A and F. Structural model for intersected (A) or parallel (F) α9 homodimer is shown with one monomer colored brown (α9) and the other gray (α9'). The residue pairs that formed disulfide bonds after they were replaced with cysteine pairs in (B) or (D), respectively, are presented in stick form, and their β carbon atoms linked by dashed lines with the distances indicated in Å, except that the Gly179 pair is linked by a dashed line via their α carbon atoms with the distance indicated. The pdb files for the models are provided as Datasets EV2 and EV3 and named as "Helix a9 intersected dimer.pdb" and "Helix a9 parallel dimer.pdb". 