Then, a substitution reaction energy is calculated for the exchange between mimosine and phenyl sidechains. The resultant reaction energy DE r = -1.8 kcal/mol reveals a significant stabilization by mimosine dimer interaction. Notice that the stabilization is very similar to the one obtained by the constrained minimizations, namely DDE int = -1.6 kcal/mol. However, these estimations of the stabilization of stacking conformations of mimosine rings should be considered a lower limit, since as we have seen before, stacked mimosine rings can also be further stabilized by a favorable hydrogen-bond network with water molecules, a feature not possible for phenyl rings.