Analysis and computer simulation of high-Spin Fe3+ powder EPR spectra with giso approximately 30/7

McGavin, D.G.; Tennant, W. C.

doi:10.1016/0022-2364(85)90205-7

Cited by 6 publications

(4 citation statements)

References 17 publications

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“…The attribution of the component b to monomer units is further corroborated by the X-band EPR spectra measured on the same frozen solutions at T = 150 K. The main component of these spectra (Fig. 1 , right) is a signal at g eff ≈ 4.3 (at B ≈ 1540 G) that is typical for mononuclear ferric compounds with a ligand environment symmetry deviating from that of octahedral due to rhombic distortions (Oosterhuis 1974 ; McGavin and Tennant 1985 ; Klencsár and Köntös 2018 ). Polynuclear complexes containing oxygen-bridged ferric ions were shown to be silent in the same region of the EPR spectrum due to spin coupling (Evans et al 2008 ; Silva et al 2009a ).…”

Section: Resultsmentioning

confidence: 56%

Revealing the nuclearity of iron citrate complexes at biologically relevant conditions

Gracheva,

Klencsár,

Homonnay

et al. 2023

Biometals

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Citric acid plays an ubiquitous role in the complexation of essential metals like iron and thus it has a key function making them biologically available. For this, iron(III) citrate complexes are considered among the most significant coordinated forms of ferric iron that take place in biochemical processes of all living organisms. Although these systems hold great biological relevance, their coordination chemistry has not been fully elucidated yet. The current study aimed to investigate the speciation of iron(III) citrate using Mössbauer and electron paramagnetic resonance spectroscopies. Our aim was to gain insights into the structure and nuclearity of the complexes depending on the pH and iron to citrate ratio. By applying the frozen solution technique, the results obtained directly reflect the iron speciation present in the aqueous solution. At 1:1 iron:citrate molar ratio, polynuclear species prevailed forming most probably a trinuclear structure. In the case of citrate excess, the coexistence of several monoiron species with different coordination environments was confirmed. The stability of the polynuclear complexes was checked in the presence of organic solvents.

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Section: Resultsmentioning

confidence: 56%

Revealing the nuclearity of iron citrate complexes at biologically relevant conditions

Gracheva,

Klencsár,

Homonnay

et al. 2023

Biometals

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“…But because of their simplicity in programming, these methods are widely used. Hauser and Renaud (1) and McGavin and Tennant (2) fitted the powder spectra by these methods and obtained the fitted values of the Hamiltonian parameters. Other authors (3-9, who analyzed EPR powder spectra by simulation or fitting, seldom reported how to get the final values but just gave the simulated spectra.…”

Section: Introductionmentioning

confidence: 99%

A method for evaluation of Hamiltonian and line shape parameters from electron paramagnetic resonance powder spectra

She¹,

Chen²,

Yu³

1989

Can. J. Chem.

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This paper is dedicated to Professor Charles A. McDowelL on the occasion of his 70th birthdayMINGDA SHE, XIANRONG CHEN, and XN-SHENG Yu. Can. J. Chem. 67, 88 (1989). A least-square fitting method is given for exact evaluation of spin-Hamiltonian and line shape parameters from EPR powder spectra. The method is applicable to cases where the resonance fields can be analytically expressed or can only be obtained by diagonalization of Hamiltonian. It is also suitable for different line shapes and spin-Hamiltonians. The fitted spectra and corresponding refined parameters were obtained on FACOM-M340S computer with a Fortran 77 program.Key words: spin-Hamiltonian, line shape parameters, electron paramagnetic resonance, calculated spectra, least squares fitting.MINGDA SHE, XIANRONG CHEN et XIN-SHENG Yu. Can. J. Chem. 67, 88 (1989). On presente une methode d'ajustement par la methode des moindres carres pour Cvaluer d'une facon exacte I'Hamiltonien de spin et les paramttres de la forme des raies de spectres rpe de poudres. On peut appliquer la methode i i des cas oh les champs de resonance peuvent soit Stre exprimes d'une facon analytique ou ne peuvent &tre obtenus que par une diagonalisation de I'Hamiltonien. Elle est aussi approprike pour des formes de raies ou des Hamiltoniens de spin qui sont diffkrents. On a obtenu les spectres ajustes ainsi que les paramttres affines correspondants a I'aide d'un ordinateur FACOM-M340S operant avec un programme Fortran 77.Mots cle's : Hamiltonien de spin, paramttres de la forme, resonance paramagnttique electronique, spectres calculCs, ajustement par la methode de moindres carres.[Traduit par la revue]

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“…Previous simulations based on the Hamiltonian Eq. 1 have been of two types: those with the zero-field splitting or Zeeman terms dominant (8-10) and those in which the two parts have comparable magnitude (11)(12)(13)(14)(15)(16)(17). The first case can be treated by perturbation theory.…”

Section: Introductionmentioning

confidence: 99%

“…Also, B,/hv vs. D/hp plots may be inadequate for predicting the positions of maxima and minima in actual lineshapes because they cannot account for anisotropic transition probabilities. Therefore, it is necessary to perform a complete lineshape simulation to account for experimental spectra (13)(14)(15)(16)(17). In addition, recent advances in understanding the implications of fieldswept EPR (18-21) and numerous new experimental EPR spectra of high-spin ferric proteins, of which PAH is one example, provide a renewed need to compare simulated EPR spectra with experimental ones.…”

Section: Introductionmentioning

confidence: 99%

Determination of relative spin concentration in some high-spin ferric proteins using E/D-distribution in electron paramagnetic resonance simulations

Yang¹,

Gaffney²

1987

Biophysical Journal

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Lineshape simulations are presented for the multiple, overlapping X-band electron paramagnetic resonance (EPR) spectra in two non-heme, high-spin iron proteins: phenylalanine hydroxylase (PAH) and diferric transferrin. The aim of the calculations is to determine the fraction of iron contributing to each of the sites visible by EPR. The simulations are limited to the experimentally accessible transitions occurring at g-values greater than 1.7. In both PAH and transferrin, at least one of the iron sites is characterized by the ratio of zero-field splitting parameters, E/D, near 1/3 and a broad, asymmetric lineshape. A distribution in E/D-values is used in the simulations to account for this breadth and asymmetry. To test the E/D-distribution model, experimental X-band spectra of diferric transferrin at several salt concentrations are fit by simulation. In this test, first the low-field features arising from transitions between the lowest Kramers doublet levels are simulated using E/D-distributions for two sites. Second, parameters that provide a good fit for the lowest doublet transitions are shown also to fit the resonance near an effective g-value of 4.3 from the middle Kramers doublet transition. When applied to spectra of PAH in the resting state, the E/D-distribution approach accounts for the intensity of one of the two major species of iron. The other species is characterized by E/D = 0.032, and the spectrum of this portion of the resting enzyme may be simulated using a frequency-swept Gaussian lineshape. Spectra for the enzyme in an inhibitor-saturated state are also simulated. The simulations are consistent with previous biochemical studies that indicate that only the E/D = 0.032 form of iron participates in catalysis.

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Analysis and computer simulation of high-Spin Fe3+ powder EPR spectra with giso approximately 30/7

Cited by 6 publications

References 17 publications

Revealing the nuclearity of iron citrate complexes at biologically relevant conditions

Revealing the nuclearity of iron citrate complexes at biologically relevant conditions

A method for evaluation of Hamiltonian and line shape parameters from electron paramagnetic resonance powder spectra

Determination of relative spin concentration in some high-spin ferric proteins using E/D-distribution in electron paramagnetic resonance simulations

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