Thus, in P450BSβ (cf. Fig. ), the carboxylate oxygen, O1, interacts with the guanidine nitrogen NH1 (of R242), while O2 forms a bidentate interaction with W2 and with the guanidine nitrogen (NH2) of R242. Figure compares the time evolution of these key interactions in P450OleT (black) and P450BSβ (red). In summary, the MD simulations of P450OleT vs. P450BSβ show that a single site-difference in residues 85, of H vs. Q, changes the active site architecture in the two peroxygenases. The manner by which this difference is translated to different functions of the peroxygenases is detailed in the next section with the help of hybrid QM/MM calculations.