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PubMed1993

Decomposition rate of hydrogen peroxide bleaching agents under various chemical and physical conditions.

The decomposition rate of 30% hydrogen peroxide was measured when hydrogen peroxide was mixed with 36% hydrochloric acid and anaesthesia either in 5:5:1 solution and in a solution of 20% sodium hydroxide at temperatures of 16 degrees to 20 degrees C and at 45 degrees C, respectively. The effect of ferris chloride on the decomposition of hydrogen peroxide was also observed. The decomposition of 30% hydrogen peroxide in sodium hydroxide solution was faster than that in the mixture of hydrochloric acid and ether at low temperature (16 degrees to 20 degrees C). The decomposition of hydrogen peroxide was accelerated by heat. The experiment implies that the bleaching effect of hydrogen peroxide can be achieved without heat by use of a sodium hydroxide solution. Further study on the rationale of the compound of the McInnes solution (hydrogen peroxide, hydrochloric acid, and anaesthesia ether mixed at a ratio of 5:5:1) is needed.

Chemical Phenomena↗
PubMed1997

High-performance liquid chromatographic determination of seratrodast and its metabolites in human serum and urine.

A high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of seratrodast, a new antiasthmatic drug, and its metabolites (M-I to M-III) in human serum and urine. The method for serum and urine with and without enzymatic hydrolysis using beta-glucuronidase involved liquid-liquid extraction and chemical oxidation with iron(III) chloride. The compounds in the extract were analyzed using HPLC with UV detection at 266 nm. The detection limits of seratrodast, M-I, M-II and M-III in serum and urine were 5-10 and 5-20 ng/ml, respectively, and those of deconjugated compounds in urine were 10-50 ng/ml. The method was applicable for human serum and urine from clinical trials.

Anti-Asthmatic Agents↗
PubMed2001

Anaerobic degradation of aromatic compounds coupled to Fe(III) reduction by Ferroglobus placidus.

Aromatic compounds are an important component of the organic matter in some of the anaerobic environments that hyperthermophilic microorganisms inhabit, but the potential for hyperthermophilic microorganisms to metabolize aromatic compounds has not been described previously. In this study, aromatic metabolism was investigated in the hyperthermophile Ferroglobus placidus. F. placidus grew at 85 degrees C in anaerobic medium with a variety of aromatic compounds as the sole electron donor and poorly crystalline Fe(III) oxide as the electron acceptor. Growth coincided with Fe(III) reduction. Aromatic compounds supporting growth included benzoate, phenol, 4-hydroxybenzoate, benzaldehyde, p-hydroxybenzaldehyde and t-cinnamic acid (3-phenyl-2-propenoic acid). These aromatic compounds did not support growth when nitrate was provided as the electron acceptor, even though nitrate supports the growth of this organism with Fe(II) or H2 as the electron donor. The stoichiometry of benzoate and phenol uptake and Fe(III) reduction indicated that F. placidus completely oxidized these aromatic compounds to carbon dioxide, with Fe(III) serving as the sole electron acceptor. This is the first example of an Archaea that can anaerobically oxidize an aromatic compound. These results also demonstrate for the first time that hyperthermophilic microorganisms can anaerobically oxidize aromatic compounds and suggest that hyperthermophiles may metabolize aromatic compounds in hot environments such as the deep hot subsurface and in marine and terrestrial hydrothermal zones in which Fe(III) is available as an electron acceptor.

Anaerobiosis↗
PubMed2006

A novel function for selenium in biological system: selenite as a highly effective iron carrier for Chinese hamster ovary cell growth and monoclonal antibody production.

