Computer model of the HRSV F protein. The molecular structure of HRSV F protein ECD was modeled using the human parainfluenza virus 3 virus F protein ECD structure as template as described in methods. Ribbon diagrams of the F1-F2 monomer (left) and F protein homotrimer (right) are shown. Heptad repeat 1 (HR1) and heptad repeat 2 (HR2) are indicated with arrows. Cysteine residues are depicted as yellow balls with specific residue disulfide pairs indicated on the monomer.