Langevin dynamics (LD) simulations were conducted to study the collapse of polyelectrolyte brushes made 4-arm stars induced by trivalent salt counterions. Consistent with previous studies fully charged linear polymer in presence counterions, electrostatic bridging grafted star chains counterions plays a critical role bundle formation. In sharp contrast dominant probability inter-chain between i...

Cell-penetrating peptides (CPPs), or protein transduction domains (PTDs), are a special class of membrane-active proteins that can cross the cell membrane with unusual efficiency. They have attracted considerable attention because of their ability to readily cross biological membranes, in spite of their highly charged nature. While the exact mechanism of this transport remains under intense inv...

Structuring of DNA counterions around the double helix has been studied by the molecular dynamics method. A DNA dodecamer d(CGCGAATTCGCG) in water solution with the alkali metal counterions Na, K, and Cs has been simulated. The systems have been considered in the regimes without excess salt and with different salts (0.5 M of NaCl, KCl or CsCl) added. The results have showed that the Na counteri...

We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo and molecular dynamics simulation steps. Monte Carlo steps were used to perform small ion excha...

Screening of a strongly charged macroion by its multivalent counterions cannot be described in the framework of a mean-field Poisson-Boltzmann (PB) theory because multivalent counterions form a strongly correlated liquid (SCL) on the surface of the macroion. It was predicted that a distant counterion polarizes the SCL as if it were a metallic surface and creates an electrostatic image. The attr...

Multivalent counterions can induce an effective attraction between like-charged rodlike polyelectrolytes, leading to the formation of polyelectrolyte bundles. In this paper, we calculate the equilibrium bundle size using a simple model in which the attraction between polyelectrolytes (assumed to be pairwise additive) is treated phenomenologically. If the counterions are pointlike, they almost c...

Abstract. A Ginzburg-Landau theory is presented on surfactants in polar binary mixtures, which aggregate at an interface due to the amphiphilic interaction. They can be ionic surfactants coexisting with counterions. Including the solvation and image interactions and accounting for a finite volume fraction of the surfactant, we obtain their distributions and the electric potential around an inte...

We formulate a self-consistent field theory for polyelectrolyte brushes in the presence of counterions. We numerically solve the self-consistent field equations and study the monomer density profile, the distribution of counterions, and the total charge distribution. We study the scaling relations for the brush height and compare them to the prediction of other theories. We find a weak dependen...

The functionality of conjugated polymer systems often relies on oxidations or reductions, in most cases mediated by the presence of counterions. The effect that the common counterion hexafluorophosphate (PF6-) has on the intermolecular interactions between charged oligothiophenes is investigated here using ab initio quantum chemistry methods. Counterions are explicitly included in the simulatio...

We explore, using the recently developed efficient Monte Carlo simulation method, the interaction of an anionic polyelectrolyte solution with a like-charged dielectric surface. In addition to polyions, the solution also contains salt with either monovalent, divalent, or trivalent counterions. In agreement with recent experimental observations, we find that multivalent counterions can lead to st...