How to Prepare a Sample for Gel Electrophoresis

Electrophoretic separation is one of the most widely used methods in biochemistry. Although electrophoresis can be carried out freely in a solution, it is more convenient to use some kind of supporting medium. The two most commonly used supporting media are paper and gel. Gel electrophoresis is a technique much used with proteins and nucleic acids. DNA analysis is a significant case where gel electrophoresis is performed. DNA are polyelectrolytes that can be separated based on size alone.

Things You'll Need

• Sample solution
• Standard solution
• Buffer solution
• Gel medium
• Tracking dye

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Instructions

• 1

  Prepare the sample solution and the standard solution of known molecular weight.

• 2

  Prepare a buffer solution with the nearest pH value to your sample.

• 3

  Prepare the supporting medium (gel); common gel-forming materials are polyacrylamide, a water-soluble, cross-linked polymer, agarose and polysaccharide.

• 4

  Place the gel between electrode compartments, with the bottom selected as anode or cathode, depending on whether anions or cations are being separated.

• 5

  With a pipette, carefully drop a little amount of solution of each sample into one of several precast notches on top of the gel.

• 6

  Add glycerol and a water-soluble tracking dye to the sample. The glycerol makes the sample solution dense, so that it does not mix into the buffer solution in the upper electrode chamber.