| binding of hydrophobic hydroxamic acids enhances peroxidase's stereoselectivity in nonaqueous sulfoxidations. | horseradish peroxidase exhibits a meager stereoselectivity (e) in the sulfoxidation of thioanisole (1a) in 99.8% (v/v) methanol. the e value, however, is greatly enhanced when the enzyme forms a complex with benzohydroxamic acid (2a). these findings are rationalized by means of molecular dynamics simulations and energy minimization which correctly explain (i) why the free enzyme is not stereoselective, (ii) why 2a inhibits peroxidase-catalyzed sulfoxidation of 1a but the enzymatic formation of o ... | 2002 | 11817954 |
| redox intermediates of plant and mammalian peroxidases: a comparative transient-kinetic study of their reactivity toward indole derivatives. | a comparative study on the reactivity of five indole derivatives (tryptamine, n-acetyltryptamine, tryptophan, melatonin, and serotonin), with the redox intermediates compound i (k2) and compound ii (k3) of the plant enzyme horseradish peroxidase (hrp) and the two mammalian enzymes lactoperoxidase (lpo) and myeloperoxidase (mpo), was performed using the sequential-mixing stopped-flow technique. the calculated bimolecular rate constants (k2, k3) revealed substantial differences regarding the oxida ... | 2002 | 11811944 |
| design and characterization of immobilized enzymes in microfluidic systems. | herein we report the fabrication, characterization, and use of total analytical microsystems containing surface-immobilized enzymes. streptavidin-conjugated alkaline phosphatase was linked to biotinylated phospholipid bilayers coated inside poly(dimethylsiloxane) microchannels and borosilicate microcapillary tubes. rapid determination of enzyme kinetics at many different substrate concentrations was made possible by carrying out laminar flow-controlled dilution on-chip. this allowed lineweaver-b ... | 2002 | 11811412 |
| horseradish peroxidase mediates dna and deoxyguanosine 3'-monophosphate adduct formation in the presence of ochratoxin a. | ochratoxin a (ota) gives rise to dna and deoxyguanosine-3'-monophosphate (dgmp) adducts in vitro using mice kidney microsomes in the presence of arachidonic acid. this result points to the involvement of prostaglandin h synthases, which are present at high levels in the kidney, urinary bladder and seminal vesicles, and/or of lipoxygenases in the metabolic activation of ota to genotoxic compounds. these enzymes have peroxidase activities. incubation of ota with dna in the presence of horseradish ... | 2001 | 11808918 |
| spectrofluorimetric determination of hydrogen peroxide with 2-hydroxy-1-naphthaldehyde salicyloylhydrazone (hnsh) as the substrate for horseradish peroxidase (hrp). | the oxidation reaction of hnsh with h2o2 under the catalysis of hrp was studied in detail. the possible reaction mechanism was discussed. under optimum experimental conditions, the oxidized product of hnsh had excitation and emission maxima at 296 and 414 nm, respectively. a study to prove the existence of -o-o-h in polyethylene glycols was carried out. the proposed method was successfully applied to the determination of -o-o-h in polyethylene glycols. | 2002 | 11808641 |
| optic lobe commissures in a three-dimensional brain model of the cockroach leucophaea maderae: a search for the circadian coupling pathways. | the circadian rhythm of locomotor activity in the cockroach leucophaea maderae is controlled by bilaterally symmetric, apparently directly coupled, circadian pacemakers in the optic lobes. strong evidence predicts that ventromedial to the medulla, the accessory medulla with associated pigment-dispersing hormone-immunoreactive neurons is this circadian clock. in search for direct coupling pathways between both clocks, we performed horseradish peroxidase backfills from one optic stalk as well as d ... | 2002 | 11807846 |
| areal and callosal connections in the somatosensory cortex of the star-nosed mole. | star-nosed moles have a well-developed somatosensory cortex with multiple cortical areas representing the behaviorally important tactile star. in each of three cortical representations, the 11 mechanosensory appendages from the contralateral nose are represented in a series of dark cytochrome oxidase modules. here the connections of this complex cortical network were explored with injections of the neuroanatomical tracer wheat germ agglutinin conjugated to horseradish peroxidase (wga-hrp). the m ... | 2001 | 11794732 |
| unilateral optic nerve transection alters light response of suprachiasmatic nucleus and intergeniculate leaflet. | the suprachiasmatic nucleus (scn), the circadian pacemaker, receives photic input directly from the retina to synchronize the pacemaker to the environment. additionally, the intergeniculate leaflet (igl), which innervates the scn, is known to modulate the retinal photic input to the scn. to further understand the role of the igl in mediating the photic input to the scn, this study examined the effects of unilateral optic nerve transection (uonx) on the photic response of the scn and igl in adult ... | 2002 | 11792668 |
| adsorption of differently charged forms of horseradish peroxidase on metal electrodes of different nature: effect of surface charges. | the adsorption and bioelectrocatalytical activity in the reaction of h(2)o(2) reduction of two forms of horseradish peroxidase (hrp) offering different surface charges at ph 6.0 were studied on gold and silver electrodes. positively charged hrp was assessed at ph 6.0 for the case of native hrp (isoenzyme c, pi=8.8), and negatively charged hrp for the case of native hrp exposed to previous oxidation of carbohydrate residues and further introduction of sulfonate groups (pi=5.0). under oxidative pr ... | 2002 | 11786357 |
| sequential changes in synaptic vesicle pools and endosome-like organelles during depolarization near the active zone of central nerve terminals. | during periods of high-frequency stimulation the maintenance of synaptic transmission depends on a continued supply of synaptic vesicles. local recycling in the terminals ensures synaptic vesicle replenishment, but the intermediate steps are still a matter of debate. we analyzed changes in synaptic vesicle pools and endosome-like organelles near the active zone in central nerve terminals during depolarization at the ultrastructural level by electron microscopy. a short, 100 ms, depolarization-in ... | 2002 | 11784710 |
| biomaterials for molecular electronics development of optical biosensor for retinol. | molecular electronics involves expertise from several branches of science. various biomaterials and electronics are involved in the fabrication of such devices. while passive biomaterials are involved in anchoring the active biomolecules, the latter are involved in switching and/or signal transduction. in the present investigation we have used a glass-capillary-based approach to design a biosensor for retinol. the sensing element is retinol-binding protein (rbp). the affinity of retinoic-acid-ho ... | 2013 | 11783895 |
| mediated electrochemistry of horseradish peroxidase. catalysis and inhibition. | a precise determination of the complex mechanism of catalysis and inhibition involved in the reaction of hrp with h(2)o(2) as substrate and an outersphere single electron donor ([os(bpy)(2)pycl](+)) as cosubstrate is made possible by a systematic analysis of the cyclic voltammetric responses as a function of the scan rate and of the substrate and cosubstrate concentrations, complemented by spectrophotometric steady-state and stopped-flow experiments. the bell-shaped calibration curve relating th ... | 2002 | 11782176 |
| endocytic routes of exogenous antigen in murine dendritic cells and macrophages. | to compare the endocytic routes of exogenous antigen between murine dendritic cells (dcs) and macrophages (m phi s). | 2001 | 11779447 |
