Figure 4.
The valence bond structures representing the reactants, intermediates, and products, used for modeling the pol-β catalyzed nucleotide insertion reaction with (A) stepwise associative mechanism and (B) a concerted mechanism. Resonance states (I-IV) of A, corresponds to the initial proton transfer (PT) to bulk water mechanism and the resonance states (V-VII) of A corresponds to the PT to Asp256 mechanism. However, the concerted mechanism (B) is explored only for the PT to bulk water mechanism.