Fig. 1.
The observed isomorphous difference Fourier maps. (A) Fo(6w1v/2F)-Fo(6w1o/0F) difference map contoured at +5σ (blue), +4σ (cyan), +3σ (green), −4σ (red), and −3σ (salmon) superimposed on the 6w1v/2F atomic model of ref. 1. (B) Fo(6w1v/2F)-Fo(6w1p/1F) difference map. The black arrows indicate the proposed position of Ox at which there is clearly no positive feature in either Fo-Fo map. The green arrow indicates the nearest positive peak to Ox, which is 1.1 Å away. It is also 1.6 Å away from O5. If one could model this peak as an O atom, this O atom and O5 would become a peroxide species.