The adenylate_mobilities program was written by Chris Bruns to demonstrate molmodel's ability to select any bond in the molecule and set its bond mobility to Free, Torsion, or Rigid.

Free means there are no constraints (similar to a conventional Molecular Mechanics analysis). Torsion means that the bond length and bond angles are fixed, but the dihedral angle about the bond is free to change. Rigid means that dihedral, angles, and bond length are all fixed. Some users may wish to set all bonds in a structural domain or subunit to Rigid.