SoNar (sensor of NAD(H) redox) is a genetically encoded fluorescent sensor that allows dynamic live imaging of the co-enzymes NAD+ and NADH (reduced form of NAD+). It is a fusion protein composed of circularly permuted yellow fluorescent protein inserted into the NADH-binding domain of Rex protein from Thermus aquaticus ( UnitProtKB:Q9X2V5 ) (PMID:27362337). SoNar can bind to either NAD+ or NADH with specific conformations and excitatory wavelengths, allowing live imaging of the NAD+/NADH ratio.