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1.
Pseudomonas aeruginosa samples were studied using Mössbauer spectroscopy and electron paramagnetic resonance (EPR). Samples included whole cells, membranes, and soluble fractions from cells which had been grown with57ferric chloride,57ferric citrate or incubated with57ferripyoverdine. These experiments show for the first time thatP. aeruginosa can accumulate iron in a bacterioferritin when grown under conditions of iron limitation and incubated with its cognate ferrisiderophore, ferripyoverdine. Soluble fraction fromP. aeruginosa cells which were grown iron starved and incubated with57ferripyoverdine for 120 min showed the presence of both a ferric and ferrous complex whose Mössbauer spectra matched that of bacterioferritin extracted fromAzotobacter vinelandii and whose EPR spectra showed a characteristic ferritin-like resonance. A second soluble fraction sample from cells which had been grown with57ferric citrate also showed the presence of a species with the same EPR and Mössbauer parameters. In addition Western blotting confirmed the presence of bacterioferritin in the soluble fraction of the cells which had been incubated with ferripyoverdine.  相似文献   

2.
The iron(II) clathrochelates with apical adamantyl substituents were synthesized by the direct template reaction on a metal ion matrix. The nucleophilic substitutions of reactive hexachloride precursors with adamantylthiolate anion afforded hexa- and octaadamantyl cage iron(II) complexes. Clathrochelates obtained have been characterized using elemental analysis, MALDI-TOF mass, IR, UV-Vis, 57Fe Mössbauer and 1H, 13C NMR spectroscopies, and X-ray crystallography. Configurations intermediate between trigonal prismatic and trigonal antiprismatic have been deduced for the low-spin iron(II) ion coordination polyhedra of all clathrochelates obtained using 57Fe Mössbauer parameters and confirmed by X-ray crystallography data. Two apical and up to six ribbed adamantyl substituents allow one to change the physical properties of clathrochelates synthesized in wide range. In particular, these substituents form second (hydrophobic) shell that opens up the possibility to membrane and cellular transport of the cage complexes.  相似文献   

3.
Reaction in air of iron(III) salts with tripodal ligands formed from the condensation of tris-(2-aminoethyl)amine (tren) with three equivalents of 2-pyridinecarboxaldehyde (py) or 1-methyl-2-imidazolecarboxaldehyde (NCH3Im) yielded exclusively the iron(II) complexes, [Fetren(py)3]X2 (X=ClO4 − or PF6 −) or [Fetren(NCH3Im)3](ClO4)2. The complexes were characterized by EA, IR, UV, Mössbauer, and mass spectroscopy. The structure of [Fetren(py)3](ClO4)2 was determined at 100 and 290 K. The structures are essentially the same and feature an octahedral iron with facial coordination of pyridine and imine nitrogen atoms with average bond distances of 1.9747 and 1.9523 Å, respectively, at 290 K. The short Fe-N bond distances and lack of variation with temperature support a low spin, 1A, assignment for the iron atom. The center nitrogen atom of the tren is essentially planar and is outside of bonding interaction with the iron, 3.45 Å. The low spin assignment is supported by Mössbauer spectroscopy, which reveals the presence of two low spin forms that are not in thermal equilibrium. In contrast, the Mössbauer spectrum of [Fetren(NCH3Im)3](ClO4)2 reveals the presence of both high spin, 5T, and low spin, 1A, forms at room temperature, which on cooling to 77 K simplify to the low spin form.  相似文献   

4.
The interaction of the antitumor agent daunomycin (DN) with ferric iron has been analysed by M?ssbauer spectroscopy, EPR, extended X-ray absorption fine structure (EXAFS), and magnetic susceptibility measurements. In contrast to literature data, at millimolar iron and anthracycline concentrations no solitary Fe(DN)3 complexes are formed in appreciable amounts. The M?ssbauer spectroscopic analysis revealed severe dependencies on temperature, on the preparation procedure, the time allowed for equilibration, and on the metal/ligand ratio. The M?ssbauer spectra exhibit two components: a broad magnetic sextet and a quadrupole doublet at an Fe/DN molar ratio of 1:3 and exclusively a doublet at a molar ratio of 1:20, indicating an equilibrium of these two spectral components. The EPR spectra are dominated by a signal at g(eff) = 2. Double integration of the EPR signals enabled the determination of their spin density and a correlation between EPR and M?ssbauer spectra. The M?ssbauer sextet species is EPR invisible and corresponds to magnetically ordered polynuclear aggregates with high magnetic anisotropy. EXAFS and susceptibility measurements provide additional evidence for the formation of polynuclear aggregates of ferric daunomycin. The quadrupole doublet species in the M?ssbauer spectra correlates with the g = 2 signal in EPR. This species is also related to a magnetically ordered system, exhibiting, however, superparamagnetic behavior due to less magnetic anisotropy. Since daunomycin forms dimers in aqueous solution at millimolar concentrations, we conclude that the cooperative phenomena observed in EPR and M?ssbauer spectra are a consequence of its stacking effects.  相似文献   

