SARS-CoV-2 Spike S1 receptor binding domain (RBD), also known as SARS-CoV-2 Spike 1 RBD, novel coronavirus Spike 1 RBD and nCoV Spike 1 RBD, GenBank Accession No. QHD43416.1, a.a. 319-541 with a V367F mutation and a with C-terminal Avi-His-tag, expressed in a HEK293 cell expression system. MW= 28 kDa. This protein runs at a higher M.W. by SDS-PAGE due to glycosylation.