are applicable over the range of 2–9 mg and 1–7 mg, respectively. In spectrophotometric methods, Beer's law is obeyed over the concentration ranges of 0.75–6.0 μg mL-1 (method C and 0.3–3.0 μg mL-1 (method D. The applicability of the developed methods was demonstrated by the determination of FMT in pure drug as well as in tablets.

  8. Determination of urea in milk based on N-bromosuccinimide-dichlorofluorescein postchemiluminescence method. (United States)

    Nie, Fei; Wang, Na; Xu, Pan; Zheng, Jianbin


    A new postchemiluminescence (PCL) reaction was observed when urea was injected into the reaction mixture after the CL reaction of N-bromosuccinimide and dichlorofluorescein. A possible reaction mechanism was proposed based on the studies of the CL kinetic characteristics, CL spectra, fluorescence spectra, and other experiments. A new flow injection CL method for the determination of urea was established based on the PCL reaction. The relative standard deviation for the determination of urea was 1.3% (n = 11, c = 5.0 × 10-8 g/mL). The CL intensity responded linearly to the concentration of urea in the range 2.0 × 10-9-1.0 × 10-6 g/mL (r = 0.9992). The detection limit was 7 × 10-10 g/mL. The method had been applied to the determination of urea in milk with satisfactory results. Copyright © 2016. Published by Elsevier B.V.

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

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    Akram M. El-Didamony


    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.

  10. Kinetic, Thermodynamic and Structural Studies of Native and N-Bromosuccinimide-Modified Mushroom Tyrosinase

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    Saeed Emami


    Full Text Available Background Mushroom tyrosinase (MT as a metalloenzyme is a good model for mechanistic studies of melanogenesis. To recognize the mechanism of MT action, it is important to investigate its inhibition, activation, mutation, and modification properties. Objectives In this study, the chemical modification of MT tryptophan residues was carried out by using N-bromosuccinimide (NBS and then, the activity, stability, and structure of the native and modified enzymes were compared. Methods Chemical modification of MT tryptophan residues was accomplished by enzyme incubation with different concentrations of NBS. The relative activity of native and modified MT was investigated through catecholase enzyme reaction in presence of dihydroxyphenylalanine (L-Dopa as substrate. Thermodynamic parameters including standard Gibbs free energy change (∆G25°C and Melting temperature (Tm were obtained from thermal denaturation of the native and modified enzymes. The circular dichroism and intrinsic fluorescence techniques were used to study secondary and tertiary structure of MT, respectively. All experiments were conducted in 2015 in biophysical laboratory of Qazvin University of Medical Sciences and Islamic Azad University, Science and Research Branch, Tehran. Results The relative activity reduced from 100% for native enzyme to 10%, 7.9%, and 6.4% for modified MT with different NBS of concentrations 2, 10, and 20 mM, respectively. Thermal instability of modified enzyme was confirmed by decreased Tm and ∆G25°C values after modification. In accordance with kinetic and thermodynamic results, the lower stability of modified MT was observed from the changes occurred on its secondary and tertiary structures. Conclusions Chemical modification of tryptophan residues with NBS reduces the activity and stability of MT simultaneously with its structural change. Thus, this study emphasizes the crucial role of tryptophan residues in the structure-function relationship of MT

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

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    K. Basavaiah


    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.

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

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    Minu Singh


    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.

  13. N-Bromosuccinimide as an oxidant for the transition-metal-free synthesis of 2-aminobenzoxazoles from benzoxazoles and secondary amines. (United States)

    Wang, Xiaoe; Xu, Daqian; Miao, Chengxia; Zhang, Qiaohong; Sun, Wei


    A facile and transition-metal-free method was developed through merging the ring opening of benzoxazoles with secondary amines and N-bromosuccinimide (NBS) mediated oxidative cyclization toward the synthesis of 2-aminobenzoxazoles. NBS was selected as a powerful oxidant in the oxidative cyclization of ring-opening amidines to provide the desirable 2-aminobenzoxazoles in excellent yields (up to 94%).

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

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    Kanakapura Basavaiah Vinay


    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

  15. Spectrophotometric Method for Determination of Five 1,4-Dihydropyridine Drugs Using N-Bromosuccinimide and Indigo Carmine Dye

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    Mohamed A. El Hamd


    Full Text Available Indirect spectrophotometric method is described for quantification of five of 1,4-dihydropyridine (1,4-DHP drugs using N-bromosuccinimide (NBS with the aid of indigo carmine (INC dye. The method is based on addition of known excess of NBS to an acidified solution of 1,4-DHP drugs and determining the residual of NBS through its ability to bleach the colour of the used dye; the amount of NBS that reacted corresponded to the amount of drugs. Beer’s law is obeyed in the concentration range 1.25–13.00 μg/mL. Good correlation coefficients (0.998-0.999 were found between the absorbance values and the corresponding concentrations. Limits of detections ranged from 0.141 to 0.500 μg/mL. The proposed method was successfully applied to the analysis of dosage forms; percent of recoveries ranged from 97.31 to 99.46% without interference from any common excipients. The statistical comparison by Student’s t-test and variance ratio F-test showed no significant difference between the proposed and official or reported methods.

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

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    Kudige Nagaraj Prashanth


    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.

  17. KH 2PO4 as a novel catalyst for regioselective monobromination of aralkyl ketones using N-bromosuccinimide: a green methodology

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    P. Md. Khaja Mohinuddin


    Full Text Available A simple, regioselective and green method has been developed for the preparation of monobrominated ketones from various aralkyl ketones by using N-bromosuccinimide in presence of KH 2PO 4 in EtOH at reflux temperature. The present method is of short reaction time and simple with excellent isolated yields of products. The use of eco-friendly solvent, reuse of organic waste (succinimide and recyclable catalyst used for 4 times without loss of activity are advantageous. This is the first example of the use of KH 2PO 4 as a useful catalyst in organohalogen chemistry and the present method meets reduce-reuse-recycle (RRR principle towards development of green protocol.

