(b).

Secondary structures	Chain	Length in C α	C α index
α-helix Gα 1	A	25	59–83
α-helix Gα 2	A	31	141–170
α 3-domain	A	92	184–275
β-sheet	A	52	2–13, 21–29, 30–37, 93–103, 110–118, 124–127
TCR α var	D	104	385–488
TCR β var	E	117	586–702

Structural elements are given in terms of consecutive numbers of C _α atoms, renumbered throughout the whole modelled TCR/pMHC/CD8 complex, as if the complex as a whole was taken from one single PDB file.

Molecule 1 (TCR/pMHC): Chain A–Chain E. Molecule 2 (TCR/pMHC/CD8): Chain A–Chain G.