Kinetics of Filament Bundling with Attractive Interactions

Xueping Yu, A.E. Carlsson
2004 Biophysical Journal  
We study the kinetics of filament bundling by variable time-step Brownian-dynamics simulations employing a simplified attractive potential based on earlier atomic-level calculations for actin filaments. Our results show that collisions often cluster in time, due to memory in the random walk. The clustering increases the bundling opportunities. Small-angle collisions and collisions with short center-to-center distance are more likely to lead to bundling. Increasing the monomermonomer attraction
more » ... ecreases the bundling time to a diffusional limit, which is determined by the capture cross-section and diffusion coefficients. The simulations clearly show that the bundling process consists of two sequential phases: rotation, by which two filaments align parallel to each other; and sliding, by which they maximize their contact length. Whether two filaments bundle or not is determined by the competition between rotation to a parallel state and escape. Increasing the rotational diffusion coefficient and attraction enhances rotation; decreasing attraction and increasing the translational diffusion coefficients enhance escape. Because of several competing effects, the filament length only affects the bundling time weakly. R ij is the distance between the centers of i and j; R d is a decay length (R d ¼ 7 Å ); R max is the distance cutoff for this short-ranged interaction; and H(x) is
doi:10.1529/biophysj.104.047373 pmid:15377526 pmcid:PMC1304882 fatcat:nmvjpztusfe73ffckiwhcc4nuu