The full pore motif predictions for spermine are unambiguously the experimentally characterized structure. The single amine binding energies tell a different story. One possible reason for this discrepancy is because the longer length of the center alkane chain (compared to norspermine) causes a buck- ling in the column-bound configuration, forcing the molecule to expand in the ab-plane, thereby interacting with its columnbound neighbors in the full pore. The diagonally bound configuration is further stabilized by inter-molecular hydrogen bonding between adjacent molecules along the c-axis.