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PubMed2001

Evaluating the basidiomycetes Poria medula-panis and Wolfiporia cocos for xylanase production.

Xylanase, oxidative enzymes and iron-binding compounds were detected in the filtrates of Wolfiporia cocos and Poria medula-panis grown in wheat bran liquid medium. Xylanase and iron-binding compounds were produced at high levels by the brown-rot fungus (BR) W. cocos and at low levels by the white-rot fungus (WR) P. medula-panis. Phenoloxidase was produced only by P. medula-panis. Polyacrylamide gel electrophoresis (PAGE) (SDS-PAGE) showed a wide variety of bands for extracellular proteins produced by W.cocos, with low molecular weight (<30 kDa) and minor bands with molecular weight above 45 kDa. Two bands with xylanase activity derived from W. cocos extracts were detected in the gels, whereas many different bands with xylanase activity were found in the extracts from P. medula-panis. P. medula-panis is a selective lignin degrader, whereas W. cocos preferentially removes cellulose from wood.

Journal Article↗
PubMed1997

Acute iron intoxication: significant differences between sexes.

Iron, one of the common medications in use among children and adults, is the leading cause of pediatric unintentional ingestion fatalities and is not an uncommon poisoning among adults. Accidental ingestion is common because iron-containing compounds are readily available, brightly colored, often sugar coated, and frequently considered harmless vitamins. There are no data on differences between sexes with regard to iron intoxication, and the management of iron overdose is the same for females and males. After oral administration by gavage of the LD50 of iron to Wistar rats, the pharmacokinetics of iron, baseline and peak serum iron levels, and mortality rates were compared between sexes. Prepubertal females died significantly more than males (p < 0.01), pubertal females died significantly earlier than males (p < 0.04), and the same was true among adult rats (p = 0.02). Baseline serum iron levels were not significantly different between prepubertal female and male rats, but female pubertal rats had significantly higher baseline iron levels than males (p = 0.006). After iron administration, females had significantly higher peak serum iron concentrations (p < 0.03). Mechanisms of iron absorption are still not completely known and, probably, there are differences in iron absorption between sexes, which may account for the differences in serum iron levels and mortality rates. While the therapeutic approach in cases of intoxication is individual, iron intoxication, as may be true for other poisonings also, treatments administered to females may need to be different from that given to males.

Administration, Oral↗
PubMed1975

Bioavailability of trivalent iron in oral iron preparations. Therapeutic efficacy and iron absorption from simple ferric compounds and high- or low-molecular weight ferric hydroxide-carbohydrate complexes.

All available results from critical hemoglobin regeneration tests, postabsorption serum iron concentration studies, 59Fe erythrocyte incorporation and 59Fe whole-body retention measurements demonstrate that humans do absorb ferrous iron between 4 and 10 times (in the average about 5 times) better than ferric iron from therapeutic oral 50--250 mg iron doses. Ferrous sulfate iron is 3 to 4 times better available than the iron from ferric ammonium citrate or sulfate. Whereas 100 mg of ferrous sulfate iron/day are sufficient for an optimal oral compensation iron therapy and to produce initial hemoglobin regeneration rates of about 0.26 g/100 ml/day, 400 to 1000 mg of ferric iron/day are necessary for the same therapeutic effect because of the poor bioavailability of ferric iron. The ratio of the dose-absorption relationships for ferric and ferrous 59Fe was shown to decrease from 0.43 for a diagnostic 0.56 mg Fe dose to 0.21 for the therapeutic 50 mg Fe dose in subjects with normal iron stores. Absorption ratios of 0.65 for the 0.56 mg Fe dose and 0.26 for the 50 mg Fe dose were measured in subjects with depleted iron stores. At all dose levels the superior bioavailability of ferrous iron was demonstrable. A high-molecular weight ferric hydroxide-carbohydrate complex (MW similar to 30 000) was palatable but so poorly absorbed that is was practically without effect on hemoglobin regeneration even at a daily 300 mg Fe dose. Following several warnings such a useless commerecial oral iron preparation was finally withdrawn from the market. The iron from any high-molecular weight carbohydrate complex of ferric hydroxide has to be suspected to be poorly absorbed and therefore therapeutical useless, unless the opposite has been demonstrated with a reliable bioassay (59Fe absorption whole-body retention and hemoglobin regeneration test). A low-molecular weight so-called ferric hydroxide-fructose complex was shown to contain iron of more or less the same poor bioavailability as contained in ferric chloride since the iron from ferrous sulfate was about 5 times better absorable. The good absorption of ferrous sulfate iron was not further augmented by even very large oral doses of fructose since this carbohydrate did not improve the ferrous iron absorption at a fructose: Fe molar ratio of 106:1. Trivalent iron in simple compounds like ferric ammonium citrate or in low- and high-molecular weight carbohydrate complexes of ferric hydroxide is so poorly available for intestinal iron absorption in man that it cannot be used for a fast and reliable oral iron therapy with reasonably low doses as it can be easily practised with quick-lease preparations of ferrous sulfate at a 100 mg Fe2

Anemia, Hypochromic↗
PubMed1980

On some derivatives of ferrocene, novel acetylcholinesterase inhibitors.

