As we have just seen, the stability of Cpd II/substrate-radical appears to control the decarboxylations vs hydroxylations reactions. As such, we proceeded to calculate the local electric fields (LEFs) and the dipole moments (), which are required in order to assess the stabilization (cf. Eq. 1) of the RC, TS and IM1 species belonging to the respective reaction mechanisms of OleT vs. BS (cf. Figs and). To do so, we used the bare systems without residues, and applied the LEFs due to the residues within a radius of 3Å around the species, using the in-house program TITAN (see method section for details). Figure shows the conventions for positive vectors along the Z-axis, while Figures and show the LEF and  vectors, for the two enzymes, as well as the angle between these vectors. It is apparent that for all the species, OleT has more favorable LEFs and dipole moments for each of the species. It is apparent that the LEF contributes also to a lower barrier for H-abstraction in OleT vs. BS (~4.6 kcal/mol). However, the QM/MM-calculated energy-barrier difference is 10.6 kcal/mol. This suggests that effects other than the LEF contribute to the energy barrier differences between the two enzymes. We propose that the more pronounced energy-barrier lowering in OleT vs. BS, is contributed by the relative thermodynamic driving forces of the corresponding H-abstraction steps. This step is endothermic in BS (cf. Fig. ), due to the instability of the corresponding Cpd II species, whereas in OleT it is exothermic (cf.