SDS-PAGE

SDS-PAGE or Sodium dodecyl sulfate polyacrylamide gel electrophoresis is a technique widely used in biochemistry, forensics, genetics, molecular biology and biotechnology to separate proteins according to their electrophoretic mobility (a function of the length of a polypeptide chain and its charge) and no other physical feature.

Overview

SDS-PAGE is a method that enables the separation of molecules by size. The technique is based on the principle that a charged molecule will migrate in an electric field towards an electrode with opposite sign. The rate of migration of a molecule through a gel is inversely proportional to the logarithm of its size. Therefore, smaller molecules will migrate faster and further than larger molecules.

Procedure

The procedure of SDS-PAGE can be divided into several steps:

1. Sample preparation: The protein sample is mixed with a buffer containing SDS and a reducing agent. The mixture is then heated to denature the proteins.
2. Gel preparation: The gel is prepared by polymerizing a mixture of acrylamide and bis-acrylamide.
3. Electrophoresis: The samples are loaded into the wells of the gel and an electric current is applied. The proteins migrate towards the positive electrode at a rate proportional to their size.
4. Staining: After electrophoresis, the gel is stained to visualize the proteins.

Applications

SDS-PAGE is used in various fields for different purposes:

1. In biochemistry and molecular biology, it is used to determine the molecular weight of proteins and to analyze their relative abundance in different samples.
2. In forensics, it is used to compare samples from crime scenes with samples from suspects.
3. In biotechnology, it is used to monitor the purity of protein products.

See also

• Protein electrophoresis
• Gel electrophoresis
• Polyacrylamide gel electrophoresis

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