Pyronic is a genetically-encoded FRET nanosensor for pyruvate (the variant with the largest response is termed Pyronic, Pyruvate Optical Nano Indicator from CECs; PMID: 24465702). The 2,287 bp fragment contains the sensor, made up of Ecol\pdhR (a bacterial transcriptional regulator that controls the expression of the pyruvate dehydrogenase gene in response to pyruvate) flanked with the fluorescent proteins mTFP1 and Venus, as respective FRET donor and acceptor.