Photogeneration of NADPH by oligothiophenes coupled with ferredoxin-NADP reductase

Abstract

The photogeneration of nicotinamide adenine dinucleotide hydrophosphate (NADPH) and its associated reaction were studied in a novel photo-energy conversion system. The system was composed of the oligothiophene, dimethyl-4,4′-bipyridinium (MV 2+), EDTA, and combined with ferredoxin-NADP reductase (FDR, E.C.1.18.1.2). The NADPH was generated by the FDR catalysis via the reduction of MV 2+ by the photocatalysis of oligothiophene and EDTA as the sacrificial electron donor. As a result, the rate of the NADPH generation depended on the concentrations of nicotinamide adenine dinucleotide phosphate (NADP +) and MV 2+. The effect of the intension of applied light showed the same tendency. Rate values of photoreduction of MV 2+ and photogeneration of NADPH systems were investigated as a function of the concentration of MV 2+. The production rates of methyl viologen radical cation (MV ·+) were a 1000-fold more than the NADPH production rates in the oligothiophenes. These results suggest that the electron transfer between FDR and its substrates is the rate-determining step.