Photoisomerization of the green fluorescence proteinchromophore and the meta- and para-amino analogues

Abstract

The Z → Ephotoisomerization and fluorescence quantum yields for the wild-type green fluorescence protein (GFP) chromophore (p-HBDI) and its meta- and para-amino analogues (m-ABDI and p-ABDI) in aprotic solvents (hexane, THF, and acetonitrile) and protic solvents (methanol and 10–20% H₂O in THF) are reported. The dramatic decrease in the quantum yields on going from aprotic to protic solvents indicates the important role of solvent–solute hydrogen bonding in the nonradiative decay pathways. The enhanced fluorescence of m-ABDI is also discussed.