Recombinant SARS-CoV-2 Spike protein S1 subunit, encompassing amino acids 16-685. This protein corresponds to SARS-CoV-2 Variant B.1.617.2 also known as variant Delta originally identified in India, and contains mutations T19R, G142D, R158G, L452R, T478K D614G and P681R. It was constructed with a C-terminal Avi-Tag™ followed by a His-tag (6xHis). The protein was enzymatically biotinylated using the Avi-Tag™ and affinity purified.