title: Looped star polymers show conformational transition from spherical to flat toroidal shapes.
abstract: Inspired by the topological organization of the circular Escherichia coli chromosome, which is compacted by separate domains, we study a polymer architecture consisting of a central ring to which either looped or linear side chains are grafted. A shape change from a spherical to a toroidal organization takes place as soon as the inner ring becomes large enough for the attached arms to fit within its circumference. Building up a torus, the system flattens, depending on the effective bending rigidity of the chain induced by entropic repulsion of the attached loops and, to a lesser extent, linear arms. Our results suggest that the natural formation of a toroidal structure with a decreased amount of writhe induced by a specific underlying topology could be one driving force, among others, that nature exploits to ensure proper packaging of the genetic material within a rod-shaped, bacterial envelope.
authors.affiliation: Institute for Theoretical Physics, University of Heidelberg, Heidelberg, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Reiss
authors.forename: Miriam
authors.initials: M
authors.lastname: Fritsche
authors.forename: Dieter W
authors.initials: DW
authors.lastname: Heermann
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D002876:Chromosomes, Bacterial / Q000737:chemistry; D004926:Escherichia coli; D008958:Models, Molecular; D008968:Molecular Conformation; D011108:Polymers / Q000737:chemistry*; D012399:Rotation
chemical_list: D011108:Polymers