Preparing, pouring, and polymerizing polyacrylamide gels can be tedious. Fortunately pre-cast gels are available including the Hitachi R3™ Precast Gel Electrophoresis System or Longer Ranger gels from Cambrex BioScience Rockland, Inc. (formerly FMC Bioproducts, Rockland, ME). In order to reduce the number of gels that have to be prepared to analyze a large set of samples, a method has been developed to re-use gels (Tereba et al. 1998).
After imaging a gel on the FMBIO II, it can be placed back in the gel box and electrophoresed in reverse for a short period of time to remove the DNA samples from the gel. Typically the gel reverse electrophoresis is performed for 15-30 minutes longer than the previous forward electrophoresis, in order to fully remove all of the DNA bands from the gel. The gel can then be reloaded with fresh samples and another set of data determined. The Promega scientists have published protocols for the re-use of gels up to four or more times (Tereba et al. 1998, Micka et al. 1999).
Amazingly the resolution of the gel does not degrade with this re-use. However, edge effects, such as 'frowning' of the outer lanes, become progressively worse with each run. With the use of internal lane standards though, the frowning effects do not impact the ability to accurately size the unknown DNA fragments in the gel. The re-use of gels for four or five times or even more over the period of several days translates to savings in terms of labor and reagent costs. The re-use of gels also minimizes the number of times that a laboratory has to clean the glass gel plates.
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