Effect of Hill Reaction Inhibitors on the Photoreduction of Ferricyanide and Cyclic Photophosphorylation by Spinach Chloroplasts

Some derivatives of phenylurea, N-phenylcarbamate, s-triazine and acylanilide inhibited the cyclic photophosphorylation of spinach chloroplasts catalyzed by phenazine methosulfate and accelerated the photosystem I-dependent electron flow estimated as the disproportionation of diphenylcarbazone. Acceleration was slightly stimulated by the simultaneous addition of methylamine. Thus, these Hill reaction inhibitors act as uncouplers of cyclic photophosphorylation as does methylamine. The inhibiting activities of the chemicals on the photoreduction of ferricyanide and on photophosphorylation had a parabolic relation to the partition coefficient in the octanol-water system of the chemicals.