Actin Networks and Polymer Physics

Erwin Frey

HMI Berlin and FU Berlin

The cytoskeleton of eukaryotic cells is a three-dimensional polymer network
composed of rather stiff protein fibres like actin filaments and microtubules.
The physics of these biopolymers is fundamentally different from the physics
of synthetic polymers such as polyethylene. Due to the high flexibilityof the
C-C bonds along their backbone, synthetic polymers are well characterized
in terms of freely jointed chains, i.e. the physics of random walks.  In contrast,
actin filaments have a persistence length comparable to their total length.
This implies that the physics is determined by a subtle interplay between
energetic and entropic contributions. These systems open up a new field
of soft condensed matter research, which has a great potential for interesting
new phenomena as well as technological applications. We will introduce
into a statistical mechanics description of semiflexible polymers and
networks. This will cover physics concepts ranging from diffusion on a unit
sphere over scaling theories to continuum percolation models.