Protein tags are protein or peptide sequences located either on the C- or N- terminal of the target protein, which facilitates one or several of the following characteristics: solubility, detection, purification, localization and expression. The DYKDDDDK(FLAG) peptide has been used extensively as a general tag in expression vectors. This peptide can be expressed and detected with the protein of interest as an amino-terminal or carboxy-terminal fusion. N-terminal FLAG vectors provide an Ek cleavage site for removal of the fusion tag. The FLAG peptide is likely to be located on the surface of a fusion protein because of its hydrophilic nature. As a result, the FLAG peptide is more likely to be accessible to antibodies. A FLAG-tag can be used in many different assays that require recognition by an antibody, such as western blotting, immunocytochemistry, immunoprecipitation, flow cytometry, protein purification, and in the study of protein-protein interactions, cell ultrastructure, and protein localization and so on. This antibody is a mouse monoclonal antibody raised against 3xFlag (3xDYKDDDDKT) sequence and recognizes the (3x)DYKDDDDK peptide and detects FLAG-tagged proteins.