Research ArticleAPPLIED SCIENCES AND ENGINEERING

Biogenic metallic elements in the human brain?

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Science Advances  09 Jun 2021:
Vol. 7, no. 24, eabf6707
DOI: 10.1126/sciadv.abf6707
  • Fig. 1 STXM images, metal maps, and iron and copper L2,3-edge x-ray absorption spectra of an amyloid plaque core from subject X.

    (A) STXM image showing the overall plaque morphology. (B) Composite STXM image showing plaque morphology (blue), Cu2+ (green), Cu+/Cu0 (red), and iron (gray) content. (C) Iron oxidation state difference map of the region highlighted in (B). Strongly absorbing oxidized iron (Fe3+) is shown as light contrast, and chemically reduced iron (Fe2+ and/or Fe0) is shown as dark contrast. (D) High-resolution composite image and (E) copper oxidation state difference map of the region highlighted in (B). In the oxidation state difference map, oxidized copper (Cu2+) is shown as light contrast, and chemically reduced copper (Cu+ and/or Cu0) is shown as dark contrast. (F) Iron x-ray absorption spectra from the regions highlighted in (C). (G) Copper x-ray absorption spectra from the regions highlighted in (E). Energies corresponding to Cu2+ and Cu+/Cu0 content are shown as dashed and dotted-dashed lines, respectively. (H and I) Reference x-ray absorption spectra from iron and copper standards of varying oxidation states. (H) Iron L2,3-edge and (I) copper L2,3-edge. The energies corresponding to the oxidized and reduced states of the metals are shown by the dotted-dashed and dashed lines, respectively. Copper x-ray absorption spectra. Reprinted from Jiang et al. (42) with the permission of AIP Publishing.

  • Fig. 2 STXM images, metal maps, and copper and iron x-ray absorption spectra from a subject Y amyloid plaque.

    (A) STXM image showing the overall plaque morphology. (B) Cu+/Cu0 map. (C) Iron map. (D) Composite STXM image showing plaque morphology (blue), Cu+/Cu0 (red), and iron (gray) content. (E) Copper x-ray absorption spectrum from the copper area highlighted in (B) (cyan trace) and a Cu0 reference (black trace). Reprinted from Jiang et al. (42) with the permission of AIP Publishing. The energies corresponding to Cu2+ and Cu+/Cu0 content are shown by the dashed and dotted-dashed lines, respectively. Asterisks highlight extended x-ray absorption fine structure (EXAFS) indicative of metallic copper (Cu0). (F) Iron x-ray absorption spectra from the areas highlighted in (C).

  • Fig. 3 STXM images, metal maps, and copper and iron x-ray absorption spectra from a subject X amyloid plaque core.

    (A) Overall plaque morphology. (B) Cu+/Cu0 map. (C) Iron map. (D) Composite STXM image showing plaque morphology (blue), Cu+/Cu0 (red), and iron (gray) content. (E) Copper x-ray absorption spectrum from the copper deposit highlighted in (B). The energies corresponding to Cu2+ and Cu+/Cu0 content are shown by the dashed and dotted-dashed lines, respectively. (F) High-resolution iron map and (G) iron XMCD map from the region highlighted in yellow in (C). In the XMCD map, areas of bright and dark contrast represent the presence of magnetic iron. (H) Iron x-ray absorption spectra from the iron deposits highlighted in (C), (F), and (G).

  • Fig. 4 Schematic displaying the experimental setup for the magnetically sensitive XMCD measurements.

    A magnet array was inserted into the rear face of the sample holder (magnetic field lines shown in orange), placing the sample (located on the front face of the holder) under a magnetic field of 250 mT. The incident x-ray beam was tuned to contain either left circularly polarized (LCP) or right circularly polarized (RCP) light. Sample regions were examined under both LCP and RCP light, with differences between these two measurements representing the XMCD effect (see also Materials and Methods).

  • Fig. 5 XMCD measurements of a subject X amyloid plaque core.

    (A) LCP and RCP iron x-ray absorption spectra, and (B) XMCD spectra from the amyloid plaque iron shown in Fig. 3, and a thin Fe0 reference film.

Supplementary Materials

  • Supplementary Materials

    Biogenic metallic elements in the human brain?

    James Everett, Frederik Lermyte, Jake Brooks, Vindy Tjendana-Tjhin, Germán Plascencia-Villa, Ian Hands-Portman, Jane M. Donnelly, Kharmen Billimoria, George Perry, Xiongwei Zhu, Peter J. Sadler, Peter B. O�Connor, Joanna F. Collingwood, Neil D. Telling

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