Figure 3. Affinity binding curves of NIH-CoVnb-112 against SARS-CoV-2 RBD variants.
Using Biolayer Interferometry on a BioForte Octet Red96 system, association and dissociation rates were determined by immobilizing biotinylated-NIH-CoVnb-112 onto streptavidin-coated optical sensors (a-e). The nanobody-bound sensors were incubated with a concentration range (18.75 – 300nM) of recombinant RBDs, (a) Prototype, (b) Alpha (B.1.1.7), (c) Beta (B.1.351), (d) Gamma (P.1), and (e) Delta (B.1.617.2), for an initial time interval to allow association. The sensors were then moved to an RBD-free solution and allowed to dissociate over a second time interval. Curve fitting using a 1:1 interaction model allows for the affinity constant (KD) to be measured for each RBD variant as detailed in Supplementary Table 2.