Five things we learned about electrophoresis

Agarose gel electrophoresis is one of the most versatile techniques in the biotechnology laboratory. However, we rarely think about how the technique was developed! So we decided to hit the literature to learn more about the research and development that went into the creation of this powerful biotechnology.

Things we learned:

• The theory behind electrophoresis was inspired by Faraday’s Laws of Electrolysis, which were first published in 1833. These equations describe the way that charged ions in solution move through electrical fields.  In the 1900’s, researchers began to apply these concepts to more complex molecules, and to mixtures of molecules, which was the genesis of electrophoresis.
• Arne Tiselius, a Swedish Biochemist, built the first electrophoresis chamber in the 1930’s by fitting a U-shaped tube with electrodes at either end.  The tube was filled with the sample and buffer, and then charge was applied to the ends of the apparatus to create an electric field. Molecules either moved towards the anode or the cathode at different speeds based on their charge. Using this apparatus, Tiselius proved that blood plasma was a mixture of proteins.
• To detect the molecules being separated, Tiselius measured the speed that light passed through the apparatus at different locations. Any changes in this measurement, known as the refractive index, indicated the presence (or absence) of a molecule. Today, we visualize the molecules within our experimental samples using fluorescent dyes or visible stains.
• The first electrophoresis experiments didn’t separate similarly charged molecules very well. This is because they’d all be similarly influenced by the electric field. To address this, researchers introduced a porous matrix to the electrophoresis system to physically separate molecules during electrophoresis. As the molecules are moved by electrical field, they pass through the pores in the gel.  Since it’s easier for small molecules to move through the gel than larger ones, the molecules separate into bands by size, with larger ones near the wells, and smaller ones further down the gel.  Many substrates were tested, including paper and starch, before researchers settled on the use of agarose for DNA and polyacrylamide for protein.
• In 1948, Tiselius won the Nobel Prize in Chemistry “for his research on electrophoresis and adsorption analysis, especially for his discoveries concerning the complex nature of the serum proteins.” Your students can learn more about the scientist and his work by reading his Nobel Lecture, which is freely available online.

The next time you teach electrophoresis, be sure to share the rich history of its development with your students!