Electrophoresis supporting media for

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. 

Cellulose acetate strips have some other distinct advantages over paper strips as support media in electrophoresis. These strips greatly improve electrophoretic separations of polar molecules. Cellulose acetate may be cleared more easily than paper to produce transparent strips for automatic scanning. Further, cellulose acetate strips are thinner, more homogenous and chemically purer than paper strips. 

Laurent, et al. specifically promise a subsequent paper in which. ..it will be shown that this sieving ejfect can be used for the separation of various compounds that would otherwise sediment together in the ultracentrifuge... 5). The polymer solution sieving effect is the differential effect of polymer solutions on the sedimentation rate of particles of different size, as reflected in the dependence of B on particle radius. This proposal to use polymer solutions as a path to biochemical separations has come to fruition a half-century later in the use of polymer solutions as support media in electrophoresis. 

Zone electrophoresis is used mainly as an analytical technique and, to a lesser extent, for small-scale preparative separations. The main applications are in the biochemical and clinical fields, particularly in the study of protein mixtures. Like chromatography, zone electrophoresis is mainly a practical subject, and the most important advances have involved improvements in experimental technique and the introduction and development of a range of suitable supporting media. Much of the earlier work involved the use of filter paper as the supporting medium however, in recent years filter paper has been somewhat superseded by other materials, such as cellulose acetate, starch gel and polyacrylamide gel, which permit sharper separations. 

For clinical application in paper electrophoresis, however, the use of additives which decrease vapor pressure has not become established usage, but may receive renewed interest with new substrates (supporting media) where it is difficult to maintain the water content at a sufficiently high level. 

Dialysis is not currently performed on samples intended to be applied on buffered supporting media. Theoretically, however, this precaution should be taken because increased conductivity, increased ionic strength, and modification of pH cause several disturbances at the application spot, the most important being local depression of the electric field intensity (G10). Some substitute for dialysis is realized if the sample is diluted with a solution of buffer and serum salts, with volume and concentration calculated to give a final salt concentration corresponding to the expected result of combined dialysis and dilution (S31). This method was successful for free electrophoresis of serum and should also be useful in zone electrophoresis on stabilizing media. 

The electrophoretic separation technique is based on the principle that, under the influence of an applied potential field, different species in solution will migrate at different velocities from one another. When an external electric field is applied to a solution of charged species, each ion moves toward the electrode of opposite charge. The velocities of the migrating species depend not only on the electric field, but also on the shapes of the species and their environmment. Historically, electrophoresis has been performed on a support medium such as a semisolid slab gel or in nongel support media such as paper or cellulose acetate. The support media provide the physical support and mechanical stability for the fluidic buffer system. Capillary electrophoresis (CE) has emerged as an alternative form of electrophoresis, where the capillary wall provides the mechanical stability for the carrier electrolyte. Capillary electrophoresis is the collective term which incorporates all of the electrophoretic modes that are performed within a capillary. 

Most types of electrophoresis using supporting media are simple to carry out and the apparatus can be easily constructed, although inexpensive equipment is commercially available. High-resolution techniques such as two-dimensional electrophoresis and capillary electrophoresis require more sophisticated equipment, both for separation and analysis (see later). 

Because buffers used in electrophoresis are good culture media for the growth of microorganisms, they should be refi igerated when not m use. Moreover, a cold buffer is preferred in an electrophoretic run, because it improves resolution and decreases evaporation fi om the electrophoretic support. Buffer used in a small-volume apparatus should be discarded after each run because of pH changes resulting from the electrolysis of water that accompany electrophoresis. If volumes used are larger than 100 mL, buffer from both reservoirs may be combined, mixed, and reused up to four times. 

Electrophoresis using support media like starch gel or polycrylamide gel has now largely superseded thin sheet electrophoresis systems for the separation of biomolecules such as proteins. The gel methods have the great advantage that besides their useful chracteristics purely as support media, gels act as molecular sieves so that the movement of components is controlled by the size and shape of molecules in addition to charge and this results in more efficient electrophoretic separations. 

Lipoprotein electrophoresis provides a relatively simple method to study gross changes of the major lipoproteins various support media, buffers systems, and electrophoretic equipment and detection reagents have been employed (Groulade et al. 1981 Oppermann, Hubner, and Ehlers 1983). Electrophoresis may also be used to check the suitability of some methods for HDL and LDL. The Friedewald formula is used to determine LDL-cholesterol with human samples by measuring plasma cholesterol, triglycerides, and HDL-cholesterol (Friedewald, Levy, and Fredrickson... 

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