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Bonds make a sacrifice for tough bones

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10:57am, December 12, 2001

Most bumps and falls don't break bones, but it's not entirely clear why these structures are so resilient. Now, scientists have discovered molecular details that may help explain skeletal toughness.

Bones are composite materials made of both brittle hydroxyapatite crystals and a toughening network of fibers, composed mainly of the natural polymer known as collagen. The researchers suggest that bone's resilience comes from bonds in or between collagen molecules that, in effect, sacrifice themselves for the overall good of the fibers. These bonds break easily in an impact and quickly dissipate energy before forces build up to break collagen molecules' chainlike backbones.

Because of the sacrificial bonds, "the polymer network doesn't fail," says molecular biologist Daniel E. Morse.

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