Enhanced counterion localization induced by surface charge modulation

Lukatsky, D. B.; Safran, S. A.; Lau, Andy T. Y.; Pincus, P.

doi:10.1209/epl/i2002-00418-8

Cited by 46 publications

(65 citation statements)

References 21 publications

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“…This in turn implies that φ(z; N b > 0) > φ(z; 0) for any z > 0. Thus, the two state model predicts that charge discretization of a planar macromolecule leads to enhanced counterion localization, in agreement with the results of [5,6].…”

supporting

confidence: 85%

“…For small charge modulation, it is appropriate to use a perturbative expansion of the Poisson-Boltzmann (PB) equation to describe the meanfield behavior of the counterion distribution. It has already been shown that such an expansion leads to enhanced counterion localization for planes [6], and it is straightforward to show that the same conclusion holds for surfaces of arbitrary geometry [13]. For a discrete surface charge distribution, however, pair association between discrete macromolecular charges and the discrete counterions [14,15] can become important; that is, a large number of counterions can become localized near the macromolecular surface.…”

mentioning

confidence: 82%

“…Theoretically, the effects of surface charge inhomogeneities on the counterion distribution has been studied for planar [5,6], cylindrical [7][8][9][10], and spherical [11,12] geometries. In particular, both Moreira et al [5] and Lukatsky et al [6] have shown analytically that the heterogeneity of a planar charge distribution leads to an enhanced localization of the counterions near the macromolecular surface. Thus, theoretical models that assume homogeneous surface charge distributions -including OM condensation theory -must be modified for realistic charge distributions.…”

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confidence: 99%

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Distribution of counterions near discretely charged planes and rods

et al. 2004

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Abstract. -Realistic charged macromolecules are characterized by discrete (rather than homogeneous) charge distributions. We investigate the effects of surface charge discretization on the counterion distribution at the level of mean-field theory using a two-state model. Both planar and cylindrical geometries are considered; for the latter case, we compare our results to numerical solutions of the full Poisson-Boltzmann equation. We find that the discretization of the surface charge can cause enhanced localization of the counterions near the surface; for charged cylinders, counterion condensation can exceed Oosawa-Manning condensation.Introduction. -The interaction between charged macromolecules and counterions is a crucial component of the physics of charged systems [1]. Although realistic macromolecules are often composed of discrete charges, theoretical models typically assume a homogeneous surface charge distribution. In the case of cylindrical polyelectrolytes (PEs), this assumption leads to Oosawa-Manning (OM) condensation [2,3], in which counterions become closely associated with the macromolecule, effectively lowering its overall charge. A similar effect also occurs for spherical macromolecules [4]. Theoretically, the effects of surface charge inhomogeneities on the counterion distribution has been studied for planar [5,6], cylindrical [7][8][9][10], and spherical [11,12] geometries. In particular, both Moreira et al. [5] and Lukatsky et al. [6] have shown analytically that the heterogeneity of a planar charge distribution leads to an enhanced localization of the counterions near the macromolecular surface. Thus, theoretical models that assume homogeneous surface charge distributions -including OM condensation theory -must be modified for realistic charge distributions.In this letter, we explore the effects of surface charge discretization on the counterion distribution in the absence of added salt. For small charge modulation, it is appropriate to use a perturbative expansion of the Poisson-Boltzmann (PB) equation to describe the meanfield behavior of the counterion distribution. It has already been shown that such an expansion

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confidence: 85%

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confidence: 82%

mentioning

confidence: 99%

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Distribution of counterions near discretely charged planes and rods

et al. 2004

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“…Collapse of counterions and surface ions is prevented by a truncated Lennard-Jones term acting between all particles. The model we consider includes the combined effects of discrete surface charges, surface corrugations, and counterion excluded volume [123], which are all neglected in the classical mean-field approaches but have been considered quite recently [54,124,125,91,126,127,128,129,130,131,132,133]. We employ Browniandynamics simulations where the velocity of all particles follows from the position Langevin equation.…”

Section: Charged Structured Surfacesmentioning

confidence: 99%

“…The presence of excess ionic polarizabilities was proposed to lead to corrections to the usual van-der-Waals interaction energy, which could be one of the factors determining ion-specific interactions [293,294,295,296]. But it was also shown that even with pure Coulomb interactions, one obtains strong deviations from the standard mean-field approaches if one takes into account that the charge distribution on all charged surfaces is laterally modulated [54,124,125,127,128]. Specifically, the counterion density right at a charged surface (which for a homogeneously charged surface and in the absence of additional interactions is exactly given by Eq.…”

