Fig. 2.

The UNRES model of the polypeptide chain. Dark circles represent united peptide groups (p), open circles represent the C^α atoms, which serve as geometric points. Ellipsoids represent side chains, with their centers of mass at the SC’s. The p’s are located half-way between two consecutive C^α atoms. The virtual-bond angles θ, the virtual-bond dihedral angles γ, and the angles α_SC and β_SC that define the location of a side chain with respect to the backbone are also indicated.