SDS-PAGE (Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis) is a technique used to separate proteins based on their molecular weight. SDS, a detergent, denatures proteins and imparts a uniform negative charge, allowing them to migrate through a polyacrylamide gel under an electric field. The separated proteins can then be visualized, typically through staining methods, to analyze their size and purity.