title: Cross-linked biopolymer bundles: cross-link reversibility leads to cooperative binding/unbinding phenomena.
abstract: We consider a biopolymer bundle consisting of filaments that are cross-linked together. The cross-links are reversible: they can dynamically bind and unbind adjacent filament pairs as controlled by a binding enthalpy. The bundle is subjected to a bending deformation and the corresponding distribution of cross-links is measured. For a bundle consisting of two filaments, upon increasing the bending amplitude, a first-order transition is observed. The transition is from a state where the filaments are tightly coupled by many bound cross-links, to a state of nearly independent filaments with only a few bound cross-links. For a bundle consisting of more than two filaments, a series of first-order transitions is observed. The transitions are connected with the formation of an interface between regions of low and high cross-link densities. Combining umbrella sampling Monte Carlo simulations with analytical calculations, we present a detailed picture of how the competition between cross-link shearing and filament stretching drives the transitions. We also find that, when the cross-links become soft, collective behavior is not observed: the cross-links then unbind one after the other leading to a smooth decrease of the average cross-link density.
authors.affiliation: Institute of Theoretical Physics, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany. rlcvink@gmail.com
authors.forename: Richard L C
authors.initials: RL
authors.lastname: Vink
authors.forename: Claus
authors.initials: C
authors.lastname: Heussinger
mesh_terms: D001665:Binding Sites; D001704:Biopolymers / Q000737:chemistry*; D003198:Computer Simulation; D009010:Monte Carlo Method; D013816:Thermodynamics
chemical_list: D001704:Biopolymers