| redox thermodynamics of the fe(3+)/fe(2+) couple in horseradish peroxidase and its cyanide complex. | the thermodynamics of fe3+ to fe2+ reduction for the five-coordinate high-spin native form of horseradish peroxidase and for its six-coordinate low-spin cyanide adduct have been determined from variable-temperature uv-vis spectroelectrochemical experiments. in both cases, the deltah degrees 'rc and deltas degrees 'rc values are positive. hence, the negative reduction potentials turn out to be the result of two opposing and partially compensating contributions: a large enthalpic term, which is th ... | 2002 | 11772056 |
| cyclodextrin-modified biosensors: comparision of cyclodextrin-linked ferrocenes as mediators in sol-gel and screen-printed formats for sensing acetylcholine. | this work reports the comparison of a sol-gel and a screen-printed biosensor format using new mediators and a sensitive thin-film (ref. 1: p. kataky and d. parker, analyst, 1996, 121, 1829) to enhance the sensitivity and stability of biosensors. the new mediators were per-alkylated cyclodextrin linked ferrocenes and a control, ferrocene aminocarboxylic acid. the thin film comprised a cocktail with polyurethane, plasticiser, lipophilic anion and a perethylated beta-cd. the analyte targeted was ac ... | 2001 | 11763084 |
| effect of interfering substances on current response of recombinant peroxidase and glucose oxidase-recombinant peroxidase modified graphite electrodes. | graphite electrodes have been modified with different forms of horseradish peroxidase (hrp). these included native hrp, wild-type recombinant hrp, and two single-point recombinant hrp mutants, n70v and n70d. the mediator-less response of these electrodes to h2o2 was studied indicating that electrodes modified with recombinant hrp forms are more stable than those modified with native hrp. various interfering compounds were investigated for their effect on the current response to h2o2. it was foun ... | 2001 | 11763069 |
| molecular immunolabeling with recombinant single-chain variable fragment (scfv) antibodies designed with metal-binding domains. | to study the molecular structure and function of gene products in situ, we developed a molecular immunolabeling technology. starting with cdna from hybridomas producing monoclonal antibodies against biotin, catalase, and superoxide dismutase, we bioengineered recombinant single-chain variable fragment antibodies (scfv) and their derivatives containing metal-binding domains (scfv:mbd). as tested with surface plasmon resonance and enzyme-linked immunosorbent assay, affinity binding constants of th ... | 2002 | 11756693 |
| the enzyme horseradish peroxidase is less compressible at higher pressures. | fluorescence line-narrowing (fln) spectroscopy at 10 k was used to study the effect of high pressure through the prosthetic group in horseradish peroxidase (hrp), which was mg-mesoporphyrin (mgmp) replacing the heme of the enzyme. the same measurement was performed on mgmp in a solid-state amorphous organic matrix, dimethyl sulfoxide (dmso). series of fln spectra were registered to determine the (0, 0) band shape through the inhomogeneous distribution function (idf). in the range of 0-2 gpa a re ... | 2002 | 11751329 |
| resonance raman spectroscopy and density functional theoretical calculations of manganese corroles. a parallelism between high-valent metallocorroles and metalloporphyrins, relevant to horseradish peroxidase and chloroperoxidase compound i and ii intermediates. | soret-excited resonance raman (rr) spectra are reported for the mn(iii) and mn(iv)cl derivatives of meso-tris(p-(trifluoromethyl)phenyl)corrole, h(3)t(p-cf(3)-p)cor, and the mn(iii) derivative of beta-octabromo-meso-tris(p-(trifluoromethyl)phenyl)corrole, h(3)br(8)t(p-cf(3)-p)cor. three high-frequency bands in the rr spectrum of mn(iii)[t(p-cf(3)-p)cor] at 1465, 1524 and 1615 cm(-1) appear to upshift to 1486, 1528 and 1620 cm(-1) for mn(iv)[t(p-cf(3)-p)cor]cl. this suggests that the electronic c ... | 2002 | 11750033 |
| chemoselective oxidative polymerization of m-ethynylphenol by peroxidase catalyst to a new reactive polyphenol. | enzymatic oxidative polymerization of m-ethynylphenol possessing two reactive groups, phenol and acetylene moieties, was carried out in aqueous methanol under air. horseradish peroxidase and hydrogen peroxide were used as catalyst and oxidizing agent, respectively. (1)h nmr and ir analysis showed that only the phenolic moiety was polymerized to produce the polymer having the ethynyl group in the side chain. the reaction of the monomer using a copper/amine catalyst, a conventional catalyst for ox ... | 2000 | 11749146 |
| structure-function correlation in transient amacrine cells of goldfish retina: basic and multifractal analyses of dendritic trees in distinct synaptic layers. | amacrine cells generating light-evoked transient on-off responses were stained by intracellular injection of horseradish peroxidase after determining their input-output (voltage response vs. light intensity) profiles. ten cells specifically having bistratified dendritic trees were analyzed. the cross-sectional area of the dendrites in each sublamina (a and b) of the inner plexiform layer was initially measured. although some variability was observed, there was no statistically significant overal ... | 2001 | 11746454 |
| location of crosslinks in chemically stabilized horseradish peroxidase: implications for design of crosslinks. | the bifunctional compound, ethylene-glycol bis(n-hydroxysuccinimidylsuccinate) (egnhs), stabilizes horseradish peroxidase c (hrp) by reaction with the enzyme's lysine residues. in this study we compare native and modified hrp by proteolytic fragmentation, peptide sequencing, and mass spectroscopy, and identify the sites of modification. most significantly, egnhs is shown to form a crosslink between lys232 and lys241 of hrp and modifies lys174 without formation of a crosslink. these findings are ... | 2001 | 11745154 |
| mutation of residues critical for benzohydroxamic acid binding to horseradish peroxidase isoenzyme c. | aromatic substrate binding to peroxidases is mediated through hydrophobic and hydrogen bonding interactions between residues on the distal side of the heme and the substrate molecule. the effects of perturbing these interactions are investigated by an electronic absorption and resonance raman study of benzohydroxamic acid (bha) binding to a series of mutants of horseradish peroxidase isoenzyme c (hrpc). in particular, the phe179 --> ala, his42 --> glu variants and the double mutant his42 --> glu ... | 2001 | 11745121 |
| capillary zone electrophoresis of coniferyl alcohol oxidation products. | capillary zone electrophoresis (cze) was developed for the quantitative determination of dimers obtained by horseradish peroxidase-catalyzed oxidation of coniferyl alcohol. the influence of ph, electrolyte concentration, applied voltage, and temperature on cze performance was investigated, resulting in an efficient and rapid separation. coniferyl alcohol-derived dimers were directly analyzed from their reaction mixtures, without any extraction or derivatization step. in addition, these dimers we ... | 2001 | 11743754 |
| peroxidase- and nitrite-dependent metabolism of the anthracycline anticancer agents daunorubicin and doxorubicin. | oxidation of the anticancer anthracyclines doxorubicin (dxr) and daunorubicin (dnr) by lactoperoxidase(lpo)/h(2)o(2) and horseradish peroxidase(hrp)/h(2)o(2) systems in the presence and absence of nitrite (no(2)(-)) has been investigated using spectrophotometric and epr techniques. we report that lpo/h(2)o(2)/no(2)(-) causes rapid and irreversible loss of anthracyclines' absorption bands, suggesting oxidative degradation of their chromophores. both the initial rate and the extent of oxidation ar ... | 2001 | 11735418 |