As the market for biopharmaceuticals especially monoclonal antibodies (MAbs) rapidly grows, their manufacturing methods are coming under increasing regulatory scrutiny, particularly due to concerns about the potential introduction of adventitious agents from animal-sourced components in the media used for their production in mammalian cell culture. Chinese hamster ovary (CHO) cells are by far the most commonly used production vehicles for these recombinant glycoproteins. In developing animal-component free media for CHO and other mammalian cell lines, the iron-transporter function of serum or human/bovine transferrin is usually replaced by certain organic or inorganic chelators capable of delivering iron for cell respiration and metabolism, but few of them are sufficiently effective. Selenium is a well-known essential trace element (TE) for cell growth and development, and its positive role in biological system includes detoxification of free radicals by activating glutathione peroxidase. In cell culture, selenium in the form of selenite can help cells to detoxify the medium thus protect them from oxidative damage. In this presentation, we describe the discovery and application of a novel function of selenite, that is, as a highly effective carrier to deliver iron for cell growth and function. In our in-house-developed animal protein-free (APF) medium for CHO cells, using an iron-selenite compound to replace the well-established tropolone delivery system for iron led to comparable or better cell growth and antibody production. A high cell density of >10 x 10(6) viable cells/mL and excellent antibody titer of approximately 3 g/L were achieved in 14-day fed-batch cultures in shake flasks, followed by successful scale-up to stirred bioreactors. The preparation of the commercially unavailable iron-selenite compound from respective ions, and its effectiveness in cell-culture performance, were dependent on reaction time, substrates, and other conditions.

Animals↗
PubMed1995

Systemic effects of different perfluorochemical agents.

PURPOSE: An intravitreal injection of Fluosol-DA leads to a higher alteration of the macrophage system of the retina than perfluorooctane and perfluorodecalin administered by the same route. The difference may be due to different kinds of oxidative damage caused by the three chemicals. To test the validity of this assumption, the degree of cell alteration, expressed as reduction of cytoplasmic motility, caused by these three perfluorochemicals was examined. METHODS: Using the hepatic macrophage system of the rat, cell alteration was examined by magnetometry after intravenous application of various perfluorochemicals [emulsified perfluorodecalin (C10F18), perfluorooctane (C8F17Br) and Fluosol-DA (corresponding to a 20% emulsion of 70% perfluorodecalin and 30% perfluorotripropylamine, C9F21N)]. RESULTS: After administration of high doses, all perfluorochemicals led to cytoskeleton alteration. This alteration, expressed as retardation of the relaxation period of ferromagnetic iron oxide particles, was most pronounced after administration of Fluosol-DA. CONCLUSION: The compromising effect of perfluorochemicals is dose dependent and differs among the three compounds tested, with Fluosol-DA showing the greatest decrease in cytoplasmic motility.

Animals↗
PubMed1994

Purification and characterization of a novel metal-containing nonheme bromoperoxidase from Pseudomonas putida.

A novel bromoperoxidase was purified to homogeneity from the bacterium Pseudomonas putida IF-3 strain, which produces the antibiotic pyrrolnitrin. The enzyme had a molecular mass of 68,000 and was composed of two identical subunits (33,000). It was specific for I- and Br- and inactive toward Cl- and F- in the monochlorodimedone assay system. The optimum pH of the enzyme was around 4.2 and it rapidly lost its activity below 3.5, but it was stable over of range pH of 4 to 11. The purified enzyme was activated several fold by incubation with only cobalt ions, and did not contain an organic prosthetic group such as heme, flavin and cobalamin. Analyses of prosthetic metal compounds in the enzyme using plasma atomic emission spectroscopy (ICP-AES) combined with mass-spectroscopy (MS) and trace metal determination by high performance liquid chromatography (HPLC)-spectrometry, revealed that the enzyme contained 0.35 +/- 0.1 mol of cobalt ions, 1.0 +/- 0.2 mol of nickel ions, 0.8 +/- 0.2 mol of zinc ions and 2.0 +/- 0.2 mol of ferric iron per mol of enzyme, assuming the molecular weight of 68,000. There was no trace of vanadium in the enzyme, unlike in some nonheme haloperoxidases. Thus the bromoperoxidase of P. putida is a novel nonheme metal-containing bromoperoxidase.

Amino Acid Sequence↗
PubMed2001

Syntheses and structural characterization of dinuclear and tetranuclear iron(III) complexes with dinucleating ligands and their reactions with hydrogen peroxide.

