Electronic Structure of the Chromophore in Green Fluorescent Protein (GFP)

The intense fluorescence requires further interactions between this chromophore and a surrounding protein matrix whose threedimensional structure has recently been solved. 4,5 Because no exogenous fluorescent dyes are needed, the DNA coding for GFP can be fused with that of any protein whose expression and transport can then be monitored by sensitive fluorescence methods. The room-temperature absorption spectrum of AequoreaGFP exhibits two distinct bands located at 396 and 476 nm. These bands are thought to arise from the protonated (State A) and deprotonated (State B) forms of the chromophore, respectively. 3,6