The model on the right is a tripeptide (Trp34–Glu35–Ser36 within the protein lysozyme).
This page illustrates the meaning of phi (ϕ) and psi (ψ) angles, both around the alpha carbon of the central residue (Glu35).
You can run animations that continuously rotate the model changing one of the angles, or use the slider or controls to manually progress through different values of the angles.
Bright magenta cylinders are displayed where neighbour atoms collide (hence there is an unfavourable conformation for those ϕ, ψ values).
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