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Many biological macromolecules, such as proteins and nucleic acids (DNA and RNA), have an electrical charge and will move through a fluid medium when they are exposed to an electrical field. The direction of movement will depend on the sign of the electrical charge and the rate of migration will depend on the amount of charge and on the shape or size of the molecule. If two molecules have the same amount of charge, the smaller molecule will move faster than the larger molecule. The differences in the rate of movement of the molecules can be used to separate the molecules in a mixture. This separation can be done to determine the number and amounts of the components in a mixture or it can be used to purify one component from the other components.
Equipment is available to perform electrophoretic separations in either a horizontal or vertical mode in a gel matrix made from either agarose or polyacrylamide. The sizes of gels can be as small as 5cm x 7.5cm for rapid analysis of samples to 35cm x 45cm for a high resolution gel for DNA sequencing. Several power supplies are available so that an electrical field of up to 2000 volts may be used.