Long Polymers Catch the Wave express
Polymers are long threads of carbon and hydrogen atoms. In living cells, they encounter streams of chemical signals that pulse like the surf. Long chains and closed rings behave like skilled surfers: they catch the wave and glide with it. Short fragments and tight coils, counterintuitively, move strictly against it. The reason is entropy, a measure of molecular freedom. Flexible long threads manage to synchronize with the rhythm and dissipate less energy, while short ones are forced to swim against the current to maintain their shape. The most surprising trick comes from ring polymers: with no ends to untangle, the wave can't unwind them — instead, they start spinning like a carousel, turning into nature's perfect nanogears.
Original abstract
as written by the authors arXiv:2603.02777
Directed transport is a characteristic feature of numerous biological systems in response to signals such as nutrient and chemical gradients. These signals often depend on time owing to the high complexity of interactions in these systems. In this study, we focus on the steady-state behavior of polymeric systems responding to such time-dependent signals. We model them as ideal Rouse polymers submerged in a nonequilibrium bath, which is described by a spatially and temporally varying self-propulsion wave field. Through a coarse-graining analysis, we show that these polymers display rich emergent response to the temporal stimuli as a function of their length and topology. In particular, long polymers and structures with ring and star topologies ride the wave, displaying a positive drift in the direction of the wave. Whereas, shorter polymers and fully connected structures drift against the wave signal. We confirm these analytical predictions with robust numerical simulations, showing that the response of polymeric systems to temporal stimuli can be controlled by the topology or the length of the polymer.
The longest polymers in our body, DNA strands, also catch molecular waves: they unravel and glide, syncing with the cell's rhythm.