Figure 1. Backbone-independent distribution of rotameric and non-rotameric χ.

Panel A shows a probability density distribution of dihedral angles for a rotameric degree of freedom tightly and symmetrically clustered near the canonical values of 60°, 180° and 300° based on Met χ₁ data regardless of χ₁, χ₂ or χ₃ rotamer (*, *, *). Panels B and C depict distribution of the non-rotameric χ₂ degree of freedom of Asn and Trp respectively for each of their χ₁ rotamers: g⁺, t and g⁻. Panels D, E, and F show the backbone-independent distribution of non-rotameric χ₃ of Gln for each of its (χ₁, χ₂) rotamers. Non-rotameric χ₃ distributions for Gln are dependent on both the χ₁ and χ₂ rotamers. The distributions of the non-rotameric degrees of freedom are very broad and asymmetric and cannot be modeled with a rotameric model.