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At least 793 records · Page 44Linked to original sources
PubMed1980

Antibacterial effect of scandium and indium complexes of enterochelin on Klebsiella pneumoniae.

A number of studies point to the conclusion that enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, may be an essential metabolite for bacterial multiplication within the host. The compound removes iron from complexes with the host iron-binding proteins transferrin and lactoferrin, and the resulting ferric enterochelin is assimilated by the bacterial cell. It was reasoned that complexes of enterochelin with ions other than Fe3+ might act as antimetabolites and inhibit bacterial multiplication by interfering with the assimilation of ferric enterochelin. Enterochelin forms complexes with a number of group III and transition metal ions. The complex containing scandium exerts a bacteriostatic effect on Klebsiella pneumoniae in serum, whereas the indium complex induces a large increase in the generation time. The Fe3+ complexes of other microbial iron-transporting compounds are capable of reversing the bacteriostatic effect of the Sc3+ complex of enterochelin, suggesting that the compound acts solely by interfering with the enterochelin system of iron transport. Preliminary experiments show that the Sc3+ complex probably acts as a competitive inhibitor of ferric enterochelin. The Sc3+ complex of enterochelin exerts a therapeutic effect on intraperitoneal K. pneumoniae infections in mice similar to that obtained with kanamycin sulfate.

Animals↗
PubMed2005

Treatment of groundwater polluted by arsenic compounds by zero valent iron.

Batch experiments were carried out to study the kinetics and efficiency of inorganic arsenic removal by zero valent iron (ZVI) powder, and as well as the effects of pH, anions, and humic material (HM) on this process. Moreover, column experiment was conducted for 31 days to treat arsenate solution of 500 microg As/L using waste iron chippings as filling. Batch experiments showed that both arsenate and arsenite compounds could be removed efficiently from simulated groundwater by ZVI under aerobic and relative anaerobic conditions. Aerobic condition was favorable to arsenic removal especially for arsenate, while arsenite could be removed more rapidly than arsenate in relative anaerobic condition. Oxidation of arsenite to arsenate by iron species in aerobic environment was observed, which is thought to be an important pathway of arsenite removal. In an unsealed system, the removal efficiency of both arsenate and arsenite decreased at higher pH value. In a sealed system, acidic and alkaline condition seemed to be favorable for arsenate and arsenite removal, respectively. Phosphate and low concentration sulfate caused a decrease in arsenate removal, while high concentration sulfate as well as nitrate caused slight increase in arsenate removal. Presence of HM in solution slightly inhibited arsenic removal. Arsenic removal efficiency in column study was influenced by flow rate and work period of the column. More than 98% of arsenate could be removed stably with a hydraulic resident time of 2 h at last, and the effluent meet the drinking water standard.

Arsenic↗
PubMed1980

Iron uptake with ferripyochelin and ferric citrate by Pseudomonas aeruginosa.

Pyochelin is an iron-binding compound produced by Pseudomonas aeruginosa and demonstrates siderophore activity by its involvement in iron transport. During the transport process, an energy-independent association of [55Fe]ferripyochelin with bacteria occurred within the initial 30 s of reaction, followed by an energy-dependent accumulation of iron. The energy-independent association with iron appeared to be at the surface of the bacteria because the iron could be washed from the cells with thioglycolate, whereas accumulated iron was not washed from the bacteria. Energy-independent association of iron with bacteria and energy-dependent accumulation of iron in the presence of ferripyochelin varied concomitantly in cells grown under various conditions, but pyochelin synthesis appeared to be controlled separately. 55Fe complexed with citrate was also taken up by P. aeruginosa with a lower level of initial cell association. Bacterial mechanisms for iron uptake from ferric citrate were present in cells grown in a variety of media and were in lowest levels in cells grown in citrate. The synthesis of bacterial components for iron uptake from ferric citrate and from ferripyochelin was inhibited by high concentrations of iron supplied in growth media.

Biological Transport↗
PubMed2001

A method for the quantitative analysis of iron speciation in meat by using a combination of spectrophotometric methods and high-performance liquid chromatography coupled to sector field inductively coupled plasma mass spectrometry.

The determination of the heme and non-heme iron fractions in raw and cooked beef steak by using spectrophotometric methods and high-performance liquid chromatography coupled to a double-focusing sector field inductively coupled plasma mass spectrometer (HPLC-SF-ICPMS) is reported. Size exclusion chromatography coupled to SF-ICPMS was used to measure the iron-containing biomolecules in the samples. This approach allowed for the direct on-line detection of the most abundant iron isotope 56Fe without interference from 40Ar16O. The HPLC-ICPMS results for the iron speciation analysis of a raw beef steak, used as an analytical quality control (AQC) sample, showed that the main iron biomolecule present was the heme iron-containing protein myoglobin. For the AQC sample, the agreement among the HPLC-ICPMS method, the non-heme iron spectrophotometric method, and the total iron concentration showed 100% recovery of iron. The sum of the different iron-containing compounds determined using the developed HPLC-ICPMS method accounted for all the iron-containing compounds extracted. The analysis of myoglobin in steak by HPLC-ICPMS showed that on cooking the concentration was reduced by 85%. However, a spectrophotometric method specific for heme iron showed that it was still intact, even after heating to 80 degrees C. The measurement of the total iron in the cooked steak and the HPLC extracts by inductively coupled plasma optical emission spectroscopy (ICP-OES) indicated that the extraction method for the HPLC analysis was no longer applicable and that loss of the heme group from the protein rendered it incompatible with the size exclusion separation. The detection limit (concentration equivalent to 3 times the baseline for a blank injection) of the HPLC-ICPMS method was 2.4 ng as iron. The results demonstrate that a combination of analytical methods can be used to provide valuable information about dietary levels of nutritionally important metal-containing compounds as well as the efficiency of established extraction methods for raw and cooked meat samples.

