Oxidative chemistry in the GFP active site leads to covalent cross-linking of a modified leucine side chain with a histidine imidazole: Implications for the mechanism of chromophore formation

A study demonstrates that the initially colorless Y66L variant, designed to trap chromophore precursor states, is oxidatively modified to generate yellow chromophore that absorbs at 412 and 374 nm. The data suggest that hydration-dehydration equilibrium exists in the cyclic form of the peptide, and that dehydration is favored upon extensive conjugation with the modified side chain.