| mechanism of reaction of hydrogen peroxide with horseradish peroxidase: identification of intermediates in the catalytic cycle. | the mechanism of the reaction of horseradish peroxidase isoenzyme c (hrpc) with hydrogen peroxide to form the reactive enzyme intermediate compound i has been studied using electronic absorbance, rapid-scan stopped-flow, and electron paramagnetic resonance (epr) spectroscopies at both acid and basic ph. the roles of the active site residues his42 and arg38 in controlling heterolytic cleavage of the h(2)o(2) oxygen-oxygen bond have been probed with site-directed mutant enzymes his42 --> leu (h42l ... | 2001 | 11724589 |
| electrochemical and quartz crystal microbalance detection of the cholera toxin employing horseradish peroxidase and gm1-functionalized liposomes. | an ultrasensitive method for the detection of the cholera toxin (ct) using electrochemical or microgravimetric quartz crystal microbalance transduction means is described. horseradish peroxidase (hrp) and gm1-functionalized liposomes act as catalytic recognition labels for the amplified detection of the cholera toxin based on highly specific recognition of ct by the ganglioside gm1. the sensing interface consists of monoclonal antibody against the b subunit of ct that is linked to protein g, ass ... | 2001 | 11721931 |
| surface-grafted molecularly imprinted polymers for protein recognition. | a technique for coating microplate wells with molecularly imprinted polymers (mips) specific for proteins is presented. 3-aminophenylboronic acid was polymerized in the presence of the following templates: microperoxidase, horseradish peroxidase, lactoperoxidase, and hemoglobin, via oxidation of the monomer by ammonium persulfate. this process resulted in the grafting of a thin polymer layer to the polystyrene surface of the microplates. imprinting resulted in an increased affinity of the polyme ... | 2001 | 11721930 |
| influence of static and dynamic disorder on the visible and infrared absorption spectra of carbonmonoxy horseradish peroxidase. | spectroscopy of horseradish peroxidase with and without the substrate analog, benzohydroxamic acid, was monitored in a glycerol/water solvent as a function of temperature. it was determined from the water infrared (ir) absorption that the solvent has a glass transition at 170-180 k. in the absence of substrate, both the heme optical q(0,0) absorption band and the ir absorption band of co bound to heme broaden markedly upon heating from 10-300 k. the q(0,0) band broadens smoothly in the whole tem ... | 2001 | 11721008 |
| steady-state and picosecond time-resolved fluorescence studies on native and apo seed coat soybean peroxidase. | seed coat soybean peroxidase (sbp) belongs to class iii of the plant peroxidase super family. the protein has a very similar 3-dimensional structure with that of horseradish peroxidase (hrp-c). the fluorescence characteristics of the single tryptophan (trp117) present in sbp and apo-sbp have been studied by steady-state and pico-second time-resolved fluorescence spectroscopy. fluorescence decay curve of sbp was best described by a four exponential model that gave the lifetimes, 0.035 ns (97.0%), ... | 2001 | 11716491 |
| enzyme-mediated free radical polymerization of styrene. | horseradish peroxidase-mediated polymerization of styrene at ambient temperature is reported. molecular weight and yield of polystyrene were influenced by solvent, concentration of hydrogen peroxide, and initiator (beta-diketones, coumarin). thf:h2o (v/v) and hydrogen peroxide (0.082 mol/l) provided maximum yield of polymer (21.2% weight conversion of styrene to polystyrene) with 2,4-pentanedione as initiator. 1,3-cyclopentanedione and dibenzoylmethane as initiators resulted in higher yield of p ... | 2000 | 11710186 |
| horseradish peroxidase mediated free radical polymerization of methyl methacrylate. | this paper reports the free radical polymerization of methyl methacrylate (mma) catalyzed by horseradish peroxidase (hrp). a novel method was developed whereby mma polymerization can be carried out at ambient temperatures in the presence of low concentrations of hydrogen peroxide and 2,4-pentanedione in a mixture of water and a water-miscible solvent. polymers of mma formed were highly stereoregular with predominantly syndiotactic sequences (syn-dyad fractions from 0.82 to 0.87). analyses of the ... | 2000 | 11710143 |
| chemoselective oxidative polymerization of m-ethynylphenol by peroxidase catalyst to a new reactive polyphenol. | enzymatic oxidative polymerization of m-ethynylphenol possessing two reactive groups, phenol and acetylene moieties, was carried out in aqueous methanol under air. horseradish peroxidase and hydrogen peroxide were used as catalyst and oxidizing agent, respectively. 1h nmr and ir analysis showed that only the phenolic moiety was polymerized to produce the polymer having the ethynyl group in the side chain. the reaction of the monomer using a copper/amine catalyst, a conventional catalyst for oxid ... | 2000 | 11710092 |
| interaction of 2,4,6-trinitrotoluene (tnt) and 4-amino-2,6-dinitrotoluene with humic monomers in the presence of oxidative enzymes. | oxidative coupling of nitroaromatic compounds involving soil organic matter was examined as a means of soil remediation. humic monomers, serving as model compounds for soil humic substances, were used as cosubstrates, applying phenoloxidases (laccase from trametes villosa and peroxidase from horseradish) as oxidative biocatalysts. without the addition of a cosubstrate, only 30% of 4-amino-2,6-dinitrotoluene (4adnt) and no 2,4,6-trinitrotoluene (tnt) were transformed in the presence of the laccas ... | 2002 | 11706361 |
| thermodynamic analysis of the binding of aromatic hydroxamic acid analogues to ferric horseradish peroxidase. | peroxidases typically bind their reducing substrates weakly, with k(d) values in the millimolar range. the binding of benzhydroxamic acid (bha) to ferric horseradish peroxidase isoenzyme c (hrpc) [k(d) = 2.4 microm; schonbaum, g. r. (1973) j. biol. chem. 248, 502-511] is a notable exception and has provided a useful tool for probing the environment of the peroxidase aromatic-donor-binding site and the distal heme cavity. knowledge of the underlying thermodynamic driving forces is key to understa ... | 2001 | 11705389 |
| estimation of free radical-quenching activity of leaf pigment extracts. | the chromogen 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) radical (abts.+) can be directly generated by the enzymatic system formed by hydrogen peroxide and horseradish peroxidase in ethanolic media. the reaction is time- and concentration-dependent, and the abts.+ generated shows excellent stability. the method is an adaptation of the decolouration method previously reported (cano et al. 1998. phytochem anal 9:196-202), which was used for estimating anti-oxidant activity in aqueous ... | 2015 | 11705243 |
| chiral analysis of amino acids using electrochemical composite bienzyme biosensors. | the construction and performance of bienzyme amperometric composite biosensors for the selective determination of l- or d-amino acids is reported. d- or l-amino acid oxidase, horseradish peroxidase, and the mediator ferrocene were coimmobilized by simple physical inclusion into the bulk of a graphite-70% teflon electrode matrix. working conditions including amino acid oxidase loading and ph were optimized. studies on the repeatability of the amperometric response obtained at +0.00 v, with and wi ... | 2001 | 11700983 |
