The green fluorescent protein (GFP) is a 27 kDa polypeptide, which converts the blue chemiluminescence of the Ca -sensitive photoprotein, aequorin, into green light (Chalfie, 1994; Cody et al., 1993). Inouye and Tsuji (1994a) showed the active chromophore is a tripeptide and is dependent on the presence of oxygen to maturate.