code: def align_nab(tar, ref):
      
      rot_trans_1 = find_transformations(
          tar['N'].array, tar['CA'].array, ref['N'].array, ref['CA'].array)
      apply_trans_rot(tar, *rot_trans_1)
      rot_ang_ca_cb = dihedral(tar['CB'], ref['CA'], ref['N'], ref['CB'])
      tar.rotate(rot_ang_ca_cb, ref['N'].array - ref['CA'].array, ref['N'].array)
      return
docs: Aligns the N-CA and CA-CB vector of the target monomer.
  
      Parameters
      ----------
      tar: ampal.Residue
          The residue that will be aligned to the reference.
      ref: ampal.Residue
          The reference residue for the alignment.