Anabaena Sensory Rhodopsin: A biological model system to decipher the quantum mechanics of photochemical reactions through conical intersections

• Applicant: Dr. Tiago Buckup
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259037069

The ultrafast photo-induced isomerization of retinal, present in its Schiff base form in photoactive proteins (rhodopsins), is among the most important photo-reactions in Nature as it enables higher and lower living organisms to transform photons into chemical energy. In spite of a sustained and intensive research, only a partial understanding of the reaction mechanism and the role of the protein environment to it are available. One of the major open puzzles is the dramatic differences in the efficiency and time constants of the reaction observed for visual and microbial retinal proteins. In this project, we will investigate the retinal's photophysics and -chemistry in Anabaena Sensory Rhodopsin (ASR) by exploiting new ultrafast coherent non-linear spectroscopy combined with quantum mechanical calculations. ASR offers the ideal experimental and theoretical test ground to clarify this puzzle, since it is possible to compare the photodynamics of two biologically active retinal configurations, cis and trans, within the same protein surroundings. We will focus on a combined experimental and theoretical investigation of the interplay between electronic and vibrational dynamics along the photoreaction. To that end, we will develop and apply state-of-the-art ultrafast spectroscopies based on time-resolved Vibrational Coherence Spectroscopy and 2D Electronic Spectroscopy. Since these methods are highly sensitive to different molecular degrees of freedom, they will allow a complete mapping of the evolution of populations and coherences (electronic and vibrational) during the non-adiabatic photoisomerization of ASR. Quantum chemical simulations based on innovative excited state trajectory computations will be developed and applied to quantitatively understand the molecular reaction, including the identification of the vibrational modes contributing to the reaction coordinate and the mechanisms that control the reaction yields.

• DFG Programme: Research Grants
• International Connection: France
• Participating Persons: Professor Dr. Nicolas Ferré; Professor Dr. Stefan Haacke