In calculations of protein-ligand interaction energies, one is often interested in relative protein-ligand interaction energies for different conformers in order to identify the correct binding pose of a ligand. Moreover, relative energies present a more challenging test case for quantum-chemical fragmentation schemes, as they probe more subtle effects that might otherwise be masked by large total interaction energies. Therefore, we consider as an additional test case the solution structure of the SMN Tudor domain in complex with symmetrically dimethylated arginine (PDB-code: 4A4E / protein: 971 atoms, charge: -4 / ligand: 33 atoms, charge: +1).