On universal aspects of the left-handed helix region

We inspect the geometry of proteins by identifying their backbones as framed polygons. We find that the left-handed helix region of the Ramachandran map for non-glycyl residues corresponds to an isolated and highly localized sector in the orientation of the Cβ carbons, when viewed in a Frenet frame that is centered at the corresponding Cα carbons. We show that this localization in the orientation persists to Cγ and Cδ carbons. Furthermore, when we extend our analysis to the neighboring residues we conclude that the left-handed helix region reflects a very regular and apparently residue independent collective interplay of at least seven consecutive amino acids.