Anabaena Sensory Rhodopsin: Ein biologisches Modellsystem zur Untersuchung der Mechanismen von photochemischen Reaktionen durch konische Durchschneidungen
Zusammenfassung der Projektergebnisse
The light-triggered isomerization of retinal, present in the form of Schiff-base in rhodopsin proteins, is among the most important photochemical reactions in nature. The ultrafast structural changes that retinal undergoes enables all types of organisms to transform light into chemical energy. This project was able to explain why the isomerization reaction of retinal varies so vastly depending on the protein environment. The central investigation aspect of this combined project was the systematic variation of environment around the retinal chromophore, in order to disentangle the different effects on the dynamic and static properties of the excited states. This has been experimentally and theoretically performed by changing the environmental pH as well as by point mutations of the ASR protein residuals. State-of-the-art traditional (like QM/MM) methods as well as new theoretical protocol (like Constant pH Molecular Dynamics) together with ultrafast time-resolved multidimensional spectroscopy techniques (like pump-DFWM and –IVS) were able to pinpoint the effect of those environmental changes. One of major findings of this project was that the excited state lifetime of retinal is strongly modified by the interaction with the protein environment. This mutantspecific interaction comes in many forms like steric effects but also due to electrostatic effects generating (i) pre-distortions of the chromophore in the ground state and/or (ii) different energy shifts for the two first optically active excited electronic states, and consequently to the formation of an energy barrier during the photo-activated isomerization. The environmental pH also alters the way retinal in ASR interacts with light, inducing changes in the absorption and/or emission spectrum but also affecting the duration of the photocycle steps. Modeling such nontrivial phenomena has shown for the first time which amino-acids in the ASR protein are responsible for the fine-tuning of the ASR photophysics. Understanding how complex photochemical reactions, like the isomerization of retinal, take place has been a long goal in photochemistry. By combining experiment and theory we were not only able to map the vibrational and electronic degrees of freedom involved in this reaction, but we have also provided how to fine-tune the photophysical properties of a biological chromophore. We believe the results of this project will assist the systematic design of biologically active chromophores with tailored photophysical properties.
Projektbezogene Publikationen (Auswahl)
- An Average Solvent Electrostatic Configuration Protocol for QM/MM Free Energy Optimization: Implementation and Application to Rhodopsin Systems. J. Chem. Theory Comput. 2017, 13 (12), 6391-6404
Orozco-Gonzalez, Y.; Manathunga, M.; Marin, M. D.; Agathangelou, D.; Jung, K. H.; Melaccio, F.; Ferre, N.; Haacke, S.; Coutinho, K.; Canuto, S.; Olivucci, M.
(Siehe online unter https://doi.org/10.1021/acs.jctc.7b00860) - pH-Dependent absorption spectrum of a protein: a minimal electrostatic model of Anabaena sensory rhodopsin. Phys. Chem. Chem. Phys. 2017, 19 (21), 14073-14084
Stenrup, M.; Pieri, E.; Ledentu, V.; Ferre, N.
(Siehe online unter https://doi.org/10.1039/c7cp00991g) - Effect of point mutations on the ultrafast photo-isomerization of Anabaena sensory rhodopsin. Faraday Discuss. 2018, 207, 55-75
Agathangelou, D.; Orozco-Gonzalez, Y.; Marin, M. D.; Roy, P. P.; Brazard, J.; Kandori, H.; Jung, K. H.; Leonard, J.; Buckup, T.; Ferre, N.; Olivucci, M.; Haacke, S.
(Siehe online unter https://doi.org/10.1039/c7fd00200a) - Mapping the Ultrafast Vibrational Dynamics of all-Trans and 13 Cis Retinal Isomerization in Anabaena Sensory Rhodopsin. Phys. Chem. Chem. Phys. 2018
Roy, P. P.; Kato, Y.; Abe-Yoshizumi, R.; Pieri, E.; Ferré, N.; Kandori, H.; Buckup, T.
(Siehe online unter https://doi.org/10.1039/c8cp05469j) - Sampling the protonation states: the pH-dependent UV absorption spectrum of a polypeptide dyad. Phys. Chem. Chem. Phys. 2018, 20 (36), 23252-23261
Pieri, E.; Ledentu, V.; Huix-Rotllant, M.; Ferre, N.
(Siehe online unter https://doi.org/10.1039/c8cp03557a)
