We investigated the geometry of the iron ligand sphere of the native rabbit 15-lipoxygenase (15-LOX) by X-ray absorption spectroscopy using synchrotron radiation. The soybean LOX-1 was used as a reference compound because its iron ligand... more
We investigated the geometry of the iron ligand sphere of the native rabbit 15-lipoxygenase (15-LOX) by X-ray absorption spectroscopy using synchrotron radiation. The soybean LOX-1 was used as a reference compound because its iron ligand sphere is well characterized. For structural information the X-ray absorption spectra were evaluated using the Excurve Program (CCLRC Daresbury Laboratory, Warrington, U.K.). From the positions of the absorption edges and from the intensities of the 1s–3d pre-edge transition peaks a six-coordinate ferrous iron was concluded for the rabbit 15-LOX. Evaluation of the extended region of the absorption spectra suggested six nitrogen and/or oxygen atoms as direct iron ligands, and the following binding distances were determined (means±S.D.; estimated accuracy is ±0.001 nm for bond distances, on the basis of more than 22 X-ray absorption spectra): 0.213±0.001 nm, 0.213±0.001 nm, 0.236±0.001 nm, 0.293±0.001 nm, 0.189±0.001 nm and 0.242±0.001. Lyophilization...
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Research Interests:
Research Interests: Chemistry, Analytical Chemistry, Cultural Heritage, Textiles, Painting, and 15 moreMass Spectrometry, Scanning Electron Microscopy, Medicine, Synchrotron Radiation, Cellulose, Spain, X Rays, Synchrotron, Paintings, Paint, X ray diffraction, X ray Fluorescence, X Ray Crystallography, Organic Compound, and Oxidation-Reduction
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ABSTRACT A quantification tool for energy-dispersive X-ray fluorescence (ED-XRF) spectral data is presented, based on the application of Monte Carlo simulations in an iterative, inverse manner. Acting as an open-source plug-in to the... more
ABSTRACT A quantification tool for energy-dispersive X-ray fluorescence (ED-XRF) spectral data is presented, based on the application of Monte Carlo simulations in an iterative, inverse manner. Acting as an open-source plug-in to the widespread PyMca package, it provides users with a superior alternative to the fundamental parameter method based built-in quantification tool, taking into account higher order interactions, M-lines and cascade effects. Examples are shown demonstrating the usefulness of our implementation through data recorded at the synchrotron X-ray fluorescence microprobe installed at the HASYLAB Beamline L, Hamburg, Germany.
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A versatile instrument for the in situ study of catalyst surfaces by surface x-ray diffraction and grazing incidence small angle x-ray scattering in a 13 ml flow reactor combined with reaction product analysis by mass spectrometry has... more
A versatile instrument for the in situ study of catalyst surfaces by surface x-ray diffraction and grazing incidence small angle x-ray scattering in a 13 ml flow reactor combined with reaction product analysis by mass spectrometry has been developed. The instrument bridges the so-called “pressure gap” and “materials gap” at the same time, within one experimental setup. It allows for the preparation and study of catalytically active single crystal surfaces and is also equipped with an evaporator for the deposition of thin, pure metal films, necessary for the formation of small metal particles on oxide supports. Reactions can be studied in flow mode and batch mode in a pressure range of 100–1200 mbar and temperatures up to 950 K. The setup provides a unique combination of sample preparation, characterization, and in situ experiments where the structure and reactivity of both single crystals and supported nanoparticles can be simultaneously determined.
Research Interests: Engineering, Materials Science, Surfaces and Interfaces, High Pressure, Mass Spectrometry, and 15 moreMedicine, Sample Preparation, Heterogeneous Catalysis, Scientific Instruments, Single crystal surface, Physical sciences, Diamond Anvil cell, Diffraction, Chemical Analysis, Product Distribution, CHEMICAL SCIENCES, Single Crystal, Scattering, Catalytic Activity, and Shock Tube
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Fe K-edge XANES spectra have been measured in more than 35 Fe(II) and Fe(III)-bearing minerals. The separation between the average pre-edge centroid positions for Fe(II) and Fe(III) is 1.4 ± 0.1 eV. Examination of calculated pre-edge... more
Fe K-edge XANES spectra have been measured in more than 35 Fe(II) and Fe(III)-bearing minerals. The separation between the average pre-edge centroid positions for Fe(II) and Fe(III) is 1.4 ± 0.1 eV. Examination of calculated pre-edge features of mechanical mixtures of phases containing different proportions of Fe(II) and Fe(III) reveals that different trends of pre-edge position vs. pre-edge intensity can be observed, depending on the coordination environment. Both pre-edge parameters have been used to estimate the ferric/ferrous ratio in 12 natural minerals.
