The effect of discrete charges on the electrical properties of membranes. II

Enos, B.; McQuarrie, Donald A.

doi:10.1016/0022-5193(81)90216-2

Cited by 47 publications

(4 citation statements)

References 19 publications

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“…This model does not appear adequate for liposome populations, which consist of fluid lipid bilayers with varying charge distributions that may behave more like point charges on a two-dimensional spherical surface. 32,33 Moreover, an applied potential field can result in the migration of the charged species within such bilayers. 34,35 This type of migration has been shown to lead to polarization and an accompanying elongation of vesicles along the direction of the applied field.…”

Section: Resultsmentioning

confidence: 99%

“…The established theories assume that there is a uniform charge distribution on the surface of the particle and that the ionic atmosphere around the particle is only slightly distorted by the applied field. This model does not appear adequate for liposome populations, which consist of fluid lipid bilayers with varying charge distributions that may behave more like point charges on a two-dimensional spherical surface. , Moreover, an applied potential field can result in the migration of the charged species within such bilayers. , This type of migration has been shown to lead to polarization and an accompanying elongation of vesicles along the direction of the applied field. − This field-induced alignment is the basis for the adjustments made in developing eq 4. The extent of this shape deformation would be fundamentally dependent on the intrinsic deformability of the particle.…”

Section: Resultsmentioning

confidence: 99%

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Examination of the Electrophoretic Behavior of Liposomes

Pysher

Hayes

2004

Langmuir

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The electromigration of liposomes is a complex process resulting in many unexpected behaviors that are difficult to address with existing theories. In this study, the electrophoretic behaviors of liposome populations under various conditions were examined through the use of capillary electrophoresis and the results compared to classical electrokinetic, colloid, and spheroid theories. To elucidate the possible effects of applied field strength, bilayer rigidity, and surface charge on these behaviors, the electrophoretic mobilities of liposome populations were monitored while varying the applied potential, ionic strength of the medium, and the surface charge and cholesterol content of the liposomes. On the basis of comparisons made to the theoretical predictions, our results suggest that liposomal deformation and field-induced polarization may occur during electrophoresis and these mechanisms help to describe many of the observed behaviors.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Examination of the Electrophoretic Behavior of Liposomes

Pysher

Hayes

2004

Langmuir

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“…The assumption of a uniformly smeared charge is itself a problem, since at the level of macromolecules, such as ion channels, the charges are discrete. However, several investigations have paid attention to this problem (Cole, 1969 ;Brown, 1974 ;Nelson & McQuarrie, 1975 ;Sauve & Ohki, 1979 ;Enos & McQuarrie, 1981 ;Gilbert & Ehrenstein, 1984 ;Winiski et al 1986 ;Mathias et al 1992). A general conclusion is that the smeared charge assumption is valid if the charge density is high enough.…”

Section: The Classical Approachmentioning

confidence: 99%

Metal ion effects on ion channel gating

Elinder

Århem

2003

Quart. Rev. Biophys.

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Metal ions affect ion channels either by blocking the current or by modifying the gating. In the present review we analyse the effects on the gating of voltage-gated channels. We show that the effects can be understood in terms of three main mechanisms. Mechanism A assumes screening of fixed surface charges. Mechanism B assumes binding to fixed charges and an associated electrostatic modification of the voltage sensor. Mechanism C assumes binding and an associated non electrostatic modification of the gating. To quantify the non-electrostatic effect we introduced a slowing factor, A. A fourth mechanism (D) is binding to the pore with a consequent pore block, and could be a special case of Mechanisms B or C. A further classification considers whether the metal ion affects a single site or multiple sites. Analysing the properties of these mechanisms and the vast number of studies of metal ion effects on different voltage-gated on channels we conclude that group 2 ions mainly affect channels by classical screening (a version of Mechanism A). The transition metals and the Zn group ions mainly bind to the channel and electrostatically modify the gating (Mechanism B), causing larger shifts of the steady-state parameters than the group 2 ions, but also different shifts of activation and deactivation curves. The lanthanides mainly bind to the channel and both electrostatically and non-electrostatically modify the gating (Mechanisms B and C). With the exception of the ether-à-go-go-like channels, most channel types show remarkably similar ion-specific sensitivities.

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“…For weakly charged surfaces or on sufficiently small length scales, the discreteness of the electric charge will become noticeable. This has inspired a number of authors to compute the electrostatic potential produced by an ordered array of surface charges [19][20][21] or even a single surface charge [22][23][24][25] and others to use virial expansions [26,27] and Monte Carlo simulations [28][29][30][31][32][33][34][35][36][37] to account for charge discreteness. Some studies have focused on the pressure that acts across electrolytes due to the presence of discrete charges [28,35,38], yet-perhaps somewhat surprisingly-there has not been an attempt so far to compute the free energy of a single planar dielectric interface with discrete charges and compare this with the corresponding free energy derived for a continuous charge distribution.…”

Section: Introductionmentioning

confidence: 99%

Debye-Hückel Free Energy of an Electric Double Layer with Discrete Charges Located at a Dielectric Interface

Bossa

May

2021

Membranes

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Poisson–Boltzmann theory provides an established framework to calculate properties and free energies of an electric double layer, especially for simple geometries and interfaces that carry continuous charge densities. At sufficiently small length scales, however, the discreteness of the surface charges cannot be neglected. We consider a planar dielectric interface that separates a salt-containing aqueous phase from a medium of low dielectric constant and carries discrete surface charges of fixed density. Within the linear Debye-Hückel limit of Poisson–Boltzmann theory, we calculate the surface potential inside a Wigner–Seitz cell that is produced by all surface charges outside the cell using a Fourier-Bessel series and a Hankel transformation. From the surface potential, we obtain the Debye-Hückel free energy of the electric double layer, which we compare with the corresponding expression in the continuum limit. Differences arise for sufficiently small charge densities, where we show that the dominating interaction is dipolar, arising from the dipoles formed by the surface charges and associated counterions. This interaction propagates through the medium of a low dielectric constant and alters the continuum power of two dependence of the free energy on the surface charge density to a power of 2.5 law.

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The effect of discrete charges on the electrical properties of membranes. II

Cited by 47 publications

References 19 publications

Examination of the Electrophoretic Behavior of Liposomes

Examination of the Electrophoretic Behavior of Liposomes

Metal ion effects on ion channel gating

Debye-Hückel Free Energy of an Electric Double Layer with Discrete Charges Located at a Dielectric Interface

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