Noise-Induced Resonances in Stretched Biopolymers: Stochastic Resonance (SR) and Resonant Activation (RA)

Wokyung Sung
(Department of Physics and PCTP,POSTECH)

The biopolymers are situated in thermally fluctuating, liquid environments and are often subject to external constraints. It is important to understand how they respond to a temporal athermal noises that are produced from a plethora of active processes. To this end, we study dynamics of a stretched chain extension in response to an oscillatory perturbation. The first example is a specific case of an RNA hairpin, which shows thermally- induced folding and unfolding transitions under a constant tension. Strikingly, our molecular simulations show that even at a high tension that renders the hairpin folding improbable, the weak oscillatory force at certain frequencies can synchronously enhances the folding dynamics (SR) and increases the mean transition rate (RA). Second example is nonspecific cases of stretched worm-like chains (such as dsDNA and actin filaments), which we study analytically. Including hydrodynamic interactions between the segments, we evaluate the chain extension in linear response to an additional oscillatory force. We find the response is maximized not only at an optimal temperature but also at an optimal contour length, which is a new type of the entropic SR. The hydrodynamic interaction is found to enhance the SR, representing unique polymer cooperativity which the fluid background can induce despite its overdamping nature. Our study, amenable to experimental tests using optical tweezers, will be of great significance to understanding the in-vivo dynamics of biopolymers in coherence to a specific temporal noise.