| germinating barley selenium-containing peroxidase is one of the peroxidase isoenzymes. | a selenium-containing peroxidase from the germinating barley grown on a selenium-containing artificial medium was isolated and purified by means of cold acetone precipitation, sephadex-g150 filtration, followed by deae-sepharose chromatography and sodium dodecyl sulfate--polyacrylamid gel electrophoresis. the form of selenium existing in the peptide assayed with paper chromatography was selenomethionine. the amino acid composition of this enzyme was similar to those peroxidases from other source ... | 2001 | 11694005 |
| peroxidase enzyme sensor for on-line monitoring of disinfection processes in the food industry. | for desirable environmental reasons, peroxides have replaced halogenated substances for disinfection purposes in the food and beverage industry. however, cost issues and the requirement to remove these agents completely after disinfection necessitate simple, low-cost and sensitive test methods with a wide dynamic range and on-line capability. the development and performance of such a method is detailed here. low-cost peroxide sensors were fabricated using a single deposition procedure, in which ... | 2001 | 11693615 |
| a tissue-specific marker of ecdysozoa. | over the past few years, molecular studies of phylogeny have challenged the traditional view of evolutionary relationships among protostomian animal phyla. based on analysis of 18s ribosomal rna gene sequences, it has been suggested that some traditional groups, like the articulata and the pseudocoelomata, should be completely abandoned and that instead the protostomians should be split into two major clades: the ecdysozoa and the lophotrochozoa. however, this new molecular phylogeny still await ... | 2001 | 11685577 |
| enzyme-linked immunosorbent assay for the determination of blood coagulation factor xiii a-subunit in plasma and in cell lysates. | a new one-step elisa was developed for the determination of the concentration of blood coagulation factor xiii subunit a (fxiii-a) in plasma and in cell lysates. monoclonal antibodies directed against different epitopes on fxiii-a were used for the assay. the capture antibody was biotinylated on its carbohydrate moiety and the detection antibody was labelled with horseradish peroxidase. the antigen-antibody reaction was carried out in the well of a streptavidin-coated microplate. complex formati ... | 2001 | 11684129 |
| vesicular and non-vesicular sterol transport in living cells. the endocytic recycling compartment is a major sterol storage organelle. | we examined the intracellular transport of sterol in living cells using a naturally fluorescent cholesterol analog, dehydroergosterol (dhe), which has been shown to mimic many of the properties of cholesterol. by using dhe loaded on methyl-beta-cyclodextrin, we followed this cholesterol analog in pulse-chase studies. at steady state, dhe co-localizes extensively with transferrin (tf), a marker for the endocytic recycling compartment (erc), and redistributes with tf in cells with altered erc morp ... | 2002 | 11682487 |
| classical dot-blot format implemented as an amperometric hybridisation genosensor. | a new electrochemical hybridisation genosensor has been designed. this genosensor is based on a concept adapted from classical dot-blot dna analysis, but implemented in an electrochemical biosensor configuration. the use of amperometric transduction and the enzyme label method--that increases the genosensor sensitivity--are the main features of this new approach. the analytical procedure consists of five steps: dna target immobilisation by adsorption onto a nylon membrane, hybridisation between ... | 2001 | 11679299 |
| chronopotentiometry and faradaic impedance spectroscopy as signal transduction methods for the biocatalytic precipitation of an insoluble product on electrode supports: routes for enzyme sensors, immunosensors and dna sensors. | the biocatalyzed precipitation of an insoluble product produced on electrode supports is used as an amplification path for biosensing. enzyme-based electrodes, immunosensors and dna sensors are developed using this biocatalytic precipitation route. faradaic impedance spectroscopy and chronopotentiometry are used as transduction methods to follow the precipitation processes. while faradaic impedance spectroscopy leads to the characterization of the electron-transfer resistance at the electrode, c ... | 2001 | 11679244 |
| fungal auxin antagonist hypaphorine competitively inhibits indole-3-acetic acid-dependent superoxide generation by horseradish peroxidase. | plant peroxidases (ec 1.11.1.7) including horseradish peroxidase (hrp-c), but not the nonplant peroxidases, are known to be highly specific indole-3-acetic acid (iaa) oxygenases which oxidize iaa in the absence of h2o2, and superoxide anion radicals (o2*-) are produced as by-products. hypaphorine, a putative auxin antagonist isolated from ectomycorrhizal fungi, inhibited the iaa-dependent generation of o2*- by hrp-c, which occurs in the absence of h2o2. hypaphorine has no effect on the nonspecif ... | 2001 | 11676477 |
| semisynthetic enzymes in asymmetric synthesis: enantioselective reduction of racemic hydroperoxides catalyzed by seleno-subtilisin. | the serine protease subtilisin was chemically converted into the peroxidase-active seleno-subtilisin. this semisynthetic enzyme catalyzes the enantioselective reduction of racemic hydroperoxides in the presence of thiophenols to yield optically active hydroperoxides and alcohols on the semipreparative scale. the kinetic parameters and enantioselectivities of seleno-subtilisin-catalyzed reduction of various chiral hydroperoxides were determined. the catalytic efficiency of this semisynthetic enzy ... | 1999 | 11674154 |
| an ultrathin platinum film sensor to measure biomolecular binding. | a sensitive conductimetric immunosensor has been demonstrated based on an ultrathin platinum film on an oxidized silicon base. the film is about 25 a thick and is seen to consist of a discontinuous layer with channels 20-30 a wide. monoclonal antibodies were bound to the sensor surface using conventional biosensor chemistry. impedance at fixed frequencies across the film was used to track modification and binding at the surface. impedance increased 55% at 20 hz during the activation of the surfa ... | 2001 | 11672651 |
| horseradish peroxidase-catalyzed enantioselective reduction of racemic hydroperoxy homoallylic alcohols: a novel enzymatic method for the preparation of optically active, unsaturated diols and hydroperoxy alcohols. | the kinetic resolution of chiral diastereomeric hydroperoxy homoallylic alcohols 1 by horseradish peroxidase-catalyzed asymmetric reduction affords the optically active (r,r) or (r,s) allylic diols 2 and (s,s) or (s,r) hydroperoxy homoallylic alcohols 1 in high enantiomeric excess (up to 99%). | 1998 | 11672239 |
| neurotrophin-4 deficient mice have a loss of vagal intraganglionic mechanoreceptors from the small intestine and a disruption of short-term satiety. | intraganglionic laminar endings (igles) and intramuscular arrays (imas) are the two putative mechanoreceptors that the vagus nerve supplies to gastrointestinal smooth muscle. to examine whether neurotrophin-4 (nt-4)-deficient mice, which have only 45% of the normal number of nodose ganglion neurons, exhibit selective losses of these endings and potentially provide a model for assessing their functional roles, we inventoried igles and imas in the gut wall. vagal afferents were labeled by nodose g ... | 2001 | 11606648 |
