Fig 8. Contours and 3D surface helical pitch (n d) overlaid on 2D φ, ψ plot.

Positions of classic α-helix (φ = −57, ψ = −47), 3₁₀-helix (φ = −49, ψ = −26), and experimental Némethy-, N- or 3.6_13/10-helix (φ = −62, ψ = −43) are indicated. Note that the helical pitch is nearly identical for the α- and 3.6_13/10-helices—they lie on a contour of essentially equal value.