a Left panel: Sharpened 3.2-Å-resolution C3-symmetric cryo-EM map of SARS S 2P ectodomain52 visualized at a high contour level with disordered S1 receptor-binding and N-terminal domains extending out from the central core. Middle panel: Low-pass filtered (lpf) cryo-EM map of the glycoprotein visualised at a low contour level along with a simulated peptide-only map overlaid. Right panel: SPARX 3D variability map51. b Same as in (a) but for HIV-1 Env BG505 SOSIP.664 construct in complex with three copies of RM20A3 base-specific Fabs51.