Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separates proteins based on molecular weight by binding to proteins and imparting a uniform negative charge-to-mass ratio, making citations unnecessary for this standard biochemical definition.
The claim describes the foundational, textbook definition of how SDS-PAGE functions in biochemistry (using SDS to denature proteins and confer a uniform negative charge so they separate by size). This is a well-established scientific fact and common knowledge, so no literature citation is required.