"The project is aimed at studying photoactive proteins at the atomic level theoretically as well as experimentally. Photoactive proteins are widespread in nature and enable the signal transduction in biological photoreceptors triggered by the absorption of a photon with a particular wavelength. Opsin proteins containing a protonated Schiff-base retinal chromophore are perhaps the best known as they provide vision in vertebrates.We will study the photophysical and photochemical properties of the chromophores of these proteins at different levels: intrinsic properties of the isolated chromophore units, then the well-defined atomic-scale interactions with the hosting protein medium in the binding site of the chromophore, and finally, whole proteins. One of the highlight goals is to understand the catalytic role played by proteins in the ultrafast excited-state reaction dynamics of biological photoreceptors and in the self-regulation of their photo-physical properties at the atomic-scale. Ultimately, this will lead to an understanding of both wavelength tuning and efficiency of the primary photoreaction in the vision process.Our strategy is to combine the expertise of the applicant in the field of the state-of-the-art quantum methods, who is a co-developer of one of the leading quantum chemistry packages, with the leadership of the hosting university when it comes to laser-action spectroscopy techniques for studying the biomolecular ions in the gas phase. We believe, that such collaboration forms a firm ground for the joint project with the mutual benefit of supporting experimental findings by theory and achieving a better understanding of the underlying fundamental atomic-scale interactions and excited-state dynamics in photoactive biosystems."