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  • 1
    Language: English
    In: Chemical Communications, 2018, Vol. 54, pp. 7770-7773
    Description: The molecular water oxidation catalyst [Ru(bda)(L)(2)] has been incorporated into pyridine-decorated MIL-101(Cr) metal-organic frameworks. The resulting MIL-101@Ru materials exhibit turnover frequencies (TOFs) up to ten times higher compared to the homogenous reference. An unusual dependence of the formal TOFs on oxidant concentration is observed that ultimately arises from differing amounts of catalysts in the MOF crystals being active.
    Keywords: Natural Sciences ; Chemical Sciences ; Inorganic Chemistry ; Naturvetenskap ; Kemi ; Oorganisk Kemi ; Natural Sciences ; Chemical Sciences ; Materials Chemistry ; Naturvetenskap ; Kemi ; Materialkemi
    ISSN: 1359-7345
    E-ISSN: 1364548X
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  • 2
    Language: English
    In: Biophysical Journal, 29 March 2016, Vol.110(6), pp.1304-1311
    Description: The biological influence of radiation on living matter has been studied for years; however, several questions about the detailed mechanism of radiation damage formation remain largely unanswered. Among all biomolecules exposed to radiation, DNA plays an important role because any damage to its molecular structure can affect the whole cell and may lead to chromosomal rearrangements resulting in genomic instability or cell death. To identify and characterize damage induced in the DNA sugar-phosphate backbone, in this work we performed x-ray absorption spectroscopy at the P K-edge on DNA irradiated with either UVA light or protons. By combining the experimental results with theoretical calculations, we were able to establish the types and relative ratio of lesions produced by both UVA and protons around the phosphorus atoms in DNA.
    Keywords: Biology
    ISSN: 0006-3495
    E-ISSN: 1542-0086
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  • 3
    Language: English
    In: Applied Spectroscopy, February 2016, Vol.70(2), pp.264-271
    Description: The use of synchrotron radiation may shed more light on the study of prostate cancer, one of the leading diseases among men. In the presented study the microbeam setup at the PSI Swiss Light Source combined with fluorescence detected X-ray absorption spectroscopy (XAS) was applied to determine two-dimensional (2D) imaging of distributions of various chemical sulfur forms in prostate cancer tissue sections, since sulfur is considered important and essential in cancer progression. The research focused on prostate tissues obtained during routine prostatectomies on patients suffering from prostate cancer. Our previous studies using μ-XAS point measurements on prostate cancer cell lines showed the differences in fractions of various forms of sulfur between cancerous and non-cancerous cells. Therefore, in this experiment the chosen areas of prostate cancer tissues were scanned to get the full picture of the chemical composition of tissue, which is highly heterogeneous. The incident X-ray beams of energies tuned to spectroscopic features of the near-edge region of sulfur K-edge absorption spectra were used to provide contrast between chemical species presented in the tissue. Next, the relative content of the three main sulfur forms, found in biological systems, was calculated and the results are presented in a form of 2D color maps. These maps are correlated with the microscopic histological image of the scanned area. The main findings show that sulfur occurs in prostate tissue mainly in reduced form. The oxidized form of sulfur is present mostly in prostatic stroma, while sulfur in intermediate oxidation state is present in trace amount.
    Keywords: Sulfur ; X-Ray Absorption Spectroscopy (Xas) Imaging ; Prostate Cancer ; Chemistry
    ISSN: 0003-7028
    E-ISSN: 1943-3530
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  • 4
    Language: English
    In: Chemical Physics, 17 August 2017, Vol.493, pp.49-55
    Description: Resonant X-ray emission spectroscopy (RXES) technique was applied to probe electronic states of three Fe compounds: Fe, α-Fe O (hematite) and Fe(NO ) × 9 H O (ferric nitrate) around Fe K-absorption edge with simultaneous detection of Kβ and valence-to-core transitions. We show that deep insights on the valence and conduction band position, such as main orbital contribution to band-gap formation and ligand orbital contributions, can be retrieved from RXES data. Moreover applicability of Kβ and valence-to-core RXES measurements to extract band gap energies is demonstrated. Obtained results were supplemented with calculations allowing precise determination of orbital contributions to the measured spectral features. Good agreement with experimental results has shown that proposed approach is promising tool in further applications.
    Keywords: Rxes ; Iron ; X-Ray Spectroscopy ; Feff ; Density of States ; Chemistry ; Physics
    ISSN: 0301-0104
    Source: ScienceDirect Journals (Elsevier)
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  • 5
    Language: English
    In: Nuclear Inst. and Methods in Physics Research, B, 15 November 2017, Vol.411, pp.121-128
    Description: Neurodegenerative diseases are one of the malfunctions of human nervous system, being a class of complex and prominent pathologies. The human prion Protease Resistant Protein (PrP) is protein regulating copper metabolism in mammalian cells through binding of Cu(II) ions to specific fragments. Nowadays misfolding of this protein is associated with development of prion diseases. Therefore, it is crucial to obtain structural information about coordination of Cu(II) by PrP protein. Herein, we report X-ray absorption spectroscopy (XAS) measurements, carried out on SuperXAS beamline (SLS, PSI Villigen) on PrP -Cu(II) complexes. Obtained results were compared with theoretical predictions done by FEFF 9.6 software. Complementary to XAS data, Atomic Force Microscopy (AFM) measurements were conducted to obtain low resolution structural information about prepared sample that allow to develop protocol of fixing PrP molecules on solid substrate used for further experiments. It has been established that folded C-terminal domain of PrP protein has around 5 nm in diameter. Presented results showed that both XAS and AFM methods are useful tools in detailed examination of complexes of human PrP either with Cu(II) or with other divalent metal ions.