| fluorometric determination of ethanol in liquor samples by flow-injection analysis using an immobilized enzyme-reactor column with packing prepared by coupling alcohol oxidase and peroxidase onto chitosan beads. | a flow-injection system was developed for the determination of ethanol with an immobilized enzyme-reactor column. this system, which consisted of hand-made reactor columns packed with alcohol oxidase and horseradish peroxidase immobilized onto chitosan beads, and a fluorometric detector, was applied to the determination of ethanol in liquor samples. under the recommended conditions, the ethanol, which was present in the pretreated samples, was converted to hydrogen peroxide when it was passed th ... | 2013 | 11601467 |
| enzymatic oxidative treatments of wheat bran layers: effects on ferulic acid composition and mechanical properties. | enzymatic treatments known to induce the gelation of feruloylated arabinoxylans solutions were applied to tissue strips isolated from peripheral layers of wheat grain to tentatively produce in situ arabinoxylan reticulation. the treatments by horseradish peroxidase (hrp) and manganese dependent peroxidase (mnp) induced a dimerization of ferulic acid (fa) in wheat bran with concomitant decrease of arabinoxylan solubility. similar results were obtained, but to a lesser extent, by simple incubation ... | 2001 | 11600009 |
| liquid chromatographic determination of total and beta-n-oxalyl-l-alpha,beta-diaminopropionic acid in lathyrus sativus seeds using both refractive index and bioelectrochemical detection. | a further improved chromatographic method for the simultaneous determination of the total amount of odap, selectively the amount of its neurotoxic form, beta-odap, and free l-glutamate in raw lathyrus sativus (grass pea) seed samples is described using post-column refractive index in combination with bioelectrochemical detection. the biosensor is based on crosslinking horseradish peroxidase (hrp) and an os-containing mediating polymer with poly(ethyleneglycol)(400) diglycidyl ether (pegdge), for ... | 2001 | 11594394 |
| inhibitory effect of aluminium on the axonal transport of hrp microinjected into dorsal root ganglion neurons in vitro. | in the present study the function of axonal transport in individual neurons under aluminium intoxication was investigated experimentally in comparison with controls. we used the technique of microinjection of horseradish peroxidase (hrp) in dissociated dorsal root ganglia (drg) neurons and neurons of explant cultures of drg. different exposure periods (1 and 6 hours as well as 6 and 10 days) to aluminium were analysed quantitatively. this analysis revealed an impaired anterograde transport of hr ... | 2001 | 11577246 |
| rapid isolation, characterization, and glycan analysis of cup a 1, the major allergen of arizona cypress (cupressus arizonica) pollen. | a rapid method for the purification of the major 43-kda allergen of cupressus arizonica pollen, cup a 1, was developed. | 2001 | 11576077 |
| purification and properties of a neutral peroxidase isozyme from turnip (brassica napus l. var. purple top white globe) roots. | a neutral peroxidase isozyme (pi 7.2) from turnip roots (tnp) was purified to homogeneity and partially characterized. tnp is a monomeric glycoprotein with 9.1% carbohydrate content and a molecular weight of 36 kda. optimum ph values for activity using 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid (abts) and guaiacol as h donors were 4.5 and 5.5, whereas the k(m) values were 0.7 and 3.7 mm, respectively. the abts k(m) was approximately 7 times higher than that reported for basic commercial ... | 2001 | 11559153 |
| beta-fluoro-coniferyl alcohol does not inhibit lignin biosynthesis in suspension cultures of picea abies (l.) karst. | a fluorinated analogue of coniferyl alcohol has been reported to be a specific inhibitor of oxidases involved in the biosynthesis of lignin. the z isomer of beta-fluoro-coniferyl alcohol was synthesized and used for the preparation of dehydrogenation polymers (dhps) and was also tested on lignin producing suspension cultures of spruce (picea abies (l.) karst.). the growth of the cells or the production of lignin by the suspension cultures was not significantly affected by the addition of fluoroc ... | 2001 | 11551546 |
| oxidation of melatonin and tryptophan by an hrp cycle involving compound iii. | we recently described that horseradish peroxidase (hrp) and myeloperoxidase (mpo) catalyze the oxidation of melatonin, forming the respective indole ring-opening product n(1)-acetyl-n(2)-formyl-5-methoxykynuramine (afmk) (biochem. biophys. res. commun. 279, 657-662, 2001). although the classic peroxidatic enzyme cycle is expected to participate in the oxidation of melatonin, the requirement of a low hrp:h(2)o(2) ratio suggested that other enzyme paths might also be operative. here we followed th ... | 2001 | 11549265 |
| combined effects of an oxidative enzyme and dissolved humic substances on 13c-labelled 2,4-d herbicide as revealed by high-resolution 13c nmr spectroscopy. | phenoxyalkanoic acids are a widely used class of herbicides. this work employed high-resolution 13c nmr to study the structural changes induced by humic substances and horseradish perodixase on 2,4-dichlorophenoxyacetic acid (2,4-d) 13c-labelled in the side chain. nmr spectra showed that humic substances chemically catalyze abiotic splitting of [13c]2,4-d into 2,4-dichlorophenol and [13c]acetic acid at ph 7 but not at ph 4.7. peroxidase did not catalyze the oxidative degradation of [13c]2,4-d at ... | 2013 | 11548751 |
| sulfur-centered radical formation from the antioxidant dihydrolipoic acid. | lipoic acid and its reduced form, dihydrolipoic acid, are thought to be strong antioxidants. there are also reports of dihydrolipoic acid acting as a pro-oxidant under certain circumstances. this article reports the direct observation by esr spectrometry of the disulfide radical anion and the spin trapping of the primary thiyl radical formed from the oxidation of dihydrolipoic acid through thiol pumping with phenol and horseradish peroxidase. the disulfide radical anion reacts rapidly with oxyge ... | 2001 | 11546802 |
| the critical role of the proximal calcium ion in the structural properties of horseradish peroxidase. | the extent to which the structural ca(2+) ions of horseradish peroxidase (hrpc) are a determinant in defining the heme pocket architecture is investigated by electronic absorption and resonance raman spectroscopy upon removal of one ca(2+) ion. the fe(iii) heme states are modified upon ca(2+) depletion, with an uncommon quantum mechanically mixed spin state becoming the dominant species. ca(2+)-depleted hrpc forms complexes with benzohydroxamic acid and co which display spectra very similar to t ... | 2001 | 11546788 |
| tonotopic projections of the auditory nerve to the cochlear nucleus angularis in the barn owl. | the nucleus angularis (na), one of the two cochlear nuclei of birds, plays an important role in the processing of sound intensity. to begin investigating the na in detail in the barn owl, which is a popular animal model for neural mechanisms of sound localization, a frequency map for this nucleus is presented here. focal injections of horseradish peroxidase or neurobiotin were placed either in the na or in the cochlear nucleus magnocellularis, labeling small groups of auditory nerve fibers of kn ... | 2001 | 11545149 |
| dioxin detection based on immunoassay using a polyclonal antibody against octa-chlorinated dibenzo-p-dioxin (ocdd). | an enzyme-linked immunosorbent assay (elisa) using a polyclonal antibody against octa-chlorinated dibenzo-p-dioxin (ocdd) is presented. this method is based on a competitive reaction between ocdd and ocdd-hrp (horseradish peroxidase) conjugate against the antibody, whereby ocdd-hrp is detected colorimetrically at 450 nm. the detection limit of ocdd was 0.78 pg ml(-1). optimizing the reaction conditions of the assay, cross reactivities of some dioxins against the antibody are discussed. | 2001 | 11534580 |
