  In addition to thermal noise, which is essential to promote conformational
transitions in biopolymers, cellular environment is replete with a spectrum of
athermal fluctuations that are produced from a plethora of active processes. To
understand the effect of athermal noise on biological processes, we studied how
a small oscillatory force affects the thermally induced folding and unfolding
transition of an RNA hairpin, whose response to constant tension had been
investigated extensively in both theory and experiments. Strikingly, our
molecular simulations performed under overdamped condition show that even at a
high (low) tension that renders the hairpin (un)folding improbable, a weak
external oscillatory force at a certain frequency can synchronously enhance the
transition dynamics of RNA hairpin and increase the mean transition rate.
Furthermore, the RNA dynamics can still discriminate a signal with resonance
frequency even when the signal is mixed among other signals with nonresonant
frequencies. In fact, our computational demonstration of thermally induced
resonance in RNA hairpin dynamics is a direct realization of the phenomena
called stochastic resonance (SR) and resonant activation (RA). Our study,
amenable to experimental tests using optical tweezers, is of great significance
to the folding of biopolymers in vivo that are subject to the broad spectrum of
cellular noises.
