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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The magnetic field dependence of 1/T1 over the range 0.01 to 50 MHz proton Larmor frequency (NMRD profile) is reported for water protons in solutions of horse spleen apoferritin, and of ferritin reconstituted at both low and high iron levels. The apoferritin results are in every way typical of diamagnetic spherical proteins of their size (K. Hallenga and S. H. Koenig, Biochemistry 15, 4255 (1976)). Titration of up to 24 ferrous ions per protein molecule, with subsequent oxidation to ferric, shows a nonlinear saturating contribution to the NMRD profile which is interpreted as arising from a small number of ferric ions (six to eight) bound close to the outside of each ferritin molecule, and a comparable number of interior sites. The latter become multiply occupied as the core grows and do not contribute measurably to 1/T1 in this state. The former sites are never more than singly occupied, and their contribution to the solvent proton relaxation rates is independent of the loading of the core. Measurements of 1/T2 at 20 MHz are quite in accord with theoretical expectations for apoferritin and ferritin with up to 24 ferric ions per molecule. However, a marked increase in 1/T2 is observed at higher iron loadings that we are unable to account for within the framework of the theory of outer sphere relaxation, even when the effects arising from inhomogeneities in the local magnetic field are included. A sample of human spleen hemosiderin was found to have the same 1/T1 NMRD profile as a comparable sample of ferritin.
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PMID:Relaxometry of ferritin solutions and the influence of the Fe3+ core ions. 378 91

Single frog mesenteric capillaries have been perfused with Ringer solutions containing the neutral macromolecule Ficoll 70 at a concentration of 40 mg ml-1, while the tissues have been washed with Ringer solution containing no macromolecules but otherwise of similar composition. The effective osmotic pressures (sigma delta II) set up across the capillary wall by the Ficoll 70 were used to assess the wall's molecular selectivity. The hydraulic conductivities, Lp, of the capillary walls were also measured. In seven capillaries the addition of bovine serum albumin (BSA) to the perfusate at concentrations of 1 and 10 mg ml-1 increased sigma delta II from a mean value of 7.14 +/- 1.81 cm H2O to one of 18.71 +/- 2.33 cm H2O and at the same time halved Lp. In another eight capillaries, the addition of a form of cationised ferritin (CF) to the perfusate at a concentration of 1 mg ml-1 increased sigma delta II from a mean value of 5.69 +/- 0.87 cm H2O to one of 16.69 +/- 0.262 cm H2O and reduced Lp to between a third and a half of its original value. In a further seven capillaries, the addition of native ferritin at a concentration of 1 mg ml-1 to the perfusate had no effect on either sigma delta II or Lp. It is suggested that both CF and BSA increase the reflection coefficients of capillary walls to Ficoll 70 by binding to the surface coat of the endothelium. The results are discussed in terms of a development of the fiber matrix theory of Curry and Michel (1980).
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PMID:The effects of bovine serum albumin and a form of cationised ferritin upon the molecular selectivity of the walls of single frog capillaries. 387 88

When biological materials are infiltrated by a water-soluble melamine resin and hardened, they become as hard as glass. This is a prerequisite for extreme thin-sectioning. In this paper, the structural information from unsupported transparent thin sections of beef liver catalase, calf thymus DNA, horse spleen ferritin, insect muscle and rat microtubules is compared to that of normal thin sections. While ferritin molecules (12 nm diameter), microtubule subunits (8 nm long axis) and catalase crystals (8 nm subunit diameter) appear to become mechanically damaged in a 10 nm section (as measured by resectioning), DNA-molecules (3 nm diameter) are satisfactorily preserved during sectioning. Remarkably, for electron phase contrast imaging of unstained cross-sectioned insect muscle, a minimum section thickness of about 30-40 nm is required.
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PMID:Choosing the appropriate section thickness in the melamine embedding technique. 388 13

