Pyridine nucleotides play an important role in metabolism and, thus, there is continual interest in monitoring their concentration levels. Quantitative determination of NAD+/NADH has applications in research pertaining to energy transformation and redox state of cells or tissue. BioAssay Systems' EnzyFluoTM NAD+/NADH assay kit is based on a lactate dehydrogenase cycling reaction, in which the formed NADH reduces a probe into a highly fluorescent product. The fluorescence intensity of this product, measured at ex/em = 530/585 nm, is proportional to the NAD+/NADH concentration in the sample. This assay is highly specific for NAD+/NADH with minimal interference (