In order to validate this, the accessible surface areas are calculated for all the different norspermine binding configurations in full-pore loading by Zeo++ 68,69 with a 1.2 Å probe, shown in Table . The SD, SC, and LD motifs all have similar surface areas, whereas the LC has one that is notably higher. This, along with the relatively small interaction energy in the linear, column-bound motif, can help explain its unexpected stability. This means when using GGA functionals, the diagonally bound amines destabilize the system more than the linear, column bound. On the other hand, when it comes to only absorbing 1 norspermine, the loss of surface area does not differ too much for different binding configurations, so that the column bound is never predicted to be close to the stability of SD or LD.