Examples of problematic secondary-structure (SS) annotations shown as pairs of cartoon representation and corresponding Ramachandran plot. (a) The α-helix looks plausible although slightly distorted, but most residues are Ramachandran plot outliers. (b) The α-helix is obviously distorted; there are no Ramachandran plot outliers, but only one angle belongs to the α-helix region of the plot. (c) Distorted α-helix with all but one residue belonging to the expected Ramachandran plot region. (d) Apparently two α-helices annotated as one with many (φ, ψ) pairs being out of the α-helix region.