Fig. 1
The fabrication and characterization of double-layered N-S1 protein nanoparticle. A The schematic diagram of the SARS-CoV-2 isolate Wuhan-Hu-1 spike (top) and nucleocapsid phosphoprotein (bottom), showing signal sequence (SS); N-terminal domain (NTD); receptor binding domain (RBD); subdomains 1 and 2 (SD1/ SD2); furin cleavage (S1/S2); cleavage site (S2′); heptad repeats 1 and 2 (HR1/HR2); transmembrane domain (TM). B Schematic diagram of generating double-layered protein nanoparticle. Soluble N protein was self-assembled into PNp by ethanol desolvation. An additional layer of S1 proteins was crosslinked onto the desolvated N PNp particulate core surface as coating via DTSSP crosslinking. C Coomassie blue staining and Western blotting analysis of soluble N or S1 protein and protein nanoparticles using anti His-tag monoclonal antibody and S1 monoclonal antibody. Line 1, double-layered N-S1 protein nanoparticle; Line 2, soluble S1 protein; Line 3, soluble N protein; Line 4, N protein nanoparticles. D The size spectrum of protein nanoparticles. Red, N-S1 PNp; Blue, N PNp. E TEM image of N PNp and N-S1 PNp.Bar scale, 200 nm (left) and 500 nm (right). F The affinity of the ACE2 protein to soluble S1 protein or N-S1 PNp was evaluated (top unfitted, bottom affinity). The KD value of soluble S1 protein (left) and N-S1 PNp (right) was determined using SPR