Initial structures were obtained from the Protein Data Bank when an experimentally determined geometry is available, or from ChemPub . Full geometry optimizations were performed at the HF/6-31G(d)//HF/6-31G(d) theory level. Optimizations at more rigorous theory levels will be performed (e.g. B97-D3(BJ)/cc-pVTZ and MP2/cc-pVTZ) as time allows. The B97-D3(BJ) is believed to be a fairly reliable density functional approximation (i.e. GGA+dispersion) for computing geometries and energetics . Frequencies calculations were performed on selected minima using finite-differences of gradients at the same theory level reported for the relative energies. Initial 3D structure generation: