Global analysis of the ground-state wrapping conformation of a charged polymer on an oppositely charged nano-sphere

TL;DR

This study maps the global phase behavior of charged polymer chains wrapping around oppositely charged nano-spheres, revealing various conformational phases and transitions based on system parameters.

Contribution

It introduces a comprehensive phase diagram for polymer-sphere complexes using a reduced model, encompassing flexible and semiflexible chains, including DNA-histone systems.

Findings

Identified distinct conformational phases of polymer-sphere complexes.

Mapped phase transitions as functions of charge, size, and salt concentration.

Applicable to a wide range of biological and synthetic polymer-nano-sphere systems.

Abstract

We investigate the wrapping conformations of a strongly adsorbed polymer chain on an oppositely charged nano-sphere by employing a reduced (dimensionless) representation of a primitive chain-sphere model. This enables us to determine the global phase behavior of the chain conformation in a wide range of values for the system parameters including the chain contour length, its linear charge density and persistence length as well as the nano-sphere charge and radius, and also the salt concentration in the bathing solution. The phase behavior of a charged chain-sphere complex can be described in terms of a few distinct conformational symmetry classes (phases) separated by continuous or discontinuous transition lines which are determined by means of appropriately defined (order) parameters. Our results can be applied to a wide class of strongly coupled polymer-sphere complexes including, for instances, complexes that comprise a mechanically flexible or semiflexible polymer chain or an extremely short or long chain and, as a special case, include the previously studied example of DNA-histone complexes.