| oxidative stress during peripheral angioplasty. implication for late restenosis? | percutaneous transluminal angioplasty (pta) is routine treatment for patients with peripheral arterial disease (pad). the procedure induces local generation of reactive oxygen species (ros), such as h2o2. since these have been shown to stimulate vascular smooth muscle cell growth (vsmcg), we investigated peroxide levels in patients with pad during pta and related these results to late clinical outcome. | 2001 | 11533520 |
| oxidation of hydroquinones by the versatile ligninolytic peroxidase from pleurotus eryngii. h2o2 generation and the influence of mn2+. | formation of h2o2 during the oxidation of three lignin-derived hydroquinones by the ligninolytic versatile peroxidase (vp), produced by the white-rot fungus pleurotus eryngii, was investigated. vp can oxidize a wide variety of phenols, including hydroquinones, either directly in a manner similar to horseradish peroxidase (hrp), or indirectly through mn3+ formed from mn2+ oxidation, in a manner similar to manganese peroxidase (mnp). from several possible buffers (all ph 5), tartrate buffer was se ... | 2001 | 11532015 |
| n-dealkylation of an n-cyclopropylamine by horseradish peroxidase. fate of the cyclopropyl group. | cyclopropylamines inactivate cytochrome p450 enzymes which catalyze their oxidative n-dealkylation. a key intermediate in both processes is postulated to be a highly reactive aminium cation radical formed by single electron transfer (set) oxidation of the nitrogen center, but direct evidence for this has remained elusive. to address this deficiency and identify the fate of the cyclopropyl group lost upon n-dealkylation, we have investigated the oxidation of n-cyclopropyl-n-methylaniline (3) by h ... | 2001 | 11525657 |
| structural change and catalytic activity of horseradish peroxidase in oxidative polymerization of phenol. | the effects of solvent and reaction conditions on the catalytic activity of horseradish peroxidase (hrp) were investigated for oxidative polymerization of phenol in water/organic mixtures using hydrogen peroxide as an oxidant. also, the structural changes of hrp were investigated by cd and absorption spectroscopy in these solvents. the results suggest that the yield of phenol polymer (the conversion of phenol to polymer) is strongly affected by the reaction conditions due to the structural chang ... | 2001 | 11515542 |
| cationic ascorbate peroxidase isoenzyme ii from tea: structural insights into the heme pocket of a unique hybrid peroxidase. | the novel class iii ascorbate peroxidase isoenzyme ii from tea leaves (tcapxii), with an unusually high specific ascorbate peroxidase activity associated with stress response, has been characterized by resonance raman (rr), electronic absorption, and fourier transform infrared (ft-ir) spectroscopies. ferric and ferrous forms and the complexes with fluoride, cyanide, and co have been studied at various ph values. the overall blue shift of the electronic absorption spectrum, the high rr frequencie ... | 2001 | 11513615 |
| intestinal permeability is reduced and il-10 levels are increased in septic il-6 knockout mice. | sepsis is associated with increased intestinal permeability, but mediators and mechanisms are not fully understood. we examined the role of interleukin (il)-6 and il-10 in sepsis-induced increase in intestinal permeability. intestinal permeability was measured in il-6 knockout (il-6 -/-) and wild-type (il-6 +/+) mice 16 h after induction of sepsis by cecal ligation and puncture or sham operation. in other experiments, mice or intestinal segments incubated in ussing chambers were treated with il- ... | 2001 | 11507020 |
| direct electrochemistry and electrocatalysis with horseradish peroxidase in eastman aq films. | stable films made from ionomer poly(ester sulfonic acid) or eastman aq29 on pyrolytic graphite (pg) electrodes gave direct electrochemistry for incorporated enzyme horseradish peroxidase (hrp). cyclic voltammetry of hrp-aq films showed a pair of well-defined, nearly reversible peaks at about -0.33 v vs. sce at ph 7.0 in blank buffers, characteristic of hrp heme fe(iii)/fe(ii) redox couple. the electron transfer between hrp and pg electrode was greatly facilitated in aq films. the electrochemical ... | 2001 | 11506977 |
| an electrochemical multienzymatic biosensor for determination of cholesterol. | this paper describes an electrochemical biosensor for free cholesterol monitoring. the sensor is a multienzymatic electrodic system in which horseradish peroxidase and cholesterol oxidase are simultaneously immobilized within a polymeric film, on the surface of a pyrolitic graphite electrode. from voltammetric and amperometric (flow-injection) data obtained, the efficiency, reproducibility and stability of the system are discussed. results obtained, of interest for basic and applied biochemistry ... | 2001 | 11506970 |
| impact of peroxidase addition on the sorption-desorption behavior of phenolic contaminants in surface soils. | the impact of peroxidase addition on sorption-desorption of phenol, o-cresol, 2,4-dichlorophenol (dcp), and 1-naphthol was evaluated using two surface soils. target chemicals were added to soils as single solutes or binary mixtures. seven-day adsorption studies were followed by sequential fill-and-draw extractions with synthetic groundwater. addition of horseradish peroxidase (hrp) with h2o2 was the primary treatment evaluated. hrp-mediated sorption enhancementwas related to contaminant solubili ... | 2001 | 11505995 |
| rapid and simple single nanogram detection of glycoproteins in polyacrylamide gels and on electroblots. | the fluorescent hydrazide, pro-q emerald 300 dye, may be conjugated to glycoproteins by a periodic acid schiff's (pas) mechanism. the glycols present in glycoproteins are initially oxidized to aldehydes using periodic acid. the dye then reacts with the aldehydes to generate a highly fluorescent conjugate. reduction with sodium metabisulfite or sodium borohydride is not required to stabilize the conjugate. though glycoprotein detection may be performed on transfer membranes, direct detection in g ... | 2001 | 11503209 |
| structural alterations of sugar chains in urine fibronectin from bladder cancer patients and its enzymatic mechanism. | to study the structural alterations of asparagine-linked sugar chains (n-glycans) on urine fibronectin (fn) from bladder cancer (bca) patients and its enzymatic mechanism. | 2001 | 11501752 |
| direct projections from serotonergic neurons in the dorsal and median raphe nuclei of midbrain to the suprachiasmatic nucleus in tupaia belangeri chinensis. | this study investigated the direct serotonergic projections to the suprachiasmatic nucleus (scn) from the dorsal and median raphe nuclei (dr/mr) of the midbrain in tupaia belangeri chinensis (tbc) by combined application of retrograde horseradish peroxidase (hrp) tract tracing, immunohistochemistry, and electron microscope techniques. the results provide evidence for the direct projections to the scn from serotonergic neurons distributed predominantly in the mr (mainly in its lateral portion) an ... | 2001 | 11496107 |
| in situ observation of the generation of isothiocyanates from sinigrin in horseradish and wasabi. | sulfur k-edge x-ray absorption spectroscopy has been used to determine the chemical identity of the sulfur-containing species in horseradish (armoracia lapthifolia) and wasabi (wasabia japonica) in situ, before and after cell disruption. the major sulfur-containing species in the intact root is sinigrin (1-thio-beta-d-glucopyranose 1-n-(sulfoxy)-3-buteneimidate) and related congeners. disrupting the cells by applying local pressure allowed the conversion of the sulfur moieties in sinigrin to iso ... | 2001 | 11479032 |
