Staining proteins in gels

Once proteins are separated by gel electrophoresis, staining can be used to visualize the proteins. This unit presents protocols for numerous staining methods. The most common method is staining with Coomassie blue, which after washing gives blue bands on a clear background. This technique can also be applied to isoelectric focusing gels. A second, more sensitive but also more technically challenging method is silver staining. Here the proteins are seen as dark brown to black bands on a clear background. If the gel is incubated with SYPRO Ruby, a fluorescent compound that interacts specifically with proteins, the bands fluoresce when illuminated on a standard transilluminator. Finally, proteins can be reversibly stained with zinc, which precipitates the SDS from the gel leaving protein bands as clear spots against an opaque white background.