Studies on the surface structure of the intracytoplasmic membrane in the photosynthetic purple bacterium Chromatium vinosum by means of chemical modification.

By means of a chemical modification technique, the surface structure of the intracytoplasmic membrane (chromatophores) of the photosynthetic bacterium Chromatium vinosum was investigated. Trinitrobenzenesulfonate was employed to modify the primary amino groups of phosphatidylethanolamine and proteins. The experimental results indicate that upon the chemical modification of intact cells, the amino groups on the inner surface of the chromatophores are trinitrophenylated, while upon the modification of isolated chromatophores, the amino groups of the outer surface are trinitrophenylated. Phosphatidylethanolamine is essentially equally distributed on the inner and outer surfaces of the chromatophores, while most proteins exist at the outer surface. In particular, a protein fraction, which is soluble in a mixture of chloroform/methanol, is located at the outer surface exposing a part of the amino groups in the aqueous phase.