The iron(III) complexes [Fe(2)(HPTB)(mu-OH)(NO(3))(2)](NO(3))(2).CH(3)OH.2H(2)O (1), [Fe(2)(HPTB)(mu-OCH(3))(NO(3))(2)](NO(3))(2).4.5CH(3)OH (2), [Fe(2)(HPTB)(mu-OH)(OBz)(2)](ClO(4))(2).4.5H(2)O (3), [Fe(2)(N-EtOH-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3CH(3)OH.1.5H(2)O (4), [Fe(2)(5,6-Me(2)-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3.5CH(3)OH.C(2)H(5)OC(2)H(5).0.5H(2)O (5), and [Fe(4)(HPTB)(2)(mu-F)(2)(OH)(4)](ClO(4))(4).CH(3)CN.C(2)H(5)OC(2)H(5).H(2)O (6) were synthesized (HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, N-EtOH-HPTB = N,N,N',N'-tetrakis(N' '-(2-hydroxoethyl)-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, 5,6-Me(2)-HPTB = N,N,N',N'-tetrakis(5,6-dimethyl-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane). The molecular structures of 2-6 were established by single-crystal X-ray crystallography. Iron(II) complexes with ligands similar to the dinucleating ligands described herein have been used previously as model compounds for the dioxygen uptake at the active sites of non-heme iron enzymes. The same metastable (mu-peroxo)diiron(III) adducts were observed during these studies. They can be prepared by adding hydrogen peroxide to the iron(III) compounds 1-6. Using stopped-flow techniques these reactions were kinetically investigated in different solvents and a mechanism was postulated.

Crystallography, X-Ray↗
PubMed2003

Nitrilotriacetate stimulation of anaerobic Fe(III) respiration by mobilization of humic materials in soil.

An enrichment culture capable of naphthalene mineralization reduced Fe(III) oxides without direct contact in anaerobic soil microcosms when the Fe(III) was placed in dialysis membranes or entrapped within alginate beads. Both techniques demonstrated that a component in soil, possibly humic materials, facilitated Fe(III) reduction when direct contact between cells and Fe(III) was not possible. The addition of the synthetic Fe(III) chelator, nitrilotriacetic acid (NTA), to soil enhanced Fe(III) reduction across the dialysis membrane and alginate beads, with the medium changing from clear to a dark brown color. An NTA-soil extract was more effective in Fe(III) reduction than the extracted soil itself. Characteristics of the NTA extract were consistent with that of humic substances. The results indicate that NTA improved Fe(III) reduction not by Fe(III) solubilization but by extraction of humic substances from soil into the aqueous medium. This is the first study in which stimulation of Fe(III) reduction through the addition of chemical chelators is shown to be due to the extraction of electron-shuttling compounds from the soil and not to solubilization of the Fe(III) and indicates that mobilization of humic materials could be an important component of anaerobic biostimulation.

Anaerobiosis↗
PubMed1988

Iron and dental caries.

Studies of human and animal caries, experiments in vitro and laboratory reports initiated the present study of a possible caries preventing effect of iron. The study comprises two sections. (I) Coatings on teeth of hamsters treated with iron salts and films formed on various solutions containing ferrous ions were examined with scanning electron microscopy and x-ray fluorescence analysis. (II) Enamel surface layers, remineralized caries lesions, fluorosed rat bone, coatings on teeth of hamsters treated with iron salts and films formed on solutions containing ferrous ions were examined with transmitting electron microscopy and electron diffraction. Based on the findings the following effects were visualized. When brought into the mouth, even in small amounts, iron ions will be precipitated on the enamel surface as thin acid resistant coatings containing gels and crystals of hydrous iron oxides. In addition, by adsorbing salivary calcium and phosphate ions these iron compounds seem to be able to nucleate the formation of apatites, thus mediating a replacement of minerals, which have been dissolved during the acid phases of the caries process.

Animals↗
PubMed2000

Supersonic jet/multiphoton ionization/mass spectrometry of dioxins formed by the thermal reaction of phenols in the absence and presence of an FeCl3 catalyst.

