Agarose, 380 also

As mentioned above, the large pore size of agarose also allows the subfractionation of VLDL. Upon isoelectric focusing of VLDL which had been isolated by ultracentrifugation, we found three groups of bands which differ in respect to density, Upid and apolipoprotein composition. Functional differences were seen after an oral fat load and upon heparin-induced lipolysis. Acidic subfractions rich in triglycerides and apolipoprotein C-III increased after the fat load and were apparently the preferred substrate for the action of heparin-released lipases (Fig. 3). 

Agarose also presents other problems It lacks thermal stability, cannot be dried or frozen readily, and shrinks and swells upon changes of ionic strength or dielectric constant of the medimn, especially in the presence of organic solvents. Thus, commercial agarose is completely soluble in dimethyl sulfoxide at 100°C or in 4 M sodimn iodide, whereas agarose cross-hnked with epichlorohydrin is essentially imaffected imder the same condition (<1% soluble) (8). 

Distinction is also made among electrophoretic techniques in terms of the type of matrix employed for analysis. Matrices include polymer gels such as agarose and polyacrjiamide, paper, capillaries, and flowing buffers. Each matrix is used for different types of mixtures, and each has unique advantages. 

Various support media may be employed in electrophoretic techniques. Separation on agarose, acrylamide, and paper is influenced not only by electrophoretic mobiUty, but also by sieving of the samples through the polymer mesh. The finer the weave of selected matrix, the slower a molecule travels. Therefore, molecular weight or molecular length, as well as charge, can influence the rate of migration. 

Monolithic columns, formed from the co-polymerization of divinylbenzene and vinylbenzyl chloride or styrene, were observed to be resistant to bubble formation.11 Application of pressure in electrochromatography, discussed below, also reduces bubble formation. A massively parallel detector capable of scanning up to 1000 capillaries using planar confocal fluorescence has been used for DNA sequencing.1213 Recovery of fluorescence following pho-tobleaching has been used to measure DNA mobility in agarose gel.14... 

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