What is the primary purpose of SDS-PAGE in protein analysis?

• A. To enhance protein function
• B. To denature proteins and mask native charges
• C. To improve binding affinity in chromatography
• D. To measure protein concentration

Answer: (B)

The primary purpose of SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) is to denature proteins and mask their native charges. SDS is an anionic detergent that binds to proteins, imparting a negative charge proportional to the length of the polypeptide chain. This process unfolds the proteins and eliminates their native three-dimensional structures, allowing them to be separated based solely on their molecular weight during electrophoresis.

By denaturing the proteins, SDS-PAGE ensures that the mobility of each protein in the gel is determined primarily by its size, rather than its charge or conformation. This makes it a crucial technique for analyzing protein purity, size, and for determining the subunit composition of multi-subunit proteins. The masking of native charges facilitates a more accurate comparison of proteins with different charge-to-mass ratios.

While the other options touch on different aspects of protein analysis, they do not accurately capture the primary role of SDS-PAGE in the context of denaturation and separation based on size.