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At least 19 recordsLinked to original sources
PubMed1991

An investigation of Chromatium vinosum high-potential iron-sulfur protein by EPR and Mossbauer spectroscopy; evidence for a freezing-induced dimerization in NaCl solutions.

The high-potential iron-sulfur protein (HiPIP) from Chromatium vinosum contains a cubane prosthetic group that shuttles between the [4Fe-4S]3+,2+ states. We find that the EPR spectra from this protein can be explained as a sum of two components, a major one with g = 2.02; 2.04; 2.12, and a minor one with g = 2.04; 2.07; approximately 2.13. In the presence of 0.1-2.0 M NaCl, freezing induces polymerization of the protein (presumably dimers), which is detected as intercluster spin-spin interaction in the EPR. The observed spin-spin interactions are interpreted as being due to two very similar dimeric structures in an approx. 1:2 ratio. Computer simulation of the X- and Q-band EPR spectra shows that the z-components of the g-tensors in each dimer pair must be co-linear, with center-to-center distances between the clusters of approximately 13 A and approximately 16 A. Inspection of possible dimeric structures of C. vinosum HiPIP by standard molecular graphics procedures revealed that the Fe/S cluster is exposed toward a flattened surface and is accessible to solvent. Moreover, the Fe/S clusters in two HiPIP molecules can easily achieve a center-to-center distance of approximately 14 A when approaching along a common 3-fold axis that extends through the S4 sulfur atom of the cubane; the z-component of the EPR g-tensor is co-linear with this symmetry axis.

Chromatium↗
PubMedDate not supplied

[Possible effects of the influence of dynamic disorder of biological systems on characteristics of intramolecular mobility, determined by Mossbauer spectroscopy].

A model for describing dynamic properties of proteins is proposed. The model involves the distribution over amplitudes and correlation times of intramolecular dynamics. It has been shown that distribution parameters and its temperature dependence have a great influence upon the values of experimental dynamic characteristics. Besides the discrepancy between the real and experimental temperature, dependence of characteristics on intramolecular dynamics can be observed.

Models, Chemical↗
PubMed1989

[Application of Mossbauer spectroscopy to the study of hemoglobinopathies. Preliminary experience].

37Fe Moessbauer spectroscopy has been applied to the study of iron deposits in patients with altered iron metabolism. Haematological parameters were also studied in order to analyse their relationship with Moessbauer results. Within the aim of this research, 12 samples of packed red blood cells were analysed: 6 with beta-thalassaemia major, 2 with S-beta-thalassaemia, 1 with sickle cell anaemia and 3 from normal subjects used as control for Moessbauer spectroscopy. Moessbauer spectra of 6 red blood cells samples showed that besides the two components, i.e., oxy and deoxy haemoglobin present in samples of normal subjects, appears a third component with Moessbauer parameters corresponding to ferritin-like iron. Correlation of % transferrin saturation (TS %) with ferritin-like iron (r = 0.90, p less than 0.05) as well as between TS % and the ratio ferritin-like iron/Hb iron (r = 0.91, p less than 0.05) was found. A tendency to correlation of serum ferritin (SF) with ferritin-like iron (r = 0.90, p less than 0.05) as well as between TS % and the ratio ferritin-like iron/Hb iron (r = 0.91, p less than 0.05) was found. A tendency to correlation of SF with ferritin-like iron (r = 0.78) and with the ratio ferritin-like iron/Hb iron, was also observed. It can be concluded that Moessbauer spectroscopy could be a useful technique in the study of this kind of pathology.

Adolescent↗
PubMed1990

Glutaraldehyde effect on hemoglobin: evidence for an ion environment modification based on electron paramagnetic resonance and Mossbauer spectroscopies.

Glutaraldehyde is a widely used reagent for hemoglobin cross-linking in blood substitutes research. However, hemoglobin polymerization by glutaraldehyde involves modifications of its functional properties, such as oxygen affinity, redox potentials, and autoxidation kinetics. The aim of this article is to investigate, by electron paramagnetic resonance and Mossbauer spectroscopies, the changes that occur in the iron environment after glutaraldehyde cross-linking. Spectrometric studies were performed with native hemoglobin and hemoglobin cross-linked as soluble and insoluble polymers. Spectrometry data comparison with glutaraldehyde-modified hemoglobin functional properties allows to interpret from a structural point of view that glutaraldehyde action occurs as a decrease of the O--N(F8His) distance, an increase of the Fe--N(F8His) bond length, and the decrease of the distal-side steric hindrance.

Cross-Linking Reagents↗
PubMed1975

On the nature of the iron sulfur cluster in a deuterated algal ferredoxin.

A protonated and a completely deuterated two-iron algal ferredoxin from Synechococcus lividus have been studied by optical, electron paramagnetic resonance, electron-nuclear double resonance, proton magnetic resonance and Mossbauer spectroscopies; temperature dependent magnetic susceptibility measurements are reported as well. These studies have confirmed the electron localized model of the active center in the two-iron ferredoxins, as previously deduced from studies of spinach ferredoxin, have yielded much more precise spectroscopic parameters for this center, and have thus greatly increased the confidence in this model.

