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Journal of Physical Chemistry B, Vol.113, No.51, 16443-16448, 2009
Electronic Spectrum of Tryptophan-Phenylalanine. A Correlated Ab Initio and Time-Dependent Density Functional Theory Study
The theoretical electronic spectrum of the tryptophan-phenylalanine bichromophoric dipeptide was obtained for one of the lowest-energy conformer by various high-level computational methods such as complete active space with second order perturbation theory, second-order approximate coupled-cluster theory, and time-dependent density functional theory. The results show that the first excited state is located on the tryptophan residue and called L-b state in the amino-acid. The second and third excited states correspond respectively to the L-a state of Trp and the excited state in the Phe residue. Time-dependent density functional methods appeared to be not efficient to calculate the excited states of such a peptide (except the first one) due to the inclusion of charge transfer states.