Einstein Science Reporting for Kids
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4-Mar-2010

Contact: Science Press Package
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American Association for the Advancement of Science

Why are mussels' muscles so strong?



Mussels attach to hard surfaces on the rocky seashore with the byssus. Byssal threads are protected from abrasive damage by a hard and extensible knobby coating composed of proteins complexed with iron.
[Image courtesy of Matthew Harrington]

Marine mussels attach themselves to rocky seashores with strong fibers they produce, called byssal threads. Despite the constant motions of the tide—pushing and pulling the mussels in different directions—the byssal threads remain strong, yet stretchable at the same time. For researchers, this combination of physical properties is very attractive, and understanding how the mussels form these byssal threads might even improve industrial materials for humans in the future.



Mussels attach to hard surfaces on the rocky seashore with the byssus. Byssal threads are protected from abrasive damage by a hard and extensible knobby coating composed of proteins complexed with iron.
[Image courtesy of Susan Weichold]

So, Matthew Harrington and colleagues turned some high-powered microscopes onto mussels' byssal threads, and found that they were coated in a sticky protein covered with metal ions. The protein, called dopa, is known to be a strong adhesive—and the researchers found that most of the metal ions ingrained into the dopa were iron. This combination of "sticky" dopa and "hard" iron is what gives the mussels' byssal threads their tremendous strength and flexibility—at the same time.

In light of their discovery, the researchers made a model of this biological material, and describe its unusual clustering of protein and metal. The material is exceptionally strong where the iron ions are densely packed in with the dopa protein, but it becomes stretchable where there are fewer cross-links between the two.

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