Effect of Inhibitors and Uncouplers on the Separate Light and Dark Reactions in Photophosphorylation

Abstract

The 2-stage technique of photophosphorylation was used for the study of a nonphosphorylated high-energy intermediate formed by Swiss chard chloroplasts. The properties of the Swiss chard system were similar to the spinach rather than to the wheat seedling systems described previously. The intermediate formed in the Swiss chard system was not a soluble compound. The effect of various inhibitors and uncouplers on either the light or the dark stages separately was tested by introducing a technique which virtually eliminated any effect on the dark stage of compounds present in the light stage. DCMU and 2-n-nonyl-4-hydroxyquinoline-N-oxide were thus found to inhibit only the light stage, while atebrin inhibited only the dark stage. All of the other uncouplers tested (NH4Cl, carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone, octyl guanidine) inhibited both the light and dark stages.