Chlorophyll-Carotenoid Protein Complexes from the Diatom, Phaeodactylum Tricornutum: Spectrophotometric, Pigment and Polypeptide Analyses

Chloroplast membranes of the diatom Phaeodactylum tricornutum were dissociated by means of mild detergents, digitonin and lauryl-dimethylamide oxide. After electrophoresis on polyacrylamide gel, all the pigments were still attached to proteins, and six pigment-protein complexes were obtained. Three Chl α-β-carotene complexes had the characteristics of Photosystem I and Photosystem II antennae. The other three contained Chl α, Chl c and fucoxanthin and were related to light-harvesting complexes. Chlorophyllide α, a product of the hydrolysis of Chl α by chlorophyllase, has been found only in light-harvesting complexes. The spectral properties, pigment and polypeptide compositions of the complexes are discussed in relation to those of other plants and to the particular organization of the chloroplasts of diatoms.