5.
Summary We have analyzed ferrioxamine-E-mediated iron uptake and metabolization inErwinia herbicola K4 (Pantoea agglomerans) by means of in vivo Mössbauer spectroscopy and radioactive labeling techniques. A comparison of cell spectra with the spectrum of ferrioxamine clearly demonstrates that ferrioxamine E is not accumulated in the cell, indicating a fast metal transfer. Only two major components of iron metabolism can be detected, a ferric and a ferrous species. At 30 min after uptake, 86% of the internalized metal corresponded to a ferrous ion compound and 14% to a ferric iron species. Metal transfer apparently involves a reductive process. With progressing growth, the oxidized species of the two major proteins becomes dominant. The two iron metabolites closely resemble species previously isolated fromEscherichia coli. These components of iron metabolism differ from bacterio-ferritin, cytochromes and most iron-sulfur proteins. All other iron-containing cellular components are at least one order of magnitude lower in concentration. We suggest that the ferrous and ferric iron species correspond to two different oxidation states of a low-molecular mass protein.  相似文献   

6.
Transport and metabolization of iron bound to the fungal siderophore rhizoferrin was analyzed by transport kinetics, Mössbauer and EPR spectroscopy. Saturation kinetics (v max=24.4 pmol/(mg min), K m=64.4M) and energy dependence excluded diffusion and provided evidence for a rhizoferrin transport system in M. smegmatis. Based on the spectroscopic techniques indications for intracellular presence of the ferric rhizoferrin complex were found. This feature could be of practical importance in the search of novel drugs for the treatment of mycobacterial infections. EPR and Mössbauer spectroscopy revealed different ferritin mineral cores depending on the siderophore iron source. This finding was interpreted in terms of different protein shells, i.e. two types of ferritins.  相似文献   

7.
Single-crystal X-ray structure of an iron(III) complex of 2-acetyl-1,3-indandione is resolved which reveals that a racemic mixture, composed of Δ-fac and Λ-fac stereoisomers, is formed. Both species have octahedral geometry, but slightly distinguishable. Detailed Mössbauer data indicate a high-spin electronic structure of the Fe(III) centres Fe1 and Fe2 with spin-spin magnetic relaxation process. Two different approaches for computer processing of the experimental Mössbauer spectra are considered.  相似文献   

8.
Summary Preliminary results of the Mössbauer effect study of human adult oxyhemoglobin in erythrocytes exposed to gamma-irradiation with doses of 100, 300 and 600 kGy are presented. Mössbauer spectra measured at 87 K have been analyzed in two ways. At first, to fit these spectra we used the four components oxyhemoglobin, deoxyhemoglobin, hemochromes and nonheme Fe(III) compound which had been obtained earlier from Mössbauer spectra of X-irradiated oxyhemoglobin by Chevalier et al. (1983). However, this approximation was not satisfactory. Then a new model of spectral fitting with five components was used. These were oxyhemoglobin, deoxyhemoglobin and components marked1, 2 and3. Using Mössbauer hyperfine parameters of each component the valence/spin states of iron ions were determined and possible complexes were considered. The most probable compounds for components1, 2 and3 were hematin and/orµ-oxodimers, methemoglobin hydroxide and/or hemichromes, and the high spin Fe(III) complex, respectively. Changes of the relative areas of Mössbauer subspectra of all components (its content in samples) versus doses were evaluated and the presence of the high and low spin aquomethemoglobin was indicated.  相似文献   

