Correlation between Omega and Psi Dihedral Angles in Protein Structures

The planarity of the peptide group is one of the fundamental features of protein structure that is described in every chem. and biochem. textbook. By surveying a dataset of 163 at. resoln. protein structures we here identify the stereochem. conditions that favor significant deformations of peptide bond planarity. In particular, we demonstrate that the values of the w dihedral angle are strictly correlated to the values of the adjacent psi angle. This trend is also obsd. in highly strained states such as those occurring in vicinal disulfide bridges. These findings provide direct evidence for the mutual influence of the geometrical parameters that describe the protein structure.