Eight novel methylcarbamates, derivates of ferrocenylketoximes and aldoximes, and ferrocenyl-p-hydroxyphenylaldimine were prepared. They are the first carbamates in the field of ferrocene derivatives. Their anticholinesterase activity was tested and found to fall in the range of 10(-4) through 10(-6) M (I50). The correlation between the activity of the compounds and the kind of substituents grafted on the methylene carbon atom is discussed.

Acetylcholinesterase↗
PubMed2006

High-valent nonheme iron-oxo species in biomimetic oxidations.

High valent iron-oxo species are often invoked as the key oxidizing agents in the catalytic cycles of oxygen activating nonheme iron enzymes, and three of these intermediates have in fact been characterized. To gain further insight into such species, a number of biomimetic complexes have been designed and investigated as functional models for these enzymes. Progress since 2000 is summarized in this review. Many of the model complexes discussed in this review carry out oxidative transformations of relevance to the enzymatic reactions; however, the participation of a high-valent iron-oxo species (Fe(IV)O or Fe(V)O) can only be inferred. Arguments in support of a metal-based oxidant (rather than an oxygen radical species) usually hinge on the high conversion for the transformation and the nature of the reaction products, as well as the incorporation of label into these products from H(2)(18)O or related species. Within this time period, the first bona fide nonheme Fe(IV)O complexes have been generated and identified spectroscopically, three of which are crystallographically characterized. Taken together, these studies emphasize the important role the supporting polydentate ligand plays in eliciting the desired high-valent iron-oxo chemistry.

Biomimetic Materials↗
PubMed2005

Single-ion and molecular contributions to the zero-field splitting in an iron(III)-oxo dimer studied by single crystal W-band EPR.

Detailed knowledge of the type and strength of pair interactions between high-spin metal ions is paramount to the understanding and design of molecular magnetic materials. In this work, the anisotropic magnetic interactions in a beta-diketonate-alkoxide iron(III) dimer compound, [Fe2(OCH3)2(dbm)4, Hdbm=dibenzoylmethane] (Fe2) have been investigated by single crystal electron paramagnetic resonance (EPR) in the W-band (at 95GHz). The diamagnetic substitution method was employed using the isomorphous gallium(III)-based compound doped with iron(III) to produce Ga-Fe dimers (GaFe). The single-ion zero-field splitting (ZFS) tensor could be separately determined in GaFe with the iron ion in a local environment quasi-identical to the one in Fe2. Its principal directions are found to point in arbitrary directions, uncorrelated with the Fe-O bonds. The Fe2 EPR spectra consist of transitions within the lowest multiplet states S=1,2,3, which were analyzed using the full spin Hamiltonian description of an exchange coupled pair of s=5/2 spins. The anisotropic spin-spin interaction tensor of Fe2 possesses a principal axis close to the Fe-Fe direction and was shown to arise both from through-space (dipolar) and through-bond (anisotropic exchange) contributions. The latter involves an rhombic component JE=(JX-JY)/2 approximately 0.093 cm-1 of magnitude comparable to the dipolar interaction, and even to the rhombic part of the single-ion ZFS (E=0.097 cm-1). Our results show that the anisotropic exchange, usually neglected for S-type ions, is significant for the anisotropic interactions in exchange-coupled iron(III) clusters, including the Fe4 and Fe8 families of single-molecule magnets and the antiferromagnetic iron wheels.

Journal Article↗
PubMed2002

Iron transport and signaling in Escherichia coli.

Bacteria solve the iron supply problem caused by the insolubility of Fe(3+) by synthesizing iron-complexing compounds, called siderophores, and by using iron sources of their hosts, such as heme and iron bound to transferrin and lactoferrin. Escherichia coli, as an example of Gram-negative bacteria, forms sophisticated Fe(3+)-siderophore and heme transport systems across the outer membrane. The crystal structures of three outer membrane transport proteins now allow insights into energy-coupled transport mechanisms. These involve large long-range structural transitions in the transport proteins in response to substrate binding, including substrate gating. Energy is provided by the proton motive force of the cytoplasmic membrane through the activity of a protein complex that is inserted in the cytoplasmic membrane and that contacts the outer membrane transporters. Certain transport proteins also function in siderophore-mediated signaling cascades that start at the cell surface and flow to the cytoplasm to initiate transcription of genes encoding proteins for transport and siderophore biosynthesis.

Anti-Bacterial Agents↗
PubMed2000

Oxidation of chlorophenols with hydrogen peroxide in the presence of goethite.