9.
The N-alkylation of iron(III) complexes of the tripodal imidazolate complexes derived from the Schiff base condensation of tris(2-aminoethyl)amine (tren) with three molar equivalents of 2-imidazolecarboxaldehyde (2ImH), 4-imidazolecarboxaldehyde (4ImH) or 4-methyl-5-imidazolecarboxaldehyde (5-Me4ImH) was investigated. While each complex possesses three nucleophilic imidazolate nitrogen atoms, only the complex derived from 2-imidazolecarboxaldehyde, Fetren(2Im)3, was completely alkylated under the ambient conditions used in this work. Using methyl iodide as the alkylating agent, a correlation between spin state of the product and degree of methylation was observed. Low spin iron complexes were more nucleophilic than high spin systems. The structure reactivity relationship was exploited in the reaction of Fetren(2Im)3 with methyl iodide and allyl iodide to give [Fetren(N-Me2Im)3]2+ and [Fetren(N-allyl2Im)3]2+. The products are iron(II) due to reduction of the iron(III) by iodide ion which builds up in the reaction mixture as the alkylation reaction proceeds. These complexes were characterized by a number of methods including EA, IR, ES-MS, Mössbauer spectroscopy, magnetic susceptibility and X-ray diffraction.  相似文献   

10.
In this work, we present the synthesis and characterization of three mononuclear iron(III) complexes: dichloro[N-propanamide-N,N-bis-(2-pyridylmethyl)amine]iron(III) perchlorate (1), trichloro[N-methylpropanoate-N,N-bis-(2-pyridylmethyl)amine]iron(III) (2) and trichloro[bis-(2-pyridylmethyl)amine]iron(III) (3). The complexes were characterized by cyclic voltammetry, conductivimetry, elemental analyses, and by electronic, infrared and Mössbauer spectroscopies. Complex 1 was also characterized by X-ray structural analysis, which showed an iron center coordinated to one amide, one tertiary amine, two pyridine groups and two chloride ions. While for 1 the X-ray molecular structure and the infrared spectrum confirm the coordination of the amide group by the oxygen atom, the infrared spectrum of 2 indicates that the ester group present in the ligand is not coordinated, resulting in a N3Cl3 donor set, similar to the one present in 3. However, in 3 there is a secondary amine while in 2 a tertiary amine exists. These structural differences result in distinguishable variations in the Lewis acidity of the iron center, which could be evaluated by the analysis of the redox potential of the complexes, as well as by Mössbauer parameters. Thus, the Lewis acidity decreases in the following order: 1 > 2 > 3. It is important to notice that 1 has the amide group coordinated to the iron center, a feature present in metalloenzymes as lipoxygenase and isopenicillin N synthase, and in a small number of mononuclear iron(III) complexes.  相似文献   

11.
Protocatechuate 3,4-dioxygenase (EC 1.13.11.3) from Pseudomonas aeruginosa has been investigated by EPR and M?ssbauer spectroscopy. Low temperature M?ssbauer data on the native enzyme (Fe3+, S = 5/2) yields a hyperfine field Hsat=-525 kG at the nucleus. This observation is inconsistent with earlier suggestions, based on EPR data of a rubredoxin-like ligand environment around the iron, i.e. a tetrahedral sulfur coordination. Likewise, the dithionite-reduced enzyme has M?ssbauer parameters unlike those of reduced rubredoxin. We conclude that the iron atoms are in a previously unrecognized environment. The ternary complex of the enzyme with 3,4-dihydroxyphenylpropionate and O2 yields EPR signals at g = 6.7 and g = 5.3; these signals result from an excited state Kramers doublet. The kinetics of the disappearance of these signals parallels product formation and the decay of the ternary complex as observed in the optical spectrum. The M?ssbauer and EPR data on the ternary complex establish the iron atoms to be a high-spin ferric state characterized by a large and negative zero-field splitting, D = approximately -2 cm-1.  相似文献   

12.
The direct template condensation of diacetylmonooxime hydrazone with the 1,4-pentadienylboronates as Lewis acids on an iron(II) ion matrix led to the 1,4-pentadienylboron-capped semiclathrochelate iron(II) oximehydrazonates. The H+-ion-catalyzed macrocyclization of these precursors with an excess of triethyl orthoformate resulted in macrobicyclic complexes with a single apical 1,4-pentadienyl substituent. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV-Vis, 1H, 11B{1H} and 13C{1H} NMR, 57Fe Mössbauer spectroscopies, and X-ray crystallography. The X-ray diffraction and NMR data for complexes obtained showed the syn,syn,syn-orientation of all ethoxy substituents in 1,3,5-triazacyclohexane capping fragment in relation to a clathrochelate framework.  相似文献   

