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Spun from bone

Scientists at Pacific Northwest National Laboratory recently announced a milestone discovery for those who would wish to nano-engineer tissues, implants and synthetic coatings. A team of PNNL scientists has discovered how protein in teeth controls bone-like crystals to form steely enamel.

Bone and enamel start with the same calcium-phosphate crystal building material but end up quite different in structure and physical properties. The difference in bone and enamel microstructure is attributed to a key protein in enamel that molds crystals into strands thousands of times longer and much stronger than those in bone. But how that protein achieves this feat of crystal-strand shape-shifting has remained elusive. Scientists recently reported the first direct observation of how this protein, amelogenin, interacts with crystals like those in bone to form the hard, protective enamel of teeth.

A model derived at PNNL shows how an active portion of the enamel-building protein interacts with the crystal hydroxyapatite used by the body to engineer both bone and enamel.

The study, by a team from PNNL and the University of Southern California, identifies the region of the protein that interacts with the enamel crystals. The results explain how 100-nanometer spheres of amelogenin cluster like bowling balls around developing enamel crystals, forcing the crystals to elongate into thin, weaved strands that endow enamel with the strength of steel.

"The proteins determine the crystal structure," said Wendy Shaw, lead author and PNNL staff scientist. "Like bone, teeth are made of hydroxyapatite, but the proteins present when teeth form create enamel, a material with entirely different properties from bone. If you can control the interactions between proteins and crystals, the same principle can be applied to nano-patterning and nano-building."

For more information, see PNNL's Web site at
http://www.pnl.gov/news/2004/04-56.htm.

Peering inside the body, with a new spin—literally

This story is all spin. A mouse in a form-fitted Plexiglas tube performs the honors, spinning like an old phonograph record, at a leisurely one to three revolutions a second. The mouse chamber is tilted just so inside a magnetic field being pelted with radio waves. The tiny rodent is put under and is no worse for the wear.

This technique, called slow magic-angle spinning magnetic resonance spectroscopy or "slow MAS," has provided researchers a new glimpse inside living tissue and cells that other biomedical imaging methods cannot render. The difference between conventional nuclear magnetic resonance, or NMR, and slow MAS is akin to a near-sighted person looking at a mountain range without her glasses one moment and with glasses the next. Previously indistinguishable peaks and valleys appear, the peaks representing previously unseen biochemical compounds as they appear in living tissues.

"It's a noninvasive way to look at the function of living organs and the components at work in them such as fat, glucose and other metabolites," said Robert Wind, a physicist and laboratory fellow at Pacific Northwest National Laboratory, and slow-spin technique inventor. "We think this new technique can be used to diagnose diseases and assess the body's response to drugs and even to observe the working physiology of living cells."

Scientists hope slow MAS can be used to see the physiology of internal organs in real time.

Living tissue holds the most promise for this method, Wind said, because there is no good way to see what is happening in many areas of the body, especially at the boundaries of organs and tissues and bone or air cavities such as lungs and sinuses. Here, the large magnet used in NMR generates small magnetic fields that broaden the spectral lines so much that information about those fine details is lost.

Wind found he could get detailed spectra in biological samples at record-slow MAS speeds by using pulsed radio waves to separate the obscuring spinning side bands from the main spectrum. With this technique, scientists could look at full bodies or zero in on specific organs or parts of tissues.

For more information, see PNNL's Web site at
http://www.pnl.gov/news/2004/04-53.htm.

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