Protocols for detection and purification of proteins tagged with a particular epitope, the FLAG tag, although the same general approach can be applied to other epitope tags. The protocols employ the anti-FLAG M2 antibody to detect and purify FLAG-tagged proteins. The methods presented are immunoprecipitation of FLAG fusion proteins from cells using an anti-FLAG M2 affinity gel, detection of FLAG fusion proteins by western blotting, and purification of FLAG fusion proteins by anti-FLAG. - [Read Epitope Tagging of Recombinant Proteins Protocol]