Severe acute respiratory Coronavirus 2 Spike Glycoprotein S1 (SARS-CoV-2 Spike S1), also known as novel coronavirus spike S1 and nCoV spike S1, GenBank Accession No. QHD43416.1, a.a. 319-541, with a C-terminal mouse Fc-tag (mFc), expressed in a HEK293 cell expression system. MW=50 kDa. This protein runs at a higher MW by SDS-PAGE due to glycosylation.