(A) Size exclusion chromatography of the purified biotinylated SARS-CoV-2 RBD-SD1 probes, including original WA-1 RBD-SD1 and 12 other variant RBD-SD1 in PBS buffer.
(B) SDS-PAGE of SARS-CoV-2 RBD-SD1 variant probes with and without reducing agent. Molecular weight marker (MWM) and the WA-1 RBD-SD1 probe were run alongside the variant RBD-SD1 probes.
(C) Biotinylation of the SARS-CoV-2 variant RBD-SD1 probes. The level of biotinylation was evaluated by capture of the RBD-SD1 probes at 5 μg/ml onto the streptavidin biosensors using Octet. Error bars represent standard deviation of triplicate measurements.
(D) Antigenicity assessment of the SARS-CoV-2 variant RBD-SD1 probes. Responses to RBD-directed, NTD-directed, and S2 subunit-directed antibodies were shown in cyan, orange, and rose, respectively. Bar scale between 0 and 3. Negative values not depicted. Variants with the L452R mutation lost binding to A19–46.1.