Tandem affinity purification allows rapid purification under native conditions of complexes, even when expressed at their natural level. Prior knowledge of complex composition or function is not required. The TAP method requires fusion of the a multiple tag, either N- or C-terminally, to the target (or bait) protein of interest. The multiple tag allows two steps purification steps ensuring a highly selective complex purification. [ http://www.ncbi.nlm.nih.gov/pubmed/11403571 ]