SDS-PAGE and Western Blotting

Proteins can be separated according to their molecular sizes and charges, since these factors will determine the speed at which they will travel through a gel. The SDS-PAGE method involves the denaturation of proteins with the detergent sodium dodecyl sulfate (SDS) and the use of an electric current to pull them through a polyacrylamide gel, a process termed polyacrylamide gel electrophoresis (PAGE). SDS binds strongly to proteins, with approximately one detergent molecule binding to two amino acids when SDS is present at 0.1% (1,2). When boiled with SDS, proteins gain a negative charge in proportion to their molecular size, and thus travel in the acrylamide gel according to their molecular sizes. The smaller the size of the running protein, the faster it travels through the pores of the gel Fig. 1 ).