Isolation and Fractionation of the Photosynthetic Membranous Organelles fromRhodopseudomonas spheroides

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Abstract
Molecular sieve chromatography and sucrose gradient centrifugation were used to prepare large quantities of purified chromatophores fromRhodopseudomonas spheroides. Electron micrographs of these chromatophores revealed that the final preparations were very homogeneous and free of non-chromatophore particulate material. As an additional check on purity,14C-l-phenylalanine-labeled aerobic cells, devoid of chromatophores, were mixed with unlabeled photosynthetic cells. The resulting preparation contained less than 1% of the radioactivity, originally located in non-chromatophore protein. The purified chromatophores were solubilized in 2-chloroethanol and separated into two fractions. Fraction P1contained 3 to 5% of the total chromatophore protein and could be resolved into 10 electrophoretic components. The second fraction, PII, contained five electrophoretic components. One of these components had associated with it all of the pigment and phospholipid present in PII. Preliminary immunochemical studies on these fractions are also reported.