Stabilization of iron in a ferrous form by ferritin. A study using dispersive and conventional x-ray absorption spectroscopy.

Rohrer, Jeffry S.; Joo, Minsoo; Dartyge, E.; Sayers, D. E.; Fontaine, A.; Theil, Elizabeth C.

doi:10.1016/s0021-9258(19)76437-0

Cited by 52 publications

(10 citation statements)

References 21 publications

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“…These current−potential data also show that oxidation can take place after iron uptake, suggesting that some Fe(II) can be loaded into the protein. These results are consistent with EXAFS experiments, which reveal that Fe(II) can load into ferritin without oxidizing …”

Section: Resultssupporting

confidence: 91%

Uptake and Release of Iron by Ferritin Adsorbed at Tin-Doped Indium Oxide Electrodes

et al. 1999

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In this work, the uptake and release of iron by ferritin using direct electrochemical techniques have been investigated for the first time. Adsorption of ferritin from phosphate solution onto tin-doped indium oxide (ITO) at open circuit potential gives about one monolayer of ferritin. The ferritin layer is electroactive and therefore lends itself to electrochemical analysis; cyclic voltammetry was the principal method used in this study. In the presence of EDTA, iron is not removed at open circuit potential. However, when the ITO/ ferritin electrode is subjected to -0.70 V, the anodic branch is no longer present in the current-potential curve, indicating that the reduction of core iron had induced the removal of iron from the protein shell. Adsorbed ferritin, emptied in this fashion, was exposed to ferrous ion at 0.20 V. The ensuing currentpotential curve showed the original peak pattern, suggesting that iron had been reincorporated into the apoferritin shell. An authentic sample of adsorbed apoferritin exposed to ferrous ion, exhibited the same current-potential response as electrochemically emptied ferritin, supporting the conclusion that apoferritin results from the reduction of ITO/ferritin in the presence of an iron chelator. These studies show that ferritin adsorbed at an ITO electrode is a promising venue to study not only ferritin's electrochemistry but also its functions.

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Section: Resultssupporting

confidence: 91%

Uptake and Release of Iron by Ferritin Adsorbed at Tin-Doped Indium Oxide Electrodes

et al. 1999

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“…A preliminary account of some of the work described here is given in Bauminger et al (1988). We also provide some information on the rate at which Fe(II) is oxidized in the presence of apoferritin and show that although Fe(II) is oxidized rapidly at pH 6.4 or above at low iron concentration and low Fe atoms per molecule, Fe(II) can persist for longer periods at high Fe atoms per molecule, as reported previously (Rohrer et al, 1987), or at low pH.…”

supporting

confidence: 69%

Moessbauer spectroscopic study of the initial stages of iron-core formation in horse spleen apoferritin: evidence for both isolated iron(III) atoms and oxo-bridged iron(III) dimers as early intermediates

Bauminger¹,

Harrison²,

Nowik³

et al. 1989

Biochemistry

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Ferritin stores iron within a hollow protein shell as a polynuclear Fe(III) hydrous oxide core. Although iron uptake into ferritin has been studied previously, the early stages in the creation of the core need to be clarified. These are dealt with in this paper by using Mössbauer spectroscopy, a technique that enables several types of Fe(II) and Fe(III) to be distinguished. Systematic Mössbauer studies were performed on samples prepared by adding 57Fe(II) atoms to apoferritin as a function of pH (5.6-7.0), n [the number of Fe/molecule (4-480)], and tf (the time the samples were held at room temperature before freezing). The measurements made at 4.1 and 90 K showed that for samples with n less than or equal to 40 at pH greater than or equal to 6.25 all iron was trivalent at tf = 3 min. Four different Fe(III) species were identified: solitary Fe(III) atoms giving relaxation spectra, which can be identified with the species observed before by EPR and UV difference spectroscopy; oxo-bridged dimers giving doublet spectra with large splitting, observed for the first time in ferritin; small Fe(III) clusters giving doublets of smaller splitting and larger antiferromagnetically coupled Fe(III) clusters, similar to those found previously in larger ferritin iron cores, which, for samples with n greater than or equal to 40, gave magnetically split spectra at 4.1 K. Both solitary Fe(III) and dimers diminished with time, suggesting that they are intermediates in the formation of the iron core. Two kinds of divalent iron were distinguished for n = 480, which may correspond to bound and free Fe(II).

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“…This new, more hydrophobic, reduced expanded porphyrin system was obtained in ca. 90% yield by condensing 1,2-diamino-4,5-dimethylbenzene with 2,5-bis((3-ethyl-5-formyl-4-methylpyrrol-2-yl)methyl)-3,4-diethylpyrrole26 under acid-catalyzed conditions identical with those used to prepare 10.26 Treatment of this expanded porphyrin precursor with Gd(OAc)3, Eu(OAc)3, and Sm(OAc)3, under reaction and workup conditions similar to those used to obtain 3, then gave the cationic complexes 7-9, as their dihydroxide adducts,30 in 22%, 33%, and 37% yields, respectively: As near as we have been able to determine, these increased yields derive directly from the increased hydrophobicity of the new dimethyl-substituted expanded porphyrin ligand system (6). Apparently, this increased hydrophobicity serves to improve both the initial extractive isolation of the complexes and the subsequent chromatographic purification.…”

Section: Discussionmentioning

confidence: 61%

A water-stable gadolinium(III) complex derived from a new pentadentate "expanded porphyrin" ligand

Sessler¹,

Murai²,

Hemmi³

1989

Inorg. Chem.

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Stabilization of iron in a ferrous form by ferritin. A study using dispersive and conventional x-ray absorption spectroscopy.

Cited by 52 publications

References 21 publications

Uptake and Release of Iron by Ferritin Adsorbed at Tin-Doped Indium Oxide Electrodes

Uptake and Release of Iron by Ferritin Adsorbed at Tin-Doped Indium Oxide Electrodes

Moessbauer spectroscopic study of the initial stages of iron-core formation in horse spleen apoferritin: evidence for both isolated iron(III) atoms and oxo-bridged iron(III) dimers as early intermediates

A water-stable gadolinium(III) complex derived from a new pentadentate "expanded porphyrin" ligand

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