Immobilization of Chloroplast Photosystems within Polyacrylamide Gel Formed by the Redox Polymerization

Abstract

Chloroplast electron flow system was successfully immobilized inside polyacrylamide gel formed by the redox polymerization. The immobilization system consisted of acrylamide monomer (15%, final concentration), N, N'-methylene-bisacrylamide (0.8%), ammonium persulfate (0.02%), ascorbate (0.06%), bovine serum albumin (1%), D-mannitol (0.01%) and the broken chloroplasts, type C, in 0.05M Tris buffer Tris buffer containing 0.4M sucrose and 0.01M NaCI (STN buffer). Incubation of the reaction mixture at 10°C for 2 hr yielded the gel keeping Photosystem I activity as 11.3% of the native chloroplasts (control) and Photosystem II activity as 11.2% of the control. The immobilized chloroplast gel retained activities of Photosystem I and Photosystem II even after being allowed to stand for several weeks in the STN buffer at 4°C. The optimum pHs of the immobilized Photosystem I and Photosystem II were the same as those of the untreated chloroplasts: pH 8.6 for Photosystem I and pH 6.2 for Photosystem II. However, the Photosystem II activity of the gel was completely lost in 2 days on standing above pH 8. The thermo-stabilization of Photosystem I and Photosystem II was also attained by the immobilization. Under anaerobic condition, electric current was observed on illumination onto the chloroplast photo-cell system which was composed of the gel, methyl viologen as an electron acceptor, glucose plus glucose oxidase as an oxygen dissipating system and sodium azide in the STN buffer.