Figure 1. Binding of S glycoprotein trimers to hACE2-Fc and mvACE2-Fc receptors. (A) Representative binding profiles of S glycoprotein trimers to the hACE2-Fc receptor. The hACE2-Fc receptor was immobilized to biosensors, and binding to S glycoprotein trimers (SD614G, SD614G+Y453F, and SD614G+ Δ69-70+Y453F) was measured by bio-layer interferometry. (B) Representative binding profiles of S glycoprotein trimers to dimeric mvACE2-Fc receptors. The mvACE2-Fc receptor was immobilized to biosensors and binding to S glycoprotein trimers (SD614G, SD614G+Y453F, and SD614G+ Δ69-70+Y453F) was measured by bio-layer interferometry (C) Comparison of binding affinity (Kd) measured by bio-layer interferometry of S glycoprotein trimers to hACE2-Fc or mvACE2-Fc receptors.