With a hypothesis established for the reaction mechanism we attempted to determine protein structural features critical for activity of these laccases. To this end, we used the quantum mechanical calculations in conjunction with Rosetta 47 to dock AFB1 into the active sites of P07788 and C0STU6. The PDB structures used for the modeling were 1gsk and 4e9x for P07788 and C0STU6, respectively. According to calculated spin density values, seen in Figure , there are several sites that would be ideal for efficient SET, with the most likely being C7, C14, or C12. To predict the likelihood of the reaction beginning with one of these carbons, we docked AFB1 into both laccases of interest using a distance constraint between the nitrogen of the electron-withdrawing histidine and one of the potential carbons. We used the distance constraint (3.3 ± 0.5 Å) to penalize binding modes that deviated from a catalytically relevant distance for SET. Results were then analyzed by filtering by constraint score, screening out everything but the lowest 20% interface energy scores, and finally the remaining designs were sorted by the lowest 20% of Rosetta's total score (Figure ). Our modeling predicted that P07788 can fulfill the distance constraint to each carbon individually and C0STU6 can only satisfy the distance constraint to C12 (Figure ). The seeming ability for P07788 to effectively bind AFB1 in several more orientations than C0STU6 paradoxically may help to explain why it appears to degrade this particular mycotoxin more slowly. With a larger range of possible binding orientations, AFB1 is more likely to bind in sub-optimal positions for the second electron withdrawing event, which our quantum mechanical calculations suggest will occur at C3. With C0STU6, the only successful binding orientation appears to be ideal for both the single electron transfers due to high electron spin densities and minimal reorganization. Theoretically, AFB1 could reorient in the active site of P07788 between the first and second SET, but this would be slow and improbable.