Peredox is a genetically encoded fluorescent sensor that allows dynamic live imaging of cytosolic NAD+/NADH ratios, as described in PMID:21982714. It is a fusion protein composed of circularly permuted variant of T-Sapphire inserted into a tandem dimer of the Rex protein from Thermus aquaticus (UniProtKB:Q9X2V5), between the two subunits.