Recombinant SARS-CoV-2 Spike protein S1 subunit, encompassing amino acids 16-685. This protein corresponds to SARS-CoV-2 Variant B.1.1.529 BA.1, also known as variant Omicron BA.1 originally identified in South Africa, and contains genetic alterations indicated below. 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.