A new strategy to make an artificial enzyme: photosystem II around nanosized manganese oxide†
Herein we report a new strategy to disperse Mn oxide into the apoenzyme of photosystem II. The compound was characterized by scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction and some electrochemical methods. Under electrochemical conditions, the peaks attributed to Mn(II)/(III), Mn(III)/(IV) and Mn(II)/(IV) were assigned and compared with other manganese oxides. Linear sweep voltammetry shows that water electro-oxidation occurs at 80 mV less than that for the apoenzyme of photosystem II. Thus, Mn oxide maintains its water-oxidizing activity under these conditions. The compound is a new type of structural and functional model for the water-oxidizing complex in photosystem II.