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Ekanayake RSK, Streltsov VA, Best SP, Chantler CT. Using XAS to monitor radiation damage in real time and post-analysis, and investigation of systematic errors of fluorescence XAS for Cu-bound amyloid-β. J Appl Crystallogr 2024; 57:125-139. [PMID: 38322727 PMCID: PMC10840304 DOI: 10.1107/s1600576723010890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 12/20/2023] [Indexed: 02/08/2024] Open
Abstract
X-ray absorption spectroscopy (XAS) is a promising technique for determining structural information from sensitive biological samples, but high-accuracy X-ray absorption fine structure (XAFS) requires corrections of systematic errors in experimental data. Low-temperature XAS and room-temperature X-ray absorption spectro-electrochemical (XAS-EC) measurements of N-truncated amyloid-β samples were collected and corrected for systematic effects such as dead time, detector efficiencies, monochromator glitches, self-absorption, radiation damage and noise at higher wavenumber (k). A new protocol was developed using extended X-ray absorption fine structure (EXAFS) data analysis for monitoring radiation damage in real time and post-analysis. The reliability of the structural determinations and consistency were validated using the XAS measurement experimental uncertainty. The correction of detector pixel efficiencies improved the fitting χ2 by 12%. An improvement of about 2.5% of the structural fitting was obtained after dead-time corrections. Normalization allowed the elimination of 90% of the monochromator glitches. The remaining glitches were manually removed. The dispersion of spectra due to self-absorption was corrected. Standard errors of experimental measurements were propagated from pointwise variance of the spectra after systematic corrections. Calculated uncertainties were used in structural refinements for obtaining precise and reliable values of structural parameters including atomic bond lengths and thermal parameters. This has permitted hypothesis testing.
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Affiliation(s)
| | - Victor A. Streltsov
- School of Physics, University of Melbourne, Australia
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia
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Ekanayake RSK, Chantler CT, Sier D, Schalken MJ, Illig AJ, de Jonge MD, Johannessen B, Kappen P, Tran CQ. High-accuracy measurement of mass attenuation coefficients and the imaginary component of the atomic form factor of zinc from 8.51 keV to 11.59 keV, and X-ray absorption fine structure with investigation of zinc theory and nanostructure. JOURNAL OF SYNCHROTRON RADIATION 2021; 28:1492-1503. [PMID: 34475296 DOI: 10.1107/s1600577521005981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
High-accuracy X-ray mass attenuation coefficients were measured from the first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron. Experimentally measured mass attenuation coefficients deviate by ∼50% from the theoretical values near the zinc absorption edge, suggesting that improvements in theoretical tabulations of mass attenuation coefficients are required to bring them into better agreement with experiment. Using these values the imaginary component of the atomic form factor of zinc was determined for all the measured photon energies. The zinc K-edge jump ratio and jump factor are determined and results raise significant questions regarding the definitions of quantities used and best practice for background subtraction prior to X-ray absorption fine-structure (XAFS) analysis. The XAFS analysis shows excellent agreement between the measured and tabulated values and yields bond lengths and nanostructure of zinc with uncertainties of from 0.1% to 0.3% or 0.003 Å to 0.008 Å. Significant variation from the reported crystal structure was observed, suggesting local dynamic motion of the standard crystal lattice. XAFS is sensitive to dynamic correlated motion and in principle is capable of observing local dynamic motion beyond the reach of conventional crystallography. These results for the zinc absorption coefficient, XAFS and structure are the most accurate structural refinements of zinc at room temperature.
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Affiliation(s)
| | | | - Daniel Sier
- School of Physics, University of Melbourne, Australia
| | | | | | | | | | - Peter Kappen
- ANSTO, Australian Synchrotron, Melbourne, Australia
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Ekanayake RSK, Chantler CT, Sier D, Schalken MJ, Illig AJ, de Jonge MD, Johannessen B, Kappen P, Tran CQ. High-accuracy mass attenuation coefficients and X-ray absorption spectroscopy of zinc - the first X-ray Extended Range Technique-like experiment in Australia. JOURNAL OF SYNCHROTRON RADIATION 2021; 28:1476-1491. [PMID: 34475295 DOI: 10.1107/s1600577521005993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 06/08/2021] [Indexed: 06/13/2023]
Abstract
The first X-ray Extended Range Technique (XERT)-like experiment at the Australian Synchrotron, Australia, is presented. In this experiment X-ray mass attenuation coefficients are measured across an energy range including the zinc K-absorption edge and X-ray absorption fine structure (XAFS). These high-accuracy measurements are recorded at 496 energies from 8.51 keV to 11.59 keV. The XERT protocol dictates that systematic errors due to dark current nonlinearities, correction for blank measurements, full-foil mapping to characterize the absolute value of attenuation, scattering, harmonics and roughness are measured over an extended range of experimental parameter space. This results in data for better analysis, culminating in measurement of mass attenuation coefficients across the zinc K-edge to 0.023-0.036% accuracy. Dark current corrections are energy- and structure-dependent and the magnitude of correction reached 57% for thicker samples but was still large and significant for thin samples. Blank measurements scaled thin foil attenuation coefficients by 60-500%; and up to 90% even for thicker foils. Full-foil mapping and characterization corrected discrepancies between foils of up to 20%, rendering the possibility of absolute measurements of attenuation. Fluorescence scattering was also a major correction. Harmonics, roughness and bandwidth were explored. The energy was calibrated using standard reference foils. These results represent the most extensive and accurate measurements of zinc which enable investigations of discrepancies between current theory and experiments. This work was almost fully automated from this first experiment at the Australian Synchrotron, greatly increasing the possibility for large-scale studies using XERT.