A method for isolating ferritin from human term placenta was described. The placenta was homogenized in water containing protease inhibitor and heated at 70 degrees C. The ferritin was precipitated with ammonium sulfate at pH 5.2 and purified by repeated cycles of ultracentrifugation and molecular sieve chromatography through Sepharose 4B columns. Isoelectric focusing revealed a broad spectrum of isoferritins. These isoferritins were separated by ion-exchange chromatography on Sephadex A-25 at pH 7.5 and stepwise elution with increasing concentrations of NaCl. By this method "basic," "intermediate," and "acid" isoferritins were separated. The most basic placental isoferritin was shown to be identical to splenic ferritin by isoelectric focusing, subunit analysis, and fluorescent ELISA. The acid placental isoferritin had similar characteristics to heart-type ferritin. It was suggested that the easily available placental tissue could serve as a source for human isoferritins in research and in clinical assays.
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PMID:Isolation and fractionation of ferritin from human term placenta--a source for human isoferritins. 392 39

Hydrolytic polymerization of iron(III) occurs in many reactions in vivo, for example, the formation of bacterial magnetite in magnetotactic organisms, biomineralization of iron and the synthesis of the metallic core of the iron-storage protein ferritin. The ferritin core contains aggregates of up to 4,500 oxygen-bridged, octahedrally coordinated, high-spin iron(III) centres and is attached to the protein shell through carboxylate groups of amino-acid side chains. The X-ray and electron-diffraction patterns of this core resemble those of the mineral ferrihydrite, a hydrated iron oxide formed in nature, inter alia, by iron-dependent bacteria. The preparation and structural characterization of such large poly-iron aggregates has been a challenge to inorganic chemists. We have recently shown that tri- and tetranuclear iron(III) oxo complexes of the type thought to be important in ferritin-core formation can be prepared by reacting mononuclear [FeCl4]- and binuclear [Fe2OCl6]2- components in aprotic solvents (ref. 9 and S.M.G., W. H. Armstrong and S.J.L., in preparation). Here we report the discovery of a remarkable new molecule, [Fe11O6(OH)6(O2CPh)15], obtained by hydrolysis of the [Fe2O]4+ unit in the presence of limited amounts of water and carboxylate salts. The synthesis and properties of this soluble iron(III) oxohydroxo aggregate should help to elucidate the mechanism of formation of poly-iron centres.
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PMID:A new synthetic approach to the ferritin core uncovers the soluble iron(III) oxo-hydroxo aggregate [Fe11O6(OH)6(O2CPh)15]. 395 37

The route by which water, solutes, and macromolecules traverse the endothelial cell has long been a subject of study for both physiologists and cell biologists. Recent physiologic studies describe a slit-shaped pore (5.1-5.7-nm wide) as the communicating channel, although no channel of such dimensions has been visible in electron microscopic preparations. That this channel should be found within the fenestral diaphragm has long been suggested. In this report, by the aid of a new technique in tissue processing, we are able to demonstrate a possible morphologic correlate within the fenestral diaphragm of fenestrated capillaries. Quick-freezing and deep-etching of whole tissue blocks allows the sublimation of water from the endothelial pores, thus leaving the channels through the diaphragms empty and readily replicated with a platinum-carbon shadow. The structure of the diaphragm was revealed thus to be composed of radial fibrils of 7 nm in diameter, interweaving in a central mesh, and creating by their geometric distribution, wedge-shaped channels around the periphery of the pore. The average channel had a maximum arc length of 5.46 nm. Fenestrated endothelia from various tissues, including endocrine and exocrine pancreas, adrenal cortex, and kidney peritubular capillaries, displayed the same diaphragmatic structure, whereas continuous capillaries in muscle had no such diaphragm. Photographic augmentation of electron micrographs of etched replicas displayed marked enhancement at n = 8, confirming an octagonal symmetry of the fenestral diaphragm. Finally, cationic ferritin, clearly visible as a marker after etching, heavily bound to the flowerlike structure within the fenestral pore. We conclude that the fenestral diaphragm contains the structure responsible for fenestrated capillary permeability and that the communicating channel has the shape of a wedge.
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PMID:Endothelial fenestral diaphragms: a quick-freeze, deep-etch study. 396 70

