THEORY OF SDS-PAGE

Firstly, the proteins molecules are exposed to ionic detergent SDS (sodium dodecylsulfate) before or during the gel electrophoresis, where this SDS will then denatures the proteins and binds to the uncoiled molecules.

Generally, SDS binding confers a negative charge on all the proteins, hence in an electric field proteins will migrate solely as a function of their molecular weight. Hereby, can be illustrate that, the SDS treatment eliminates the effects of differences in shape so the mass plays the vital role in protein separation. SDS is very significant as it can separate chain that differ in molecular weight by less than 10 percent, and the molecular weight of that particular protein can be measured by comparing with the protein ladder or molecular weight ladder which is run on the same gel at the other lane.

In addition, it is a technique separating macromolecules such as DNA, RNA, and proteins. It is widely used for displaying proteins, for generating Western blots, and for separating nucleic acids that differ in length. The condition for separating by size the whole spectrum of typical cellular polypeptides, recommended from about 10, 000 to more than 100, 000 Da.

In general, electrophoresis is the process of applying an electric field to move charged molecules through a solution. The essence of this technique;

The mobility of a charged molecule = Net charge / Resistance of the solution through which it is moving