Understanding Collaborative Effects between the Polymer Gel Structure and the Applied Electrical Field in Gel Electrophoresis Separation (original) (raw)
Related papers
1999
The effects of various geometrical parameters on effective diffusive, convective and electroconvective transport coefficients are studied by using models of constricted and expanded pores. The analysis of these simple pores offers insight into the transport behavior of macromolecules in media consisting of anisotropic aligned pores. A number of cases are analyzed including hydrodynamic flow, hindered transport with hydrodynamic flow, and electrophoretic transport with and without hindrance. The effects of the geometrical parameters of the model pores on the effective transport parameters are determined. The implications of changes of these geometrical parameters, applied electrical fields, and bulk flow rates on separations are illustrated using the time required to separate a binary mixture of solutes for specified resolutions. The results show that by appropriately selecting the flow rate in the case of hydrodynamic flow or the electrical field strength for the case of electrophoresis an optimum or minimum time of separation can be determined for the separation of two comparably sized molecules with sizes close to those of the narrower part of the pore.
Electrokinetic Flow and Dispersion in Capillary Electrophoresis
Annual Review of Fluid Mechanics, 2006
Electrophoretic separation of a mixture of chemical species is a fundamental technique of great usefulness in biology, health care, and forensics. In capillary electrophoresis (which has evolved from its predecessor, slab-gel electrophoresis), the sample migrates through a single microcapillary instead of through the network of pores in a gel. A fundamental design problem is to minimize dispersion in the separation direction. Molecular diffusion is inevitable and sets a theoretical limit on the best separation that can be achieved. But in practice, there are a number of effects arising out of the interplay between fluid flow, chemistry, thermal effects, and electric fields that result in enhanced dispersion. This paper reviews the subject of fluid flow in such capillary microchannels and examines the various causes of enhanced dispersion that limit the efficiency of separation.
Electrophoretic mobilities of counterions and a polymer in cylindrical pores
The Journal of chemical physics, 2014
We have simulated the transport properties of a uniformly charged flexible polymer chain and its counterions confined inside cylindrical nanopores under an external electric field. The hydrodynamic interaction is treated by describing the solvent molecules explicitly with the multiparticle collision dynamics method. The chain consisting of charged monomers and the counterions interact electrostatically with themselves and with the external electric field. We find rich behavior of the counterions around the polymer under confinement in the presence of the external electric field. The mobility of the counterions is heterogeneous depending on their location relative to the polymer. The adsorption isotherm of the counterions on the polymer depends nonlinearly on the electric field. As a result, the effective charge of the polymer exhibits a sigmoidal dependence on the electric field. This in turn leads to a nascent nonlinearity in the chain stretching and electrophoretic mobility of the...
Gel electrophoretic mobility of charged particles in a medium with curved channels
Electrophoresis, 1997
Gel electrophoretic mobility of charged particles in a medium with curved channels A model of electrophoretic mobility of small charged particles (for example short DNA fragments) in media with curved channels is proposed. The medium is represented by a dense material embedding the curved channels accessible to the charged particles. The steady flow method is used to obtain an analytical expression of the particles' electrophoretic mobility as a function of the channel's shape. The analogy between the statistical properties of the channels and polymer chains (free-jointed and with the persistent mobility mechanism) is used.
ELECTROPHORESIS, 2002
The effect of obstacle conductivity and electric field on effective mobility and dispersion in electrophoretic transport: A volume averaging approach The method of volume averaging has been used to determine the effective electrophoretic mobility and dispersion coefficients for molecular transport of point-like solutes in a two-phase porous medium where the electrical conductivity and the diffusion and mobility coefficients may vary in both phases. The formal theory, derived in previous work, is numerically evaluated for cases where the obstacle phase has a large or small conductivity relative to the fluid phase and where the diffusion coefficient of the solute in the obstacle phase can be large or small relative to that in the fluid phase. In agreement with previous Monte Carlo methods, the effective electrophoretic mobility is not a function of media conductivity or electric field when the obstacles are impermeable to solute transport or have small diffusion solute diffusion coefficients. However, the dispersion coefficient is a strong function of electric field and varies with obstacle conductivity when diffusive transport is small in the obstacles relative to the fluid. In contrast, the effective electrophoretic mobility is a function of electric field when conductivity of the obstacles is much larger than the fluid and when the obstacles are very permeable to solute but have low electrical conductivity.
