BACTERIOCHLOROPHYLL PHEOPHYTINIZATION IN CHROMATOPHORES AND SUBCHROMATOPHORES FROM RHODOSPIRILLUM RUBRUM

1. Spectral changes of Rhodospirillum rubrum chromatophores and subchromatophores at low pH have been investigated both in the absence and presence of the nonionic detergent, Triton X-100. 2. Bchl 800 readily undergoes pheophytinization below pH 3, whereas Bchl 880 is not easily converted to bacteriopheophytin until Triton X-100 is added. 3. In appropriate concentrations of Triton X-100, Bchl 880 is transformed to Bph 755 via some intermediates absorbing at 770-790 nm. The Bph 755 is subsequently converted to Bph 850. 4. These changes are more clearly observed with subchromatophores at different pH values. When subchromatophore particles reaggregate upon removal of Triton X-100, Bchl 880 again becomes resistant to acid treatment. 5. Treatment of chromatophores with Triton X-100 at low pH also causes a considerable decrease of absorbance in the wavelength region where carotenoids absorb. 6. The disintegrating action of Triton X-100 is enhanced by lowering pH, and a carotenoid complex can be separated from a heavier bacteriopheophytin complex. © 1969.