Dioxins, which are thermally produced from several precursor molecules, were investigated by supersonic jet/multiphoton ionization/time-of-flight mass spectrometry (SSJ/MPI/TOF-MS). Dibenzofuran and dibenzo-p-dioxin were efficiently generated from o-chlorophenol and also from phenol after a chlorination reaction with FeCl3. The present technique was employed for the continuous monitoring of a specified isomer, e.g., m-chlorophenol, which is formed at relatively low temperatures by chlorination of phenol with FeCl3. A dimerization reaction that forms a dibenzo-p-dioxin, e.g., dichlorodibenzo-p-dioxin from 2,4-dichlorophenol, at relatively high temperatures was also investigated. The number of chlorine atoms in the dioxin molecule was largely correlated with the number of chlorine atoms in the precursor molecule. However, some unexpected compounds, which probably occur by dechlorination and rearrangement reactions, were also found. Thus, the SSJ/MPI/TOF-MS technique represents a sensitive, as well as selective, analytical method for monitoring thermally generated dioxins.

Catalysis↗
PubMed2006

Ultrasonically induced opening of polyelectrolyte microcontainers.

The effect of ultrasonic treatments of different intensity and duration on the integrity and permeability of polyelectrolyte capsules was investigated both in poly(allylamine)/poly(styrene sulfonate) and Fe(3)O(4)/poly(allylamine)/poly(styrene sulfonate) polyelectrolyte capsules. Ultrasonic treatment of polyelectrolyte capsules induces the destruction of the polyelectrolyte shell and the release of the encapsulated material even at short (5 s) sonification times. The presence of magnetite nanoparticles significantly improves the efficiency of the ultrasonically stimulated release of the encapsulated compounds and enables magnetically controlled delivery to the desired site before ultrasonic treatment. Release of the encapsulated compound induced at ultrasonic power comparable to those of ultrasonic generators applied in medicine, demonstrating practical application of the ultrasonically triggered capsule opening in medicine.

Allylamine↗
PubMed2001

Quantitative analysis of cell death and ferritin expression in response to cortical iron: implications for hypoxia-ischemia and stroke.

Iron that is not bound to storage proteins can catalyse the generation of toxic hydroxyl radicals. Iron can be released from brain storage proteins by hypoxic conditions, such as those that accompany stroke, and the situation can be compounded by iron released from hemoglobin in extravasated blood cells. Despite the neurotoxicity of iron, there is little quantitative data concerning the spatio-temporal extent of its toxicity in vivo. The present study measures the effects of a pathologically relevant concentration of iron (1.0 mM) on neuronal death and on ferritin expression in vivo. Injection of iron (1 microl ferric ammonium citrate) into rat parietal cortex resulted in 7.9-fold more ferritin-labeled cells than did control injections of ammonium citrate at 1 day post-injection. This elevated expression continued for at least 1 week. One day after injection, the mean number of Fluoro-Jade-labeled degenerating neurons in 100 microm sections passing through the center of ferric ammonium citrate injection sites was 664+/-64. This value was 4.5-fold higher than at ammonium citrate injection sites, and this difference increased to 56-fold by day three. By 5 days post-injection, few dying neurons were observed at the control sites, but neurodegeneration continued beyond a week at the iron-injected sites. Thus, iron released during a brief episode of hypoxia-ischemia or during a stroke may be neurotoxic for a protracted period. Therefore, our findings indicate that it may be beneficial to target iron-induced peroxidation throughout the first few weeks following an intracerebral hemorrhage or an hypoxic-ischemic episode.

Animals↗
PubMed1998

Modular fluorescent-labeled siderophore analogues.

