mAmetrine is a long-Stokes-shift monomeric yellow fluorescent protein with an excitation peak of 406nm and an emission peak of 526nm in vitro. It is an artificial derivative of the naturally occurring fluorescent protein encoded by the Aequorea victoria GFP gene (UniProtKB:P42212). Its properties make it a potentially near-ideal donor for pairing with an orange or red fluorescent protein to produce a fluorescence resonance energy transfer (FRET) pair for ratiometric imaging (PMID:18425137).