Sandwich ELISA detection of recombinant SARS-CoV-2 (COVID-19) Spike (D614G variant) protein, His tag (active) (GTX02575-pro), and SARS-CoV-2 spike (trimer) protein using SARS-CoV-2 (COVID-19) Spike RBD antibody [HL1014] (GTX635807) as capture antibody at concentration of 5 μg/mL and SARS-CoV-2 (COVID-19) Spike RBD antibody [HL1003] (HRP) (GTX635792-01) as detection antibody at concentration of 1 μg/mL.

Functional ELISA analysis of immobilized recombinant SARS-CoV-2 (COVID-19) Spike (D614G variant) protein, His tag (active) (GTX02575-pro), and SARS-CoV-2 spike (trimer) protein (coated at 2 μg/mL) binding to soluble recombinant Human ACE2 (ECD) protein , mouse IgG Fc tag (GTX135683-pro) (13-10000 ng/mL). Bound protein was detected by Goat Anti-Mouse IgG antibody (HRP) (13111-01) (1:10000).

Gel filtration analysis of 2 different batches of spike protein.
The first batch : spike protein in PBS buffer.
The second batch : spike protein in PBS, 20% glycerol.

SDS-PAGE of GTX02575-pro SARS-CoV-2 (COVID-19) Spike (D614G variant) protein, His tag.

CD spectra of different cation forms of spike protein. The scanning fluorimetry data of the two batches shows the protein is both stable and functional, with heparin binding activity.
A and C : CD spectra were recorded on J-1100 spectrometer between 180 and 260 nm of spike protein (0.5 mg/ml).
B and D : Secondary structure were analysed by program CDSSTR of A and C, respectively.
A and B : the first batch of spike protein (PBS buffer).
C and D : the second batch of spike protein (PBS, 20% glycerol).

Differential scanning fluorimetry (DFS) analysis the stability and the heparin binding ability. DSF of proteins were performed in the absence or presence of heparin (10 μM). The scanning fluorimetry data of the two batches shows the protein is both stable and functional, with heparin binding activity.
A and C : Melting curve of spike protein.
B and D : First derivative of the melting curves of spike to show its melting temperature as peak.
A and B : the first batch of spike protein (PBS)
C and D : the second batch of spike protein (PBS, 20% glycerol).