Capillary Electrophoresis Measurements of the Free Solution Mobility for Several Model Polyelectrolyte Systems

Hoagland, David A.; Arvanitidou, Evangelia; Welch, Cynthia F.

doi:10.1021/ma9903761

Cited by 138 publications

(197 citation statements)

References 76 publications

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“…In the presence of added salt, the long chain mobility is reduced, which is consistent with the experimentally observed [19] behavior. Furthermore, the shape of the curve is influenced, and the maximum at intermediate chains is suppressed for increased salt concentration.…”

Section: Electrophoretic Mobilitysupporting

confidence: 89%

Mesoscale modelling of polyelectrolyteelectrophoresis

Grass

Holm

2010

Faraday Discuss.

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The electrophoretic behaviour of flexible polyelectrolyte chains ranging from single monomers up to long fragments of hundred repeat units is studied by a mesoscopic simulation approach. Abstracting from the atomistic details of the polyelectrolyte and the fluid, a coarse-grained molecular dynamics model connected to a mesoscopic fluid described by the Lattice Boltzmann approach is used to investigate free-solution electrophoresis. Our study demonstrates the importance of hydrodynamic interactions for the electrophoretic motion of polyelectrolytes and quantifies the influence of surrounding ions. The length-dependence of the electrophoretic mobility can be understood by evaluating the scaling behavior of the effective charge and the effective friction. The perfect agreement of our results with experimental measurements shows that all chemical details and fluid structure can be safely neglected, and a suitable coarse-grained approach can yield an accurate description of the physics of the problem, provided that electrostatic and hydrodynamic interactions between all entities in the system, i.e., the polyelectrolyte, dissociated counterions, additional salt and the solvent, are properly accounted for. Our model is able to bridge the single molecule regime of a few nm up to macromolecules with contour lengths of more than 100 nm, a length scale that is currently not accessible to atomistic simulations.

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Section: Electrophoretic Mobilitysupporting

confidence: 89%

Mesoscale modelling of polyelectrolyteelectrophoresis

Grass

Holm

2010

Faraday Discuss.

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“…Also as indicated in Fig. 5, the effect of the applied electric field is to reduce the charge in the vicinity of the polyelectrolyte compared to the zero-field value, in contrast to Manning's theory of the electrophoresis of polyelectrolytes for ξ > 1 [12] and its generalizations [13,14,15,16]. Experiments have just begun to probe counterion structure and dynamics in polyelectrolyte solutions at nanometer and nanosecond scales.…”

mentioning

confidence: 98%

Dynamical Clustering of Counterions on Flexible Polyelectrolytes

Khusid

Koplik

2008

Phys. Rev. Lett.

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Molecular dynamics simulations are used to study the local dynamics of counterion-charged polymer association at charge densities above and below the counterion condensation threshold. Surprisingly, the counterions form weakly-interacting clusters which exhibit short range orientational order, and which decay slowly due to migration of ions across the diffuse double layer. The cluster dynamics are insensitive to an applied electric field, and qualitatively agree with the available experimental data. The results are consistent with predictions of the classical theory only over much longer time scales.PACS numbers: 82.35. Rs, Many biochemical reactions involve local interactions between small molecules (ligands) and biological macromolecules such as DNA, which are polymers consisting of repeating ionizable groups known as polyelectrolytes [1]. When dissolved in a polar solvent such as water, polyelectrolytes ionize and counterions dissociate from the polymer, leaving an oppositely charged polymer backbone. The highly ionized polyelectrolyte in solution attracts small mobile counterions of opposite charge, partially screening the backbone charge. The approach of the small molecules to a polyelectrolyte is governed to a large degree by electrostatic interactions, which in turn depend on the local molecular environment, and in particular is sensitive to the instantaneous distribution of counterions around the polyelectrolyte. Thus, knowledge of the counterion distribution at atomic resolution is crucial for many aspects of DNA dynamics such as molecular assembly and inter-cellular transport.The difficulty in studying polyelectrolyte solutions resides in the delicate interplay of the long range electrostatic interactions, short range intermolecular interactions, and thermal energy, which are comparable to each other in magnitude. Furthermore, typical polyelectrolytes are highly charged, which precludes straightforward application of the usual Debye-Hückel theory [2] of electrolytic solutions. A key advance in understanding the equilibrium state of counterions associated with a charged polymer was the condensation theory of Manning [3], which treated the polyelectrolyte molecule as an infinite rigid rod of uniform charge density −z p e/b, as an approximation to discrete groups of equal charge −z p e separated by a distance b, and considered independent dissolved counterions of charge z c e placed in a uniform bulk solvent of dielectric constant ǫ r about the molecule. Considering the two-dimensional partition function in the plane normal to the polyelectrolyte axis, Manning found that the free counterion configuration is unstable for sufficiently strong electrostatic interaction, when the dimensionless "Manning parameter" ξ ≡ z p z c l B /b > 1, where l B = e 2 /(ǫ r k B T ) is the "Bjerrum length" at which thermal energy k B T equals electrostatic potential energy. He then hypothesized that counterions would condense uniformly on the polyelectrolyte backbone so as to reduce ξ to unity, while the remaining (dilute) unb...

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“…For example, at 0.01 M NaCl, μ was invariant with DNA length for molecular weights between 1 -130 MDa (1.5 -200 kbp) (Olivera et al, 1964 (Hoagland et al, 1999).…”

Section: Electrophoretic Mobility Of Polymeric Nucleic Acidsmentioning

confidence: 99%

“…4A demonstrates the length independence of μ for long NAs. Experimental and theoretical studies of polyion electrophoresis phenomena have been reviewed extensively (Allison et al, 2007;Hoagland et al, 1999;Slater et al, 2009;Slater et al, 2002;Viovy, 2000). …”

Section: Electrophoretic Mobility Of Polymeric Nucleic Acidsmentioning

confidence: 99%