It appears well established that a microcytic, hypochromic anaemia is present in patients receiving regular haemodialysis treatment, who also suffer from chronic aluminium intoxication. This characteristic anaemia is slightly improved following deionization or reverse-osmosis treatment of dialysate water. Iron deficiency has been tentatively excluded as a cause of this anaemia by measurement of serum ferritin levels. The exact mechanisms involved in the pathogenesis of this anaemia are still to be fully elucidated but a disturbance in haem synthesis and porphyrin metabolism seems probable, and secondary effects of PTH in the bone marrow may be involved. Evidence has accumulated that aluminium is the most likely ion responsible for this anaemia but other ions, trace metals in excess or deficiency and potentially toxic substances cannot be excluded yet.
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PMID:Aluminium-induced anaemia in haemodialysis patients. 396 84

To study the influence of acidosis on free radical formation and lipid peroxidation in brain tissues, homogenates fortified with ferrous ions and, in some experiments, with ascorbic acid were equilibrated with 5-15% O2 at pH values of 7.0, 6.5, 6.0, and 5.0, with subsequent measurements of thiobarbituric acid-reactive (TBAR) material, as well as of water- and lipid-soluble antioxidants (glutathione, ascorbate, and alpha-tocopherol) and phospholipid-bound fatty acids (FAs). Moderate to marked acidosis (pH 6.5-6.0) was found to grossly exaggerate the formation of TBAR material and the decrease in alpha-tocopherol content and to enhance degradation of phospholipid-bound, polyenoic FAs. These effects were reversed at pH 5.0, suggesting a pH optimum at pH 6.0-6.5. It is concluded that acidosis of a degree encountered in ischemic brain tissues has the potential of triggering increased free radical formation. This effect may involve increased formation of the protonated form of superoxide radicals, which is strongly prooxidant and lipid soluble, and/or the decompartmentalization of iron bound to cellular macromolecules like ferritin.
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PMID:Influence of acidosis on lipid peroxidation in brain tissues in vitro. 398 24

The out-exchange kinetics of tritium from apoferritin, ferritin of various iron contents, and apoferritin subunits were examined. The exchange kinetics indicated no detectable conformational differences in the tetracosamer with and without hydrous ferric oxide in the internal cavity of the molecule. The data for apoferritin subunits were markedly different from those for the tetracosameric state. The exchange kinetics for apoferritin were consistent with a rapid exchange of water between the internal cavity of the protein and the bulk solvent outside the protein shell.
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PMID:Hydrogen-tritium exchange by apoferritin and ferritin. 401 2

In adult germfree C(3)H mice immunized with horse spleen ferritin, either subcutaneously or intraperitoneally, plasma cells containing specific antibodies were found in lymph nodes and spleen and, in smaller numbers, also in the lamina propria of the intestine. In extraintestinal sites, these antiferritin-containing plasma cells were mainly of the IgM class after a single stimulation, and of the IgG(1) class after repeated stimulation. In the intestine, all the anti-ferritin-containing cells appeared to be of the IgA class. Circulating antibodies, after repeated stimulation, were for the major part IgG(1) and IgG(2). In germfree mice given ferritin in their drinking water, antiferritin-containing cells were abundant in the intestinal mucosa, much less numerous in the mesenteric lymph nodes, and extremely scarce in other lymphoid tissues. All these cells, whatever their location, appeared to belong exclusively to the IgA class. Similarly, all the circulating antibody in these animals was found to be IgA. These findings illustrate the role of the gut as a site of antibody synthesis, as well as its selective commitment to the production of antibodies of the IgA class.
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PMID:Antibodies of the IgA type in intestinal plasma cells of germfree mice after oral or parenteral immunization with ferritin. 418 43


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