Eosin Y: a reversible stain for detecting electrophoretically resolved protein.

A method for the rapid staining of polypeptides in low-pH, urea-containing polyacrylamide gels is described. After 30 s of immersion in an alkaline solution of eosin Y, a variety of proteins stained with intensities similar to those seen with Coomassie R-250. By subjecting eosin-stained bands to electrophoretic elution, the eosin-protein complex was dissociated. This allowed for recovery of milligram quantities of electrophoretically resolved, stain-free protein. High recoveries of total protein as well as enzymatic activity were achieved using hen egg white lysozyme as a model protein.