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).