  18. NBS as a Powerful Catalyst for the Synthesis of β-Hydroxysulphides ...

    African Journals Online (AJOL)

    N-Bromosuccinimide (NBS) catalyses the ring opening of various epoxides with different thiols in CH3CN at room temperature under mild reaction conditions. The corresponding β-hydroxysulphides are obtained in short reaction times and in good to high yields with nearly complete regioselectivity. The catalyst was ...

  19. short communication sensitive and validated spectrophotometric ...

    African Journals Online (AJOL)


    Two simple, sensitive and rapid methods are described for the determination pantoprazole sodium sesqui hydrate ... The methods utilize N-bromosuccinimide, ammonium thiocyanate and Tiron as reagents. The methods ..... excipients and additives such as talc, starch, lactose, sodium alginate, magnesium stearate, calcium ...

  20. A facile one-pot synthesis of alpha-bromo-alpha,beta-unsaturated esters from alcohols. (United States)

    Karama, Usama; Al-Othman, Zeid; Al-Majid, Abdullah; Almansour, Abdulrahman


    Treatment of N-bromosuccinimide (NBS) with (carboethoxymethylene) triphenylphosphorane (1) in CH(2)Cl(2) 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 alpha-bromo-alpha,beta-unsaturated esters in good to excellent yield.

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

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    Usama Karama


    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.

  2. Enhanced Superconductors (United States)


    and benzoyl peroxide ( BPO , Aldrich Chemicals) were used as received. N- bromosuccinimide (NBS, 98%, Aldrich Chemicals) was recrystallized from...funnel and a reflux condenser were added 4.5 g TFPX (25 mmol), benzoyl peroxide ( BPO ) (30 mg), and 100 ml CC14. 13 g sulfuryl chloride (SO2C12 ) (96 mmol...allylic fluorine in the polymer chain. This quatemization does not reduce the conjugation length in the PFA, but the bulkiness of the amine group will

  3. Efficient intramolecular cyclizations of phenoxyethynyl diols into multisubstituted α,β-unsaturated lactones. (United States)

    Egi, Masahiro; Ota, Yuya; Nishimura, Yuka; Shimizu, Kaori; Azechi, Kenji; Akai, Shuji


    AgOTf-catalyzed intramolecular cyclization of phenoxyethynyl diols proceeded under mild conditions to afford the multisubstituted α,β-unsaturated-γ-lactones in 55-98% yields. This method was also applicable to the synthesis of α,β-unsaturated-δ-lactones. A similar cyclization proceeded when AgOTf was replaced with a stoichiometric amount of N-bromosuccinimide to furnish the α-bromo-substituted α,β-unsaturated lactones.

  4. Palladium-Catalyzed Directed Halogenation of Bipyridine N-Oxides. (United States)

    Zucker, Sina P; Wossidlo, Friedrich; Weber, Manuela; Lentz, Dieter; Tzschucke, C Christoph


    The palladium-catalyzed directed C-H halogenation of bipyridine N-oxides was investigated. Using NCS or NBS (N-chloro- or N-bromosuccinimide) and 5 mol % Pd(OAc)2 in chlorobenzene (0.10 molar) at 110 °C, pyridine-directed functionalization took place and 3-chloro- or 3-bromobipyridine N-oxides were obtained in high yields. The reaction is sensitive to steric hindrance by 4- and 6'-substituents. Only in the latter case, where coordination of palladium by the pyridine is hindered, 3'-halogenation directed by the N-oxide function was observed. The halogenated products were deoxygenated by PCl3 or PBr3.

  5. Modification of sodium channel inactivation in single myelinated nerve fibers by methionine-reactive chemicals. (United States)

    Wang, G K


    Several methionine-reactive reagents, including N-bromoacetamide, N-bromosuccinimide, chloramine-T, and N-chlorosuccinimide, irreversibly slowed and prevented Na channel inactivation in single myelinated nerve fibers, whereas sulfhydryl- or tyrosine-modifying reagents had little effect. The activation process was not modified by the reagents that altered inactivation and could be modulated normally by Ca++ ions and Centruroides scorpion toxin II alpha. These results suggest that externally applied N-bromoacetamide and its related compounds specifically affect Na channel inactivation by modifying methionine residues of the channel. PMID:6331542

  6. 5-Bromo-1H-thieno[2,3-d]imidazole

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    Fen Wang


    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].

  7. TiO{sub 2} nanoparticles supported on the Fe{sub 3}O{sub 4}@SiO{sub 2} nanocomposites: a novel magnetic nanocatalyst for the synthesis of 2-aminothiazoles

    Energy Technology Data Exchange (ETDEWEB)

    Safari, Javad, E-mail:, E-mail:; Abedi-Jazini, Zahra; Zarnegar, Zohre, E-mail:; Sadeghi, Masoud [University of Kashan, Laboratory of Organic Compound Research, Department of Organic Chemistry, College of Chemistry (Iran, Islamic Republic of)


    Nano TiO{sub 2} supported on the Fe{sub 3}O{sub 4}@SiO{sub 2} nanocomposites is introduced as a novel catalyst for the environmental synthesis of 2-aminothiazoles in PEG-200 as a green medium at room temperature. In this reaction, thiourea and N-bromosuccinimide were reacted with various ketones affording the desired 2-aminothiazole compounds. This green protocol has promising features for the reaction response such as simple procedure, high yields, and the ease of separation of pure product, short reaction time, and convenient manipulation. This catalyst was easily separated by an external magnet, and the recovered catalyst was reused several times without any significant loss of activity.Graphical abstract.

