Figure 2.

In vitro monitoring of the SARS-CoV-2 S-RBD/ACE2 interaction. SARS-CoV-2 S-RBD(His)₆ and human ACE2-Biot interaction have been first monitored by typical pull down assay using streptavidin coupled magnetic beads (A) using 500 ng of each protein. Input, co-precipitated proteins (pull down) and non-specific binding of each partner on beads are reported in the figure. Pull downs have been performed at different NaCl concentration and the percentage of retained S-RBD protein is reported in (B). Data were obtained from at least three independent experiments and are reported as means ±SD. The S-RBD/ACE2 complex has been further analyzed using AlphaLISA assay. Cross titration experiments of ACE2-Biot (0.3 to 100 nM) against S-RBD(His)₆ (0.3 to 100 nM) using anti-6X His acceptor beads and streptavidin donor acceptor beads are reported in (C). Evaluation of the tolerance for dimethyl sulfoxide (DMSO) has been performed as describe above with addition of 0.3 to 20% (v/v) of DMSO in the ACE2-Biot/S-RBD(His)₆ binding step. In these conditions, binding data with DMSO were compared to the control condition without DMSO (D). Data were obtained from at least two independent experiments and are reported as means ±SD.