(A) Size exclusion chromatography of purified biotinylated SARS-CoV-2 NTD probes, including original WA-1 NTD and 14 other variant NTD in PBS buffer.
(B) SDS-PAGE of SARS-CoV-2 NTD variant probes with and without reducing agent. Molecular weight marker (MWM) and the WA-1 NTD probe were run alongside the variant NTD probes.
(C) Biotinylation of the SARS-CoV-2 variant NTD probes. The level of biotinylation was evaluated by capture of NTD probes at 5 μg/ml onto streptavidin biosensors using Octet. Error bars represent standard deviation of triplicate measurements.
(D) Antigenicity assessment of the SARS-CoV-2 variant NTD 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.