This antibody is optimally suited for monitoring the expression of FLAG(TM) tagged fusion proteins. As such, this antibody can be used to identify fusion proteins containing the FLAG(TM) epitope. The antibody recognizes the epitope tag fused to either the amino- or carboxy- termini of targeted proteins. The epitope tag peptide sequence was first derived from the 11-amino-acid leader peptide of the gene-10 product from bacteriophage T7. DYKDDDDK is the most commonly used hydrophilic octapeptide tag.