Binding Sites↗
PubMed1975

Mossbauer spectra of bicarbonate-free ferric-transferrin complex.

The bicarbonate-free ferric-transferrin complex was investigated by Mossbauer Spectroscopy under anaerobic conditions. No evidence of specific binding was found. The spectral results indicates that the apparent binding is due to the formation of antiferromagnetic ferric hydroxide polymers which are firmly attached to the transferrin molecule. Specific binding would only occur in the presence of bicarbonate or other low molecular weight chelators.

Animals↗
PubMed1992

[Investigation on the incidence of high altitude polycythemia and its hemoglobin characteristics in a Tibetan population].

The incidences of high altitude polycythemia (HAPC) and its hemoglobin characteristics in natives and immigrants at 2 different altitudes in the Tibet Autonomous Region were investigated. The results were as follows: 1) The incidences of HAPC among residents in Lhasa (3650 meters above sea level) and in Naqu-Ando district (4500-4800 meters above sea-level) were 2.39% and 12.95%, respectively. The incidence of HAPC increased with increasing altitude. The incidences in immigrants and in men were higher than those in natives and in women. 2) The MetHb concentration in RBC from patients with HAPC was 10.14%, distinctly higher than that in healthy adults (6.35%) in the same area. This may be one of the causes leading to oxygen carrying malfunction in the RBCs of HAPC patients. 3) The Mossbauer spectra of RBCs from patients with HAPC had a third component "c" in addition to the two normal components, oxy-Hb "a" and deoxy-Hb "b." The third component "c" may be adenatured Hb in the RBCs of the patients. The question of whether it is related to oxygen carrying power requires further study.

Adolescent↗
PubMed1989

Fe2+ binding to apo and holo mammalian ferritin.

The binding of Fe2+ to both apo and holo mammalian ferritin has been investigated under anaerobic conditions as a function of pH. In the pH range 6.0-7.5, 8.0 +/- 0.5 Fe2+ ions bind to each apoferritin molecule, but above pH 7.5, a pH-dependent Fe2+ binding profile is observed with up to 80 Fe2+ ions binding at pH 10.0. This Fe2+ binding is reversible and is accompanied by up to two H+ being released per Fe2+ bound at pH 10.0. The Fe2+ binding to apoferritin probably occurs in the 3-fold channels. A much larger and more complex pH-dependent Fe2+ binding stoichiometry was observed for holoferritin with up to 300 Fe2+ ions binding at pH 10.0. This pH-dependent Fe2+ binding was interpreted as Fe2+ interaction at the FeOOH mineral surface with displacement of H+ from -OH or phosphate surface groups by the incoming Fe2+ ions. Mossbauer spectroscopic measurements using 57Fe-labeled Fe2+ under anaerobic conditions showed that 57Fe2+ binding to holoferritin was accompanied by electron transfer to the core, yielding 57Fe3+, presumably bound to the mineral surface. Removal of added iron by Fe2+-specific chelating agents yielded 57Fe2+, demonstrating the reversibility of this electron-transfer process. The Fe2+ bound to apo- and holoferritin is readily converted to Fe3+ by exposure to O2 and strongly retained by the respective ferritin species.

Animals↗
PubMedDate not supplied

[Study of the dynamics of human serum albumin by coherent Rayleigh dispersion of Mossbauer radiation].

The measurements of angle dependencies of total and elastic Rayleigh scattering of Mossbauer radiation intensities have been performed for human serum albumin (HSA) with hydration degrees h = 0.13 and h = 0.4. The extended model was developed for calculating the inelastic intensity of Rayleigh scattering. Original data for HSA and published data on met-Mb were fitted within the frame of this model. The best agreement with experiment was obtained when two types of intraglobular motions were taken into account: individual motions of small side-chain groups and cooperative (mechanical) motions of segments (most probable alpha-helices). Long-range correlated motions are essential at low hydration degree. The possibilities of application of the coherent version of RSMS technique are described.

Humans↗
PubMed1991

Hemoglobin dynamics in rat erythrocytes investigated by Mössbauer spectroscopy.

Rats have been enriched in 57Fe and erythrocytes were isolated from the blood. Mössbauer absorption spectroscopy on the hemoglobin of these erythrocytes has shown rather similar dynamics as found earlier in crystals of myoglobin, in frozen solutions of human hemoglobin and in a number of other proteins. The results strongly indicate that the motion of the heme and presumably some part of the F-helix is mainly influenced by the average viscosity of the sample determined by a network of hydrogen bridges and other weak interactions. Extrapolations of Mössbauer results from protein crystals to proteins in their physiological surroundings seem to be suitable for heme proteins.

Animals↗
PubMed1992

Influence of protein dynamics on the metal-sites of ovotransferrin.

