A. Tagliabue, C. Micheletti and M. Mella
Tunable knot segregation in co-polyelectrolyte rings carrying a neutral segment
ACS Macro Letters, 2021, 10 , 1365-1370
Link to online article

Abstract
We use Langevin dynamics simulations to study the knotting properties of co- polyelectrolyte rings carrying neutral segments. We show that by solely tuning the relative length of the neutral and charged blocks, one can achieve different combinations of knot con- tour position and size. Strikingly, the latter is shown to vary non-monotonically with the length of the neutral segment; at the same time, the knot switches from being pinned at the block's edge to becoming trapped inside it. Model calculations relate both effects to the competition between two adversarial mechanisms: the energy gain of localizing one or more of the knot's essential crossings on the neutral segment and the entropic cost of such localiza- tion. Tuning the length of the neutral segment sets the balance between the two mechanisms and hence the number of localised essential crossings, which in turn modulates the knot's size. This general principle ought to be useful in more complex systems, such as multi-block co-polyelectrolytes, to achieve a more granular control of topological constraints.