6x His tagged influenza hemagglutinin HA1 (H5N1) (A/Bar-headed Goose/Qinghai/12/2005) (GenBank Accession No. ABE68927) (amino acid 17-530), glycosylated recombinant protein. There is a deletion at its cleavage site (RRRKKR). Majority of the protein exists as trimer/oligomer.