RT Journal Article
SR Electronic
T1 Random bursts determine dynamics of active filaments
JF Proceedings of the National Academy of Sciences
JO Proc Natl Acad Sci USA
FD National Academy of Sciences
SP 201421322
DO 10.1073/pnas.1421322112
A1 Weber, Christoph A.
A1 Suzuki, Ryo
A1 Schaller, Volker
A1 Aranson, Igor S.
A1 Bausch, Andreas R.
A1 Frey, Erwin
YR 2015
UL http://www.pnas.org/content/early/2015/08/06/1421322112.abstract
AB Biological active systems like swimming bacteria or molecular motors in the cell cytoskeleton consume energy locally to create movements or stresses. Although the surrounding fluid gives rise to thermal fluctuations of the system’s dynamic variables, the corresponding statistics can deviate significantly from a thermal Boltzmann distribution. To quantify these differences, we compare the statistics and dynamics of actin filaments driven by molecular motors with Brownian filaments. In both cases, energy injection is local and random; however, for active filaments, motors can generate sudden jump-like changes in the system’s dynamic variables, leading to nonequilibrium energy dissipation. Motor activity results in a nonthermal distribution of filament curvatures and a faster relaxation of filament bends than in the thermal case.Constituents of living or synthetic active matter have access to a local energy supply that serves to keep the system out of thermal equilibrium. The statistical properties of such fluctuating active systems differ from those of their equilibrium counterparts. Using the actin filament gliding assay as a model, we studied how nonthermal distributions emerge in active matter. We found that the basic mechanism involves the interplay between local and random injection of energy, acting as an analog of a thermal heat bath, and nonequilibrium energy dissipation processes associated with sudden jump-like changes in the system’s dynamic variables. We show here how such a mechanism leads to a nonthermal distribution of filament curvatures with a non-Gaussian shape. The experimental curvature statistics and filament relaxation dynamics are reproduced quantitatively by stochastic computer simulations and a simple kinetic model.