Helicity of a confined bottlebrush ring polymer.

We report coarse-grained molecular dynamics simulation data for a bottlebrush "loops-on-a-ring" polymer confined to a cylindrical space, motivated by its utility as a model of the bacteria nucleoid. Simulations reveal that this confined polymer adopts a helical configuration due to the tendency of the side loops to fill space with uniform density while maintaining the ring architecture. We further investigate how the helical conformation is affected by the distribution of side chains, demonstrating that switching from uniform grafting (a bottlebrush architecture) to asymmetric grafting (a coil-brush architecture) drives a conformational transition from a double helix to a single helix at a fixed number of grafts. In addition to elucidating the complex effects of side chains on the global configuration of ring bottlebrush polymers under confinement, the simulation results provide a biophysical model for the experimentally-observed helicity of E. coli and C. crescentus nucleoids.