Electrophoresis field dependence

Nonlinear electrophoresis Field-dependent electrophoretic mohiUty... 

A molecule with a net charge will move in an electric field. This phenomenon, termed electrophoresis, offers a powerful means of separating proteins and other macromolecules, such as DNA and RNA. The velocity of migration (v) of a protein (or any molecule) in an electric field depends on the electric field strength (E), the net charge on the protein (z), and the frictional coefficient (f). 

Molecules can be separated in an electrical field based on their electrical charges. This method is called electrophoresis and was developed by Swedish scientist Arne Teselius for this development, he was later awarded the Nobel Prize in 1948. Molecules are applied on a solid support such as paper or gel and then subjected to an electrical field. The molecules move in an electrical field depending on their electrical charges. Proteins are usually separated on a gel matrix as discussed below. 

Chemically, molecular conformations with large electric moments increase in concentration at the expense of those configurations with smaller moments. Secondly, the presence of electric fields increases the dissociation of weak acids and bases and promotes the separation of ion pairs into the corresponding free ions (dissociation field effect, second Wien effect). The free ions or ionized structures then may move in the direction of the electric field (electrophoresis) and a field-dependent stationary state in the ion distribution may be established. 

Field-dependent electrophoretic mobility Nonlinear electrophoresis... 

Aperiodic electrophoresis refers to the use of an unbalanced AC field to separate charged polarizable particles due to the Stotz-Wien effect of field-dependent electrophoretic mobility. 

Dielectrophoresis (DEP) is a phenomenon different from electrophoresis (EP). In fact, any nonpolar material experiences a certain degree of polarization when exposed to an electric field. Depending on the material properties of the particle, electric dipoles are generated on opposing ends of the particle. The DEP force is due to the interaction between the dipole induced by an appfied electric field and the spatial gradient of that electric field. The general expression of the DEP force exerted on a particle in an electric field is... 

The first experiments demonstrating field-dependent electrophoretic mobility of colloids (Stotz-Wien effect) were reported by several groups in the 1970s [14], and the possibility of using this effect for particle separation using unbalanced AC fields has begun to be explored [14]. This work focused on nonlinear corrections to the classical phenomenon of electrophoresis, where a particle moves in the direction of the applied electric field, U = b(E)E, rather than on the associated ICEO flows and more complicated ICEP motion. 

An important application of the preceding material is to the determination of the molar mass of biological macromolecules. Electrophoresis is the motion of a charged species, such as DNA and ionic forms of amino acids, in response to an electric field. Electrophoretic mobihty is a result of a constant drift speed, so the mobility of a macromolecule in an electric field depends on its net charge, size (and hence molar mass), and shape. 

The E dependence of R implied by Eqs. (24) and (25) introduces into the dynamic equations retarded field-dependent features which are at the heart of the complexity of conventional and pulsed electrophoresis of flexible chains. The model predicts two regimes which crossover for... 

Electrophoresis (qv), ie, the migration of small particles suspended in a polar Hquid in an electric field toward an electrode, is the best known effect. If a sample of the suspension is placed in a suitably designed ceU, with a d-c potential appHed across the ceU, and the particles are observed through a microscope, they can all be seen to move in one direction, toward one of the two electrodes. AH of the particles, regardless of their size, appear to move at the same velocity, as both the electrostatic force and resistance to particle motion depend on particle surface this velocity can be easily measured. 

Auxiliary electrodes are placed into the solution to set up the electric field that is needed to produce electrophoresis or electroosmosis. Under these conditions an electric current passes through the solution and the external circuit its value depends on the applied voltage and on solution conductivity. The lower this conductivity, the higher will be the electric field strength E (or ohmic voltage drop) in the solution that can be realized at a given value of current. 

Theory Cross-flow-electrofiltration can theoretically be treated as if it were cross-flow filtration with superimposed electrical effects. These electrical effects include electroosmosis in the filter medium and cake and electrophoresis of the particles in the slurry. The addition of the applied electric field can, nowever, result in some qualitative differences in permeate-flux-parameter dependences. 

Tinland, B., Pernodet, N., and Weill, G., Field and pore size dependence of the electrophoretic mobility of DNA A combination of fluorescence recovery after photobleaching and electric birefringence measurements, Electrophoresis, 17, 1046, 1996. 

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