Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is commonly used to obtain high resolution separation of complex mixtures of proteins.
In SDS-PAGE, the use of sodium dodecyl sulfate (SDS, also known as sodium lauryl sulfate) and polyacrylamide gel largely eliminates the influence of the structure and charge, and proteins are separated solely based on polypeptide chain length/Molecular weight.
Coomassie blue dyes are a family of dyes commonly used to stain proteins in SDS-PAGE gels. The gels are soaked in dye, and excess stain is then eluted with a solvent ("destaining"). This treatment allows the visualization of proteins as blue bands on a clear background.
SDS-PAGE is a reliable method for determining the molecular weight (MW) of an unknown protein, since the migration rate of a protein coated with SDS is inversely proportional to the logarithm of its MW.