13.
The static magnetic susceptibilities of different ferric high spin and low spin compounds of myoglobin (Mb(H2O), Mb(H2O) frozen under high pressure, MbF, MbCN) were measured in the temperature region between 4.2 K and 130 K. Mössbauer absorption experiments on Mb(H2O) and MbF were perormed at different temperatures between 4.2 K and 180 K and in small magnetizing fields H1 kOe. The evaluation of our experimental data was performed with a Hamiltonian describing the 3d 5-configuration of the ferric iron by taking into account the Coulomb repulsion of the five electrons within the 3d-shell, the crystal electric field of -symmetry, and the spin-orbit coupling. The Hamiltonian contains the splitting energies of the five antibonding d-orbitals (d xy , d xz , d yz , d x 2y 2, d z 2) as parameters. The values of these energies were obtained by a least squares fitting procedure using our magnetic susceptibility data together with the g-factors taken from the literature. In the case of MbF the energy difference between the two lowest Kramers doublets was also determined from present Mössbauer data. The results of the susceptibility and the Mössbauer data are in good agreement.The splitting energies of the 3d-orbitals can be correlated to the distances between the iron and its nearest neighbours. The different positions of the iron in the compounds investigated are discussed.  相似文献   

14.
Summary The calculation of the magnetic susceptibility from a published term scheme for the ferrous iron in deoxygenated human haemoglobin is discussed and a procedure for the simultaneous least squares fit of susceptibility and Mössbauer data is presented. The application of this procedure to the appropriate measurements on human haemoglobin leads to a rearrangement of the low lying electronic levels of the iron. The term schemes received as results of two different sets of susceptibility data used in combination with one set of Mössbauer data overlap with their error bars. The obtained level scheme of the Fe is correlated with the distance of the iron atom from the haem plane and the distance Fe-HIS F8, and some biological implications of these correlations are discussed.  相似文献   

15.
Recoil-free measurements were carried out on a 2 Fe-ferredoxin, which was isolated and purified from an extreme halophile, Halobacterium of the Dead Sea. The spectrum of this ferredoxin in the oxidized state at 82 K is a superposition of two quadrupole doublets, representing two non-equivalent Fe3+ sites of equal intensity. The spectrum of the reduced ferredoxin is consistent with the presence of two pure classes of iron atoms, ferric (lower isomer shift) and ferrous (higher isomer shift). Interpretations of the recoil-free spectra are discussed. Mössbauer measurements were also carried out on frozen whole bacterial cells and the resulting spectrum was found to be quite different from that observed in the isolated ferredoxin. Tentative conclusions are reached concerning the localization of this ferredoxin in the cytosol of the Halobacteria.The EPR spectrum of the reduced ferredoxin obtained at 24 K exhibits rhombic symmetry with the following g values: 1.894, 1.984 and 2.07. These values are similar to those obtained with 2 Fe-ferredoxins of the plant type, except that the g y and g z values are somewhat higher. Both from the EPR and Mössbauer data, it is deduced that the spin relaxation times in reduced halophilic ferredoxins are faster than in the reduced plant ferredoxins.  相似文献   

16.
Siderocalin (also lipocalin 2, NGAL or 24p3) binds iron as complexes with specific siderophores, which are low molecular weight, ferric ion-specific chelators. In innate immunity, siderocalin slows the growth of infecting bacteria by sequestering bacterial ferric siderophores. Siderocalin also binds simple catechols, which can serve as siderophores in the damaged urinary tract. Siderocalin has also been proposed to alter cellular iron trafficking, for instance, driving apoptosis through iron efflux via BOCT. An endogenous siderophore composed of gentisic acid (2,5-dihydroxybenzoic acid) substituents was proposed to mediate cellular efflux. However, binding studies reported herein contradict the proposal that gentisic acid forms high-affinity ternary complexes with siderocalin and iron, or that gentisic acid can serve as an endogenous siderophore at neutral pH. We also demonstrate that siderocalin does not induce cellular iron efflux or stimulate apoptosis, questioning the role siderocalin plays in modulating iron metabolism.  相似文献   