  8. Spiro[pyrrolidine-3, 3´-oxindole] as potent anti-breast cancer compounds: Their design, synthesis, biological evaluation and cellular target identification (United States)

    Hati, Santanu; Tripathy, Sayantan; Dutta, Pratip Kumar; Agarwal, Rahul; Srinivasan, Ramprasad; Singh, Ashutosh; Singh, Shailja; Sen, Subhabrata


    The spiro[pyrrolidine-3, 3´-oxindole] moiety is present as a core in number of alkaloids with substantial biological activities. Here in we report design and synthesis of a library of compounds bearing spiro[pyrrolidine-3, 3´-oxindole] motifs that demonstrated exceptional inhibitory activity against the proliferation of MCF-7 breast cancer cells. The synthesis involved a one pot Pictet Spengler-Oxidative ring contraction of tryptamine to the desired scaffolds and occurred in 1:1 THF and water with catalytic trifluoroacetic acid and stoichiometric N-bromosuccinimide as an oxidant. Phenotypic profiling indicated that these molecules induce apoptotic cell death in MCF-7 cells. Target deconvolution with most potent compound 5l from the library, using chemical proteomics indicated histone deacetylase 2 (HDAC2) and prohibitin 2 as the potential cellular binding partners. Molecular docking of 5l with HDAC2 provided insights pertinent to putative binding interactions.

  9. Chemiluminescence determination of trimetazidine via inducing the aggregation of gold nanoparticles (United States)

    Li, Jiao; Quan, Jie; Du, Jianxiu; Liu, Mei


    A simple, rapid and sensitive chemiluminescence (CL) method combined with flow injection analysis was developed for the determination of trimetazidine. Trimetazidine was found to significantly increase the CL signal arising from N-bromosuccinimide-luminol reaction in the presence of gold nanoparticles. The enhanced CL intensity was proportional to trimetazidine concentration in the range of 0.01-5.0 μg/mL, with a limit of detection (3sb) of 6.7 ng/mL. The relative standard deviation was 2.8% for 11 repetitive measurements of 0.1 μg/mL trimetazidine solution. The practicality of the method was evaluated by determining trimetazidine in pharmaceutical formulations and in spiked human serum samples. Moreover, the possible CL reaction mechanism was also discussed.

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

    DEFF Research Database (Denmark)

    Mazzanti, Virginia; Cacciarini, Martina; Broman, Søren Lindbæk


    Background: The dihydroazulene (DHA)/vinylheptafulvene (VHF) system (with two cyano groups at C1) functions as a photo-/thermoswitch. Direct ionic bromination of DHA has previously furnished a regioselective route to a 7,8-dibromide, which by elimination was converted to a 7-bromo-substituted DHA....... This compound has served as a central building block for functionalization of the DHA by palladium-catalyzed cross-coupling reactions. The current work explores another bromination protocol for achieving the isomeric 3-bromo-DHA and also explores the outcome of additional bromination of this compound as well...... 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 (1)H NMR spectroscopic study...

  11. Production and Characterization of an Alkaline Lipase from Thermophilic Anoxybacillus sp. HBB16

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    Z. Burcu Bakir


    Full Text Available A thermophilic lipase-producing bacterium (Anoxybacillus sp. HBB16 was analyzed using 16S rRNA. The maximum growth rate and intracellular lipase production occurred at 50 °C and pH 6.5. Among the various nitrogen and carbon sources tested, meat extract, olive oil and olive mill wastewater (OMW were the best sources for lipase production. Enzyme production increased when the strain HBB16 was grown at a 180 rpm shaking speed. The maximum activity of the lipase occurred at 55 °C and pH 9.5. The presence of phenylmethylsulfonyl fluoride (PMSF, N-cyclohexyl-N′-(2-morpho-linoethyl carbodiimidemetho-p-toluenesulfonate (CMC, N-bromosuccinimide (NBS and sodium dodecyl sulfate (SDS inhibited enzyme activity. Bivalent metal ions caused a significant inhibition in enzyme activity, whereas univalent metal ions displayed no negative effects.

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

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    Tanveer Mahamadali Shaikh


    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.

  13. A novel flow injection chemiluminescence method for automated and miniaturized determination of phenols in smoked food samples. (United States)

    Vakh, Christina; Evdokimova, Ekaterina; Pochivalov, Aleksei; Moskvin, Leonid; Bulatov, Andrey


    An easily performed fully automated and miniaturized flow injection chemiluminescence (CL) method for determination of phenols in smoked food samples has been proposed. This method includes the ultrasound assisted solid-liquid extraction coupled with gas-diffusion separation of phenols from smoked food sample and analytes absorption into a NaOH solution in a specially designed gas-diffusion cell. The flow system was designed to focus on automation and miniaturization with minimal sample and reagent consumption by inexpensive instrumentation. The luminol - N-bromosuccinimide system in an alkaline medium was used for the CL determination of phenols. The limit of detection of the proposed procedure was 3·10 -8 ·molL -1 (0.01mgkg -1 ) in terms of phenol. The presented method demonstrated to be a good tool for easy, rapid and cost-effective point-of-need screening phenols in smoked food samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Radioiodination and biological evaluation of candesartan as a tracer for cardiovascular disorder detection. (United States)

    Sanad, M H; Sallam, Kh M; Marzook, F A; Abd-Elhaliem, S M


    The goal of the study aims to evaluate newly radioiodinated candesartan (CAN) as a potential cardiovascular tracer. CAN was labeled using 125 I with chloramine-T (Ch-T) and N-bromosuccinimide (NBS) with full characterization of cold Iodo-candesartan. Factors such as pH, reaction temperature, reaction time, substrate, and oxidizing agent amounts were studied to optimize the radioiodination of CAN. The optimum radiochemical yield of 125 I-CAN was 98%. The labeled compound was separated and purified using high-pressure liquid chromatography. The biological distribution indicates the suitability of 125 I-CAN as a novel tracer to detect cardiovascular disorders. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Metal and base free synthesis of primary amines via ipso amination of organoboronic acids mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA). (United States)

    Chatterjee, Nachiketa; Goswami, Avijit


    A metal and base free synthesis of primary amines has been developed at ambient temperature through ipso amination of diversely functionalized organoboronic acids, employing a combination of [bis(trifluoroacetoxy)iodo]benzene (PIFA)-N-bromosuccinimide (NBS) and methoxyamine hydrochloride as the aminating reagent. The amines were primarily obtained as their trifluoroacetate salts which on subsequent aqueous alkaline work up provided the corresponding free amines. The combination of PIFA-NBS is found to be the mildest choice compared to the commonly used strong bases (e.g. n-BuLi, Cs2CO3) for activating the aminating agent. The reaction is expected to proceed via activation of the aminating reagent followed by B-N 1,2-aryl migration.

  16. Proton nuclear magnetic resonance studies of the effects of ligand binding on ryptophan residues of selectively deuterated dihydrofolate reductase from Lactobacillus casei

    Energy Technology Data Exchange (ETDEWEB)

    Feeney, J.; Roberts, G.C.; Thomson, J.W.; King, R.W; Griffiths, D.V.; Burgen, A.S.


    We have prepared a selectively deuterated dihydrofolate reductase in which all the aromatic protons except the C(2) protons of tryptophan have been replaced by deuterium and have examined the 1H NMR spectra of its complexes with folate, trimethoprim, methotrexate, NADP+, and NADPH. One of the four Trp C(2)-proton resonance signals (signal P at 3.66 ppm from dioxane) has been asigned to Trp-21 by examining the NMR spectrum of a selectively deuterated N-bromosuccinimide-modified dihydrofolate reductase. This signal is not perturbed by NADPH, indicating that the coenzyme is not binding close to the 2 position of Trp-21. This contrasts markedly with the 19F shift (2.7 ppm) observed for the 19F signal of Trp-21 in the NADPH complex with the 6-fluorotryptophan-labeled enzyme. In fact the crystal structure of the enzyme . methotrexate . NADPH shows that the carboxamide group of the reduced nicotinamide ring is near to the 6 position of Trp-21 but remote from its 2 position. The nonadditivity of the 1H chemical-shift contributions for signals tentatively assigned to Trp-5 and -133 indicates that these residues are influenced by ligand-induced conformational changes.

  17. 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


    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.

  18. Purification, properties, and partial amino acid sequences of thermostable xylanases from Streptomyces thermoviolaceus OPC-520

    Energy Technology Data Exchange (ETDEWEB)

    Tsujibo, Hiroshi; Miyamoto, Katsushiro; Kuda, Takashi; Minami, Kazushi; Sakamoto, Takashi; Inamori, Yoshihiko (Osaka Univ., Matsubara City (Japan)); Hasegawa, Toru (Inst. for Fermentation, Osaka, Yodogawaku (Japan))


    Two types of xylanases (1,4-{beta}-D-xylan xylanohydrolase, EC were isolated from the culture filtrate of a thermophilic actinomycete, Streptomyces thermoviolaceus OPC-520. The enzymes (STX-I and STX-II) were purified by chromatography with DEAE-Toyopearl 650 M, CM-Toyopearl 650 M, Sephadex G-75, Phenyl-Toyopearl 650 M, and Mono Q HR. The purified enzymes showed single bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weights of STX-I and STX-II were 54,000 and 33,000, respectively. The pIs were 4.2 (STX-I) and 8.0 (STX-II). The optimum pH levels for the activity of STX-I and STX-II were pH 7.0. The optimum temperature for the activity of STX-I was 70C, and that for the activity of STX-II was 60C. The enzymes were completely inhibited by N-bromosuccinimide. The enzymes degraded xylan, producing xylose and xylobiose as the predominant products, indicating that they were endoxylanases. STX-I showed high sequence homology with the exoglucanase from Cellulomonas fimi (47% homology), and STX-II showed high sequence homology with the xylanase from Bacillus pumilus (46% homology).

  19. Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials. (United States)

    Yue, Chunlin; Sun, Huaming; Liu, Wen-Jing; Guan, Binbin; Deng, Xudong; Zhang, Xu; Yang, Peng


    The extraction of gold from ores and electronic waste is an important topic worldwide, as this precious metal has immense value in a variety of fields. However, serious environmental pollution and high energy consumption due to the use of toxic oxidation reagents and harsh reaction conditions is a well-known problem in the gold industry. Herein, we report a new chemical method based on the combined use of N-bromosuccinimide (NBS) and pyridine (Py), which has a greatly decreased environmental impact and reagent cost, as well as mild reaction requirements. This method can directly leach Au0 from gold ore and electronic waste to form AuIII in water. The process is achieved in a yield of approximately 90 % at room temperature and a nearly neutral pH. The minimum dose of NBS/Py is as low as 10 mm, which exhibits low toxicity towards mammalian cells and animals as well as aquatic creatures. The high leaching selectivity of Au over other metals during gold leaching is demonstrated, showing that this method has great potential for practical industrial application towards the sustainable refining of gold from ores and electronic waste. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Characterisation of an acidic peroxidase from papaya (Carica papaya L. cv Tainung No. 2) latex and its application in the determination of micromolar hydrogen peroxide in milk. (United States)

