What are the principles of SDS-PAGE electrophoresis?

SDS PAGE or Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis is a laboratory technique that’s used to separate proteins based on their molecular weight. SDS-PAGE electrophoresis is based on two principles. 

The first principle states that when a charged molecule is exposed to or placed in an electric field, it migrates to the electrode carrying the opposite charge. 

According to the second principle, the separation of the charged molecules is affected by the relative mobility of charged species. The larger molecules migrate more slowly because of higher resistance during electrophoresis, while the smaller molecules encounter less resistance and migrate more quickly. 

The rate of migration is also affected by the structure and charge of the proteins. This impact is negated by the addition of polyacrylamide and sodium dodecyl sulphate, resulting in the proteins being separated based on the length of the polypeptide chain.