On photoabsorption of the neutral form of the green fluorescent protein chromophore Original Research Article

We present results of theoretical studies of the photoabsorption band corresponding to the vertical electronic transition S0–S1 between first two singlet states of the model chromophore from the green fluorescent protein (GFP) in its neutral form. Predictions of quantum chemical approaches including ab initio and semi-empirical approximations are compared for the model systems which mimic the GFP chromophore in different environments. We provide evidences that the protein matrix in GFP accounts for a fairly large shift of about 40 nm in the S0–S1 absorption band as compared to the gas phase.