    Keywords: Human Prion Protein ; Afm ; Xas ; Copper Binding ; Neurodegeneration Diseases ; Physics
    ISSN: 0168-583X
    E-ISSN: 1872-9584
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  • 6
    Language: English
    In: Materials Chemistry and Physics, 01 April 2018, Vol.208, pp.281-288
    Description: Herein, we report a systematic study on the electronic structure of surface and bulk TiO doped with C, N or S. The results were attained with a semi-empirical method consisting of a combination between resonant X-ray emission spectroscopy (RXES) measurements and localized density of states (LDOS) simulations. Experimental TiO RXES data was used to fit FEFF code empirical parameters, and subsequently frozen for the theoretical analysis of LDOS of TiO doped materials. The results show significant electronic structure differences between bulk and surface doping, as well as in the nearest Ti atom electronic structure if it is located at the surface or sub-surface, with potential consequences to the photo-catalytic process. The methodology can be adapted to study other dopants, morphologies, structures and surface terminations and as well as other inorganic semiconductors.
    Keywords: Tio2 Doping ; Electronic Structure Analysis ; Surface Vs Bulk ; Engineering ; Chemistry
    ISSN: 0254-0584
    E-ISSN: 1879-3312
    Source: ScienceDirect Journals (Elsevier)
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  • 7
    Language: English
    In: Applied Sciences, 01 September 2017, Vol.7(9), p.899
    Description: We report on the application of a short working distance von Hamos geometry spectrometer to measure the inelastic X-ray scattering (IXS) signals from solids and liquids. In contrast to typical IXS instruments where the spectrometer geometry is fixed and the incoming beam energy is scanned,...
    Keywords: Dispersive X-Ray Spectrometer ; Von Hamos Geometry ; Inelastic X-Ray Scattering ; X-Ray Free Electron Laser ; Swissfel ; Segmented Crystal ; Engineering ; Sciences (General)
    E-ISSN: 2076-3417
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  • 8
    Language: English
    In: Journal of Biological Inorganic Chemistry, 2015, Vol.20(5), pp.841-853
    Description: The structure-activity relationships of chiral 1,2-diaminophenylalkane platinum(II) anticancer derivatives are studied, including interactions with telomeric- and genomic-like DNA sequences, the pKa of their diaqua species, structural properties obtained from DFT calculations and resonant X-ray emission...
    Keywords: Natural Sciences ; Biological Sciences ; Biochemistry And Molecular Biology ; Naturvetenskap ; Biologiska Vetenskaper ; Biokemi Och Molekylärbiologi ; Cancer ; Platinum ; G-Quadruplex ; Conceptual Dft ; Rxes
    ISSN: 0949-8257
    E-ISSN: 14321327
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  • 9
    In: Journal of Synchrotron Radiation, 01 January 2018, Vol.25(1), pp.16-19
    Description: One of the remaining challenges for accurate photon diagnostics at X‐ray free‐electron lasers (FELs) is the shot‐to‐shot, non‐destructive, high‐resolution characterization of the FEL pulse spectrum at photon energies between 2 keV and 4 keV, the so‐called tender X‐ray range. Here, a spectrometer setup is reported, based on the von Hamos geometry and using elastic scattering as a fingerprint of the FEL‐generated spectrum. It is capable of pulse‐to‐pulse measurement of the spectrum with an energy resolution (Δ/) of 10, within a bandwidth of 2%. The Tender X‐ray Single‐Shot Spectrometer (TXS) will grant to experimental scientists the freedom to measure the spectrum in a single‐shot measurement, keeping the transmitted beam undisturbed. It will enable single‐shot reconstructions for easier and faster data analysis. A single‐shot spectrometer for the tender X‐ray range is presented, based on the von Hamos geometry and using elastic scattering as a fingerprint of the XFEL‐produced spectrum.
    Keywords: Free‐Electron Laser ; Tender X‐Ray Spectroscopy ; Single‐Shot Measurement
    ISSN: 1600-5775
    ISSN: 09090495
    E-ISSN: 1600-5775
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  • 10
    In: Analyst, 2016, Vol.141(4), pp.1226-1232
    Description: Platinum-based drugs are commonly used in cancer treatment. The biological activity of a metallodrug is obviously closely related to its chemical and stereochemical characteristics. An overlooked aspect is the effect of the ligand to the electronic structure of the metal atom (coordinated atom). We report herein a Resonant X-ray Emission Spectroscopy (RXES) study on the chemical speciation of chiral platinum complexes in which diastereomers are distinguished on the basis of their metal electronic configuration. This demonstrates RXES high chemical speciation capabilities, a necessary property to further investigate the reactivity of the Pt atom towards nucleophiles or bionucleophiles, and an important complement the previously reported RXES abilities, namely that it can be employed for in situ studies at physiological concentrations.
    Keywords: Spectrometry, X-Ray Emission ; Antineoplastic Agents -- Chemistry ; Organoplatinum Compounds -- Chemistry;
    ISSN: 0003-2654
    E-ISSN: 1364-5528
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