The researchers treated Photosystem II fragments with an oxidant called K2IrCl6. This treatment destroyed some chlorophyll but enriched the fragments in P680 and cytochrome b559. The fragments still had a fully functional reaction center, as shown by P680 photooxidation and subsequent reduction. The oxidant-treated fragments did not contain certain components like C-550 and did not show variable fluorescence. This suggests that the primary electron acceptor of Photosystem II was not affected by the oxidant treatment, indicating that neither C-550 nor the fluorescence quencher, Q, act as the primary electron acceptor of Photosystem II.