Absorption spectrum of the green fluorescent protein chromophore anion in vacuo - art. no. 2281092

A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show t hat the anion form of the chromophore of the green fluorescent protein in v acuo has an absorption maximum at 479 nm, which coincides with one of the t wo absorption peaks of the protein. Its absorption characteristics are ther efore ascribed to intrinsic chemical properties of the chromophore. Evident ly, the special beta -can structure of the protein provides shielding of th e chromophore from the surroundings without significantly changing the elec tronic structure of the chromophore through interactions with amino acid si de chains.