Dressed counterions: Polyvalent and monovalent ions at charged dielectric interfaces

Abstract

We investigate the ion distribution and overcharging at charged interfaces with dielectric inhomogeneities in the presence of asymmetric electrolytes containing polyvalent and monovalent ions. We formulate an effective "dressed counterion" approach by integrating out the monovalent salt degrees of freedom and show that it agrees with results of explicit Monte-Carlo simulations. We then apply the dressed counterion approach within the framework of the strong-coupling theory, valid for polyvalent ions at low concentrations, which enables an analytical description for salt effects as well as dielectric inhomogeneities in the limit of strong Coulomb interactions on a systematic level. Limitations and applicability of this theory are examined by comparing the results with simulations.

Energies and pressures in viruses: contribution of nonspecific electrostatic interactions

“…Usually, the aqueous solution of viruses contains a mixture of monovalent as well as polyvalent salts at relatively high and low concentrations, respectively. An intermediate approximation termed the dressed counterion (DC) approximation allows for an approximate treatment of all the components in this highly asymmetric multicomponent electrolyte system 228,229 . It starts with the observation that the concentration of polyvalent counterions is usually small and thus can be dealt with on the lowest order virial expansion level, whereas the monovalent salt ions can still be treated on the mean-field DH level.…”

“…In the limit of small concentrations and highly charged counterions the contribution of the polyvalent counterions can be well approximated by the first order virial expansion corresponding to a single counterion interacting with all the charges in the system, i.e. the monovalent salt ion charges as well as the fixed charges on the capsid 228,229 . The grand canonical potential can thus be written…”

Titratable macroions in multivalent electrolyte solutions: Strong coupling dressed ion approach

“…A possible realization would correspond to a mixture of multivalent ions in a bathing solution of monovalent ions, a situation rather typical in the context of e.g. semiflexible biopolymers, where multivalent ions are believed to play a key role in their condensation [42,43]. With the presence of polyvalent ions in the system, the WC paradigm in general breaks down and the existence of KS interactions becomes dubious [41].…”

“…With the presence of polyvalent ions in the system, the WC paradigm in general breaks down and the existence of KS interactions becomes dubious [41]. However, there exists a theory, the dressed ion theory, based on an asymmetric treatment of the different components of the bathing electrolyte solution, that would allow us to analyze the effect of charge reguation of macroions also in the presence of polyvalent salt ions in the bathing solution [42,43]. It is based on the fact, that one can use the WC DH approach in order to describe the monovalent salt ions, while a strong coupling (SC) approach is preferable for the polyvalent ion part.…”

“…The bathing solution for the macroions, assuming to be an ionic mixture of monovalent salt and polyvalent ions, is then treated within the dressed ion theory, i.e. the monovalent salt is described within the WC and the polyvalent ions within the SC paradigm, an approximate approach that has already proved valuable in other contexts [42,43]. We then further approximate the non-linear surface charge regulation free energy with a Gaussian expansion proved to be a good description on the WC level [16,17].…”