Final answer:
SDS in two-dimensional electrophoresis denatures proteins and masks their native charges, allowing for separation based on size alone. It is used in combination with other techniques to separate proteins based on their isoelectric point and relative molecular mass.
Step-by-step explanation:
SDS, or sodium dodecyl sulfate, plays several important roles in two-dimensional electrophoresis (2-DE). First, SDS acts as a detergent that denatures proteins, unfolding them and exposing their primary structure. This denaturation allows for uniform separation based on size and eliminates any influences of protein folding. Second, SDS masks the native charges of proteins, making them uniformly negatively charged. This allows for separation based on size alone, with larger proteins migrating more slowly through the gel. Finally, SDS- PAGE is often used in combination with other techniques, such as isoelectric focusing (IEF), to separate proteins based on their isoelectric point (pl) and relative molecular mass (Mr).