title: Necklace-cloverleaf transition in associating RNA-like diblock copolymers.
abstract: We consider a A{m}B{n} diblock copolymer, whose links are capable of forming local reversible bonds with each other. We assume that the resulting structure of the bonds is RNA like--i.e., topologically isomorphic to a tree. We show that, depending on the relative strengths of A-A , A-B , and B-B contacts, such a polymer can be in one of two different states. Namely, if a self-association is preferable (i.e., A-A and B-B bonds are comparatively stronger than A-B contacts), then the polymer forms a typical randomly branched cloverleaf structure with the so-called roughness exponent gamma = 1/2 . On the contrary, if alternating association is preferable (i.e., A-B bonds are stronger than A-A and B-B contacts), then the polymer tends to form a generally linear necklace structure with gamma = 1 . The transition between cloverleaf and necklace states is studied in detail, and it is shown that it is a second-order phase transition.
authors.affiliation: LPTMS, Université Paris Sud, 91405 Orsay Cedex, France and Physics Department, Moscow State University 119992 Moscow, Russia.
authors.forename: M V
authors.initials: MV
authors.lastname: Tamm
authors.forename: S K
authors.initials: SK
authors.lastname: Nechaev
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D003198:Computer Simulation; D046911:Macromolecular Substances / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D044367:Phase Transition; D012313:RNA / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D001704:Biopolymers; D046911:Macromolecular Substances; D012313:RNA