An EXAFS study of the three cation environments in Ba2YCu3O7

Gurman, S. J.; Diakun, G.P.; Dobson, BC; Abell, S.; Greaves, G.N.; Jordan, R. B.

doi:10.1088/0022-3719/21/14/004

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…We have recently determined the so-called dimpling angle in the CuO 2 planes of BiSr 2 Ca 2 Cu 2 O 8+δ [15] from a MS analysis of the Cu K-EXAFS using the FEFF code [16]; MS analysis of the EXAFS from high-T c cuprates using other codes have been reported in e.g Ref. [17,18].…”

Section: X-ray Absorption-fine-structurementioning

confidence: 99%

Local Structure Studies of the Underdoped-Overdoped Transition in YBa2Cu3Ox

Röhler

Loeffen

Müllender

et al. 1997

High-Tc Superconductivity 1996: Ten Years After the Discovery

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We have measured the extended x-ray absorption-fine-structure (EXAFS) at the Y-K edge of YBa 2 Cu 3 O x for x=6.801, 6.947, 6.968, 6.984 at T =20-300 K. The Y-Cu2 pairs vibrate harmonically but freeze out in the superconducting phase. The Y-O2,3 pairs exhibit strong anharmonicities with a singularity at T c . With increasing oxygen concentration the Cu2 layer shifts along c towards the Ba layer. Optimum doping is a notable point in the phase diagram, also concerning the structural degrees of freedom. Here the O2,3-Cu2 spacing is largest, the relative displacements of O2,3 and Cu2 layers along c invert upon doping, and the Cu2 position along c is independent on temperature in the superconducting phase.

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Section: X-ray Absorption-fine-structurementioning

confidence: 99%

Local Structure Studies of the Underdoped-Overdoped Transition in YBa2Cu3Ox

Röhler

Loeffen

Müllender

et al. 1997

High-Tc Superconductivity 1996: Ten Years After the Discovery

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“…After standard background removal using a cubic spline procedure, the data were weighted by k3 and Fourier-transformed over a range of 20-115 nmin order to obtain a general view of the observable coordination shells. The structural parameters were determined by curve-fitting the unfiltered k3-weighted fine structure using the EXCURV90 program package distributed by the Science and Engineering Research Council Daresbury Laboratory (Warrington, UK) which uses the exact curved-wave theory of EXAFS [29].…”

Section: Mossbauer Experimentsmentioning

confidence: 99%

Evidence for polynuclear aggregates of ferric daunomycin

Matzanke¹,

Bill²,

Butzlaff³

et al. 1992

European Journal of Biochemistry

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The interaction of the antitumor agent daunomycin (DN) with ferric iron has been analysed by Mossbauer spectroscopy, EPR, extended X-ray absorption fine structure (EXAFS), and magnetic susceptibility measurements. In contrast to literature data, at millimolar iron and anthracycline concentrations no solitary Fe(DN)3 complexes are formed in appreciable amounts. The Mossbauer spectroscopic analysis revealed severe dependencies on temperature, on the preparation procedure, the time allowed for equilibration, and on the metal/ligand ratio. The Mossbauer spectra exhibit two components: a broad magnetic sextet and a quadrupole doublet at an Fe/DN molar ratio of 1 : 3 and exclusively a doublet at a molar ratio of 1 :20, indicating an equilibrium of these two spectral components. The EPR spectra are dominated by a signal at g,,, = 2. Double integration of the EPR signals enabled the determination of their spin density and a correlation between EPR and Mossbauer spectra. The Mossbauer sextet species is EPR invisible and corresponds to magnetically ordered polynuclear aggregates with high magnetic anisotropy. EXAFS and susceptibility measurements provide additional evidence for the formation of polynuclear aggregates of ferric daunomycin. The quadrupole doublet species in the Mossbauer spectra correlates with the g = 2 signal in EPR. This species is also related to a magnetically ordered system, exhibiting, however, superparamagnetic behavior due to less magnetic anisotropy. Since daunomycin forms dimers in aqueous solution at millimolar concentrations, we conclude that the cooperative phenomena observed in EPR and Mossbauer spectra are a consequence of its stacking effects.

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“…Data reduction was achieved using computer programs developed at the EMBL Outstation (energy calibration: LOCREFIROTAXIOFFEN ; averaging : MEANMEANFINE; background subtraction : AREMPFl ; normalization : NLOOF) (Nolting, 1988) or at the SERC Daresbury Laboratory (averaging : EXCALIB ; background subtraction: EXBACK). Final analysis of the processed data was carried out using the SERC Daresbury Laboratory EXAFS analysis package, which consists of the fast curved-wave EXAFS simulation and fitting program EXCURV90 (Gurman et al, 1984(Gurman et al, , 1986, including MUFPOT for the ab initio calculation of phase shifts and backscattering factors.…”

Section: Methodsmentioning

confidence: 99%

Changes in the Iron Coordination Sphere of Fe(II) Lipoxygenase-1 from Soybeans upon Binding of Linoleate or Oleate

Heijdt¹,

Schilstra²,

Feiters³

et al. 1995

Eur J Biochem

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???The definitive version is available at www.blackwell-synergy.com.??? Copyright Federation of European Biochemical Societies. DOI: 10.1111/j.1432-1033.1995.0186f.x [Full text of this article is not available in the UHRA]Fe K-edge X-ray absorption spectra of the non-heme iron constituent of lipoxygenase-1 from soybeans were obtained. The spectrum of 2.5 mM Fe(II) lipoxygenase, mixed with 1.2 M linoleate in the absence of O2, was compared to the spectrum of the native (i.e. untreated) enzyme. In the lipoxygenase-linoleate complex, an edge shift to lower energy was observed. This indicated that the iron-ligand distances in this complex are slightly longer than those in the untreated enzyme species. The extended X-ray absorption fine strucutre spectrum of Fe(II) lipoxygenase, prepared by anaerobic reduction of 2.5 mM Fe(III) lipoxygenase with 1.2 M linoleate, was very similar to the spectrum of the anaerobic lipoxygenase-linoleate complex. We conclude that the conformational differences between the iron coordination spheres of native and cycled Fe(II) lipoxygenase must be ascribed to the presence of linoleate, and not to changes in the enzyme that occur only after one cycle of oxidation and reduction. Furthermore, spectra of 2.5 mM Fe(II) lipoxygenase mixed with 1.2 M oleate, either in the absence or in the presence of O2, were also identical to the spectrum of the Fe(II) lipoxygenase-linoleate complex. This finding is in agreement with our observation that oleate is a competitive inhibitor of the lipoxygenase reaction. Moreover, the similarity of the lipoxygenase-oleate complexes in the presence and absence of O2 excludes the possibility that O2 binding to the iron cofactor is induced upon binding of a fatty acid to lipoxygenase

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An EXAFS study of the three cation environments in Ba₂YCu₃O₇

Cited by 11 publications

References 10 publications

Local Structure Studies of the Underdoped-Overdoped Transition in YBa2Cu3Ox

Local Structure Studies of the Underdoped-Overdoped Transition in YBa2Cu3Ox

Evidence for polynuclear aggregates of ferric daunomycin

Changes in the Iron Coordination Sphere of Fe(II) Lipoxygenase-1 from Soybeans upon Binding of Linoleate or Oleate

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