Animals↗
PubMed1998

Effect of high irradiance and iron on volatile odour compounds in the cyanobacterium Microcystis aeruginosa.

The cyanobacterium, Microcystis aeruginosa was exposed to direct sunlight for 3, 6 or 9 h in media containing either low or high concentrations of iron, in order to determine any effects on the composition of volatile odour compounds (VOCs) released under photooxidative conditions. The most abundant VOCs detected included aliphatic hydrocarbons (C15-C21), naphthalene and the terpenoid compounds, beta-cyclocitral, and beta-ionone. Exposure to sunlight and low iron concentrations resulted in a decrease in beta-cyclocitral, beta-ionone, heptadecane and the total VOCs concentration after 9 h with respect to the control cultures. Six VOCs detected in the low iron cells were not detected in any of the high iron cells. However, those VOCs present in the high iron cells, in general, occurred at higher concentrations than the equivalent low iron cells after exposure to the sunlight conditions. Consequently, it was concluded that exposure to both high irradiance and high iron concentrations influenced the VOCs composition in cyanobacteria and this was interpreted to represent a cellular change during the photooxidation-promoting conditions.

Hydrocarbons↗
PubMed1979

Agrobactin, a siderophore from Agrobacterium tumefaciens.

A siderophore (microbial iron transport compound) was isolated from low iron cultures of Agrobacterium tumefaciens B6. The substance was characterized as a threonyl peptide of spermidine acylated with 3 residues of 2,3-dihydroxybenzoic acid, the carbonyl group of 1 residue of the latter participating in an oxazoline ring with the beta-hydroxyl of the threonine moiety. The compound, N-[3-(2,3-dihydroxybenzamido)propyl]-N-[4-(2,3-dihydroxybenzamido)butyl]-2-(2,3-dihydroxyphenyl)-trans-5-methyl-oxazoline-4-carboxamide, was given the trivial name agrobactin. Exposure to acid opened the oxazoline ring to afford agrobactin A. Ferric agrobactin A and agrobactin A itself, but not agrobactin or its ferric complex, had some capacity to feed iron to enterobactin-deficient strains of Escherichia coli and Salmonella typhimurium. Agrobactin was produced by A. tumefaciens in response to iron deficiency and was able to reverse the iron starvation in this organism precipitated by the presence of a ferric complexing agent not utilized by the cells.

Biological Transport↗
PubMed1990

Isolation and characterization of staphyloferrin A, a compound with siderophore activity from Staphylococcus hyicus DSM 20459.

A highly hydrophilic compound was isolated from low iron culture broth of Staphylococcus hyicus DSM 20459 which exhibits siderophore activity to the producer and 37 other staphylococci. The previously unknown metabolite was designated staphyloferrin A and consists of two molecules of citric acid, each linked to D-ornitine by an amide bond. Using an ion-pair HPLC-system we detected staphyloferrin A and a second iron regulated compound (staphyloferrin B) in the culture fluid of several Staphylococcus strains. We found no evidence that staphylococci synthesize catecholor hydroxamate-type siderophores.

Chromatography, High Pressure Liquid↗
PubMed1992

Antimyosin-labeled monocrystalline iron oxide allows detection of myocardial infarct: MR antibody imaging.

The synthesis and in vivo antigen targeting of a novel iron oxide compound were studied. A monocrystalline iron oxide nanoparticle (MION) was synthesized that contains a small (mean diameter, 2.9 nm +/- 0.9) single crystal core, passes through capillary membranes, and exhibits superparamagnetism. The MION was attached to antimyosin Fab (R11D10) and used for immunospecific magnetic resonance (MR) imaging of cardiac infarcts One hour after intravenous administration of MION-R11D10 in rats (100 mumol/kg), a marked decrease in the signal intensity of infarcted myocardium was observed. Immunohistochemical correlation confirmed the specific binding of the immunoconjugate to infarcted, but not to normal, myocardium. No decrease in cardiac signal intensity was observed when unconjugated MION was administered intravenously. The results indicate the feasibility of immunospecific MR imaging in living organisms.

Animals↗
PubMed1976

Stimulatory effect of dihydroxyphenyl compounds on the aerotolerance of Spirillum volutans and Campylobacter fetus subspecies jejuni.

