Figure 5

18O isotope experiments.
(A) Control experiment, unlabeled H2O was used as a solvent and unlabeled O2 was used for the reaction. (B) Labeled H218O was used as a solvent and unlabeled O2 was used for reaction. (C) Unlabeled H2O was used as a solvent and labeled 18O2 was used for the reaction. (D) Labeled H218O was used as a solvent and labeled 18O2 was used for the reaction.