Scientists discover how mother-of-pearl composes itself into a perfect structure

Scientists discover how mother-of-pearl composes itself into a perfect structure

A cross-section through a shell showing the periodically low layer on the prismatic shell structure. Credit: © Igor Zlotnikov

In a new study published in Natural Physics, researchers from the B CUBE – Center for Molecular Bioengineering at the TU Dresden and the European Synchrotron Radiation Facility (ESRF) in Grenoble, describe for the first time that structural defects in the self-collecting neck attract and eliminate each other, which eventually leads to a perfect periodic structure.

Molluscs build shells to protect their soft tissues from predators. Nacre, also known as the mother of pearl, has an intricate, very regular structure that makes it an incredibly strong material. Depending on the species, the veins can grow about ten inches long. No matter the size, each nacre is constructed of materials laid down simultaneously by a multitude of single cells. How exactly this extremely periodic and uniform structure emerges from the initial deviation was hitherto unknown.

Nacre formation begins uncoordinated with the cells depositing the material in different places simultaneously. It is not surprising that the early post-acid structure is not very frequent. At this point, it is full of flaws. “At the very beginning, the layered mineral-organic tissue is full of structural defects that propagate through a number of layers like a helix. In reality, it looks like a spiral staircase with either right- or left-handed orientation,” says Dr. Igor Zlotnikov, research group leader at the B CUBE – Center for Molecular Bioengineering at the TU Dresden. “The role of these defects in the formation of such a periodic tissue has never been determined. On the other hand, the adult neck is not defect-free, with a regular, uniform structure. How can perfection result from such disorder?

The researchers from the Zlotnikov group worked with the European Synchrotron Radiation Facility (ESRF) in Grenoble to investigate the internal structure of the early and adult necks in great detail. Using synchrotron-based holographic X-ray nano-tomography, the researchers were able to capture the growth of blood loss over time. “Nacre is an extremely fine structure with organic characteristics of less than 50 nm. Beamline ID16A to the ESRF has given us an unprecedented ability to visualize the blood in three dimensions,” explains dr. Zlotnikov. “The combination of electron-dense and extremely periodic inorganic platelets with delicate and slender organic interfaces makes nacre a challenging structure for the image. Cryogenic imaging has helped us achieve the resolution we need,” explains dr. Pacureanu of the X-ray Nanoprobe Group at the ESRF.

Scientists discover how mother-of-pearl composes itself into a perfect structure

The terminal at the holographic X-ray nano-tomography beamline (ID16A) at ESRF. Credit: © Igor Zlotnikov

Analyzing data was quite a challenge. The researchers developed a segmentation algorithm using neural networks and trained it to separate different layers nakre. In this way, they were able to follow what happens to the structural defects as the neck grows.

The behavior of structural defects in a growing nakre was surprising. Defects of the opposite screw direction attracted from great distances to each other. The right- and left-handed flaws moved through the structure until they met and canceled each other out. These events led to a tissue-wide synchronization. Over time, it developed the structure into a perfectly smooth and error-free shape.

Periodic structures similar to nature are produced by many different species of animals. The researchers believe that the newly discovered mechanism may not only drive the formation of the blood nose, but also other biogenic structures.


New material mimics strength, toughness of mother of pearl


More information:
Dynamics of topological defects and structural synchronization in a forming periodic tissue, Natural Physics (2021). DOI: 10.1038 / s41567-020-01069-z, www.nature.com/articles/s41567-020-01069-z

Provided by Dresden University of Technology

Quotation: Scientists discover how mother-of-pearl composes itself into a perfect structure (2021, 4 January) on 5 January 2021 from https://phys.org/news/2021-01-scientists-mother-of-pearl-self -assembles.html

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