QM/MM calculations of retinal protein excited states: Investigating the mechanisms of color tuning

• Applicant: Professor Dr. Marcus Elstner
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2005 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5469831

Although the proteins bR and Rh contain the same chromophore, a protonated retinal Schiff base, the absorption maxima are shifted differently in the different protein matrices compared to the spectrum of the isolated retinal (¿copsin shift ). This is due to the interaction of the chromophore with various amino acids in the different protein pockets. Further, the photoisomerization in the protein differs significantly from that in solution, concerning its velocity, the reaction coordinate and quantum yield.In this project we investigate the specific interactions of the proteins with the chromophore in its electronically excited state. These investigations are now feasible, since only recently crystal structures of various intermediates with sufficient resolution became available, and appropriate theoretical methods have been developed. The goal of this proposal is to investigate the influence of steric and electrostatic interactions of amino acid residues from the protein pocket an the optical properties of the chromophore. Further, the spectral changes due to rearrangement of the protein during the photo cycle and the changes due to mutations of the amino acid sequence will be investigated.

• DFG Programme: Research Units
• Subproject of: FOR 490: Molecular Mechanisms of Retinal Protein Action: A Combination of Theoretical Approaches
• Participating Person: Professor Dr. Thomas Frauenheim