    Chen, Li-Chun; Chung, Yun-Chin; Chang, Chen-Tien


    An acidic peroxidase isoform, POD-A, with a molecular mass of 69.4 kDa and an isoelectric point of 3.5 was purified from papaya latex. Using o-phenylenediamine (OPD) as a hydrogen donor (citrate-phosphate as pH buffer), the optimum pH for the function of POD-A was 4.6, and the optimum temperature was 50°C. The peroxidase activity of POD-A toward hydrogen donors was both pH- and concentration-dependent. Under optimal conditions, POD-A catalysed the oxidation of OPD at higher rates than pyrogallol, catechol, quercetin and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The chemical modification reagents N-bromosuccinimide and sodium azide significantly inhibited POD-A activity. The results of kinetic studies indicated that POD-A followed a ping-pong mechanism and had a K(m) value of 2.8mM for OPD. Using CPC silica-immobilised POD-A for the determination of micromolar H(2)O(2) in milk, the lower limit of determination was 0.1 μM, and the recoveries of added H(2)O(2) were 96-109%. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. Purification and characterization of pectate lyase from banana (Musa acuminata) fruits. (United States)

    Payasi, Anurag; Misra, Prakash C; Sanwal, Girdhar G


    Pectate lyase (PEL) has been purified by hydrophobic, cation exchange and size exclusion column chromatographies from ripe banana fruit. The purified enzyme has specific activity of 680 +/- 50 pkat mg protein(-1). The molecular mass of the enzyme is 43 kDa by SDS-PAGE. The pI of the enzyme is 8 with optimum activity at pH 8.5. Analysis of the reaction products by paper and anion exchange chromatographies reveal that the enzyme releases several oligomers of unsaturated galacturonane from polygalacturonate. The K(m) values of the enzyme for polygalacturonate and citrus pectin (7.2% methylation) are 0.40 +/- 0.04 and 0.77 +/- 0.08 g l(-1), respectively. PEL is sensitive to inhibition by different phenolic compounds, thiols, reducing agents, iodoacetate and N-bromosuccinimide. The enzyme has a requirement for Ca(2+) ions. However, Mg(2+) and Mn(2+) can substitute equally well. Additive effect on the enzyme activity was observed when any two metal ions (out of Mg(2+), Ca(2+) and Mn(2+)) are present together. The banana PEL is a enzyme requiring Mg(2+), in addition to Ca(2+), for exhibiting maximum activity.

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

    Directory of Open Access Journals (Sweden)



    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.

  3. A Fungal α-Galactosidase from Tricholoma matsutake with Broad Substrate Specificity and Good Hydrolytic Activity on Raffinose Family Oligosaccharides

    Directory of Open Access Journals (Sweden)

    Xueran Geng


    Full Text Available An acidic α-galactosidase designated as TMG was purified from the fruiting bodies The purification protocol entailed ion exchange chromatography on Q-Sepharose and of Tricholoma matsutake with 136-fold purification and a specific activity of 909 units/mg. Mono-Q and fast protein liquid chromatography on Superdex 75. TMG is a monomeric protein exhibiting a molecular mass of 47 kDa in SDS-PAGE and gel filtration. The purified enzyme was identified by LC-MS/MS and three inner amino acid sequences were obtained. The optimum pH and temperature for TMG with pNPGal as substrate were pH 4.5 and 55 °C, respectively. The α-galactosidase activity was strongly inhibited by K+, Ca2+, Cd2+, Hg2+, Ag+ and Zn2+ ions. The enzyme activity was inhibited by the chemical modification agent N-bromosuccinimide (NBS, indicating the importance of tryptophan residue(s at or near the active site. Besides hydrolyzing pNPGal, TMG also efficaciously catalyzed the degradation of natural substrates such as stachyose, raffinose, and melibiose. Thus TMG can be exploited commercially for improving the nutritional value of soy milk by degradation of indigestible oligosaccharides.

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


    Homodimeric proton-translocating pyrophosphatase (H+-PPase; EC 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.

  5. Characteristics of a high maltose-forming, acid-stable, and Ca(2+)-independent α-amylase of the acidophilic Bacillus acidicola. (United States)

    Sharma, Archana; Satyanarayana, T


    The purified acidic α-amylase of Bacillus acidicola is a monomer of 66.0 kDa, optimally active at pH 4.0 and 60 °C. The enzyme is Ca2+ independent with T1/2 for 18 min at 80 °C. The Km, Vmax, and catalytic efficiency (kcat/Km) of the enzyme are 1.6 mg mL(−1), 23.8 μmol mg(−1) min(−1), and 981 μmol s(−1), respectively. Among detergents, Tween 20, 40, and 80 stimulated enzyme activity, whereas sodium dodecyl sulfate and Triton X-100 inhibited even at low concentration. EGTA has not affected the activity, whereas EDTA β-mercaptoethanol, iodoacetic acid, and Dithiothreitol exhibited a slight inhibitory action. Phenylmethanesulfonyl fluoride, N-bromosuccinimide, and Hg2+ strongly inhibited enzyme activity. The experimental activation energy and temperature quotient are 50.12 kJ mol(−1) and 1.37. When thermodynamic parameters (ΔH and ΔS) of the enzyme have been determined at different temperatures, ΔG is positive suggesting that the enzyme is thermostable. The enzyme hydrolyzes raw starches, and therefore, the enzyme finds application in raw starch saccharification at sub-gelatinization temperatures that saves energy needed for gelatinization of raw starch at 105 °C.

