SDS-PAGE under focusing conditions : An electrokinetic transport phenomenon based on charge neutralization

A novel method is reported for mass separation of proteins, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Unlike conventional SDS-PAGE, in which separation by mass of SDS-laden polypeptide chains is obtained in constant concentration or porosity gradient gels, the present method, called “SDS-PAGE focusing”, exploits a “steady-state” process by which the SDS−protein micelles are driven to stationary zones along the migration path against a gradient of positive charges affixed to the neutral polyacrylamide matrix. As the total negative surface charge of such complexes matches the surrounding charge density of the matrix, the SDS−protein complex stops migrating and remains stationary, as typical of steady-state separation techniques. As a result of this mechanism, the proteins are separated in an unorthodox way, with the smaller proteins/peptides staying closer to the application point and larger proteins migrating further down toward the anodic gel end. This results in a pos...