Entkopplung der Photophosphorylierung durch 2-Alkylbenzimidazole

Abstract

The influence of benzimidazoles with saturated hydrocarbon side chains at C-2 on photosynthetic reactions of isolated spinach chloroplasts was investigated. They show little or no inhibition of the Hill- reaction, but are effective uncouplers depending on the length of the side chain. 2-Alkylbenzimidazoles with a side chain of at least eight and not more than fourteen carbon atoms uncouple non-cyclic and cyclic photophosphorylation at a concentration of less than 10~5-m., 2-decyl-benzimidazole being the most potent uncoupler. Alkyl-benzimidazoles with less than seven or more than fourteen carbon atoms in the side chain do not uncouple photophosphorylation at 10~5-m. N-Methyl-2-undecyl-benzimidazole is less effective as uncoupler than 2-undecyl-benzimidazole but is an inhibitor of oxygen evolution. 2-Undecyl-benzimidazole stimulates the Hill - reaction in the absence of the phosphorylation system and shifts the pH-optimum to a lower value, as expected from an uncoupler. Long chain alkylamines (C10-C14) are uncouplers at lower concentrations (5 ·10-5-m.) than short chain amines.