THE MOST RESILIENT NANOSPRINGS IN NATURE
15 January 2006 - National Science Foundation

In a discovery that could lead to potent new "shock absorbers" and "gate-opening springs" for molecular-scale nanomachines, as well as a new understanding of mechanical processes within living cells, researchers from Duke University have shown that a component of many natural proteins can act as one of the most powerful and resilient molecular springs in nature.

Known as an "ankyrin repeat," this component occurs in hundreds of different proteins in organisms ranging from plants to humans. In the specialized hair cells of the inner ear, for example, ankyrin repeats may play a critical role in converting sound, a mechanical stimulus, into an electrical signal that can be transmitted to the brain.

Now, the Duke scientists have shown that a sufficiently long string of ankyrin repeats will spontaneously coil into a helical structure, forming a molecule that not only looks like a spring, but functions like one. They published their findings in an advanced online publication of the journal Nature on Jan. 15, 2006.

"Whereas other known proteins can act like floppy springs, ankyrin molecules behave more like steel," said Piotr Marszalek, professor of mechanical engineering and materials science at the Duke Pratt School of Engineering, and one of lead authors on the study. "After repeated stretching, the molecules immediately refold themselves, retaining their shape and strength."

"The fully extended molecules not only bounce back to their original shape in real time, but they also generate force in the process of this rapid refolding - something that had never been seen before," added his co-author Vann Bennett, a Howard Hughes Medical Institute investigator and professor of cell biology at Duke University Medical Center and investigator.

Marszalek and Bennett are participants in the Duke University Center for Biologically Inspired Materials and Material Systems, and were supported in this work by Duke University and the National Science Foundation.

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