What is the Function of Gel in Gel Electrophoresis?

Before talking about the function of gel in gel electrophoresis, we will introduce the concept of gel electrophoresis first. It can separate biomolecules according to their size and charge as a common bio-separation technique. Its principle is based on the relationship that the migration speed of biomolecules is proportional to their size and charge in the electric field. Separation and detection of biomolecules can be obtained by migration of biomolecules in an electric field through the gel, as the separation medium. 

The function of gel in gel electrophoresis

The function of gel in gel electrophoresis is acting as a molecular sieve, which often refers to a polymer with a reticulated structure such as agarose, or polyacrylamide. The speed of migration of biomolecules through the gel is determined by the pore size of the gel. The larger pores can separate larger biomolecules and smaller pores can separate smaller biomolecules. Besides, the speed of smaller molecules moving through the gel is faster, and larger molecules stay behind to achieve the goal of separating molecules of different sizes.

The electric field effect can also separate the molecules in the gel. By applying an electric field to the gel, the charged biomolecules migrate toward the anode or cathode by the force of the electric field. The migration speed of biomolecules is directly proportional to their size and charge so that biomolecules of different sizes and charges are separated in the gel under the action of the electric field.

After separation comes to an end, the gel can show the separation bands by staining with a dye. Ethidium bromide is a fluorescent dye commonly used in gel electrophoresis. Put the gel into a dilute ethidium bromide solution and then place it on a UV transilluminator to observe the separation bands. Examine or photograph the bands immediately for future reference because they will diffuse into the gel as time goes on. To observe the migration of molecules, dyes can be put into the gel ahead of time. For example, DNA can be visualized under ultraviolet light using fluorescent dyes and special stains, and proteins can be colored using stains to view a banding pattern on a gel.

The application of gel electrophoresis

Gel electrophoresis has been widely used in a variety of fields, such as analyzing the size of DNA fragments, detecting the molecular weight of proteins, and studying the molecular structure of RNA. It is commonly used in the fields of biology, molecular biology, and biochemistry. It is very helpful for studying and diagnosing the problems related to various biomolecules.

Two types of gel electrophoresis

1. Agarose gel electrophoresis (mostly used to separate and identify nucleic acid molecules)

Agarose gel electrophoresis is an electrophoretic method using agar or agarose as the supporting medium. For samples with large molecular weight, such as large nucleic acid molecules, and viruses, agarose gels with large pore sizes are generally used for electrophoretic separation. The molecules of the substance will encounter resistance when passing through Agarose gel with a network structure, and the molecules are larger, the resistance is bigger when surging.

Both agar and agarose can be used for gel electrophoresis, but there is a difference between them. Agar is the best solidifying agent for solid culture. It only dissolves in hot water. When cooled, it solidifies into a solid form as a gel. Agarose is a polysaccharide extracted from agar and polymerized from different types of galactose. The gel filtration, gel electrophoresis, and gel diffusion experiments will often use this gel.

2. Polyacrylamide gel electrophoresis (mostly used to separate proteins)

Polyacrylamide gel electrophoresis is a kind of zone electrophoresis with polyacrylamide gel as the carrier. It is classified into two forms: non-denaturing polyacrylamide gel electrophoresis and SDS-polyacrylamide gel. With non-denaturing polyacrylamide gels, proteins keep intact during electrophoresis and are gradually separated in a gradient based on the molecular weight of the proteins, the shape of the proteins, and the amount of charge attached to the proteins. On the other hand, SDS-PAGE separates proteins based on the molecular weight of the protein subunits alone.

Conclusion

In general, according to the relationship that the migration speed of biomolecules in the electric field, gel electrophoresis can separate different molecules. The function of gel in gel electrophoresis is used as a separation medium. The rate of biomolecules moving in the gel is determined by the pore size of the gel in the electric field to achieve the separation and detection of biomolecules. Gel electrophoresis technology has very important applications in biological and practical fields, such as studying the molecular weight of proteins.