title: Motor-mediated alignment of microtubules in semidilute mixtures.
abstract: We propose and study a model of molecular motor-induced ordering in a cytoskeletal filament solution for the semidilute case. Motors attach to a pair of filaments and walk along the pair bringing them into closer alignment. In the semidilute regime multiple motors can bind a filament to several others and, for a critical motor density, induce a transition to an ordered phase with a nonzero mean orientation. The motors, on the one hand, cause closer filament alignment, and, on the other hand, induce fluctuations that are dependent on the relative orientation of the filaments to which the motors are attached. We develop a spatially homogenous, mean-field theory that explicitly accounts for a force-dependent detachment rate of motors, which in turn affects the mean and the fluctuations of the net force acting on a filament. This model considers each filament to be in motor contact with all other filaments in the solution. We show that the transition to the oriented state changes from second order to first order when the force-dependent detachment becomes important.
authors.affiliation: Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60202, USA.
authors.forename: Sumanth
authors.initials: S
authors.lastname: Swaminathan
authors.forename: Falko
authors.initials: F
authors.lastname: Ziebert
authors.forename: Dmitry
authors.initials: D
authors.lastname: Karpeev
authors.forename: Igor S
authors.initials: IS
authors.lastname: Aranson