Fusion proteins of the SARS-CoV-1 and SARS-CoV-2 spike receptor binding domain with a fluorescent protein were created in monomeric and trimeric form as tools for receptor binding studies in cultured cells and animal tissues. Here, site specific N-linked glycosylation in the proteins expressed from GnTI-/- cells is profiled with LC-MS/MS, using electron transfer high-energy collision dissociation