SDS-Polyacrylamide Gels

Electrophoretic gel containing sodium dodecyl sulfate (SDS, also called sodium lauryl sulfate [SLS], detergents) and polyacrylamide. This medium dissociates proteins into subunits and reduces aggregation. Generally, the proteins are denatured with heat and a reducing agent before loading on the gel. The polypeptides become negatively charged by binding to SDS and are separated in the gel according to size (rather than by charge). On the basis of the mobility, the molecular weight of the subunits can be estimated with the aid of appropriate molecular size markers (ladder) but caution is required because glycosylated proteins may not reflect the molecular mass of the protein. The concentration of the polyacrylamide determines the size of the polypeptides that can be separated. Polyacrylamides (bisacrylamide:acrylamide, 1:29) separates [kDa proteins] as follows: 15% [12–43], 10% [16–68], 7.5% [36–94], 5% [57–212]. gel electrophoresis, electrophoresis