Excited state dynamics in the early stages of the bR and Rh photocycle

• Applicant: Professor Dr. Thomas Frauenheim
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2005 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5469831

The very first step in the complex function of the retinal proteins is the absorption of light which is followed by an isomerization of the chromophore within the protein. The high speed, efficiency and selectivity of the process are directly related to the optimized molecular arrangement of the binding pocket.Different factors have so far limited the theoretical description of theses systems. First, the reaction occurs in an excited electronic state for which quantum chemical calculations provide accurate solutions only at high computational cost. Second, the dynamics in the retinal proteins are believed to happen an strongly coupled potential energy surfaces. This makes the use of advanced nonadiabatic molecular dynamics schemes mandatory in order to obtain realistic values for reaction time scales and quantum yields. Finally, the complexity of the protein interaction with the chromophore requires the inclusion of a large part of the binding pocket in structural models for the active site, which involves a high computational effort. In the first half of this project we developed methods which cope with these specific problems and can be used in the second half to analyze the early stages of the bR and Rh photocycies. These calculations will provide structural Information an intermediates in the photocycle and lead to a detailed picture of the complex retinal photoreaction.

• DFG Programme: Research Units
• Subproject of: FOR 490: Molecular Mechanisms of Retinal Protein Action: A Combination of Theoretical Approaches
• Participating Persons: Professor Dr. Marcus Elstner; Professor Dr. Thomas Niehaus