  6. Identification of essential tryptophan in amylomaltase from Corynebacterium glutamicum. (United States)

    Rachadech, Wanitcha; Nimpiboon, Pitchanan; Naumthong, Wachiraporn; Nakapong, Santhana; Krusong, Kuakarun; Pongsawasdi, Piamsook


    This work aims to identify essential tryptophan residue(s) of amylomaltase from Corynebacterium glutamicum (CgAM) through chemical modification and site-directed mutagenesis techniques. The recombinant enzyme expressed by Escherichia coli was purified and treated with N-bromosuccinimide (NBS), a modifying agent for tryptophan. A significant decrease in enzyme activity was observed indicating that tryptophan is important for catalysis. Inactivation kinetics with NBS resulted in pseudo first-order rate constant (kinact) of 2.31 min(-1). Substrate protection experiment confirmed the active site localization of the NBS-modified tryptophan residue(s) in CgAM. Site-directed mutagenesis was performed on W330, W425 and W673 to localize essential tryptophan residues. Substitution by alanine resulted in the loss of intra- and intermolecular transglucosylation activities for all mutated CgAMs. Analysis of circular dichroism spectra showed no change in the secondary structure of W425A but a significant change for W330A and W673A from that of the WT. From these results in combination with X-ray structural data and interpretation from the binding interactions in the active site region, W425 was confirmed to be essential for catalytic activity of CgAM. The hydrophobicity of this tryptophan was thought to be critical for substrate binding and supporting catalytic action of the three carboxylate residues at the active site. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. The role of tryptophan residues in the hemolytic activity of stonustoxin,a lethal factor from stonefish (Synanceja horrida) venom. (United States)

    Yew, W S; Khoo, H E


    Stonustoxin (SNTX) is a pore-forming cytolytic lethal factor, isolated from the venom of the stonefish Synanceja horrida, that has potent hemolytic activity. The role of tryptophan residues in the hemolytic activity of SNTX was investigated. Oxidation of tryptophan residues of SNTX with N-bromosuccinimide (NBS) resulted in loss of hemolytic activity. Binding of 8-anilino-1-naphthalenesulphonate (ANS) to SNTX resulted in occlusion of tryptophan residues that resulted in loss of hemolytic activity. Circular dichroism and fluorescence studies indicated that ANS binding resulted in a conformational change of SNTX, in particular, a relocation of surface tryptophan residues to the hydrophobic interior. NBS-modification resulted in oxidised surface tryptophan residues that did not relocate to the hydrophobic interior. These results suggest that native surface tryptophan residues play a pivotal role in the hemolytic activity of STNX, possibly by being an essential component of a hydrophobic surface necessary for pore-formation. This study is the first report on the essentiality of tryptophan residues in the activity of a lytic and lethal factor from a fish venom.

  8. Synthesis of highly substituted spiropyrrolidines via 1, 3-dipolar cycloaddition reaction of N-metalated azomethine ylides. A new access to spiropyrroline derivatives

    Directory of Open Access Journals (Sweden)

    Chourouk Mhiri


    Full Text Available 1,3-dipolar cycloaddition of (E-arylidene-(2H-indanones 1 (Ar = Ph, p-MeC6H4, p-MeOC6H4, p-ClC6H4 and (E-2-arylidene-(2H-tetralones 2 (Ar = Ph, p-MeC6H4, p-MeOC6H4, p-ClC6H4 to N-metalated azomethine ylides 3 generated from methyl N-arylideneglycinate in the presence of silver acetate produces in good yields novel spiro[3,5-(diaryl-2-carbomethoxypyrrolidine-4:2’-indanones] 4 and spiro[3,5-(diaryl-2-carbomethoxypyrrolidine-4:2’-tetral-1-ones] 5. The cycloaddition proceeds in regio- and stereoselective manner (100% at room temperature to afford respectively the syn-endo cycloadducts 4 and 5 via metallo-azomethine ylides. The regio- and stereochemistry of the spiranic adducts has been established on the basis of spectroscopic data and elemental analyses, corroborated by single-crystal X-ray crystallographic analysis of the heterocycles 4cd, 4bb and 5bd. The endo-pyrrolidines 4 were brominated by N-bromosuccinimide to give finally the dehydrobrominated 3,4-dihydro-2H-pyrrole derivatives 6. The spiro-adducts 4 and their corresponding oxidation products 6 are fluorescent in solution. 

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

    Directory of Open Access Journals (Sweden)

    Rajdip Karmakar


    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.

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

    Directory of Open Access Journals (Sweden)

    M. Abbasian


    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.

  11. Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes. (United States)

    Weiber, E Annika; Jannasch, Patric


    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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Purification and Properties of Extracellular Lipases with Transesterification Activity and 1,3-Regioselectivity fromRhizomucor mieheiandRhizopus oryzae. (United States)

    Takó, Miklós; KotogÁn, Alexandra; Papp, TamÁs; Kadaikunnan, Shine; Alharbi, Naiyf S; VÁgvölgyi, Csaba


    Rhizomucor miehei NRRL 5282 and Rhizopus oryzae NRRL 1526 can produce lipases with high synthetic activities in wheat bran-based solid-state culture. In this study, the purification and biochemical characterization of the lipolytic activities of these lipases are presented. SDS-PAGE indicated a molecular mass of about 55 and 35 kDa for the purified R. miehei and Rh. oryzae enzymes, respectively. p -Nitrophenyl palmitate ( p NPP) hydrolysis was maximal at 40°C and pH 7.0 for the R. miehei lipase, and at 30°C and pH 5.2 for the Rh. oryzae enzyme. The enzymes showed almost equal affinity to p NPP, but the V max of the Rh. oryzae lipase was about 1.13 times higher than that determined for R. miehei using the same substrate. For both enzymes, a dramatic loss of activity was observed in the presence of 5 mM Hg 2+ , Zn 2+ , or Mn 2+ , 10 mM N -bromosuccinimide or sodium dodecyl sulfate, and 5-10% (v/v) of hexanol or butanol. At the same time, they proved to be extraordinarily stable in the presence of n -hexane, cyclohexane, n -heptane, and isooctane. Moreover, isopentanol up to 10% (v/v) and propionic acid in 1 mM concentrations increased the p NPP hydrolyzing activity of R. miehei lipase. Both enzymes had 1,3-regioselectivity, and efficiently hydrolyzed p -nitrophenyl ( p NP) esters with C8-C16 acids, exhibiting maximum activity towards p NP-caprylate ( R. miehei ) and pNP-dodecanoate ( Rh. oryzae ). The purified lipases are promising candidates for various biotechnological applications.

