Development of a Selective, Sensitive, and Reversible Biosensor by the Genetic Incorporation of a Metal-Binding Site into Green Fluorescent Protein

There when the light goes out: A copper biosensor was created by the introduction of the metal‐chelating noncanonical amino acid L‐DOPA in place of L‐tyrosine into green fluorescent protein by genetic‐code engineering (see picture). The specific binding of Cu2+ in vitro by the modified protein was reversible and resulted in fluorescence quenching in proportion to the amount of Cu2+ present. EDTA=ethylenediaminetetraacetic acid.