Extraction of oxidized bacteriochlorophyll from illuminated photosynthetic reaction center particles

Illuminated and dark-adapted reaction center particles from Rhodopseudomonas spheroides were extracted with methanol, and the spectra of the extracts were compared. Spectra of extracts of illuminated reaction center particles showed less absorption due to bacteriochlorophyll than did spectra of extracts of dark-adapted reaction center particles. The lost absorption in extracts of illuminated reaction center particles was restored by the addition of ascorbate. This showed that these extracts contained oxidized bacteriochlorophyll which could be rereduced in vitro. The spectrum of the restored absorption was different from that of the original bacteriochlorophyll, indicating that an alteration of the oxidized bacteriochlorophyll had taken place. This apparent alteration may have been due to the presence of the detergent lauryl-dimethylamine oxide in the extracts. However, equilibration of the protein with this detergent may have been a requirement for the extraction of photooxidized bacteriochlorophyll.