  13. Direct oxidation of polymeric substrates by multifunctional manganese peroxidase isoenzyme from Pleurotus ostreatus without redox mediators (United States)


    VPs (versatile peroxidases) sharing the functions of LiP (lignin peroxidase) and MnP (manganese peroxidase) have been described in basidiomycetous fungi Pleurotus and Bjerkandera. Despite the importance of this enzyme in polymer degradation, its reactivity with polymeric substrates remains poorly understood. In the present study, we first report that, unlike LiP, VP from Pleurotus ostreatus directly oxidized two polymeric substrates, bovine pancreatic RNase and Poly R-478, through a long-range electron pathway without redox mediators. P. ostreatus produces several MnP isoenzymes, including the multifunctional enzyme MnP2 (VP) and a typical MnP isoenzyme MnP3. MnP2 (VP) depolymerized a polymeric azo dye, Poly R-478, to complete its catalytic cycle. Reduction of the oxidized intermediates of MnP2 (VP) to its resting state was also observed for RNase. RNase inhibited the oxidation of VA (veratryl alcohol) in a competitive manner. Blocking of the exposed tryptophan by N-bromosuccinimide inhibited the oxidation of RNase and VA by MnP2 (VP), but its Mn2+-oxidizing activity was retained, suggesting that Trp-170 exposed on an enzyme surface is a substrate-binding site both for VA and the polymeric substrates. The direct oxidation of RNase and Poly R by MnP2 (VP) is in sharp contrast with redox mediator-dependent oxidation of these polymers by LiP from Phanerochaete chrysosporium. Molecular modelling of MnP2 (VP) revealed that the differences in the dependence on redox mediators in polymer oxidation by MnP2 (VP) and LiP were explained by the anionic microenvironment surrounding the exposed tryptophan. PMID:15461584

  14. Biophysical and biochemical characterization of a hyperthermostable and Ca2+ -independent alpha-Amylase of an extreme thermophile Geobacillus thermoleovorans. (United States)

    Uma Maheswar Rao, J L; Satyanarayana, T


    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.

  15. Enhancement of hydrogen peroxide formation by protophores and ionophores in antimycin-supplemented mitochondria (United States)

    Cadenas, Enrique; Boveris, Alberto


    Rat and pigeon heart mitochondria supplemented with antimycin produce 0.3–1.0nmol of H2O2/min per mg of protein. These rates are stimulated up to 13-fold by addition of protophores (carbonyl cyanide p-trifluoromethoxyphenylhydrazone, carbonyl cyanide m-chloromethoxyphenylhydrazone and pentachlorophenol). Ionophores, such as valinomycin and gramicidin, and Ca2+ also markedly stimulated H2O2 production by rat heart mitochondria. The enhancement of H2O2 generation in antimycin-supplemented mitochondria and the increased O2 uptake of the State 4-to-State 3 transition showed similar protophore, ionophore and Ca2+ concentration dependencies. Thenoyltrifluoroacetone and N-bromosuccinimide, which inhibit succinate–ubiquinone reductase activity, also decreased mitochondrial H2O2 production. Addition of cyanide to antimycin-supplemented beef heart submitochondrial particles inhibited the generation of O2−, the precursor of mitochondrial H2O2. This effect was parallel to the increase in cytochrome c reduction and it is interpreted as indicating the necessity of cytochrome c13+ to oxidize ubiquinol to ubisemiquinone, whose autoxidation yields O2−. The effect of protophores, ionophores and Ca2+ is analysed in relation to the propositions of a cyclic mechanism for the interaction of ubiquinone with succinate dehydrogenase and cytochromes b and c1 [Wikstrom & Berden (1972) Biochim. Biophys. Acta 283, 403–420; Mitchell (1976) J. Theor. Biol. 62, 337–367]. A collapse in membrane potential, increasing the rate of ubisemiquinone formation and O2− production, is proposed as the molecular mechanism for the enhancement of H2O2 formation rates observed on addition of protophores, ionophores and Ca2+. PMID:7406888

  16. One-electron reduction of N-chlorinated and N-brominated species is a source of radicals and bromine atom formation. (United States)

    Pattison, David I; O'Reilly, Robert J; Skaff, Ojia; Radom, Leo; Anderson, Robert F; Davies, Michael J


    Hypochlorous (HOCl) and hypobromous (HOBr) acids are strong bactericidal oxidants that are generated by the human immune system but are implicated in the development of many human inflammatory diseases (e.g., atherosclerosis, asthma). These oxidants react readily with sulfur- and nitrogen-containing nucleophiles, with the latter generating N-halogenated species (e.g., chloramines/bromamines (RR'NX; X = Cl, Br)) as initial products. Redox-active metal ions and superoxide radicals (O(2)(•-)) can reduce N-halogenated species to nitrogen- and carbon-centered radicals. N-Halogenated species and O(2)(•-) are generated simultaneously at sites of inflammation, but the significance of their interactions remains unclear. In the present study, rate constants for the reduction of N-halogenated amines, amides, and imides to model potential biological substrates have been determined. Hydrated electrons reduce these species with k(2) > 10(9) M(-1) s(-1), whereas O(2)(•-) reduced only N-halogenated imides with complex kinetics indicative of chain reactions. For N-bromoimides, heterolytic cleavage of the N-Br bond yielded bromine atoms (Br(•)), whereas for other substrates, N-centered radicals and Cl(-)/Br(-) were produced. High-level quantum chemical procedures have been used to calculate gas-phase electron affinities and aqueous solution reduction potentials. The effects of substituents on the electron affinities of aminyl, amidyl, and imidyl radicals are rationalized on the basis of differential effects on the stabilities of the radicals and anions. The calculated reduction potentials are consistent with the experimental observations, with Br(•) production predicted for N-bromosuccinimide, while halide ion formation is predicted in all other cases. These data suggest that interaction of N-halogenated species with O(2)(•-) may produce deleterious N-centered radicals and Br(•).

