ABSTRACT
Using a previously developed procedure, further optimization of isolation of the functionally active pigment-protein lipid complex of the reaction center of photosystem 2 (PPLC RC PS-2) by DEAE-cellulose chromatography has been carried out. Preliminary chromatographic separation of PPLC RC PS-1 and PS-2 in the presence of a light-harvesting complex has proved to be the most efficient technique. In the latter case the admixture of P700 within PPLC RC PS-2 decreases (1.8-fold on the average) at chromatographic pH value of 8.0. During chromatography at weakly acid, neutral (6.5-7.0) and weakly alkaline (8.3-9.0) values of pH a further, more than 2-fold decrease of P700 admixture is observed. The increase in the degree of separation of PPLC RC PS-1 and PS-2 is concomitant with the increase in PPLC RC PS-2 of photochemically active pheophytin (Ph), an intermediate electron acceptor in RC PS-2 which functions between P680 and Q. The resulting preparations of PPLC RC PS-2 contain one molecule of Ph and 0.06-0.09 molecule of P700 per 31-48 molecules of chlorophyll. The peculiarities of the complexes separation are discussed in terms of the role of hydrogen ion concentration in regulation of affinity between the reaction center complexes and the light-harvesting complex.
