A DNA sequence encoding the SARS-CoV-2 Spike RBD (YP_009724390.1, with mutation G339H, R346T, L368I, S371F, S373P, S375F, T376A, D405N, R408S, K417N, N440K, V445P, G446S, F456L, N460K, S477N, T478K, E484A, F486P, F490S, Q498R, N501Y, Y505H) (Arg319-lys529) was expressed with a C-terminal polyhistidine tag followed by an AVI tag. The expressed protein was biotinylated in vivo by the Biotin-Protein ligase (BirA enzyme) which is co-expressed. The mutations were identified in the SARS-CoV-2 variant (known as variant EG.5.1).