  17. Characterization of divalent and trivalent species generated in the chemical and electrochemical oxidation of a dimeric pincer complex of nickel. (United States)

    Spasyuk, Denis M; Gorelsky, Serge I; van der Est, Art; Zargarian, Davit


    The electrolytic and chemical oxidation of the dimeric pincer complex [κ(P),κ(C),κ(N),μ(N)-(2,6-(i-Pr(2)POC(6)H(3)CH(2)NBn)Ni](2) (1; Bn = CH(2)Ph) has been investigated by various analytic techniques. Cyclic voltammetry measurements have shown that 1 undergoes a quasi-reversible, one electron, Ni-based redox process (ΔE(0)(1/2) = -0.07 V vs Cp(2)Fe/[Cp(2)Fe](+)), and spectroelectrochemical measurements conducted on the product of the electrolytic oxidation, [1](+•), have shown multiple low-energy electronic transitions in the range of 10,000-15,000 cm(-1). Computational studies using Density Functional Theory (B3LYP) have corroborated the experimentally obtained structure of 1, provided the electronic structure description, and helped interpret the experimentally obtained absorption spectra for 1 and [1](+·). These calculations indicate that the radical cation [1](+·) is a dimeric, mixed-valent species (class III) wherein most of the spin density is delocalized over the two nickel centers (Ni(+2.5)(2)N(2)), but some spin density is also present over the two nitrogen atoms (Ni(2+)(2)N(2)·). Examination of alternative structures for open shell species generated from 1 has shown that the spin density distribution is highly sensitive toward changes in the ligand environment of the Ni ions. NMR, UV-vis, electron paramagnetic resonance (EPR), and single crystal X-ray diffraction analyses have shown that chemical oxidation of 1 with N-Bromosuccinimide (NBS) follows a complex process that gives multiple products, including the monomeric trivalent species κ(P),κ(C),κ(N)-{2,6-(i-Pr(2)PO)(C(6)H(3))(CH═NBn)}NiBr(2) (2). These studies also indicate that oxidation of 1 with 1 equiv of NBS gives an unstable, paramagnetic intermediate that decomposes to a number of divalent species, including succinimide and the monomeric divalent complexes κ(P),κ(C),κ(N)-{2,6-(i-Pr(2)PO)(C(6)H(3))(CH═NBn)}NiBr (3) and κ(P),κ(C),κ(N)-{2,6-(i-Pr(2)PO)(C(6)H(3))(CH(2)N

  18. Purification and properties of detergent-compatible extracellular alkaline protease from Scopulariopsis spp. (United States)

    Niyonzima, Francois Niyongabo; More, Sunil


    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

  19. Total synthesis of macrodiolide ionophores aplasmomycin A and boromycin via double ring contraction. (United States)

    Avery, Mitchell A; Choudhry, Satish C; Dhingra, Om Prakash; Gray, Brian D; Kang, Myung-chol; Kuo, Shen-chun; Vedananda, Thalathani R; White, James D; Whittle, Alan J


    The half structure of the symmetrical macrodiolide aplasmomycin A was synthesized by alkylation of a C3-C10 α-sulfonyl ketone subunit, prepared from (R)-pulegone and protected as a C3 ortholactone with (2R,3R)-butanediol, by a protected 15,16-dihydroxy (12E)-allylic chloride representing C11-C17. The latter was obtained from (2S,3R)-1,2-epoxy-3-butanol and propargyl alcohol. Regio- and stereoselective 5-exo-trig cyclization of the ene diol moiety in this segment, mediated by N-bromosuccinimide, led to the (2R,3S,5R)-tetrahydrofuran substructure of aplasmomycin A. Attachment of an α-acetic ester at the C3 carboxylic acid and esterification of the 3'-hydroxyl group of the tetrahydrofuran as its α-bromoacetate enabled coupling of two aplasmomycin half structures as an α-acyloxy acetate. Mukaiyama macrolactonization of this hydroxy acid afforded a symmetrical 36-membered diolide. Base-mediated double Chan rearrangement of this bis α-acyloxy dilactone caused ring contraction to the 34-membered macrocycle of desboroaplasmomycin A while generating the transannular 2-hydroxy-3-hemiketal motif of the natural product in the correct configuration. Final incorporation of boron into the tetraol core produced aplasmomycin A, isolated as its sodium borate. Extension of this route to the unsymmetrical macrodiolide boromycin was accomplished by modifications that included reversal of C12-C13 olefin geometry to (Z) for the southern half structure along with stereoselective hydride reductions of the C9 ketone that produced (9R) and (9S) alcohols for northern and southern half structures, respectively. Coupling of these half structures was made using an α-acyloxy ester linkage as for aplasmomycin A, but ring closure in this case was orchestrated via a blocked C16 alcohol that left open the C15 hydroxyl group of the southern half for Mukaiyama macrolactonization. A double Chan rearrangement of the resulting 35-membered macrocycle produced the 33-membered diolide of

  20. 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


    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