What specific feature of GFP allows it to fluoresce under UV light?

The fluorescence of Green Fluorescent Protein (GFP) primarily stems from its chromophore, which is a specific molecular structure that absorbs light at one wavelength and then emits light at a longer wavelength, resulting in visible fluorescence. This chromophore is formed through a post-translational modification of certain amino acids within the protein, specifically the cyclization and oxidation of a sequence of residues that create a stable structure capable of fluorescing.

The ability of GFP to fluoresce under UV light is a result of this chromophore being able to absorb that UV light energy and then re-emit it as visible light, typically in the green range of the spectrum. This mechanism underlies the use of GFP in various biotechnological applications, where it serves as a fluorescent marker or reporter in molecular and cellular studies.