In the experiment, millions of biological motor proteins anchored on a glass surface are responsible for transporting the actin fibers. They are the active components in the model system. After adding adenosine triphosphate (ATP), the "fuel" for the motor proteins, the fibers begin to move randomly. Next the researchers added cross-linking molecules to connect the fibers. This leads to the formation of ever-larger structures that move around on the substrate. Ultimately, all fibers are incorporated into large structures. However, these structures are no longer able to move freely across the surface. They are now fixed in place and run in circles the system is trapped in an absorbing state.
Surprisingly, the structures that develop are quite complex. The result is a collection of perfectly shaped rings made up of millions of individual fibers that rotate permanently under the influence of the motor proteins. "The amazing thing is not only the complexity of the structures themselves, but the fact that even such a simple system comprising only three components fibers, motor proteins and cross-linking molecules can run into an absorbing state," says Volker Schaller from the Institute of Cellular Biophysics at TUM, lead author of the work.
"Such a minimal system should allow us to understand the experimental results using theoretical models," adds Christopher Weber from the Department of Statistical and Biological Physics of LMU Munich. He collaborates with Professor Frey on theoretical concepts to describe active systems. Through their cooperation they successfully uncovered the underlying principles of the ring formation. Specifically, they were able to attribute the rings' properties, such as size and shape, to random movements on a molecular level.
"The mesmerizing thing about the model system, aside from the fascination evoked by the almost perfect patterns, is a seeming contradiction," says the bio
|Contact: Dr. Andreas Battenberg|
Technische Universitaet Muenchen