Conformational change and diffusion dynamics of passive and active filaments in network environments.

Structure and dynamics of filamentous molecules in cross-linked network environments are crucial for diverse biological processes. We perform a systematic study for the conformational change and diffusion dynamics of both passive and active chains in the polymer networks based on Langevin dynamics simulations. Our results demonstrate a series of intriguing phenomena, via tuning network bending modulus, volume fraction, and chain activity. For a passive chain, strong confinement of network accounts for a remarkable conformational compaction. A robust subdiffusion scaled with mean square displacement ∼ τα (α < 1) is observed in accordance with a long-time memory effect. Under the concentrated network condition, the stiffness of a network plays a role in stretching the chain and impeding the diffusion dynamics. For an active chain, self-propulsion of the chain can overcome the confinement of network, realizing a swollen conformation and a transformation from subdiffusion to normal diffusion. In a dense network with rigidity, active chain suffers from a non-monotonic conformational change. Moderate activity induces an unconventional collapse effect. Our work highlights the new physics arising from the interplay between activity, conformational degrees of freedom of the probed chain, and the cross-linked network structure, which has no analogy in a nanoparticle probe system.