One of the most important steps in modeling three-dimensional (3D) structures of proteins is the evaluation of the constructed models. The present study suggests that the correctness of a structure may be tested by using the characteristics of sequential dihedral angles (SDAs) between adjacent alpha-carbons (Cα) in the main chains of proteins. From our studies on protein structures in the protein data bank (PDB), the SDAs between the Cα in the main chains are limited in their values. In addition, the sum of the absolute values of the three sequential dihedral angles (SDAs) can never be 0 degree. Moreover, 48 degrees is the lowest value existing for the sum of the absolute values of three sequential dihedral angles (SDAs). Thus, the SDAs between the alpha-carbons along the main chains of proteins may be a useful parameter for evaluating anomalies in protein structures.
Keywords: Alpha-carbon; Model evaluation; Sequential dihedral angle (SDA); Structure of protein.