Recombinant SARS-CoV-2 Spike protein S1 subunit, encompassing amino acids 16-685. This protein corresponds to SARS-CoV-2 Variant B.1.617.1, also known as variant Kappa, originally identified in India. It contains mutations G142D, E154K, L452R, E484Q, D614G, and P681R. The construct also contains a C-terminal Avi-Tag™ followed by a C-terminal His-tag (6xHis). The protein was enzymatically biotinylated using the Avi-Tag™ and affinity purified.