17.
Background: Mössbauer and magnetization measurements, singly or in combination, extract detailed information on the microscopic or internal magnetism of iron-based materials and their macroscopic or bulk magnetization. The combination of the two techniques affords a powerful investigatory probe into spin relaxation processes of nanosize magnetic systems. The ferritin core constitutes a paradigm of such nano-magnetic system where Mössbauer and magnetization studies have been broadly combined in order to elucidate its composition, the initial steps of iron nucleation and biomineralization, particle growth and core-size distribution. In vivo produced and in vitro reconstituted wild-type and variant ferritins have been extensively studied in order to elucidate structure/function correlations and ferritin’s role in iron overloading or neurodegenerative disorders.Scope of Review: Studies on the initial stages of iron biomineralization, biomimetic synthetic analogues and ferrous ion retention within the ferritin core are presented. The dynamical magnetic properties of ferritin by Mössbauer and magnetization measurements are critically reviewed. The focus is on experiments that reveal the internal magnetic structure of the ferritin core. Novel magnetic measurements on individual ferritin molecules via AFM and nanoSQUID investigations are also mentioned. Major Conclusions: A complex two-phase spin system is revealed due to finite-size effects and non-compensated spins at the surface of the anti-ferromagnetic ferritin core. Below the blocking temperature surface spins participate in relaxation processes much faster than those associated with collective magnetic excitations of interior spins. General Significance: The studies reviewed contribute uniquely to the elucidation of the spin-structure and spin-dynamics of anti-ferromagnetic nanolattices and their possible applications to nano/bio-technology.  相似文献   

18.
Four new triphenyltin(IV) complexes of composition Ph3SnLH (where LH = 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoate) (1-4) were synthesized and characterized by spectroscopic (1H, 13C and 119Sn NMR, IR, 119Sn Mössbauer) techniques in combination with elemental analysis. The 119Sn NMR spectroscopic data indicate a tetrahedral coordination geometry in non-coordinating solvents. The crystal structures of three complexes, Ph3SnL1H (1), Ph3SnL3H (3), Ph3SnL4H (4), were determined. All display an essentially tetrahedral geometry with angles ranging from 93.50(8) to 124.5(2)°; 119Sn Mössbauer spectral data support this assignment. The cytotoxicity studies were performed with complexes 1-4, along with a previously reported complex (5) in vitro across a panel of human tumor cell lines viz., A498, EVSA-T, H226, IGROV, M19 MEL, MCF-7 and WIDR. The screening results were compared with the results from other related triphenyltin(IV) complexes (6-7) and tributyltin(IV) complexes (8-11) having 2-/4-[(E)-2-(aryl)-1-diazenyl]benzoates framework. In general, the complexes exhibit stronger cytotoxic activity. The results obtained for 1-3 are also comparable to those of its o-analogs i.e. 4-7, except 5, but the advantage is the former set of complexes demonstrated two folds more cytotoxic activity for the cell line MCF-7 with ID50 values in the range 41-53 ng/ml. Undoubtedly, the cytotoxic results of complexes 1-3 are far superior to CDDP, 5-FU and ETO, and related tributyltin(IV) complexes 8-11. The quantitative structure-activity relationship (QSAR) studies for the cytotoxicity of triphenyltin(IV) complexes 1-7 and tributyltin(IV) complexes 8-11 is also discussed against a panel of human tumor cell lines.  相似文献   

19.
Mössbauer spectra obtained from the terminal dioxygenase protein of the benzene dioxygenase system from Pseudomonas putida show that it contains [2Fe--2S] centres similar to those of the two-iron plant-type ferredoxins. In the oxidized form the two iron atoms within the centre are high-spin ferric but with considerable inequivalence. In the reduced form the centre contains one extra electron, and this is localized on one of the iron atoms, which becomes high-spin ferrous.  相似文献   

20.
Alfsen  A.  Bade  D.  van Bürck  U.  Eicher  H.  Formanek  S.  Kalvius  G. M.  Lavialle  F.  Mayer  A.  Parak  F.  Tejada  J.  Thomanek  U. F. 《European biophysics journal : EBJ》1977,3(3-4):229-238
Haemoglobin Haptoglobin complexes formed when [Hp+]/[Hb] = 1/1 and [Hp]/[Hb] = 2/1 were investigated by 57Fe Mössbauer spectroscopy. Both samples gave a spectrum consisting of a single quadrupole doublet. The temperature dependence of the quadrupole splitting was also identical for both samples. This proves that in both samples the nearest neighbour environment of the iron atom must be the same. A comparison with earlier investigations on myoglobin and haemoglobin indicates that the electronic structure of iron in the HbHp-complexes is similar to that in myoglobin.This work was supported by the Deutsche Forschungsgemeinschaft...  相似文献   

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