CHARACTERIZATION OF A D1-D2-CYT B-559 COMPLEX CONTAINING 4 CHLOROPHYLL-A 2 PHEOPHYTIN-A ISOLATED WITH THE USE OF MGSO4

A D1-D2-cyt b-559 complex containing 4 chlorophyll a, 1 beta-carotene and 1 cytochrome b-559 per 2 pheophytin a has been isolated from spina ch with 30% yield using a Q-Sepharose Fast-Flow anion-exchange column equilibrated with 0.1% Triton X-100, 10 mM MgSO4 and 50 mM Tris-HC1 (p H 7.2). The preparation was then stabilized with 0.1% dodecyl-beta-D-m altoside. This method gave a yield 10 times higher than that using a F ractogel TSK-DEAE 650(S) column equilibrated with 0.1% Triton X-100, 3 0 mM NaC1 and 50 mM Tris-HC1 (pH 7.2). The PS II RC complex was charac terized using absorption and fluorescence spectroscopy at 277 and 77 K . A selective reversible bleaching under reducing conditions with maxi mum at 682 nm, associated with pheophytin a reduction, and light-induc ed absorption differences with a lifetime of 1.0 ms, ascribed to the t riplet state of P680 were measured and indicated that the isolated D1- D2-cyt b-559 complex is active in charge separation. The results are c ompared with the data obtained for a PS II RC preparation containing 6 chlorophyll a, 2 beta-carotene and 1 cyt b-559 per 2 pheophytin a.