Elasticity, dynamics and relaxation in biopolymer networks

Our cells, muscles, and connective tissue owe their remarkable mechanical properties to biopolymer networks. Their incessant assembly, disassembly, restructuring, and active and passive mechanical deformation underlies the astounding robustness, adaptability, physical strength and motility of cells and of biological tissue in general. Unlike the flexible polymer networks discussed in standard texts on polymer physics, most biological macromolecular assemblies are predominantly made from (mixtures of) stiff polymers, however. The resulting local mechanical anisotropy and persistence entail distinct mechanical and dynamic properties unlike those familiar from synthetic polymers, foams, or other cellular structures. At the same time they pose formidable difficulties to theoretical modeling efforts, which were so far unsuccessful in establishing a generally accepted view of the origin of the macroscopic elasticity and equilibrium dynamics, let alone the complex biological function of biopolymer networks.