Importance of Varying Permittivity on the Conductivity of Polyelectrolyte Solutions

Fahrenberger, Florian; Hickey, Owen A.; Smiatek, Jens; Holm, Christian

doi:10.1103/physrevlett.115.118301

Cited by 38 publications

(33 citation statements)

References 68 publications

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“…In a more realistic, orientation of water molecules near the binding sites, polar groups composing the ligand itself, and the salt concentration would influence the local dielectric constant and thus, ionic distributions [50,51]. Indeed, recently it has been shown that ionic mobility in salt solutions can be described more accurately with a non-uniform dielectric constant [52]. Similar effects can alter unbinding rates by pushing the ions from the binding site or increasing diffusion coefficient within the ionic atmosphere.…”

Section: Implicit Simulations Can Underestimate Contact Energiesmentioning

confidence: 99%

Effects of electrostatic interactions on ligand dissociation kinetics

2018

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We study unbinding of multivalent cationic ligands from oppositely charged polymeric binding sites sparsely grafted on a flat neutral substrate. Our molecular dynamics (MD) simulations are suggested by single-molecule studies of protein-DNA interactions. We consider univalent salt concentrations spanning roughly a thousandfold range, together with various concentrations of excess ligands in solution. To reveal the ionic effects on unbinding kinetics of spontaneous and facilitated dissociation mechanisms, we treat electrostatic interactions both at a Debye-Hückel (DH, or 'implicit' ions, i.e., use of an electrostatic potential with a prescribed decay length) level, as well as by the more precise approach of considering all ionic species explicitly in the simulations. We find that the DH approach systematically overestimates unbinding rates, relative to the calculations where all ion pairs are present explicitly in solution, although many aspects of the two types of calculation are qualitatively similar. For facilitated dissociation (FD, acceleration of unbinding by free ligands in solution) explicit ion simulations lead to unbinding at lower free ligand concentrations. Our simulations predict a variety of FD regimes as a function of free ligand and ion concentrations; a particularly interesting regime is at intermediate concentrations of ligands where non-electrostatic binding strength controls FD. We conclude that explicit-ion electrostatic modeling is an essential component to quantitatively tackle problems in molecular ligand dissociation, including nucleicacid-binding proteins.

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Section: Implicit Simulations Can Underestimate Contact Energiesmentioning

confidence: 99%

Effects of electrostatic interactions on ligand dissociation kinetics

2018

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“…If the gradient of the locally varying permittivity ε(r) is non-zero, this energy leads to a force that is included in the HIM method presented in our earlier work with Xu 41 and the electrostatic algorithm used in this manuscript. In this article, we expand on our previous study on the conductivity of polyelectrolyte solutions with a locally varying permittivity 59 . We first introduce the new electrostatic algorithm in detail.…”

Section: Introductionmentioning

confidence: 99%

The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions

Fahrenberger

Hickey

Smiatek

et al. 2015

The Journal of Chemical Physics

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There is a large body of literature investigating the static and dynamic properties of polyelectrolytes due both to their widespread application in industrial processes and their ubiquitous presence in biology. Because of their highly charged nature, polyelectrolytes tend to alter the local dielectric permittivity of the solution within a few nanometers of their backbone. This effect has, however, been almost entirely ignored in both simulations and theoretical work. In this article, we apply our recently developed electrostatic solver based on Maxwell's equations to examine the effects of the permittivity reduction in the vicinity of the polyelectrolyte. We first verify our new approach by calculating and comparing ion distributions around a linear fixed polyelectrolyte and find both quantitative and qualitative changes in the ion distribution. Further simulations with an applied electric field show that the reduction in the local dielectric constant increases the mobility of the chains by approximately ten percent. More importantly, variations in the local dielectric constant lead to qualitatively different behavior of the conductivity.

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“…Both of these may be brought about by the addition of either ionomer or acid. 50 However, both of these are closely related to pH in these systems. Dielectric constant and ionic strength may both be changing because of ionic group addition, which is reflected in the dispersion pH.…”

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Inherent Acidity of Perfluorosulfonic Acid Ionomer Dispersions and Implications for Ink Aggregation

2018

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Perfluorosulfonic-acid (PFSA) dispersions are used as components in a variety of electrochemical technologies, particularly in fuel-cell catalyst-layer inks. In this study, we characterize dispersions of a common PFSA, Nafion, as well as inks of Nafion and carbon. It is shown that solvent choice affects a dispersion's measured pH, which is found to scale linearly with Nafion loading. Dispersions in water-rich solvents are more acidic than those in propanolrich solvents: a 90% water versus 30% water dispersion can have up to a 55% measured proton deviation. Furthermore, because electrostatic interactions are a function of pH, these differences affect how particles aggregate in solution. Despite having different water contents, all inks studied demonstrate the same particle size and surface charge trends as a function of pH, thus providing insights into the relative influence of solvent and pH effects on these properties.3

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Importance of Varying Permittivity on the Conductivity of Polyelectrolyte Solutions

Cited by 38 publications

References 68 publications

Effects of electrostatic interactions on ligand dissociation kinetics

Effects of electrostatic interactions on ligand dissociation kinetics

The influence of charged-induced variations in the local permittivity on the static and dynamic properties of polyelectrolyte solutions

Inherent Acidity of Perfluorosulfonic Acid Ionomer Dispersions and Implications for Ink Aggregation

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