The photosensitizing action of phycobiliproteins in the adsorbed state

In connection with the elucidation of the possibility of photochemical participation of phycobiliproteins in the primary processes of photosynthesis, the ability of a mixture of phycocyanin + allophycocyanin (PC + APC) for photosensitization of redox reactions in the adsorbed state was investigated. It was shown that adsorbates of PC + APC on Sephadexes G-200 and G-25, diethylaminoethylcellulose, carboxyethylcellulose, Bacto-agar, Lifogel, polyethylene glycol, Dowex 50Wx2, and aluminum oxide are capable of sensitizing the photoreduction of methyl red by ascorbid acid. In this case the effectiveness of the sensitizing action depends on the concentration of the adsorbate, the pigment concentration on the carrier, the pH of the medium, and the nature of the solvent. It was shown that in the case of binding to a carrier, the sensitizing ability of PC + APC increases in comparison with that for pigments in the dissolved state. It is suggested that this is promoted by an increase in the concentration and a mutual approach of the reagents after adsorption, and the possible formation of complexes of some or all the participants of the reaction on the surface of the adsorbent.