Biomimetic analogues 1 of the microbial siderophore (iron carrier) ferrichrome were labeled via piperazine with various fluorescent markers at a site not interfering with iron binding or receptor recognition (compounds 10-12). These iron carriers were built from a tetrahedral carbon symmetrically extended with three strands, each containing an amino acid (G = glycyl, A = alanyl, L = leucyl and P = phenylalanyl) and terminated by a hydroxamic acid, which together define an octahedral iron-binding domain. A fourth exogenous strand provided the site for connecting various fluorescent markers via a short bifunctional linker. Iron(III) titrations, along with fluorescence spectroscopy, generated quenching of fluorescence emission of some of the probes used. The quenching process fits the Perrin model which reinforces the intramolecular quenching process, postulated previously.1 All tested compounds, regardless of their probe size, polarity, or the linker binding them to the siderophore analogue, promote growth of Pseudomonas putida with the same efficacy as the nonlabeled analogues 1, with the added benefit of signaling microbial activity by fluorescence emission. All G derivatives of compounds 10-12 were found to parallel the behavior of natural ferrichrome, whereas A derivatives mediated only a modest iron(III) uptake by P. putida. Incubation of various Pseudomonas strains with iron(III)-loaded G derivatives resulted in the build-up of the labels' fluorescence in the culture medium to a much larger extent than from the corresponding A derivatives. The fluorescence buildup corresponds to iron utilization by the cells and the release of the fluorescent labeled desferrisiderophore from the cell to the media. The fact that the microbial activity of these compounds is not altered by attachment of various fluorescent markers via a bifunctional linker proposes their application as diagnostic tools for detecting and identifying pathogenic microorganisms.

Drug Design↗
PubMed2003

Phosphate immobilization by oxide precursors: implications on phosphate availability before life on earth.

The present study is based on the proposal that if the aqueous phosphorus-capture mechanism by iron oxide precursors was inhibited in prebiotic anoxic scenarios then soluble phosphates could have been more available than what is observed now. Supporting this conjecture, we examine prevailing contemporary trapping mechanisms of orthophosphate (Pi) and pyrophosphate (PPi). To illustrate its efficiency, the attachment of (Pi) onto aggregates of iron-3 oxyhydroxide is compared with the one reported for the product of its condensation, PPi. The electrophoretic profiles of the Pi- and PPi-aggregate complexes reveal different pH-modulated interactions of the phosphorylated compounds with both the aggregate and its aqueous surrounding layers. The observed differences of Pi/PPi sorption and desorption mechanisms are discussed in terms of their consequences to the prebiotic availability of soluble orthophosphate and of a phosphorylated compound having the high-energy phosphoanhydride linkage and a molecule representative of condensed oligophosphates.

Diphosphates↗
PubMed1985

Inhibition of mucopolysaccharide sulfation using rabbit liver sulfotransferases.

A method of measuring the inhibition of sulfation of mucopolysaccharides employed the coupled-enzyme system of Wortman. The procedure utilized the phenol and mucopolysaccharide sulfotransferases of rabbit liver extract. Compounds tested as inhibitors included substituted salicylic acids and related compounds, some hydroxamic acids, other agents capable of metal-ion complexation, and miscellaneous compounds, mostly containing sulfur. The most effective inhibitors were vanillin oxime, salicylhydroxamic acid, and other substituted salicylic acid derivatives of weaker acid strength than salicylic acid.

Ammonium Sulfate↗
PubMed2002

The nature of the intermediates in the reactions of Fe(III)- and Mn(III)-microperoxidase-8 with H(2)O(2): a rapid kinetics study.

