Figure 1 Structure of coronavirus virions. (A) Schematic diagram of virus structure; (B) Diagram of virion surface. (C1) Electron micrograph of virus particles of Transmissible gastroenteritis virus (TGEV) stained with uranyl acetate (C1) or sodium phosphotungstate (C2) showing the surface of the virus particles. The peplomers are better defined using sodium phosphotungstate. (D) Cryo-electron microscopic visualization of unstained TGEV in vitreous ice. The particles contain an internal structure inside the viral envelope and well extended peplomers. MEM, lipid membrane; S, spike protein; M, large membrane protein, E, small envelope protein; HE, hemagglutinin-esterase; N, nucleocapsid protein; CS, core-shell; NC, nucleocapsid. The bars represents 100  nm.