Relaxation of a Worm-Like Chain

Thermal shape fluctuations and rigidity of microtubules in cell functions

Abstract

Microtubules are cytoskeletal protein filaments that playan essential role in a multitude of cell functions in all eucaryotes. While specializedstructures such as cilia, fla- gella, and axons require microtubule lengths ofup to several hundred micrometers, fundamental tasks like cell division andintracellular transport involve microtubules with lengths that are comparableto or smaller than typical eucaryotic cell sizes (10-20). In solution, micro­tubules undergostrong thermal shape fluctuations but, due to their rigidity, maintain anaverage direction and are therefore referred to as semiflexible. The standardmodel for semiflexible polymers is the wormlike chain which envisions ahomogeneous, isotropic, continu­ously flexible rod characterized by its bendingstiffness,.