The "LoCo" local coordinate system. Shown is a single valine residue and its local coordinate system, seen looking down the positive x-axis. The center of the Cα atom is defined to be the origin. The positive y-axis passes through the main chain N coordinates. The positive X axis is placed such that the main chain C coordinates fall within the xy plane in the positive X direction. The coordinate system is right-handed. Both stick and sphere representations are presented for clarity.