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Affiliation(s)
| | | | - Daniel Sier
- School of Physics, University of Melbourne, Australia
| | | | | | | | | | - Peter Kappen
- ANSTO, Australian Synchrotron, Melbourne, Australia
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Alkire RW. Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil. J Appl Crystallogr 2017. [DOI: 10.1107/s1600576716017544] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the Ni K edge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thick Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. This high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.
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Chantler CT, Islam MT, Rae NA, Tran CQ, Glover JL, Barnea Z. New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique. Acta Crystallogr A 2012; 68:188-95. [PMID: 22338654 DOI: 10.1107/s0108767311044990] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Accepted: 10/27/2011] [Indexed: 11/11/2022] Open
Abstract
An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.
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Affiliation(s)
- C T Chantler
- School of Physics, University of Melbourne, Melbourne, Australia.
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Sharanabasappa, Kerur B, Anilkumar S, Hanumaiah B. Determination of X-ray mass attenuation coefficients using HPGe detector. Appl Radiat Isot 2010; 68:76-83. [DOI: 10.1016/j.apradiso.2009.08.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Revised: 05/24/2009] [Accepted: 08/11/2009] [Indexed: 11/28/2022]
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Kurahashi M, Mizutani J, Hioki A. Determination of Trace Elements in Sediment Reference Materials by Monochromatic X-ray Excitation X-ray Fluorescence Spectrometry. ANAL SCI 2005; 21:827-32. [PMID: 16038504 DOI: 10.2116/analsci.21.827] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A new reliable analytical method, "Monochromatic X-ray Excitation X-ray Fluorescence Spectrometry", has been proposed. For validating the method, trace elements in sediment certified reference materials were determined. In the method X-ray fluorescence spectra are measured for specimens and pure metals; in addition the mass-attenuation coefficients of the specimens for various X-ray wavelengths are also measured. The data are analyzed by the fundamental parameter method and the uncertainty of the analysis is evaluated. The obtained results were in satisfactory agreement with the certified values within their uncertainties. This method will be applicable to the certification of reference materials, in the field of which reliable results with uncertainty statements are required.
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Affiliation(s)
- Masayasu Kurahashi
- National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba 3-10, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
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Lépy MC, Ferreux L, Plagnard J. A tunable monochromatic X-ray source for metrological studies in the 1–20keV energy range: application to the measurement of attenuation coefficients. Appl Radiat Isot 2004; 60:159-65. [PMID: 14987636 DOI: 10.1016/j.apradiso.2003.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A tunable monochromatic X-ray source operating in the 1-20 keV energy range is described. An X-ray tube provides initial photons. A dispersive crystal performs the energy selection, according to Bragg's law. An X-ray detector is connected to the monochromator fixed exit. This setup can be used for metrological studies. A first application consists in measuring attenuation coefficients in the 4-10 keV energy range. Results for aluminum and copper are given, with average relative uncertainties (1sigma) of 1% and 3% respectively.
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Affiliation(s)
- Marie-Christine Lépy
- BNM/Laboratoire National Henri Becquerel, CEA Saclay, Gif-Sur-Yvette Cedex F-91191, France.
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Kerur B, Thontadarya S, Hanumaiah B. Anomalous x-ray attenuation coefficients around the absorption edges using Mn Kα and Cu Kα x-rays. Appl Radiat Isot 1994. [DOI: 10.1016/0969-8043(94)90005-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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A study on the range of non-validity of the Bragg's additivity law for compounds at photon energies below 10 keV. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0883-2889(92)90151-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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