Pupa Gilbert (née Gelsomina De Stasio)
Research Group


Nacre

The nacre layer, or mother of pearl, at the inner surface of the abalone shell and of other mollusk shells and pearls (see images below) has a fracture resistance 3000 times greater than that of aragonite, the pure mineral of which it is composed. The toughening effect is due to well-defined nanolayers of organics at the interfaces between micro-tablets of aragonite (JD Currey 1977, 2005).

Nacre formation is poorly understood at the molecular level, and this piqued our interest in this material, exploring the organic-mineral interface (Gilbert 2005, Metzler 2010, Metzler 2010).

We strive to understand the fundamental mechanisms leading to the formation of the beautiful, extraordinarily efficient, self-assembling natural structures in nacre. We recently discovered a new polarization-dependent imaging contrast (PIC) mechanism, also known as linear dichroism. The PIC-mapping method we developed (DeVol 2014) showed that adjacent stacks of co-oriented tablets have different crystallographic c-axis orientations, and consequently the nacre growth direction cannot be identified with the c-axis (Metzler 2007). The appearance of the columns also inspired new models for the formation mechanism of nacre (Gilbert 2008).

Our hypothesis is that the physical structure of nacre is affected by the environmental conditions at the time of nacre deposition. We are currently exploring this possibility (Olson 2012, Olson 2012, Gilbert 2015 in preparation).

We recently discovered that nacre forms via two amorphous precursor phases, similar to those found in sea urchin biominerals, and not proto-aragonite (DeVol 2015).


Polarization-dependent imaging contrast in a side view of red abalone nacre. Different gray levels correspond to different c-axis orientations with respect to the illuminating x-ray polarization vector. Immediately adjacent columns are mis-aligned in c-axis direction. Data from ref. 5.


GG Publications on Nacre
  1. P.U.P.A. Gilbert, Bradley H. Frazer and M. Abrecht.
    The organic-mineral interface in biominerals.
    Reviews in Mineralogy and Geochemistry. In: Molecular Geomicrobiology. Vol 59. JF Banfield, KH Nealson, J. Cervini-Silva (eds), Mineralogical Society of America, Washington DC, p 157-185 (2005). PDF
  2. Rebecca A. Metzler, Mike Abrecht, Ronke M. Olabisi, Daniel Ariosa, Christopher J. Johnson, Bradley H. Frazer, Susan N. Coppersmith, P.U.P.A. Gilbert.
    Columnar Nacre Architecture and Possible Formation Mechanism.
    Phys. Rev. Lett. 98, 268102-1/4 (2007). PDF Also featured in Science 317, 175 (2007). PDF
  3. Rebecca A. Metzler, Dong Zhou, Mike Abrecht, Jau-Wern Chiou, Jinghua Guo, Daniel Ariosa, Susan N. Coppersmith, P.U.P.A. Gilbert.
    Polarization-dependent imaging contrast in abalone shells.
    Phys. Rev. B. 77, 064110-1/9 (2008). PDF
  4. Dong Zhou, Rebecca A. Metzler, Tolek Tyliszczak, Jinghua Guo, Mike Abrecht, Susan N. Coppersmith, P.U.P.A. Gilbert.
    Assignment of polarization-dependent peaks in carbon K-edge spectra from biogenic and geologic aragonite.
    J. Phys. Chem. B 112, 13128-13135 (2008). PDF
  5. P.U.P.A. Gilbert, Rebecca A. Metzler, Dong Zhou, Andreas Scholl, Andrew Doran, Anthony Young, Martin Kunz, Nobumichi Tamura, Susan N. Coppersmith.
    Gradual Ordering in Red Abalone Nacre.
    J. Am. Chem. Soc. 130, 17519-17527 (2008).
    PDF SI
  6. S. N. Coppersmith, P.U.P.A. Gilbert and R. A. Metzler.
    Theoretical characterization of a model of aragonite crystal orientation in red abalone nacre.
    J. Phys. A: Math. Theor. 42, 125101 (2009). PDF
  7. RA Metzler, GA Tribello, M Parrinello, and PUPA Gilbert.
    Asprich peptides are occluded in calcite and permanently disorder biomineral crystals.
    J. Am. Chem. Soc. 132, 11585-11591 (2010). PDF
  8. RA Metzler, JS Evans, CE Killian, D. Zhou, TH Churchill, N Appathurai, SN Coppersmith, PUPA Gilbert.
    Nacre Protein Fragment Templates Lamellar Aragonite Growth.
    J. Am. Chem. Soc. 132, 6329-6334 (2010). PDF
  9. IC Olson, R Kozdon, JW Valley, and PUPA Gilbert.
    Mollusk Shell Nacre Ultrastructure Correlates with Environmental Temperature and Pressure.
    J. Am. Chem. Soc. 134, 7351-7358 (2012).
    COVER PDF
  10. IC Olson and PUPA Gilbert.
    Aragonite crystal orientation in mollusk shell nacre may depend on temperature. The angle spread of crystalline aragonite tablets records the water temperature at which nacre was deposited by Pinctada margaritifera.
    Faraday Discuss. 159, 421-432 (2012). PDF
  11. PUPA Gilbert.
    Polarization-dependent Imaging Contrast (PIC) mapping reveals nanocrystal orientation patterns in carbonate biominerals.
    J. Electr. Spectrosc. and Rel. Phenom. special issue on Photoelectron microscopy, Time-resolved pump-probe PES. Eds. M Kiskinova, A Scholl. Vol 185, pages 395-405 (2012). PDF
  12. IC Olson, AZ Blonsky, N Tamura, M Kunz, B Pokroy, CP Romao, MA White, and PUPA Gilbert.
    Crystal nucleation and near-epitaxial growth in nacre.
    J. Struct. Biol. 184, 454-463 (2013). COVER PDF
  13. RT DeVol, C-Y Sun, MA Marcus, SN Coppersmith, SCB Myneni, and PUPA Gilbert.
    Nanoscale transforming mineral phases in fresh nacre.
    J Am Chem Soc, 137, 13325-13333 (2015).
    PDF
    Highlighted in Science 350, 648 (2015). PDF

Also see stories from UW NEWS July 2, 2007 by Jill Sakai
    Mother-of-pearl: Classic beauty and remarkable strength
and October 20, 2015 by Terrance Devitt
    Mother-of-pearl's genesis identified in mineral's transformation


click each for larger image and caption