question of physics: How does order emerge? What is the basis of self-organization?” said Andreas Bausch, a biophysicist at Germany’s University of Munchen. “As a model system, this is as pure as it gets.”

Unlike biologists who use E. coli to investigate genetic rules and rats to study physiological function, self-organization researchers have few model systems. It’s not easy to put a starling flock under glass.

One useful system is the cells of slime molds. Another is vibrating grains of sand. Now Bausch’s team has oberved fluctuating waves and spirals — telltale patterns of self-organization — arising in dishes of actin and myosin, the proteins that make up muscle cells.

Cultures of those proteins have been used for decades in studying muscle samples, but Bausch’s team happened to add more fibers than anyone before. “It was pure chance. We just used the fibers at high densities,” said Bausch. The findings were published September 1 in Nature.

The study is a “crucial quantitative, experimental demonstration of the emergence of collective motion and moving density patterns” in a simple system, wrote Curie Institute physicist Jean-Francois Joanny in a commentary accompanying the findings.

According to Joanny, the muscle is simple and easy to manipulate, making it an ideal experimental system for self-organization. The researchers next plan to study how proteins measured in nanometers made patterns visible to the naked eye, and lasting for up to half an hour.

“The really fascinating thing is that the patterns go up six orders of magnitude, and are very stable,” said Bausch. “We want to look at confinement effects, and how boundaries interact. What is stabilizing this?”

Videos: Self-organizing patterns of actin protein filaments./Andreas Bausch.

See Also:

• Evolution as Biological Thermodynamics
• Searching for Network Laws in Slime
• Grains of Sand Reveal Possible Fifth State of Matter
• Amazing Starling Flocks Are Flying Avalanches

Citations: “Polar patterns of driven filaments.” By Volker Schaller, Christoph Weber, Christine Semmrich, Erwin Frey & Andreas R. Bausch. Nature, Vol. 467 No. TK, September 2, 2010.

“Filaments band together.” By Jean-François Joanny and Sriram Ramaswamy. Nature, Vol. 467 No. TK, September 2, 2010.

Authors: Brandon Keim

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