Apatite X-ray linear dichroism reveals mesoscale crystal orientations in parrotfish bone and teeth

ORAL

Abstract

Apatites are an important biomineral, being a major component of bone, dentin, enamel, and enameloid in a variety of organisms. Yet, the use of x-ray linear dichroism in the study of these minerals remains largely unexplored. We observed x-ray linear dichroism at the Calcium L and K edge in geologic hydroxyapatite (Ca5(PO4)3OH), fluorapatite (Ca5(PO4)3F), and their biogenic counterparts in parrotfish bone, dentin, and enameloid. Furthermore, we explain this phenomenon with detailed models of the apatite crystal and calculated spectra, in excellent agreement with experimental spectra1. This discovery enables visualization of the nano- to micro-scale structure of apatite crystals in human teeth and bone using Polarization-dependent Imaging Contrast (PIC) maps2. Illustrative new PIC maps of parrotfish enameloid show a most complex arrangement of fluorapatite crystals, bundled and interwoven3, which makes parrotfish enameloid uniquely capable of biting stony corals.

(1) C. A. Stifler et. al. PRL 2017, under review.
(2) PUPA Gilbert et al. PNAS 108, 2011. DOI: 10.1073/pnas.1107917108
(3) MA Marcus et al. ACS Nano in press 2017, DOI:10.1021/acsnano.7b05044

*Supported by NSF grant DMR-1603192 and DOE grant DE-FG02-07ER15899

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Presenters

  • Cayla Stifler

    • Department of Physics, University of Wisconsin-Madison
    • Department of Physics, University of Wisconsin–Madison
    • Physics, Chemistry, Geoscience, Univ of Wisconsin

Authors

  • Cayla Stifler

    • Department of Physics, University of Wisconsin-Madison
    • Department of Physics, University of Wisconsin–Madison
    • Physics, Chemistry, Geoscience, Univ of Wisconsin

  • Chang-Yu Sun

    • Department of Physics, University of Wisconsin-Madison
    • Department of Physics, University of Wisconsin–Madison
    • Physics, Chemistry, Geoscience, Univ of Wisconsin
    • University of Wisconsin-Madison

  • Matthew Marcus

    • Advanced Light Source, Lawrence Berkeley National Laboratory

  • Michel Sassi

    • Physical Science Division, Pacific Northwest National Laboratory

  • Kevin Rosso

    • Physical Science Division, Pacific Northwest National Laboratory

  • Pupa Gilbert

    • Department of Physics, Chemistry, and Geoscience, University of Wisconsin-Madison
    • Department of Physics, University of Wisconsin-Madison
    • Department of Physics, University of Wisconsin–Madison
    • Physics, Chemistry, Geoscience, Univ of Wisconsin
    • Departments of Chemistry, Materials Science, and Geoscience, University of Wisconsin-Madison
    • University of Wisconsin-Madison
    • Univ of Wisconsin, Madison