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Research Interests:
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We present an explicit solver of the three-dimensional screened and unscreened Poisson's equation, which combines accuracy, computational efficiency, and versatility. The solver, based on a mixed plane-wave/interpolating scaling... more
We present an explicit solver of the three-dimensional screened and unscreened Poisson's equation, which combines accuracy, computational efficiency, and versatility. The solver, based on a mixed plane-wave/interpolating scaling function representation, can deal with any kind of periodicity (along one, two, or three spatial axes) as well as with fully isolated boundary conditions. It can seamlessly accommodate a finite screening length, non-orthorhombic lattices, and charged systems. This approach is particularly advantageous because convergence is attained by simply refining the real space grid, namely without any adjustable parameter. At the same time, the numerical method features \documentclass[12pt]{minimal}\begin{document}$\mathcal {O}(N\log N)$\end{document}O(NlogN) scaling of the computational cost (N being the number of grid points) very much like plane-wave methods. The methodology, validated on model systems, is tailored for leading-edge computer simulations of materi...
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ABSTRACT X-Ray fluorescence (XRF) is one of the most established techniques for the analysis of works of art. It offers several features—such as non-invasiveness, richness of information, in situ analysis with portable instruments and 2D... more
ABSTRACT X-Ray fluorescence (XRF) is one of the most established techniques for the analysis of works of art. It offers several features—such as non-invasiveness, richness of information, in situ analysis with portable instruments and 2D and 3D micro-imaging when performed at synchrotron sources—which are increasingly used in the field of Cultural Heritage science. However, the complexity of artistic materials may lead into complex XRFspectra. Overlapping of fluorescence emission lines can make XRF analyses prone to error. In this article, we discuss the attributes of the polycapillary-based Wavelength Dispersive X-ray Spectrometer (WDS) developed at the X-ray micro-spectroscopy ESRF beamline, ID21. With spectral resolution of a few tens of eV, this system allows better separation of neighbouring emission lines. Its pros and cons for micro-XRF point analysis, micro-XRF mapping and micro-XANES are addressed, with a particular focus on Cultural Heritage applications. Possible extensions towards micro-RIXS are also discussed.
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... In Reiche et al. (2001), optical spectroscopy, time-resolved laser-induced fluorescence (TRLIF) and X-ray absorption near edge structure (XANES) analyses of fossilised ivory showed that the oxidation state of manganese is essentially... more
... In Reiche et al. (2001), optical spectroscopy, time-resolved laser-induced fluorescence (TRLIF) and X-ray absorption near edge structure (XANES) analyses of fossilised ivory showed that the oxidation state of manganese is essentially 2+ in unheated samples and becomes 5 ...
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Applications of FTIR to the study of ancient paintings have encountered two major steps: the development of FTIR microscopes, which enable to watch the sample and to select the regions of interest; and the migration of those FTIR... more
Applications of FTIR to the study of ancient paintings have encountered two major steps: the development of FTIR microscopes, which enable to watch the sample and to select the regions of interest; and the migration of those FTIR microscopes towards synchrotron ...
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Research Interests: Chemistry, Crystallography, Medicine, Manganese, EPR Spectroscopy, and 15 moreBiological Sciences, EXAFS, Absorption spectroscopy, Nmr, Physical sciences, Magnetic Resonance, CHEMICAL SCIENCES, Oxygen, Ft, Mes, Energy Transfer, Oxygen Evolving Complex, Photosystem II, Freezing, and Electron Paramagnetic Resonance
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Research Interests: Biochemistry, Chemistry, Crystallography, Water, Medicine, and 15 moreManganese, Fourier Analysis, Absorption spectroscopy, Temperature, Oxidation State, Room Temperature, Spectrum analysis, Low Temperature, Oxygen Evolving Complex, Dimer, Photosystem II, Organometallic Compounds, Biochemistry and cell biology, protonation, and Medical biochemistry and metabolomics
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Research Interests:
X-ray fluorescence (XRF) measurements on solutions or crystals of biological macromolecules provide additional information that can be used in structure determination and/or refinement protocols. Here details are presented of an... more
X-ray fluorescence (XRF) measurements on solutions or crystals of biological macromolecules provide additional information that can be used in structure determination and/or refinement protocols. Here details are presented of an experimental setup, employed on all the ESRF Macromolecular Crystallography Group beamlines, that allows the online collection and qualitative analysis of XRF spectra. This experimental setup uses a highly attenuated beam and short exposures, meaning it is minimally destructive but retains high sensitivity.