Figure 4. Cyclic peptides contact a minimal epitope on the surface of influenza HA.

A. Models of peptides d1 and d4 (tan) were docked into the receptor-binding site of influenza HA (blue) from H3 A/Hong Kong/1/1968 (PDB ID 4fnk) and compared to the co-crystal structure of C05 IgG (PDB ID 4fp8). Cα RMSD was calculated by superimposing the HA and measuring RMSD over all residues on the peptide compared to the IgG co-crystal structure. B, C. The binding footprint (orange) of either C05 IgG or peptides d1 and d4 was calculated for two antigens for which the peptides have increased breadth, H7 A/Shanghai/02/2013 (B) and H4 A/duck/Czechoslovakia/1956 (C). Buried surface area on the HA surface was calculated and is shown below each structure.