title: Association-dissociation equilibrium of loop structures in single-chain folding into a toroidal condensate.
abstract: Recently, it has been revealed that a semiflexible polyelectrolyte chain can form a partially folded conformation stably as a result of an electrostatic interaction. Interestingly, there are cases where the appearance of this structure requires a high-salt condition of a solution. In order to solve this problem, we consider the double equilibrium of the formation of loops and their aggregation on a single-chain polymer. First, an aggregate with a typical surface energy is examined as a test case. The basic nature of the folding transition is discussed with regard to the chemical potential of loop structures. Next, we consider a charged aggregate for which the interior is completely neutralized by counter ions. In this model, a partially folded chain appears with a high-salt condition. Based on this model, screened interactions between surface charges and a toroidal shape of a folded structure are considered essential factors bihind this phenomenon.
authors.affiliation: Okayama Institute for Quantum Physics, Kyoyama 1-9-1, Okayama-shi, Okayama 700-0015, Japan. takafumi_iwaki@pref.okayama.jp
authors.forename: Takafumi
authors.initials: T
authors.lastname: Iwaki
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry*
chemical_list: D001704:Biopolymers; D012997:Solvents