GFP-Based Biosensors

Green fluorescent protein (GFP) is a 27 kD protein consisting of 238 amino acid residues [1]. GFP was first identified in the aquatic jellyfish Aequorea victoria by Osamu Shimomura et al. in 1961 while studying aequorin, a Ca2+-activated photoprotein.Aequorin and GFP are local‐ ized in the light organs of A. victoria and GFP was accidentally discovered when the energy of the blue light emitted by aequorin excited GFP to emit green light.Unlike most fluores‐ cent proteins which contain chromophores distinct from the amino acid sequence of the pro‐ tein, the chromophore of GFP is internally generated by a reaction involving three amino acid residues [2]. This unique property allows GFP to be easily cloned into numerous bio‐ logical systems, both prokaryotic and eukaryotic, which has paved the way for its utilisation in a variety of biological applications, most notably in biosensing.