Computational approaches in modeling spectra of biological chromophores

Computational approaches to describe optical spectra of biological chromophores in proteins, in solutions and in the gas phase are discussed. Recently, accurate measurements of spectral properties for the series of chromophores in different media allowed the authors to estimate the positions of the bands with a high accuracy and to challenge theoreticians by stating that the measured S₀-S₁ transition wavelengths may be used as new benchmark values for the theory. The novel computational approaches based on the multiconfigurational quasidegenerate perturbation theory present the practical means how to adapt the high level methodology for calculations of accurate excitation energies in large biological chromophores. The theory is illustrated for a series of model compounds for which experimental data are available: the retinal molecule in the protonated Shiff-base form, the chromophores from the Green Fluorescent Protein family including the kindling protein asFP595, and the chromophore from the BLUF domain containing photoreceptor proteins.