English: Formation of the GFP fluorophore (green) from the Ser₆₅-Tyr₆₆-Gly₆₇ tripeptide. In a first step (not shown), protein folding aids in positioning the Ser carbonyl and Gly nitrogen. Then, cyclization occurs at aforementioned moieties and water is eliminated. Finally, oxidation / desaturation occurs on Tyr, leading to formation of a large pi-delocalized system (green).

Reference: Reid BG, Flynn GC (1997). "Chromophore Formation in Green Fluorescent Protein". Biochemistry 36 (22): 6786–6791. DOI:10.1021/bi970281w. PMID 9184161.

Other models of fluorophore formation exist, see for example doi:10.1021/bi8007164