To understand the contribution of receptor interaction to the infectivity of SARS-CoV-2, the investigation characterized engagement of hACE2 by SARS-CoV-2 SB and SARS-CoV SB side by side. The investigation used biolayer interferometry to study binding kinetics and affinity of the purified hACE2 ectodomain to SARS-CoV-2 SB and SARS-CoV SB immobilized at the surface of biosensors.