AMES, Iowa - Bone is one of nature's surprising "building materials." Pound-for-pound it's stronger than steel, tough yet resilient. Scientists at the U.S. Department of Energy's Ames Laboratory have identified the composition that gives bone its outstanding properties and the important role citrate plays, work that may help science better understand and treat or prevent bone diseases such as osteoporosis.
Using nuclear magnetic resonance (NMR) spectroscopy, Ames Laboratory scientist and Iowa State University chemistry professor Klaus Schmidt-Rohr and his colleagues studied bone, an organic-inorganic nanocomposite whose stiffness is provided by thin nanocrystals of carbonated apatite, a calcium phosphate, imbedded in an organic matrix of mostly collagen, a fibrous protein.
By understanding the nanostructure of naturally occurring materials, researchers may be able to develop new light-weight, high-strength materials that will require less energy to manufacture and that could make the products in which they are used more energy efficient.
"The organic, collagen matrix is what makes bones tough," Schmidt-Rohr said, "while the inorganic apatite nanocrystals provide the stiffness. And the small thickness about 3 nanometers of these nanocrystals appears to provide favorable mechanical properties, primarily in prevention of crack propagation."
While bone structure has been studied extensively, how these apatite nanocrystals form and what prevents them from growing thicker was a mystery. Some research pointed to sugars being involved, but that didn't match with the NMR spectra that Schmidt-Rohr was seeing.
"We can see all the peaks clearly," he says of a spectral graph which shows the points at which specific components in bone samples resonate; these specific signatures are the key to NMR technology, "even those at the organic-inorganic interface, where the organic material's signal strength is relatively w
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