Order by motion( This press release is also available ...)

The molecules within the living cell sustain a high degree of spatial order even though they are constantly in motion. This seems to defy basic physical principles which stress the strong interplay between motion and disorder. Indeed, the simplest way to increase the motion of molecules is by heating which leads to the melting of crystals and the evaporation of liquids, i.e., to the destruction of spatial order. Scientists at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, have now proposed a simple biomimetic model system for the opposite effect, i.e., for the creation of spatial order by increased molecular motion. This system consists of molecular motors anchored to a substrate surface in contact with an isotropic liquid of cytoskeletal filaments. As one increases the density of the molecular motors, this liquid is predicted to undergo a phase transition towards a nematic liquid crystal with long-range orientational order. This ordering effect arises from the interplay of motor activity and steric filament interactions, a mechanism that should also be effective for the pattern formation processes in the living cell (Physical Review Letters 96, 258103, 30 June 2006).

The cytoskeleton is responsible for the mechanical stability of biological cells and plays an important role in intracellular transport and dynamics. Motor proteins perform directed walks on cytoskeletal filaments and enable fast transport over large intracellular distances along the filament-like railsTM provided by the cytoskeleton. In addition to their function as nano-tractors, motor proteins are also actively involved in the constant re-organization of the cytoskeleton itself, which is necessary for cell motility and mitosis. During these processes, cytoskeletal filaments are constantly in motion, yet highly or
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Contact: Dr. Jan Kierfeld
Jan.Kierfeld@mpikg.mpg.de
49-331-567-9620
Max-Planck-Gesellschaft
25-Jul-2006