CYCLING ASSAY FOR NICOTINAMIDE ADENINE DINUCLEOTIDES - NACL PRECIPITATION AND ETHANOL SOLUBILIZATION OF THE REDUCED TETRAZOLIUM

The spectrophotometric cycling assay for the determination of nicotina mide adenine dinucleotides involving -(4,5-dimethylthiazolyl-2)-2,5-di phenyltetrazolium bromide as the final electron acceptor has been impr oved. The enzyme reaction is stopped by the addition of high concentra ted NaCl, which accelerates the precipitation of the formazan. After i solation from the assay medium, the formazan is easily solubilized in ethanol. This allows more flexibility and sensitivity, offering additi onally the possibility to reduce the amount of reagents required. This method was applied for extracts of green tissues of higher plants, an d the results did not differ from those obtained with the original pro cedure. (C) 1997 Academic Press.