SARS-CoV-2 2019-nCoV Spike protein S1 subunit, receptor binding domain (RBD), also known as SARS-CoV-2 spike RBD, novel coronavirus spike RBD and nCoV spike RBD, GenBank Accession No. QHD43416.1, a.a. 319-541, with C-terminal Fc-tag, expressed in a CHO cell expression system. MW=50 kDa. This protein runs at a higher MW by SDS-PAGE due to glycosylation.