The DYKDDDDK peptide (Flag-tag) is a small component of an epitope which does not appear to interfere with the bioactivity or the biodistribution of the recombinant protein. It has been used extensively as a general epitope tag in expression vectors. It can be used for affinity chromatography, then used to separate recombinant, overexpressed protein from wild-type protein expressed by the host organism. It can also be used in the isolation of protein complexes with multiple subunits.A Flag-tag can be used in many different assays that require recognition by an antibody. If there is no antibody against the studied protein, adding a Flag-tag to this protein allows one to follow the protein with an antibody against the Flag sequence.