Analysis of photooxidized pigments in water-soluble chlorophyll protein complex isolated from Chenopodium album

A water-soluble chlorophyll (Chl) protein complex isolated from Chenopodium album is converted to another form of the pigment protein (CP740) containing bacteriochlorin type pigments by irradiation with visible light in an aqueous aerated solution. In order to investigate the photoconverted pigments in CP740, all the chlorophyllous pigments were extracted with organic solvents from CP740 and were analyzed by high-performance liquid chromatography and mass spectrometry. Two separated products were mono-oxygen adducts to Chl a at the B-ring. Their visible spectral analysis combined with model calculation supported that they would be 8-oxo- (P700) and 7,8-epoxy-derivatives (P726). During extraction, covalent bonds of pigments with proteins in CP740 would be cleaved to produce the above mono-oxygenated Chls a. Based on the molecular structures of P700 and P726, bacteriochlorophyll type pigments in CP740 were proposed.