| aromatic substrate specificity of horseradish peroxidase c studied by a combined fluorescence line narrowing/energy minimization approach: the effect of localized side-chain reorganization. | horseradish peroxidase c binds a wide variety of small h-donor compounds such as benzohydroxamic acid (bha) and 2-naphthohydroxamic acid (nha). in this work, we use the mg(ii)-mesoporphyrin prosthetic group derivative as a spectroscopic probe of the active site and of the interaction with the substrates. we report on high-resolution fluorescence line-narrowed spectra which show that the effects of substrate binding on the electronic transitions are similar for both substrates and present data on ... | 2001 | 11478890 |
| the inactivation of horseradish peroxidase isoenzyme a2 by hydrogen peroxide: an example of partial resistance due to the formation of a stable enzyme intermediate. | the inactivation of horseradish peroxidase a2 (hrp-a2) with h2o2 as the sole substrate has been studied. in incubation experiments it was found that the fall in hrp-a2 activity was non-linearly dependent on h2o2 concentrations and that a maximum level of inactivation of approximately 80% (i.e. approximately 20% residual activity) was obtained with 2,000 or more equivalents of h2o2. further inactivation was only induced at much higher h2o2 concentrations. spectral changes during incubations of up ... | 2001 | 11472014 |
| detection of multiple proteins in an antibody-based protein microarray system. | a new antibody-based protein array assay is described. this assay combines the advantages of the specificity of enzyme-linked immunosorbent assays (elisa), sensitivity of enhanced chemiluminescence (ecl) and high-throughput of microspot. in this system, the capture proteins, either antibodies or antigens are spotted onto membranes in an array format. biological samples are then incubated with membranes. after antigens or antibodies in the samples bind to their corresponding targets and unbound p ... | 2001 | 11470281 |
| horseradish peroxidase catalyzed degradation of industrially important dyes. | horseradish peroxidase (hrp) is known to degrade certain recalcitrant organic compounds such as phenol and substituted phenols. here, for the first time we have shown hrp to be effective in degrading and precipitating industrially important azo dyes. for remazol blue, the enzyme activity was found to be far better at ph 2.5 than at neutral ph. in addition, remazol blue acts as a strong competitive inhibitor of hrp at neutral ph. horseradish peroxidase shows broad substrate specificity toward a v ... | 2001 | 11460246 |
| solution 1h nmr of the molecular and electronic structure of the heme cavity and substrate binding pocket of high-spin ferric horseradish peroxidase: effect of his42ala mutation. | solution 1h nmr has been used to assign a major portion of the heme environment and the substrate-binding pocket of resting state horseradish peroxidase, hrp, despite the high-spin iron(iii) paramagnetism, and a quantitative interpretive basis of the hyperfine shifts is established. the effective assignment protocol included 2d nmr over a wide range of temperatures to locate residues shifted by paramagnetism, relaxation analysis, and use of dipolar shifts predicted from the crystal structure by ... | 2001 | 11457190 |
| dna hybridization assay for detection of nucleopolyhedrovirus in whitemarked tussock moth (orgyia leucostigma) larvae. | dna dot-blot hybridization assays utilizing a horseradish peroxidase-labelled whole genomic dna probe and enhanced chemiluminescence were conducted to quantify detection thresholds of nucleopolyhedrovirus (npv) in whitemarked tussock moth (orgyia leucostigma) larvae. the minimum detection thresholds for an aqueous suspension of occlusion bodies (obs), obs added to macerates of non-infected larvae and obs in macerates of diseased larvae were 7.8 x 10(3), 7.8 x 10(3), and 1.5 x 10(3) obs, respecti ... | 2001 | 11455634 |
| determination of horseradish peroxidase and a peroxidase-like iron porphyrin at a nafion-modified electrode. | a catalytic coupling reaction between 4-amino antipyrine and a n,n-disubstituted aniline derivative has been exploited in the indirect electrochemical detection of horseradish peroxidase (hrp) and of a biomimetic catalyst, the iron(iii) sulfonated tetraphenyl porphyrin. in the presence of hydrogen peroxide and one of the two catalysts a cationic electroactive quinone-iminium dye p+ was formed and detected by linear scan voltammetry using a screen-printed electrode coated with a nafion film. dete ... | 2001 | 11445957 |
| light-induced activation of an inert surface for covalent immobilization of a protein ligand. | a simple and mild procedure is developed for the preparation of an activated polymer surface, used for immobilization of a protein ligand through a covalent linkage. activation of the polymer surface is carried out by attaching an active functional group through 1-fluoro-2-nitro-4-azidobenzene (fnab). uv irradiation of fnab transforms its azido group into a highly reactive nitrene, which binds with the inert polymer surface, whereas the active fluoro group of fnab, now part of the polymer, remai ... | 2001 | 11444810 |
| silver ion microplates for immunoassays. | microplate wells can be coated with silver ions using glutaraldehyde as a spacer molecule and thiourea as a complexing ligand. microwells containing surface silver ions are shown to immobilize biotin-labeled horseradish peroxidase (hrp) in active form, while showing very little affinity for the unlabeled enzyme. these plates can also immobilize biotin-labeled antibodies that exhibit bioactivity after immobilization. silver ions are needed for the complexation of the biotinylated enzyme or antibo ... | 2001 | 11414228 |
| simultaneous detection of multiple cytokines from conditioned media and patient's sera by an antibody-based protein array system. | we have developed a novel technique for high-throughput simultaneous screening of multiple cytokine expression based on a protein array system. our method has the advantage of showing the specificity of enzyme-linked immunosorbent assays, sensitivity of enhanced chemiluminescence (ecl), and high-throughput of microspot. in this system, the cytokine array membranes were created by spotting capture antibodies onto the membranes. the membranes were then incubated with biological samples such as con ... | 2001 | 11412006 |
| cycline-dependent kinase inhibitor, p27 (kip1), is associated with cholesteatoma. | cyclin-dependent kinases (cdkis) can arrest the cell cycle, which in turn inhibits the cell proliferation. p27 (kip1) is a cdki and acts as a tumor suppressor gene. in this study, we aimed to investigate the role of p27 cdki in cholesteatoma, a disease characterized by the presence of hyperproliferative squamous epithelium. | 2001 | 11404617 |
| salen complexes with bulky substituents as useful tools for biomimetic phenol oxidation research. | the catalytic properties of bulky water-soluble co-, cu-, fe- and mn-salen complexes in the oxidation of phenolic lignin model compounds have been studied in aqueous water--dioxane solutions (ph 3--10). mn catalysts were found to oxidize coniferyl alcohol in a same reaction time as horseradish peroxidase (hrp) enzyme and mn and co catalysts showed different regioselectivity suggesting a different substrate to catalyst interaction in the oxidative coupling. when the oxidation of material more rel ... | 2001 | 11408183 |
| quantitative detection in the attomole range for immunochromatographic tests by means of a flatbed scanner. | this work describes the use of the combination of carbon black as an antibody label, a membrane-based immunochromatographic device, and a flatbed scanner as a quantitative test system. the scanner detected 0.4-345 ng carbon black/mm(2) on a nitrocellulose membrane (0.2-170 amol carbon black/mm(2)) with an imprecision (coefficient of variation, cv) lower than 2% for the carbon black determination and a detection limit of 0.04 ng carbon black/mm(2) (0.02 amol/mm(2)). the detection ability was comp ... | 2001 | 11399036 |
