The effect of chemical oxidation on the fluorescence of the LH1 (B880) complex from the purple bacterium Rhodobium marinum

The effect of chemical oxidation on the absorption and fluorescence emission spectra of the LH1 complex from Rhodobium marinum was investigated. Mild chemical oxidation of the LH1 complex, by addition of 10 mM potassium ferricyanide, caused a 2-3% bleaching of the 880-nm Qy absorption band. In contrast, at the same ferricyanide concentration, fluorescence emission intensity of the LH1 complex was quenched by about 50%. This result demonstrates that oxidation of very few bacteriochlorophyll (BChl) molecules in the LH1 ring is enough to completely quench its fluorescence.