Separation is therefore dependent on the size of the protein-sodium dodecyl sulfate complex.
SDS disrupts all noncovalent protein bonds and causes molecules to unfold. The charged particles are caused to migrate toward the electrode of opposite sign under the influence of an externally applied electric field. The movements of the particles are retarded by interactions with the surrounding gel matrix, which acts as a molecular sieve. The pulling force of the electrical voltage and the opposing force of the gel matrix result in different migration rates for the proteins. The low molecular weight proteins migrate faster than the larger ones.