| [not available]. | antibodies against ochratoxin a were produced in rabbits after immunization with an ochratoxin a-keyhole limpet hemocyanine conjugate. the immunogen was found to be very efficient, and high antibody titers were detected in the sera of all immunized rabbits. in a competitive enzyme immunoassay using ochratoxin a-horseradish peroxidase as the labelled antigen, low levels of ochratoxin a in buffer solution could be detected. the mean standard curve detection limit and 50% inhibition level of the op ... | 2001 | 23605865 |
| peroxidase-catalyzed removal of phenols from a petroleum refinery wastewater. | the phenol content of a petroleum refinery wastewater was reduced below the discharge limit following treatment with horseradish peroxidase and h2o2. approximately 58% of cod, 78% of bod5, and 95% of toxicity were removed along with the phenols. as a result of treatment, phenols were transformed into less biodegradable compounds which could be removed by subsequent coagulation and precipitation. optimization of the peroxide concentration led to 20% enzyme savings. the use of peg and chitosan as ... | 2001 | 11380188 |
| depletion of cortical target induced by prenatal ionizing irradiation: effects on the lateral geniculate nucleus and on the retinofugal pathways. | studies using neonatal surgical lesions to reduce the target area of the retina have supported the idea that developing axons show only a limited specificity in their targeting. this investigation tested whether retinogeniculate axons adjust for partial target depletion by repositioning of axons. we used adult swiss mice exposed to gamma rays at the time when layer iv cells are generated in the ventricular zone (16 days of gestation). nissl-stained brain sections were used for histological analy ... | 2001 | 11378307 |
| ultrastructural and permeability features of microvessels in the hippocampus, cerebellum and pons of senescence-accelerated mice (sam). | we previously reported that the accumulation of blood-borne radiolabelled serum albumin in brain parenchyma increased with aging, especially in senescence-accelerated mice (samp8), which showed age-related deficits in learning and memory. in this study, in order to examine morphological events related to the age-related increase of the brain accumulation of serum albumin, the transvascular passage of blood-borne horseradish peroxidase (hrp) and ultrastructural features of microvessels were exami ... | 2009 | 11378254 |
| kinetic studies on veratryl alcohol transformation by horseradish peroxidase. | a number of peroxidases, such as lignin peroxidase and manganese peroxidase have proved to be useful for industrial applications. some studies on the effects of temperature and ph stability have been carried out. it is known that veratryl alcohol increases their stability in the range 28-50 degrees c and is oxidized, leading to veratryl aldehyde formation. similar results with horseradish peroxidase (hrp) in the presence of cofactors were found, but the oxidation of veratryl alcohol in the absen ... | 2001 | 11374591 |
| buffer-anion-dependent ca2+ leaching from horseradish peroxidase at low ph. | despite highly conserved active-site structures, members of the plant peroxidase superfamily exhibit a wide range of ph optima. horseradish peroxidase isozyme c (hrpc) is an ideal peroxidase to investigate the structural determinants of ph stability and activity in superfamily members. conflicting reports exist on the low-ph stability of hrpc and consequently the pka of the catalytic distal histidine, which is neutral in active peroxidases. towards resolving such discrepancies, acid-induced chan ... | 2001 | 11372194 |
| the oxidation of indole derivatives catalyzed by horseradish peroxidase is highly chemiluminescent. | the indole moeity is present in many substances of biological occurrence. its metabolism, in most cases, involves an oxidative pathway. this study reports the oxidation of a series of indole derivatives, including several of biological origin, catalyzed by horseradish peroxidase in the presence of h2o2. chemiluminescence emission was observed in most cases and its intensity and spectral characteristics were correlated with structural features of the substrates. the structures of the main product ... | 2001 | 11370838 |
| iodide oxidation and iodine reduction mediated by horseradish peroxidase in the presence of ethylenediaminetetraacetic acid (edta): the superoxide effect. | ethylenediaminetetraacetic acid (edta) is an inhibitor of iodide (i-) oxidation that is catalyzed by horseradish peroxidase (hrp). hrp-mediated iodine (i2) reduction and triiodide (i3+) disappearance occur in the presence of this inhibitor. it is interesting that in the presence of edta, hrp produces superoxide radical, a reactive oxygen species that is required for iodine reduction. substitution of potassium superoxide (ko2) or a biochemical superoxide generating system (xanthine/xanthine oxida ... | 2001 | 11370764 |
| peroxidase-mediated cross-linking of a tyrosine-containing peptide with ferulic acid. | the tyrosine-containing peptide gly-tyr-gly (gyg) was oxidatively cross-linked by horseradish peroxidase in the presence of hydrogen peroxide. as products, covalently coupled di- to pentamers of the peptide were identified by lc-ms. oxidative cross-linking of ferulic acid with horseradish peroxidase and hydrogen peroxide resulted in the formation of dehydrodimers. kinetic studies of conversion rates of either the peptide or ferulic acid revealed conditions that allow formation of heteroadducts o ... | 2001 | 11368627 |
| isolation and characterization of two peroxidases from cucumis sativus. | two heme peroxidases of 35.2 and 36.5 kda have been isolated from cucumber (cucumis sativus) peelings and characterized through electronic and 1h nmr spectra in the ph range 3.5-10.5. their spectroscopic and catalytic properties, which are closely similar, are characteristic of highly homologous isoenzymes. both proteins, as isolated, exist as a mixture of two ferric forms containing a high-spin and a low-spin heme in an approximately 2:1 molar ratio. the latter form likely contains a hydroxide ... | 2001 | 11361125 |
| combined effects of an oxidative enzyme and dissolved humic substances on (13)c-labelled 2,4-d herbicide as revealed by high-resolution (13)c nmr spectroscopy. | phenoxyalkanoic acids are a widely used class of herbicides. this work employed high-resolution (13)c nmr to study the structural changes induced by humic substances and horseradish perodixase on 2,4-dichorophenoxyacetic acid (2,4-d) (13)c-labelled in the side chain. nmr spectra showed that humic substances chemically catalyze abiotic splitting of [(13)c]2,4-d into 2,4-dichlorophenol and [(13)c]acetic acid at ph 7 but not at ph 4.7. peroxidase did not catalyze the oxidative degradation of [(13)c ... | 2001 | 11360173 |
| detection of a tryptophan radical in the reaction of ascorbate peroxidase with hydrogen peroxide. | the reactivity of recombinant pea cytosolic ascorbate peroxidase (rapx) towards h2o2, the nature of the intermediates and the products of the reaction have been examined using uv/visible and epr spectroscopies together with hplc. compound i of rapx, generated by reaction of rapx with 1 molar equivalent of h2o2, contains a porphyrin pi-cation radical. this species is unstable and, in the absence of reducing substrate, decays within 60 s to a second species, compound i*, that has a uv/visible spec ... | 2001 | 11358529 |