title: The color of rhodopsins at the ab initio multiconfigurational perturbation theory resolution.
abstract: We demonstrate that "brute force" quantum-mechanics/molecular-mechanics computations based on ab initio (i.e., first principles) multiconfigurational perturbation theory can reproduce the absorption maxima of a set of modified bovine rhodopsins with an accuracy allowing for the analysis of the factors determining their colors. In particular, we show that the theory accounts for the changes in excitation energy even when the proteins display the same charge distribution. Three color-tuning mechanisms, leading to changes of close magnitude, are demonstrated to operate in these conditions. The first is based on the change of the conformation of the conjugated backbone of the retinal chromophore. The second operates through the control of the distance between the positive charge residing on the chromophore and the carboxylate counterion. Finally, the third mechanism operates through the changes in orientation of the chromophore relative to the protein. These results offer perspectives for the unbiased computational design of mutants or chemically modified proteins with wanted optical properties.
authors.affiliation: Dipartimento di Chimica, Università di Siena, via Aldo Moro 2, I-53100 Siena, Italy.
authors.forename: Pedro B
authors.initials: PB
authors.lastname: Coto
authors.forename: Angela
authors.initials: A
authors.lastname: Strambi
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D000818:Animals; D002417:Cattle; D003116:Color; D019295:Computational Biology; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012243:Rhodopsin / Q000737:chemistry*; D055672:Static Electricity
chemical_list: D012243:Rhodopsin