Influenza Hemagglutinin (HA) Peptide is a tag peptide derived from an epitope of the influenza hemagglutinin protein.

HA Peptide, derived from human influenza hemagglutinin (HA) amino acids 98–106, is a potent epitope widely utilized for isolating, purifying, detecting, and tracking proteins of interest due to its strong immunoreactivity. It is commonly employed in the separation of tagged proteins from cell culture supernatants and lysates at neutral pH, making it a valuable tool for coimmunoprecipitation and detection via western blotting. Given its small size, HA Peptide minimally impacts the biological activity and functionality of fusion partner proteins. The purification of recombinant HA-tagged proteins is facilitated by a highly specific anti-HA monoclonal antibody immobilized on resin, allowing for separation. These proteins can be eluted using a gentle method with an HA epitope at 1 mg/mL in TBS or through one of the three chemical elutions: 0.1 M glycine (pH 2-2.8), 3 M NaSCN, or 50 mM NaOH. Additionally, incorporating an N-terminal HA Peptide into mammalian expression vectors is crucial for T7 promoter-driven expression in E. coli, independent of trans-acting T7 RNAP. However, research indicates that caspase 3/7-mediated cleavage of HA Peptide abolishes its immunoreactivity, cautioning against its use in studying cell death and apoptotic mechanisms due to potential artifacts.