What role does SDS play in SDS-PAGE analysis?

In SDS-PAGE analysis, SDS (sodium dodecyl sulfate) serves a crucial role in the denaturation of proteins and imparts a uniform negative charge to them. This is essential for the separation of proteins based on their molecular weight during electrophoresis.

When SDS is added to a protein sample, it binds to the polypeptide chains and unfolds them, disrupting their secondary, tertiary, and quaternary structures. This denaturation process ensures that the proteins lose their native conformations and exist in a linear form. The binding of SDS introduces a negative charge that is proportional to the length of the polypeptide chain, allowing proteins to migrate through the polyacrylamide gel solely based on their size—larger proteins migrate more slowly than smaller ones.

This mechanism is vital for the successful separation and analysis of proteins, as it allows researchers to assess the molecular weight and purity of the proteins being studied, all while avoiding the confounding effects of charge differences and structural variations.