Isotope effect analyses provide evidence for an altered transition state for RNA 2′-O-transphosphorylation catalyzed by Zn 2

Solvent D 2 O and 18 O kinetic isotope effects on RNA 2′- O -transphosphorylation catalyzed by Zn 2+ demonstrate an altered transition state relative to specific base catalysis. A recent model from DFT calculations involving inner sphere coordination to the non-bridging and leaving group oxygens is consistent with the data.