Researchers have cracked the mystery of the abalone shell's toughness and fracture resistance, according to the June 24 issue of the journal Nature.

It's all in the stretch, according to the discovery made at the University of California, Santa Barbara, by a team of physicists, molecular biologists and chemists.

The discovery suggests a new kind of biological "rubber" and helps explain the exceptional strength of the plywood-like structure of the abalone shell.

"Now that we've elucidated some of nature's secrets, we can begin to mimic these design patterns," said Bettye L. Smith, research associate in the Department of Physics, and lead author, who is working toward designing and synthesizing strong and tough fibers based on nature's design.

The abalone shell is roughly 3,000 times more fracture resistant than a single crystal of calcium carbonate, the mineral that makes up most of its bulk. The UC Santa Barbara experiments show that the mechanism behind the fracture resistance is in the polymer adhesive that holds the crystal tablets together.

The researchers were able to reveal the properties of the adhesive in single-molecule pulling experiments using the Atomic Force Microscope (AFM) to measure the elasticity and strength of individual protein molecules. This work was done under the direction of Paul K. Hansma, professor of physics, by his laboratory group. (Hansma is a major developer of new techniques using the AFM.)

"By grabbing a single molecule and pulling on it as if it were a rubber band, you can measure the strength of a single molecular fiber," said Smith.

"Using this technique they discovered that the tiny crystal plates of mineral that make up the abalone shell are held together with many molecules of a protein that have a truly enormous capacity to absorb shock without breaking," said Dan Morse, professor of molecular genetics and biochemistry and chai
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Contact: Gail Brown
gbrown@instadv.ucsb.edu
805-893-7220
University of California - Santa Barbara
24-Jun-1999