scholarly journals Mössbauer spectroscopic studies of the terminal dioxygenase protein of benzene dioxygenase from Pseudomonas putida

1981 ◽  
Vol 195 (1) ◽  
pp. 199-203 ◽  
Author(s):  
P J Geary ◽  
D P E Dickson
Keyword(s):  
Pseudomonas Putida ◽  
High Spin ◽  
Mössbauer Spectra ◽  
Spectroscopic Studies ◽  
Reduced Form ◽  
Plant Type ◽  
Mossbauer Spectra ◽  
Extra Electron

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.

scholarly journals Mössbauer effect in Scenedesmus and spinach ferredoxins. The mechanism of electron transfer in plant-type iron–sulphur proteins

1971 ◽  
Vol 122 (3) ◽  
pp. 257-265 ◽  
Author(s):  
K. K. Rao ◽  
R. Cammack ◽  
D. O. Hall ◽  
C. E. Johnson
Keyword(s):  
Magnetic Field ◽  
Hyperfine Structure ◽  
High Spin ◽  
Mössbauer Spectra ◽  
Zeeman Splitting ◽  
Plant Type ◽  
Mossbauer Spectra ◽  
Small Magnetic Field ◽  
Similar Chemical ◽  
Reduced State

1. The Mössbauer spectra of Scenedesmus ferredoxin enriched in 57Fe were measured and found to be identical with those of two other plant-type ferredoxins (from spinach and Euglena) that had been previously measured. Better resolved Mössbauer spectra of spinach ferredoxin are also reported from protein enriched in 57Fe. All these iron–sulphur proteins are known to contain two iron atoms in a molecule that takes up one electron on reduction. 2. The Mössbauer spectra at 195°K have electric hyperfine structure only and show that on reduction the electron goes to one of the iron atoms, the other appearing to remain unchanged. 3. In the oxidized state, both iron atoms are in a similar chemical state, which appears from the chemical shift and quadrupole splitting to be high-spin Fe3+, but they are in slightly different environments. In the reduced state the iron atoms are different and the molecule appears to contain one high-spin Fe2+ and one high-spin Fe3+ atom. 4. At lower temperatures (77 and 4.2°K) the spectra of both iron atoms in the reduced proteins show magnetic hyperfine structure which suggests that the iron in the oxidized state also has unpaired electrons. This provides experimental evidence for earlier suggestions that in the oxidized state there is antiferromagnetic exchange coupling, which would result in a low value for the magnetic susceptibility. 5. In a small magnetic field the spectrum of the reduced ferredoxin shows a Zeeman splitting with hyperfine field (Hn) of 180kG at the nuclei. On application of a strong magnetic field H the spectrum splits into two spectra with effective fields Hn±H, thus confirming the presence of the two antiferromagnetically coupled iron atoms. 6. These results are in agreement with the model proposed by Gibson, Hall, Thornley & Whatley (1966); in the oxidized state there are two Fe3+ atoms (high spin) antiferromagnetically coupled and on reduction of the ferredoxin by one electron one of the ferric atoms becomes Fe2+ (high spin).

scholarly journals The two redox states of the human NEET proteins’ [2Fe–2S] clusters

2021 ◽  
Vol 26 (7) ◽  
pp. 763-774
Author(s):  
Ke Zuo ◽  
Henri-Baptiste Marjault ◽  
Kara L. Bren ◽  
Giulia Rossetti ◽  
Rachel Nechushtai ◽  
...  
Keyword(s):  
Protein S ◽  
Spectroscopic Studies ◽  
Reduced Form ◽  
Rieske Protein ◽  
Kinetic Measurements ◽  
Redox States ◽  
Extra Electron ◽  
Dynamics Simulations ◽  
Reduced State

AbstractThe NEET proteins constitute a unique class of [2Fe–2S] proteins. The metal ions bind to three cysteines and one histidine. The proteins’ clusters exist in two redox states; the oxidized protein (containing two FeIII ions) can transfer the cluster to apo-acceptor protein(s), while the reduced form (containing one ferrous ion) remains bound to the protein frame. Here, we perform in silico and in vitro studies on human NEET proteins in both reduced and oxidized forms. Quantum chemical calculations on all available human NEET proteins structures suggest that reducing the cluster weakens the Fe–NHis and Fe–SCys bonds, similar to what is seen in other Fe–S proteins (e.g., ferredoxin and Rieske protein). We further show that the extra electron in the [2Fe–2S]+ clusters of one of the NEET proteins (mNT) is localized on the His-bound iron ion, consistently with our previous spectroscopic studies. Kinetic measurements demonstrate that the mNT [2Fe–2S]+ is released only by an increase in temperature. Thus, the reduced state of human NEET proteins [2Fe–2S] cluster is kinetically inert. This previously unrecognized kinetic inertness of the reduced state, along with the reactivity of the oxidized state, is unique across all [2Fe–2S] proteins. Finally, using a coevolutionary analysis, along with molecular dynamics simulations, we provide insight on the observed allostery between the loop L2 and the cluster region. Specifically, we show that W75, R76, K78, K79, F82 and G85 in the latter region share similar allosteric characteristics in both redox states. Graphic abstract

scholarly journals On Spin Hamiltonian fits to Mössbauer spectra of high-spin Fe(II) porphyrinate systems

