An ELISA plate is coated with 50 μL of a 6x-His recombinant protein conjugated BSA at concentration ranged from 0.003 μg/mL to 3 μg/mL. The coated protein is detected with anti-His antibody (GTX628921) at 0.5 ng/mL. Bound antibodies were further detected by using HRP-conjugated goat anti-mouse IgG (GTX213112-01).