Why do small proteins run faster than large ones during SDS polyacrylamide?

During SDS polyacrylamide gel electrophoresis, small proteins run faster than large ones due to their ability to navigate through the porous gel matrix more easily. The gel acts like a molecular sieve, allowing smaller proteins to move through the spaces between the polymer chains with less resistance, while larger proteins encounter more obstacles, slowing their movement. Additionally, the SDS detergent imparts a uniform negative charge to proteins, ensuring that size is the primary factor influencing their migration rate.