Electrophoresis supports

There is often a need for a visualization procedure that is specific for a certain biomolecule, for example, an enzyme. If the enzyme remains in an active form while in the gel, any substrate that produces a colored product could be used to locate the enzyme on the gel. Although it is less desirable for detection, the electrophoresis support medium may be cut into small segments and each part extracted with buffer and analyzed for the presence of the desired component. 

The dye ethidium bromide is often used to detect the presence of nucleic acids on electrophoresis supports. Explain how it functions as an indicator. 

Because the resolution provided by a gradient is better, it should always be used in the 2-D electrophoresis. Agarose may also be used as an electrophoresis support... 

In the present section, we cover the two steps for creating stationary phases from colloidal assembly. In the first step, the colloids are assembled into a regular, close-packed structure through the evaporation of the solvent or a flow-through system. As we will see later, the colloidal crystal, when filled with electrophoresis buffer, can be used directly as a solid support for capillary electrophoresis [20,21]. Alternatively, a polymeric structure can be formed around the bead template. After dissolving the beads, one is left with a regular structure of cavities and pores that can also serve as an electrophoresis support [22]. 

In addition to polymeric support media, capillaries and flowing buffers have been used as support media for electrophoresis. Although these are not used as frequendy, there are definite advantages for certain types of samples and appHcations. 

Capillary Electrophoresis. Capillaries were first appHed as a support medium for electrophoresis in the early 1980s (44,45). The glass capillaries used are typically 20 to 200 p.m in diameter (46), may be filled with buffer or gel, and are frequendy coated on the inside. Capillaries are used because of the high surface-to-volume ratio which allows high voltages without heating effects. The only limitations associated with capillaries are limits of detection and clearance of sample components. 

Generally, electrophoresis is carried out not in free solution but in a porous support matrix such as polyacrylamide or agarose, which retards the movement of molecules according to their dimensions relative to the size of the pores in the matrix. 

The mechanism by which analytes are transported in a non-discriminate manner (i.e. via bulk flow) in an electrophoresis capillary is termed electroosmosis. Eigure 9.1 depicts the inside of a fused silica capillary and illustrates the source that supports electroosmotic flow. Adjacent to the negatively charged capillary wall are specifically adsorbed counterions, which make up the fairly immobile Stern layer. The excess ions just outside the Stern layer form the diffuse layer, which is mobile under the influence of an electric field. The substantial frictional forces between molecules in solution allow for the movement of the diffuse layer to pull the bulk... 

Raymond, S Weintranb, LS, Acrylamide Gel as a Supporting Medium for Zone Electrophoresis, Science 130, 7111,1959. 

P. S. (2007) Separation of membrane-bound compounds by solid-supported bilayer electrophoresis./. Am. Chem. Soc., 129, 8072-8073. 

Raymond, S. and Weintraub, L., Acrylamide as a supporting medium for zone electrophoresis, Science, 130, 711, 1959. 

Fig. 11-2. Schematic for preparative gel electrophoresis using a condenser for mechanical support and cooling.

Factors Affecting Ionic Migration. Effect of Temperature. pH and Ionic Strength. Electro-osmosis. Supporting Medium. Detection of Separated Components. Applications of Traditional Zone Electrophoresis. High-performance Capillary Electrophoresis. Capillary Electrochromatography. Applications of Capillary El ectrochromatography. ... 

Traditional electrophoresis paper, cellulose acetate or polymeric gels used as a supporting medium for the electrolyte solution enclosed tank with electrodes and buffer reservoirs dc power supply. 

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