Journal of Chromatography A, 1994
Experimental results on the electroosmotic mobility in fused-silica capillaries are presented for different applied voltages and solutions of different pH. The electroosmotic mobility is shown to be dependent on the applied voltage and this dependence cannot be attributed to the temperature effects. Results of the electroosmotic mobility measurements are found to be dependent also on the electrophoresis unit they have been performed in. The explanation given and the relevant theory presented are based on the hypothesis that these effects are produced by a radial electric field inevitably existing in any electrophoresis unit. The concept of the limiting e~ectrophoretic mobility, i.e. extrapotated to the zero applied voltage, is introduced in order to characterize the properties of the solution-wall interface. The slope of the electroosmotic mobility dependence on the applied voltage depends on the solution pH and the surroundings of the capillary. Theoretical estimations agree well with both experimentally found limiting mobilities and slopes. Long-term variations of the electroosmotie mobility are supposed to be related with the cation penetration into the capillary wall.
Electrophoretic mobility of composite objects in free solution: Application to DNA separation
Electrophoresis, 1996
We propose here a simple procedure to estimate the electrophoretic mobility of composite objects obtained by linking two charged subunits, stressing that this electrophoretic mobility is in general different from the ratio of the total charge to the total friction coefficient. We focus especially on the situation where at least one of the subunits is a polyelectrolyte. Our remarks in particular correct the existing theoretical analysis of separation capabilities of devices in which a buoy (sphere, protein, polymer) is attached to a DNA chain. We also predict that, in some cases, the direction of electrophoretic motion can be reversed by increasing the electric field amplitude.
Nonlinear electrophoretic response yields a unique parameter for separation of biomolecules
Proceedings of the National Academy of Sciences, 2009
We demonstrate a unique parameter for biomolecule separation that results from the nonlinear response of long, charged polymers to electrophoretic fields and apply it to extraction and concentration of nucleic acids from samples that perform poorly under conventional methods. Our method is based on superposition of synchronous, time-varying electrophoretic fields, which can generate net drift of charged molecules even when the time-averaged molecule displacement generated by each field individually is zero. Such drift can only occur for molecules, such as DNA, whose motive response to electrophoretic fields is nonlinear. Consequently, we are able to concentrate DNA while rejecting high concentrations of contaminants. We demonstrate one application of this method by extracting DNA from challenging samples originating in the Athabasca oil sands.
Electrophoresis, 2000
To gain insight into the mechanisms of size-dependent separation of microparticles in capillary zone electrophoresis (CZE), sulfated polystyrene latex microspheres of 139, 189, 268, and 381 nm radius were subjected to CZE in Tris-borate buffers of various ionic strengths ranging from 0.0003 to 0.005, at electric field strengths of 100±500 V cm ±1 . Size-dependent electrophoretic migration of polystyrene particles in CZE was shown to be an explicit function of kR, where k ±1 and r are the thickness of electric double layer (which can be derived from the ionic strength of the buffer) and particle radius, respectively. Particle mobility depends on kR in a manner consistent with that expected from the Overbeek-Booth electrokinetic theory, though a charged hairy layer on the surface of polystyrene latex particles complicates the quantitative prediction and optimization of size-dependent separation of such particles in CZE. However, the Overbeek-Booth theory remains a useful general guide for size-dependent separation of microparticles in CZE. In accordance with it, it could be shown that, for a given pair of polystyrene particles of different sizes, there exists an ionic strength which provides the optimal separation selectivity. Peak spreading was promoted by both an increasing electric field strength and a decreasing ionic strength. When the capillary is efficiently thermostated, the electrophoretic heterogeneity of polystyrene microspheres appears to be the major contributor to peak spreading. Yet, at both elevated electric field strengths (500 V/cm) and the highest ionic strength used (0.005), thermal effects in a capillary appear to contribute significantly to peak spreading or can even dominate it.