What component of SDS-PAGE allows for protein visualization?

In SDS-PAGE, protein visualization is primarily achieved through the use of Coomassie blue stain. This dye binds to proteins in the polyacrylamide gel, allowing them to be visualized as distinct bands. Coomassie blue interacts with the amino acids in the protein, especially those containing aromatic or basic side chains, resulting in a color change that makes the proteins visible against the background of the gel.

While there are other methods for visualizing proteins, such as staining with silver, using fluorescent markers, and autoradiography, Coomassie blue is one of the most commonly used and is widely recognized in laboratory protocols for its efficiency, ease of use, and ability to detect a broad range of protein concentrations. It allows researchers to qualitatively assess the presence and quantity of proteins based on the intensity of the bands formed after staining.