Section: Ion-specific Effectsmentioning

confidence: 99%

Statics and dynamics of strongly charged soft matter

Boroudjerdi¹,

Kim²,

Naji³

et al. 2005

Physics Reports

347

523

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Soft matter materials, such as polymers, membranes, proteins, are often electrically charged. This makes them water soluble, which is of great importance in technological application and a prerequisite for biological function. We discuss a few static and dynamic systems that are dominated by charge effects. One class comprises complexation between oppositely charged objects, for example the adsorption of charged ions or charged polymers on oppositely charged substrates of different geometry. Here the main questions are whether adsorption occurs and what the effective charge of the resulting complex is. We explicitly discuss the adsorption behavior of polyelectrolytes on substrates of planar, cylindrical and spherical geometry with specific reference to DNA adsorption on supported charged lipid layers, DNA adsorption on oppositely charged cylindrical dendro-polymers, and DNA binding on globular histone proteins, respectively. In all these systems salt plays an important role, and some of the important features can already be obtained on the linear Debye-Hückel level. The second class comprises effective interactions between similarly charged objects. Here the main theme is to understand the experimental finding that similarly and highly charged bodies attract each other in the presence of multi-valent counterions. This is demonstrated using field-theoretic arguments as well as Monte-Carlo simulations for the case of two homogeneously charged bodies. Realistic surfaces, on the other hand, are corrugated and also exhibit modulated charge distributions, which is important for static properties such as the counterion-density distribution, but has even more pronounced consequences for dynamic properties such as the counterion mobility. More pronounced dynamic effects are obtained with highly condensed charged systems in strong electric fields. Likewise, an electrostatically collapsed highly charged polymer is unfolded and oriented in strong electric fields. All charged systems occur in water, and water by itself is not a very well understood material. At the end of this review, we give a very brief and incomplete account of the behavior of water at planar surfaces. The coupling between water structure and charge effects is largely unexplored, and a few directions for future research are sketched. On an even more nanoscopic level, we demonstrate using ab-initio methods that specific interactions between oppositely charged groups (which occur when their electron orbitals start to overlap) are important and cause ion-specific effects that have recently moved into the focus of interest.

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Overcharging in Colloids: Beyond the Poisson–Boltzmann Approach

et al. 2003

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A broad range of manufactured products and biological fluids are colliods. The ability to understand and control the processes (of scientific, technological and industrial interest) in which such colloids are involved relies upon a precise knowledge of the electrical double layer. The traditional approach to describing this ion cloud around colloidal particles has been the Gouy-Chapman model developed on the basis of the Poisson-Boltzmann equation. Since the early 1980s, however, more sophisticated theoretical treatments have revealed both quantitative and qualitative deficiencies in the Poisson-Boltzmann theory, particularly at high ionic strengths and/or high surface charge densities. This review deals with these novel approaches, which are mostly computer simulations and approximate integral equation theories based on the so-called primitive model. Special attention is paid to phenomena that cannot be accounted for by the classic theory as a result of neglecting ion size correlations, such as overcharging, namely, the counterion concentration in the immediate neighborhood of the surface is so large that the particle surface is overcompensated. Other illustrative examples are the nonmonotonic behavior of the electrostatic potential and attractive interactions between equally charged surfaces. These predictions are certainly remarkable and, on paper, they can have an effect on experimentally measurable quantities (for instance, electrophoretic mobility). Even so, these new approaches have scarcely been applied in practice. Thus a critical survey on the relevance of ion size correlation in real systems is also included. Overcharging of macroions can also be brought about by adsorption of oppositely charged polyelectrolytes. Noteworthy examples and theoretical approaches for them are also briefly reviewed.

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Enhanced counterion localization induced by surface charge modulation

Cited by 46 publications

References 21 publications

Distribution of counterions near discretely charged planes and rods

Distribution of counterions near discretely charged planes and rods

Statics and dynamics of strongly charged soft matter

Overcharging in Colloids: Beyond the Poisson–Boltzmann Approach

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