Kinetic studies were performed with microperoxidase-8 (Fe(III)MP-8), the proteolytic breakdown product of horse heart cytochrome c containing an octapeptide linked to an iron protoporphyrin IX. Mn(III) was substituted for Fe(III) in Mn(III)MP-8. The mechanism of formation of the reactive metal-oxo and metal-hydroperoxo intermediates of M(III)MP-8 upon reaction of H(2)O(2) with Fe(III)MP-8 and Mn(III)MP-8 was investigated by rapid-scan stopped-flow spectroscopy and transient EPR. Two steps (k(obs1) and k(obs2)) were observed and analyzed for the reaction of hydrogen peroxide with both catalysts. The plots of k(obs1) as function of [H(2)O(2)] at pH 8.0 and pH 9.1 for Fe(III)MP-8, and at pH 10.2 and pH 10.9 for Mn(III)MP-8, exhibit saturation kinetics, which reveal the accumulation of an intermediate. Double reciprocal plots of 1/k(obs1) as function of 1/[H(2)O(2)] at different pH values reveal a competitive effect of protons in the oxidation of M(III)MP-8. This effect of protons is confirmed by the linear dependence of 1/k(obs1) on [H(+)] showing that k(obs1) increases with the pH. The UV-visible spectra of the intermediates formed at the end of the first step (k(obs1)) exhibit a spectrum characteristic of a high-valent metal-oxo intermediate for both catalysts. Transient EPR of Mn(III)MP-8 incubated with an excess of H(2)O(2), at pH 11.5, shows the detection of a free radical signal at g approximately equal to 2 and of a resonance at g approximately equal to 4 characteristic of a Mn(IV) (S = 3/2) species. On the basis of these results, the following mechanism is proposed: (i) M(III)MP-8-OH(2) is deprotonated to M(III)MP-8-OH in a rapid preequilibrium step, with a pK(a) = 9.2 +/- 0.9 for Fe(III)MP-8 and a pK(a) = 11.2 +/- 0.3 for Mn(III)MP-8; (ii) M(III)MP-8-OH reacts with H(2)O(2) to form Compound 0, M(III)MP8-OOH, with a second-order rate constant k(1) = (1.3 +/- 0.6) x 10(6) M(-1) x s(-1) for Fe(III)MP-8 and k(1) = (1.6 +/- 0.9) x 10(5) M(-1) x s(-1) for Mn(III)MP-8; (iii) this metal-hydroperoxo intermediate is subsequently converted to a high-valent metal-oxo species, M(IV)MP-8=O, with a free radical on the peptide (R(*+)). The first-order rate constants for the cleavage of the hydroperoxo group are k(2) = 165 +/- 8 s(-1) for Fe(III)MP-8 and k(2) = 145 +/- 7 s(-1) for Mn(III)MP-8; and (iv) the proposed M(IV)MP-8=O(R(*+)) intermediate slowly decays (k(obs2)) with a rate constant of k(obs2) = 13.1 +/- 1.1 s(-)(1) for Fe(III)MP-8 and k(obs2) = 5.2 +/- 1.2 s(-1) for Mn(III)MP-8. The results show that Compound 0 is formed prior to what is analyzed as a high-valent metal-oxo peptide radical intermediate.

Animals↗
PubMed1994

Iron uptake by Pasteurella piscicida and its role in pathogenicity for fish.

We evaluated the iron uptake mechanisms in Pasteurella piscicida strains as well as the effect of iron overload on the virulence of these strains for fish. With this aim, the capacity of the strains to obtain iron from transferrin and heme compounds as well as their ability to overcome the inhibitory activity of fish serum was analyzed. All the P. piscicida strains grew in the presence of the iron chelator ethylene-diamine-di (O-hydroxyphenyl acetic acid) or of human transferrin, which was used by a siderophore-mediated mechanism. The chemical tests and cross-feeding assays showed that P. piscicida produced a siderophore which was neither a phenolate nor a hydroxamate. Cross-feeding assays as well as preliminary chromatographic analysis suggest that this siderophore may be chemically related to multocidin. All the P. piscicida isolates utilized hemin and hemoglobin as an iron source, since the virulence of the strains increased when the fish were preinoculated with these compounds. This effect was stronger in the avirulent strains (50% lethal dose was reduced by 4 logs when fish were pretreated with hemin or hemoglobin). Only the pathogenic P. piscicida isolates were resistant to the bactericidal action of the fresh fish serum. The nonpathogenic strains grew in fish serum only when it was heat-inactivated or when it was supplemented with ferric ammonium citrate, hemin, or hemoglobin. In all the strains, at least three iron-regulated outer membrane proteins (IROMPs) (105, 118, and 145 kDa) were increased when the strains were cultured in iron-restricted medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

Ultrastructure of the haemophilic synovial membrane and electron-probe X-ray analysis of haemosiderin.

An ultrastructural study of the haemophilic synovial membrane revealed the presence of solitary siderosomes, compound siderosomes and a peppering of the cell cytoplasm with electron-dense particles. These changes were found in synovial intimal cells, subsynovial macrophages and fibroblasts. Electron-probe X-ray analysis of siderosomes revealed the presence of iron and traces of phosphorus. On the basis of previous and present studies it is postulated that haemosiderin is essentially a condensate of hydrated ferric oxide and that a variable amount of phospholipid material lies in company with it in the siderosome.

Adult↗