On universal aspects of the left-handed helix region

Abstract

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 $C_β$ carbons, when viewed in a Frenet frame that is centered at the corresponding $C_α$ carbons. We show that this localization in the orientation persists to $C_γ$ and $C_δ$ 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.

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