ENTRAPMENT OF CHLOROPLASTS AND THYLAKOIDS IN POLYVINYLALCOHOL-SBQ - OPTIMIZATION OF MEMBRANE PREPARATION AND STORAGE-CONDITIONS

Chloroplasts and thylakoids isolated from spinach were entrapped in si x different polyvinylalcohol bearing styrylpyridinium groups (PVA-SbQ) . Measurements of oxygen production were carried out in 0.01 M phospha te buffer (pH 6) at 25 degrees C. Immobilized preparations were compar ed for their electron transport activity measured as the initial rate of oxygen evolution with p-benzoquinone as artificial electron accepto r. The entrapped chloroplasts in PVA-SbQ 1700 and 3500 betaine retaine d 20% of their initial activity after 90-day storage in the dark at +4 degrees C. A membrane made with PVA-SbQ 2300 kept 20% activity after 427-day storage at -18 degrees C in the dark whereas the same membrane retained only 10% activity after 90-day storage at +4 degrees C in th e dark. A 1% BSA concentration increased the stability of the membrane . The limits of detection (corresponding to a 10% inhibition) of atraz ine were 10 mu g/l and 12 mu g/l for native and entrapped chloroplasts , respectively. The good stability of entrapped chloroplasts suggests that this system could be useful for the detection of pollutants in wa ter.