The aerotolerance of the microaerophilic bacterium Spirillum volutans was greatly stimulated in a defined medium by the presence of dihydroxyphenyl ferric iron-binding compounds such as nor-epinephrine at 10(-5) to 10(-6) M. Dihydroxyphenyl compounds at 2 X 10(-4) M, or iron salts (ferrous or ferric) at high concentration, greatly increased the aerotolerance of a strain of Campylobacter fetus subsp. jejuni when grown on streak plates of Brucella agar. The results suggest that the microaerophilism of these organisms might in part be caused by a failure to synthesize microbial ferric iron-binding compounds at sufficient levels to support aerobic growth.

Aerobiosis↗
PubMed1988

The distribution of ferritin, lactoferrin and transferrin in granulomatous lymphadenitis of bovine paratuberculosis.

Immunohistochemical examination of iron-binding proteins was carried out in the formalin-fixed mesenteric lymph nodes of normal cattle and of cattle with paratuberculosis. Ferritin (FT) and lactoferrin (LF) were found in the granulomas in ileal lymph nodes from six infected cattle. A weak reaction for transferrin (TF) was found in granulomas of a lymph node from one of the infected cattle. FT was found in the macrophages in the medullary sinuses of normal and infected nodes; however, the reaction in infected nodes was generally stronger than that in normal ones. LF in the macrophages was found in only two infected nodes. Neutrophils in both normal and infected cattle always reacted strongly for LF. The TF was always found in the blood vessels and intracellular space. These results suggest that: (1) FT and LF may be important in vivo sources of iron for Mycobacterium paratuberculosis, since their own iron-binding compounds are considered to acquire iron from FT and LF in vitro; (2) the increase in FT and LF in the granulomas may be related to inflammatory hyposideraemia associated with paratuberculosis and (3) epithelioid and giant cells may have a different iron metabolism, from normal macrophages.

Animals↗
PubMed1989

Co-ordinated expression of the components of iron transport (mycobactin, exochelin and envelope proteins) in Mycobacterium neoaurum.

Mycobacterium neoaurum was grown with a range of iron concentrations from 0.01 to 4.0 micrograms/ml. Synthesis of the extracellular siderophore, exochelin, the intracellular iron storage compound, mycobactin and the iron-repressible envelope proteins were co-ordinately expressed. All three components of the iron transport system were synthesized when low amounts of iron (0.01 to 0.2 micrograms/ml) were added to the medium and were repressed when the iron concentration was increased to 0.5 micrograms/ml and above. These results re-inforce the conclusion that the iron-regulated proteins do fulfil an essential function in iron metabolism.

Bacterial Proteins↗
PubMed2007

Quantitative geometric descriptions of the belt iron atoms of the iron-molybdenum cofactor of nitrogenase and synthetic iron(II) model complexes.

Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes. In order to document this geometry in a systematic fashion in iron(II) chemistry, we have synthesized a range of four-coordinate iron(II) complexes that vary from tetrahedral to trigonal pyramidal. Continuous shape measures are used for a quantitative comparison of the stereochemistry of the Fe atoms in the iron-molybdenum cofactor with those of the presently and previously reported model complexes, as well as with those in polynuclear iron-sulfur compounds. This understanding of the iron coordination geometry is expected to assist in the design of synthetic analogues for intermediates in the nitrogenase catalytic cycle.

Iron↗
PubMed1998

Peroxynitrite decomposition catalysts: therapeutics for peroxynitrite-mediated pathology.

Inflamed tissue is often characterized by the production of NO and superoxide. These radicals react at diffusion-limited rates to form the powerful oxidant peroxynitrite (PN). When protonated, PN decomposes into either nitrate or reactive intermediates capable of mediating tissue damage by oxidation of protein, lipid, and nucleic acid. We recently have identified porphyrin derivatives capable of catalyzing an increase in nitrate formation with a concomitant decrease in the HO.-like and NO2.-like reactivity of PN. Here, we present evidence for the efficacy of these PN decomposition catalysts both in vitro and in vivo. Cells in culture were protected from exogenously added PN by the catalyst 5,10,15,20-tetrakis(2,4, 6-trimethyl-3,5-disulfonatophenyl)porphyrinato iron (III), whereas free iron and the structurally related compound without iron 5,10,15, 20-tetrakis(2,4,6-trimethyl-3,5-disulfonatophenyl)porphyrin did not protect. Cytoprotection correlated well with a reduction in the nitrotyrosine content of released cytosolic proteins, a biochemical marker for PN formation. Carrageenan-induced paw edema is a model of acute inflammation in which PN may play a major role. When tested in this system, both 5,10,15,20-tetrakis(2,4,6-trimethyl-3, 5-disulfonatophenyl)porphyrinato iron (III) and 5,10,15, 20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) caused a dose-dependent reduction in swelling and lactate dehydrogenase release as well as a detectable shift to nitrate formation in paw tissue. In addition, the catalysts did not elevate mean arterial pressure, suggesting a lack of interaction with NO. Taken together, our data provide compelling evidence supporting the therapeutic value of manipulating PN pharmacologically. Thus, PN decomposition catalysts may represent a unique class of anti-inflammatory agents.

Animals↗