The use of goethite (alpha-FeOOH) and hydrogen peroxide was recently found that they could effectively oxidize organic compounds. The study was to investigate the effect of goethite particle size, goethite concentration, Fe2+ and Fe3+ on the 2-chlorophenol oxidation. Results indicated that 2-chlorophenol can be decomposed with hydrogen peroxide catalyzed by goethite and the oxidation rate increased with decreasing goethite particle size. 2-Chlorophenol degradation was almost retarded with 0.8 g/l of goethite because ferrous ions could not be produced at this condition. Addition of Fe2+ and Fe3+ can enhance the catalytic oxidation rate of 2-chlorophenol very efficiently. In conclusion, the main mechanism of goethite catalyzing hydrogen peroxide to oxidize 2-chlorophenol may be due to the catalysis of ferrous ions and goethite surface.

Chlorophenols↗
PubMed2004

A predictive pattern of computed barriers for C-h hydroxylation by compound I of cytochrome p450.

The communication presents DFT calculations of 10 different C-H hydroxylation barriers by the active species of the enzyme cytochrome P450. The work demonstrates the existence of an excellent barrier-bond energy correlation. The so-obtained equation of the straight line is demonstrated to be useful for predicting barriers of related C-H activation processes, as well as for assessing barrier heights within the protein environment. This facility is demonstrated be estimating the barrier of camphor hydroxylation by P450cam.

Alkanes↗
PubMed2005

Theoretical investigation of C--H hydroxylation by (N4Py)Fe(IV)=O(2+): an oxidant more powerful than P450?

DFT calculations of C-H hydroxylation by a synthetic nonheme oxoiron(IV) oxidant supported by a neutral pentadentate N5 ligand show that this reagent is intrinsically more reactive than compound I of P450. This nonheme iron oxidant is predicted to exhibit stereoselective reactions, strong solvent effect, and involve multistate reactivity with spin-state crossing.

Cytochrome P-450 Enzyme System↗
PubMed1985

Spectral and other physicochemical properties of submicron powders of hematite (alpha-Fe2O3), maghemite (gamma-Fe2O3), magnetite (Fe3O4), goethite (alpha-FeOOH), and lepidocrocite (gamma-FeOOH).

Spectral and other physicochemical properties were determined for a suite of submicron powders of hematite (alpha-Fe2O3), maghemite (gamma-Fe2O3), magnetite (Fe3O4), goethite (alpha-FeOOH), and lepidocrocite (gamma-FeOOH). The spectral reflectivity measurements were made between 0.35 and 2.20 micrograms over the temperature interval between about -110 degrees and 20 degrees C. Other physicochemical properties determined were mean particle diameter, particle shape, chemical composition, crystallographic phase, magnetic properties, and Mossbauer properties. Only the magnetite powders have significant departures from the stoichiometric phase; they are actually cation-deficient magnetites having down to about 18.0 wt % FeO as compared with 31.0 wt % FeO for stoichiometric magnetite. A structured absorption edge due to crystal field transitions and extending from weak absorption in the near-IR to intense absorption in the near-UV is characteristic of the ferric oxides and oxyhydroxides and is responsible for their intense color. Particularly for hematite, the number and position of the spectral features are consistent with significant splitting of the degenerate cubic levels by noncubic components of the crystal field. The position of the crystal-field band at lowest energy, assigned to the envelope of the components of the split cubic 4T1 level, is near 0.86, 0.91, 0.92, and 0.98 microgram at room temperature for hematite, goethite, maghemite, and lepidocrocite, respectively. Comparison with Mossbauer data suggests covalent character increases sequentially through the aforementioned series. The positions of the spectra features are relatively independent of temperature down to about -110 degrees C. The maximum shifts observed were on the order of about 0.02 microgram shortward for the ferric oxyhydroxides. Variations in the magnitude of the reflectivity of the hematite powders as a function of mean particle diameter are consistent with scattering theory. The absorption strength of the crystal-field bands increases with increasing mean particle diameter over the range 0.1-0.8 micrometer; visually this corresponds to a change in color from orange to deep purple. The position of the split cubic 4T1 band shifts longward by about 0.02 micrometer with decreasing mean particle diameter over the same range; this trend is consistent with wavelength-dependent scattering. The cation-deficient magnetite powders are very strong absorbers throughout the near-UV, visible and near-IR; their spectral properties are independent of temperature between about -110 and 20 degrees C.

Earth, Planet↗
PubMed2005

Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust.

The ubiquitous atmospheric dust on Mars is well mixed by periodic global dust storms, and such dust carries information about the environment in which it once formed and hence about the history of water on Mars. The Mars Exploration Rovers have permanent magnets to collect atmospheric dust for investigation by instruments on the rovers. Here we report results from Mössbauer spectroscopy and X-ray fluorescence of dust particles captured from the martian atmosphere by the magnets. The dust on the magnets contains magnetite and olivine; this indicates a basaltic origin of the dust and shows that magnetite, not maghemite, is the mineral mainly responsible for the magnetic properties of the dust. Furthermore, the dust on the magnets contains some ferric oxides, probably including nanocrystalline phases, so some alteration or oxidation of the basaltic dust seems to have occurred. The presence of olivine indicates that liquid water did not play a dominant role in the processes that formed the atmospheric dust.

Atmosphere↗