Principles of Electrophoresis

The intervening medium consists of a liquid, usually a buffer, that is supported by an inert solid material such as paper or a semisolid gel. The liquid allows the movement of ions, while the solid support provides frictional drag. When a voltage is applied across the electrodes, a current is generated from the movement of ions in the electric field. The electric field strength, E, determines the rates of migration of the species in the support and can be varied experimentally. 

Low-voltage electrophoresis is typically carried out at electric field strengths of 20 V/cm, while high-voltage techniques use field strengths of up to 200 V/cm.1 

Bianalytical Chemistry, by Susan R. Mikkelsen and Eduardo Corton ISBN 0-471-54447-7 Copyright 2004 John Wiley Sons, Inc. 

On the other hand, the intervening media used in electrophoresis have much lower conductivity, and an equivalent circuit for an electrophoresis cell includes a resistor between the capacitors at the electrode-solution interfaces. Across the support medium, potential is now (usually) a linear function of distance, and the electric field thus generated is responsible for driving the electrophoretic separation. Electrophoresis occurs at the electrodes used in electrophoresis, to maintain the 

The theoretical description of electrophoretic migration2 begins with a consideration of a particle of charge q suspended in an insulating medium, and exposed to an electric field E. Fundamental laws of physics state that the electric force exerted on the particle will be equal to its viscous drag, as shown in Eq. 9.2  

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R Garrett and C Grisham, Biochemistry, 2nd ed (1999), Saunders (Orlando, FL), pp 141-142,154-156,405-412 Basic principles of electrophoresis P Grabar and C Williams, Btocbim. Biopbys. Acta 10, 193-194 (1953) Application of Immunoelectrophoresis to protein separation... 

Figure 4.4 Illustration of the principle of electrophoresis, in which an electric field is applied causing dispersed species, with their charged surfaces plus some attached fluid, to move relative to stationary liquid.

The enzymatic reaction was realized in a MBR, which coupled the principle of electrophoresis with the enzymatic reaction. The optically pure (S)-naproxen was continu-... 

Other Techniques. A growing technique related to lc/ms and regarded as complementary to it is that of capillary zone electrophoresis/mass spectrometry (cze/ms) (22). Using cze/ms, high resolution separation of water-soluble compounds is accompHshed by the principles of electrophoresis (qv). The sample is then coupled to the mass spectrometer by electrospray ionization (23) or a fast atom bombardment interface (fab) to produce molecular ions (24). Biotechnology applications of cze/ms have great potential (25). 

Describe the principle of electrophoresis and its application in the separation of proteins. 

Fig. 3.1. The separation principle of electrophoresis. Particles with different charges, in this case negative charges, and different sizes migrate at different velocities in an applied electric field.

The measurements of electrochemical impedance, voltammetric (po-larographic) analysis, and spectroelectrochemistry represent a basis for analysis of molecules of biological significance in bulk of solution and at interfaces. These principles are reviewed in the first four chapters. The next three chapters demonstrate how these principles are utilized in voltammetric and interfacial analysis of biomacromolecules such as nucleic acids, proteins, polysaccharides, and viruses in vitro, in the development of biosensors with electrochemical transducers and in in vivo voltammetry. The last two chapters of this volume are devoted to the principles of electrophoresis used for separation analysis of biomolecules and to the theoretical principles and practical description of the patch-clamp technique to an extent suitable for those wishing to initiate research in electrophysiology. 

The principle of electrophoresis, the most straightforward method for electrodeposition is based on the electric field-driven charged particles (silicate, organosilicate, metal oxides, micelles, or polymer composite particles) to an electrode at an electrophoretic velocity, v, which is determined by Stoke s law. 

Although the principle of electrophoresis has been known since 1809, from the work of Reuss, it has remained confined to a very few areas of application in medical, analytical and other technological fields. The process of electrophoretically depositing paints and lacquers could only be applied industrially when new ionizable paints and resins were developed that could be diluted with water and deposited from an aqueous medium under the influence of an electric current, similarly to the electrodeposition of metals (although the electrodeposition of organic material is much more complex). It was not possible to electrodeposit conventional organic-based paints, since these did not form ions, and known water-soluble paints that could be applied by conventional immersion or spraying techniques were too expensive. 

Electrophoresis is described in a number of useful works. Introduction to Paper Electrophoresis and Related Methods by M. Lederer (Elsevier, 1955) surveys its use in organic, inorganic and biological chemistry. Principles of Electrophoresis by R. Audubert and S. de Mende (Hutchinson, 1959) covers the physical chemistry of electrophoresis with detailed descriptions of apparatus and techniques. It is a useful introduction to new developments. 

Figure 6.23 The principle of electrophoresis. A spherical particle of charge and radius a moves in a low-conductivity liquid with viscosity // under the influence of an applied electrical fleld E...

The principle of electrophoresis. A spherical particle of charge and radius a... 

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