Protein Gel Staining

Gel staining is an important visualization and detection step that follows protein polyacrylamide gel electrophoresis (PAGE), such as SDS-PAGE, native PAGE, or 2D-PAGE. After electrophoresis, proteins are separated by relative size, or in the case of 2D-gels—charge and size, but the resolved bands are not yet visible within the clear gel matrix. The next step is the application of staining compounds with specific affinities to the immobilized proteins. Over the past years, certain stains have become the established standards for protein gel staining. Coomassie Brilliant Blue is a chromogenic dye that binds electrostatically with the amino and carboxyl groups of proteins. Coomassie staining is very frequently used with SDS-PAGE because it is reversible and is compatible with downstream mass spectrometric analyses. Silver staining relies on the reduction of bound silver ions, which result in distinct markings of metallic silver. Staining with silver is very sensitive, and can detect proteins in the low nanogram amounts. A variety of ready-to-use protein staining reagents and kits are available from many suppliers. Consider the level of desired protein sensitivity and the intended downstream applications when choosing a stain.