What is the difference between SDS-PAGE method and a simple gel electrophoresis?
The two are actually related. SDS-PAGE stands for Sodium Dodecyl Sulfate-PolyAcryamide Gel Electrophoresis. It means gele electrophoresis conducted in the presence of the surfactant (detergent) SDS. In the presence of SDS proteins lose all of their secondary and tertiary structure and open up into generally straight rods coated with SDS. In this manner their molecular weight can generally be calculated since their movement in the electrophoretic field is pretty well correlated with how long the rods are which, in turn, is pretty well governed by their mass. You can do electrophoresis in the absence of SDS–this is called native gel electrophoresis. In this case the proteins will retain their activity but will not move strictly as a function of their molecular mass.
