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.