Using the perturbed angular correlations (PAC) technique, the formation of hafnium-ovotransferrin complexes has been studied. Two binding configurations at each of the two specific binding-sites of the protein have been observed. They are characterized by well-defined electric quadrupole frequencies. Information about the dynamics of the protein was derived from temperature dependent measurements of the relaxation constant. The well-resolved spectra taken with fast BaF2-detectors allow a precise determination of the relaxation behaviour of the protein. The results are compared with the predictions from a hydrodynamic model for the reorientation of macromolecules. Thus the hydrodynamic volume of ovotransferrin and its N-terminal half-molecule were determined. The ovotransferrin volume is in agreement with a value derived for human serum transferrin from small angle neutron scattering. From experiments with immobilized protein material there is evidence for internal protein dynamics which is probed by the Hf-ion bound to the specific metal-sites.

Animals↗
PubMed1990

A Mössbauer spectroscopy study of cellular acquisition of iron from pyoverdine by Pseudomonas aeruginosa.

Mössbauer spectroscopy was used to investigate the cellular acquisition of iron by Pseudomonas aeruginosa which had been incubated with ferripyoverdine for 20, 40, 60, 120 or 360 min. Studies revealed that no ferripyoverdine accumulated in the cells at any of these times and that the amounts and kinds of iron complexes produced by cellular metabolism vary with time. At 20 and 40 min a ferric species, with isomer shift delta = 0.38-0.42 mm/s and quadrupole splitting delta EQ = 0.94-0.92 mm/s, was the major iron metabolite comprising approximately 80% of the iron. At later times at least three other ferric species appeared with delta = 0.54----0.72, delta EQ = 0.84----1.07 mm/s. Ferrous species, delta = 1.43----1.77 mm/s and delta EQ = 2.69----1.82 mm/s, were also seen at times as early as 20 min and comprised as much as 17% of the total iron at 20 and 40 min. The parameters of all these species identify them as being six-coordinated high-spin complexes. In addition a low-spin species, delta = 0.19 mm/s delta EQ = 0.67----0.91 mm/s, never before reported in cells, appeared at 60, 120, and 360 min as one of the major iron metabolites (50% or more). All isomer shifts are measured with respect to natural iron.

Iron↗
PubMed1991

Transport and utilization of ferrioxamine-E-bound iron in Erwinia herbicola (Pantoea agglomerans).

We have analyzed ferrioxamine-E-mediated iron uptake and metabolization in Erwinia 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 from Escherichia 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.

Biological Transport↗
PubMed1991

Mössbauer effect study of gamma-irradiated human oxyhemoglobin.

Preliminary results of the Mössbauer effect study of human adult oxyhemoglobin in erythrocytes exposed to gamma-irradiation with doses of approximately 100, approximately 300 and approximately 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 non-heme 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 marked 1, 2 and 3. 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 components 1, 2 and 3 were hematin and/or mu-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.

Adult↗
PubMed1990

Effect of formate on Mössbauer parameters of the non-heme iron of PS II particles of cyanobacteria.

Mössbauer spectra were measured for PSII particles having an active water-splitting system. The particles were isolated from the thermophilic cyanobacterium Synechococcus elongatus enriched in 57Fe. The Mössbauer resonance absorption spectrum is a superposition of 3 doublets with the following quadrupole splitting and chemical shift: 1, delta = 0.40, delta = 0.85; II, delta = 1.35, delta = 2.35; III, delta = 0.25, delta = 1.65. The delta and delta values of doublets I, II, III are characteristic of proteins with iron-sulphur center, non-heme iron of the reaction center of higher plants and of the oxidized cytochrome b-559. Treatment with sodium formate to remove bicarbonate affects only the doublet of non-heme iron, causing its quadrupole splitting to reduce to 1.75 and the chemical shift to reduce to 0.90. After washing out the formate, the Mössbauer spectrum of non-heme iron is restored. The data suggest that bicarbonate is a ligand for the non-heme iron of the reaction center of cyanobacteria.

Bicarbonates↗
PubMed1992

Light-induced oxidation of iron atoms in a photosensitive nitrile hydratase.

The photoactivation process of a photosensitive nitrile hydratase (NHase) from Rhodococcus sp. N-771 has been investigated by 57Fe Mössbauer spectroscopy and magnetic susceptibility measurements in order to clarify the behavior of iron atoms in the enzyme. Mössbauer spectra of inactive NHase gave two symmetric-doublet components indicating the presence of two iron species, while that of the active NHase gave a single symmetric doublet indicating the presence of a single iron species. Magnetic susceptibility measurements of the inactive and active HNase both showed small effective magnetic moments. These results led us to conclude that one of the two iron atoms incorporated in the NHase is oxidized during photoactivation, namely from a low spin ferrous to a low spin ferric state. This is the first observation of an intramolecular photooxidation phenomena involving iron in a single protein molecule.

Enzyme Activation↗
PubMed1991

Mössbauer spectroscopic studies of iron in Pseudomonas aeruginosa.

The present Mössbauer spectroscopic studies of isolated bacterioferritin and whole cells of Pseudomonas aeruginosa have shown that the iron core of bacterioferritin is not altered on isolation. These studies have also shown that the bacterioferritin core is typically 85% oxidized within the cell and may contain a significant proportion of its iron as small clusters during the early stage of the stationary phase of cell growth.

Bacterial Proteins↗