Abstract
The repulsive interaction between oppositely charged macroions is investigated using Grand Canonical Monte Carlo simulations of an unrestricted primitive model, including the effect of inhomogeneous surface charge and its density, the depth of surface charge, the cation size, and the dielectric permittivity of solvent and macroions, and their contrast. The origin of the repulsion is a combination of osmotic pressure and ionic screening resulting from excess salt between the macroions. The excess charge over-reduces the electrostatic attraction between macroions and raises the entropic repulsion. The magnitude of the repulsion increases when the dielectric constant of the solvent is lowered (below that of water) and/or the surface charge density is increased, in good agreement with experiment. Smaller size of surface charge and the cation, their discreteness and mobility are other factors that enhance the repulsion and charge inversion phenomenons.
Highlights
In solution, charged macroions are expected to be surrounded by a cloud of compensating oppositely charged counterions [1,2]
At large distances from the macroion surface, the electrostatic field generated by the macroion is completely screened by the counterions, corresponding to a vanishing net charge associated with the mean-field macroion/counterion complex
That the meanfield description is inadequate in the context of highly charged surfaces and multivalent counterions are often encountered in biological systems [5,6,7,8,9,10]
Summary
In solution, charged macroions are expected to be surrounded by a cloud of compensating oppositely charged counterions [1,2]. It was further established that this critical ion concentration is reduced by decreasing the dielectric constant of the solvent surrounding the macroions and by increasing the surface charge density of the macroions. We extend previous studies by including the effect of discreteness of surface charges (as opposed to a uniform surface charge density), and their mobility, the size of cation and the surface charge, and the dielectric permittivity of solvent and macroions and their contrast.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