2006 ◽  
Vol 170 (1-3) ◽  
pp. 55-60 ◽  
Author(s):  
Charles E. Schulz ◽  
Chuanjiang Hu ◽  
W. Robert Scheidt
Keyword(s):  
High Spin ◽  
Mössbauer Spectra ◽  
Spin Hamiltonian ◽  
Mossbauer Spectra

Spin fluctuation rates from Mössbauer spectra of high-spin ferrous rubredoxin

1979 ◽  
Vol 69 (5) ◽  
pp. 360-363 ◽  
Author(s):  
H. Winkler ◽  
C. Schulz ◽  
P.G. Debrunner
Keyword(s):  
High Spin ◽  
Mössbauer Spectra ◽  
Spin Fluctuation ◽  
Mossbauer Spectra

Magnetische und Mößbauer-spektroskopische Untersuchungen von zeolithischen Eisenkontakten/ Magnetic and Mössbauer Spectroscopic Studies of Iron-Clusters in Zeolites

1975 ◽  
Vol 30 (12) ◽  
pp. 1627-1632 ◽  
Author(s):  
F. Schmidt ◽  
W. Gunsser ◽  
A. Knappwost
Keyword(s):  
Magnetic Susceptibility ◽  
Temperature Dependence ◽  
Mössbauer Spectra ◽  
Bulk Material ◽  
Spectroscopic Studies ◽  
Ferrous Ions ◽  
Iron Clusters ◽  
Mossbauer Spectra

Abstract Iron clusters have been prepared within zeolite holes by reduction of zeolites containing ferrous ions. The diameter of these particles must therefore be smaller than 13 Å. They are super-paramagnetic and their Mössbauer spectra show no HFS, even at 4 K.The temperature dependence of the magnetic susceptibility of the unreduced zeolites obeys a Curie-Weiss law with peff = 4,54 μB and Θ = 105 K. The Weiss curves of the reduced samples lie distinctly below those of the bulk material.

scholarly journals Mössbauer studies of adrenodoxin. The mechanism of electron transfer in a hydroxylase iron–sulphur protein

1971 ◽  
Vol 125 (3) ◽  
pp. 849-856 ◽  
Author(s):  
R. Cammack ◽  
K. K. Rao ◽  
D. O. Hall ◽  
C. E. Johnson
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
High Spin ◽  
Mössbauer Spectra ◽  
Adrenal Glands ◽  
Native Protein ◽  
Electron Spin Relaxation ◽  
Mossbauer Spectra ◽  
Small Magnetic Field ◽  
Magnetic Hyperfine Structure

1. Mössbauer spectra were measured of adrenodoxin purified from porcine adrenal glands. They show similarities to the spectra of the plant ferredoxins. All of these proteins contain two atoms of iron and two of inorganic sulphide per molecule, and on reduction accept one electron. 2. As with the plant ferredoxins the adrenodoxin for these measurements was enriched with57Fe by reconstitution of the apo-protein, and subsequently was carefully purified and checked by a number of methods to ensure that it was in the same conformation as the native protein and contained no extraneous iron. 3. The Mössbauer spectra of oxidized adrenodoxin at temperatures from 4.2°K to 197°K show that the iron atoms are probably high-spin Fe3+, and in similar environments, and experience little or no magnetic field from the electrons. 4. Mössbauer spectra of reduced adrenodoxin showed magnetic hyperfine structure at all temperatures from 1.7°K to 244°K, in contrast with the reduced plant ferredoxins, which showed it only at lower temperatures. This is a consequence of a longer electron-spin relaxation time in reduced adrenodoxin. 5. At 4.2°K in a small magnetic field the spectrum of reduced adrenodoxin shows a sixline Zeeman pattern due to Fe3+superimposed upon a combined magnetic and quadrupole spectrum due to Fe2+. 6. In a large magnetic field (30kG) each hyperfine pattern is further split into two. Analysis of these spectra at 4.2°K and 1.7°K shows that the effective fields at the Fe3+and Fe2+nuclei are in opposite directions. This agrees with the proposal, first made for the ferredoxins, that the iron atoms are antiferromagnetically coupled. 7. In accord with the model for the ferredoxins, it is proposed that the oxidized adrenodoxin contains two high-spin Fe3+atoms which are antiferromagnetically coupled; on reduction one iron atom becomes high-spin Fe2+.

Monosubstituted Derivatives of (L–L)Fe2(CO)6 (L–L = fluorocarbon bridged ligand)

1975 ◽  
Vol 53 (15) ◽  
pp. 2232-2239 ◽  
Author(s):  
Lian Sai Chia ◽  
William R. Cullen ◽  
John R. Sams ◽  
James C. Scott
Keyword(s):  
Mössbauer Spectra ◽  
Spectroscopic Studies ◽  
Bidentate Ligands ◽  
Group V ◽  
Mossbauer Spectra ◽  
First Time ◽  
Derivatives Of

The reaction of the ditertiary arsines and phosphines fnfars, fnfos, and fnAsP, (L–L), with Fe(CO)5 at 150° is a superior route to the complexes (L–L)Fe2(CO)6. Two are reported for the first time (L–L = f6fars, f8fars). The complexes react with monodentate and certain potentially bidentate ligands on u.v. irradiation to afford the monosubstituted derivatives L(L–L)Fe2(CO)5 and (L–L)'(L–L)Fe2(CO)5. Spectroscopic studies, in particular magnetically perturbed Mössbauer spectra, indicate that the site of substitution is trans to the FeA—FeB bond and cis to the two group V atoms (on FeA). Disubstitution seems to result in further displacement of CO from either FeA or FeB.

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