Figure 4.

Assessing an anti-S1 antibody (414-1) as an inhibitor of the S1-ACE2 interaction. Binding curve of the S1-ACE2 interaction with increasing concentrations of the anti-S1 antibody. Measurements were normalized to the average signal (designated as 100% Response) when S1 binds with ACE2, at 0 nM of the anti-S1 antibody. The orange line was fitted using a non-linear regression analysis to the log (inhibitor) versus the normalized response using GraphPad. The chi-square Goodness of fit is reported as ${\chi }^2$ (degrees of freedom, sample size). IC₅₀ and pIC₅₀, and their SEM were extracted from the fitted line and are reported as ${\mathrm{pIC}}_{50}\pm \mathrm{SEM}$ and ${\mathrm{IC}}_{50}$ (CI 95%: lower limit–upper limit). For each concentration $3\le n\le 5$.